Fender Princeton Chorus Guitar Amplifier - Review and Description

Overall Rating: 7.6 (out of 10)

The Fender Princeton Chorus guitar amplifier is a versatile and well featured little all-rounder. Though proudly badged as 'Made in the USA', the reality is more like, made in the Ensenada factory in Mexico.

At a modest 51 Watts RMS, this solid state guitar amplifier is a good choice for small venues / clubs (see note below re: power amplifier THD @ full output). This amp can provide everything from a sweet and lush stereo chorus, to a tasty rock lead guitar sound, without the need for effects pedals. All in a sturdy, compact and relatively easy to transport package.

Note:
There are several Fender amps bearing the name Princeton Chorus. This article is about the one with black knobs (not red knobs - see Wikipedia :), and without DSP. Apparently these amps were first released in/around 1990 with red knobs. There is no specific mention of them in any timeline of Fender amps that I have encountered to date - see the photo at right --->

  About Review and Description articles, click to expand

As mentioned on the Maton MS500 Mastersound page, I purchased the Fender Princeton Chorus, in part, because it happened to work exceptionally well with the Maton MS500 guitar. However this amp will work equally well with other guitars (e.g. Strat / Gibson). This is largely due to the Princeton Chorus having a relatively simple, but very flexible electronic design. It allows a guitarist plenty of scope to adjust their sound without getting bogged down with too many features, controls and endless tweaking.

The amp works fine with effects pedals or just on its own. The built-in Overdrive, Chorus and Spring Reverb offering an excellent range of sounds. For what it's worth, when using the Overdrive, the Fender Princeton Chorus comes about as close to a tube sound as a solid state amplifier is likely to get (that's going to ruffle feathers :-)

Note however, that this particular amp is the 'all analogue' version (read: zero Digital Signal Processing). The now rather dated IC (Integrated Circuit) technology employed in this Princeton Chorus won't be as quiet/clean as newer amps might be. While this might not matter on stage, it will be an issue in a recording studio. The Fender Princeton Chorus is definitely a work-horse amp and not a show pony.

Based on comments from various forums, most people who own a Princeton Chorus or who have previously owned one, regard this amp quite highly. What follows is a no-holds barred personal assessment.


Related Documents:
•  Fender Support USA - Fender Princeton Chorus User Manual
•  Local File - Fender Princeton Chorus Circuit Schematic. It appears that the source I once referenced, being Amp Archives, has been shut down. Fortunately I already had a copy of the schematic. So for those who need to do some repairs or mods ... go for it!


Ease of Use (9/10)

Since all the controls predictably do exactly what you would expect, this amp doesn't require studying the User Manual before use. The manual is quite brief and to the point, using well illustrated diagrams rather than lengthy explanations. It is still a good idea to give the manual a read, if only for the description of the Effects Sends.

Since the Chorus circuit is electronically situated in parallel with the Reverb circuit, it might have made better sense to locate the Chorus controls next to the Reverb, rather than the existing location, at end of the controls next to the Effects Send/Return sockets. A very minor complaint.

Having the Mono and Stereo Effects Send/Return sockets on the front panel is one of the few items that some guitarists might disapprove of, preferring to have them on the rear of the amp. I like them where they are, given that stomp boxes are usually in front of the amp and this deployment makes for shorter cable runs.

In all, you can have this amp singing your song in just a few minutes of tweaking the dials. It is wickedly simple and very effective to use. The downside of this 'all analogue' goodness is, no presets


Features (8/10)

For its age the Fender Princeton Chorus is quite a well appointed guitar amplifier. It does basic things, but does them well and reliably. There is no mind-blowing technology in use. It's all very straight-forward analogue circuitry. Something that will be a very handy thing if the amp ever needs to be repaired.

Note: The following items are listed in the functional/electronic order that they appear in the Circuit Diagram, not necessarily the order that the controls appear on the Front Panel of the amp.


Volume Control
The primary Volume Control is electronically located immediately after a simple input buffer amplifier stage (a TL072 FET input Op Amp) which provides a nominal input impedance of 1MΩ when only INPUT 1 is used and 168KΩ when both inputs are used.

The signal from each input reaches the input buffer amplifier via its own 68KΩ resistor (ie: a virtual earth mixer). So both inputs are identical, there is no Hi/Low input option available.

The actual Volume Control circuit includes a small capacitor across the input and output of the volume pot (potentiometer/variable resistor) which will provide a small amount of treble boost as volume settings are lowered. Simple and effective.

The TL072's are used throughout the Pre Amp, Tone and Effects circuits and are a little on the noisy side as far as Op Amp IC's go. So in short, this is no Hi-Fi front end. In their defense, the TL072 does have an excellent power bandwidth and a high slew rate (meaning it responds very well and very quickly to high energy signal transients ... like what you get from guitars). A reader suggested replacing the TL072's with quieter OPA2107 op amps if necessary.


Overdrive
The Overdrive circuit of the Fender Princeton Chorus is no doubt the most interesting part of this amp's electronics. Sandwiched between the input buffer amplifier and Tone Controls, the Overdrive is a complete section unto itself.

Being independent of the main Volume Control, the Overdrive circuit has its own Gain and Volume Controls, essentially acting like a separate channel when controlled via footswitch. This allows a guitarist to readily switch between clean and raunchy with a single stomp.

Following the schematics we have ....

• Mid Boost
  A switch operated, passive tone control (Bandpass Filter) circuit, used to boost midrange frequencies (that is, to provide some 'honk').
  
  
• Gain
  A single stage amplifier with the variable resistor (the control pot) as a part of the feedback loop to provide a considerable range of gain (the Overdrive).
  
  
• Limiter
  The Limiter/Compressor circuit uses diode clipping (the Limiter part) to create (more or less) symmetrical distortion and uses an opto-coupler (the Compressor part) to control the amount/depth of the Limiting effect.
  
  The Limiter circuit uses an opto-coupler (VTL5C4) which is an LED (Light Emitting Diode) and LDR (Light Dependant Resistor) combined in a single package. The opto-coupler and the control pot are in the feedback loop of an amplifier, thereby controlling (limiting) the overall gain of that stage.
  
  
• Presence and Volume Control
  The signal now passes through another buffer amplifier that drives the passive Presence tone control, which then feeds into the Overdrive Volume Control.
  

The resulting sound from the Overdrive circuitry is somewhat similar to the distortion from a Tube Amp.

Note that the Overdrive switch on the amp's Front Panel disables the Overdrive Footswitch when switched ON.


Tone Controls
The Tone Controls are a basic passive Bass, Mid, Treble configuration located between a pair of TL072 buffer amps that provide a small amount of gain and feed into the Mono Effects Send/Return.


Chorus (Stereo )
What is surprising about the Stereo Chorus, is that Fender managed to get such a nice result from such a simple, even basic circuit.

Based on the (now very old) MN3001 (affectionately named 'Bucket Brigade') analogue delay chip, this circuit is a classic. The MN3001 (or similar) was at the heart of many guitar Delay, Reverb, Chorus and Flanging effects for many years (1980's to 90's), before Digital Signal Processing became the accepted (and affordable) norm.

Suffice to say that it produces a very nice Stereo Chorus with just simple Rate and Depth (wet vs dry mix) controls. The Chorus can be switched In/Out at the amp or via the provided Footswitch. Note that the Chorus switch on the amp's Front Panel disables the Footswitch when switched ON.

While the Chorus is more than adequate for live playing. For recording however, you would most likely want to use something DSP based that was quieter and had greater flexibility.


Spring Reverb (Mono)
The Spring Reverb is a tried and true (and very typical) old design. This implementation for creating Reverb was around for decades before this amp and is now generally replaced by onboard DSP effects (digital Delay, Reverb, Chorus etc.). The Spring Reverb does however produce a pleasing result for what it is. The single (unswitched) Reverb Depth control simply mixes the Reverb and Dry guitar signal just prior to the Stereo Effects Send/Return.

Note: The Reverb and Stereo Chorus circuits are in parallel, so both work with the same Dry guitar or Mono Effects Return signal.


Footswitch for Overdrive and Chorus
A simple, effective and quiet Footswitch (sold/provided with the amp) allows the Overdrive and Chorus to be remotely switched in or out. This uses standard mono 6mm (1/4") jacks. It would have been nice if Fender had included an additional switch for the Reverb.
There is a relatively simple Fender Princeton Chorus Footswitch Pedal DIY page if your amp didn't come with one.

Note: When a Front Panel switch is in the depressed or 'ON' position (for either Overdrive or Chorus) the footswitch for the respective function is disabled.


Effects Send and Return
There are two Effects Send and Return options.

•  The first is a Mono Effects Send/Return which is located before the Reverb / Stereo Chorus circuitry.

•  The second Stereo Effects Send/Return is after the Reverb / Chorus circuitry. The Stereo Effects Return feeds directly into the two Power Amp stages.

I use the Mono Effects Send and Return sockets for a custom made plug-in Master Volume control (which is why I don't mind that the EFX Send/Return sockets are on the Front Panel). In my view, this amp (actually all amps) should have a Master Volume positioned just before the Power Amp stages. This allows you to push some outrageous gain through the Overdrive and still play at any output level.

I sometimes employ the Stereo Effects Return to bypass the amp's front end entirely and send a stereo signal from my Effects Patch Bay and/or Mixer straight to the two Power Amp stages. This requires a dummy stereo jack in the Stereo Effects Send socket (explained in detail in the User Manual). This is very useful to get an idea of how stereo effects combine. Like I said earlier, this is quite a flexible little amplifier.


Headphones Output
The Headphones output is simply taken directly from the speaker output via a resistive voltage divider network. There is no separate Headphones amplifier. This is a simple but adequate solution for use when practicing, that typically disconnects the output from the speakers when there are headphones plugged in.


Power Amplifier (6/10)

It is interesting to note that, though the amp generally sounds quite 'clean' (with the Overdrive switched out of course), according to the note on the circuit schematic, the rated total output of 51 Watts RMS is at an expected THD (Total Harmonic Distortion) level of 5%.

That's a rather high THD figure for a solid state amp. Generally, anything above1% equates to audible / noticeable distortion.

The distortion levels are no doubt mostly due to the use of the two NEC μPC1188H (Single In-Line Monolithic Integrated Circuit) power amp chips, which (according to the μPC1188H spec sheet) are intended to provide 20W into 8Ω at 1% THD. Not stunning performance, but acceptable.

Driving these power amp IC modules to 25W is about 20% above their intended output level. No real surprise then, that the resulting sound might get more than just a little dirty.

I've never actually noticed high distortion levels. This suggests that either, I've never run the Princeton Chorus at full output, or I've had the Overdrive switched on when I have max'd it out and just didn't notice the additional distortion.

In short ...
For a totally clean guitar sound, the Fender Princeton Chorus is at best only a 40W RMS guitar amplifier. I see this as just another fine example of a manufacturer inflating their product specifications in an attempt to impress. The 5% THD at full output power (51W) doesn't get a mention in the specifications quoted at the end of the User Manual.


Speakers and Cabinet

If the over-driven 20W per channel power amp modules are the Princeton Chorus' weakness, then the reasonably efficient pair of 25cm (10") 'Fender Special Design' 8Ω speakers are a redeeming quality.

These speakers are constructed with light-weight paper cones and use a 50mm (2") Voice Coil. Though certainly not brilliant, they really do deliver quite a punch from what is by any standard a small guitar amp. I've run all kinds of rich and deep synth sounds through this amp and it doesn't complain about anything (ie: no cone flap).

The cabinet design is a fairly typical and is only moderately durable, being particle board construction. Sadly, this does make the cabinet susceptible to travel and water damage. An open back style used by many smaller club amps means that it will deliver more bass with a wall or room corner close behind it.

There is provision, via a Velcro strap, to stow the power lead and plenty of room for the footswitch and its cable to be stored in the back when not in use. The Spring Reverb is mounted/attached to the floor of the cabinet (perhaps not so good), so take care not to damage the In/Out reverb leads during transit. Again nothing fancy, just does a job.
See a short note on speaker upgrade suggestions below. It has been suggested that more efficient speakers can make a marked difference to output sound pressure level. This however comes at considerable cost, potentially more than the value of the amp.


Build Quality (8/10) - Durability / Reliability (9/10)

Having owned a Fender Princeton Chorus for years, without a single issue in that whole time, I'd have to give this amp high marks for durability and reliability. Apart from some typical cabinet damage (knocks and scrapes), it's all functional. Admittedly, it hasn't had to work too hard during much of that time, as I haven't been playing professionally. However it got powered up on an almost daily basis for the better part of 15 years. That's a lot of (probably close to 8K) run-time hours, and I still do occasionally test its limits.

The build quality is perhaps a little less impressive than you would expect, from a supposedly 'American-made' Fender product. There is some shoddy workmanship: E.g. Like screws that poke into the cabinet because they were misaligned, spilt glue on the front panel (behind the silver grille) and the Princeton Chorus logo on the grille is crooked (what?). Some might not care, but I happen to like attention to detail and severely dislike obviously 'sloppy' workmanship.


Summary

This is not a modern, multi-tasking, squeaky clean studio amplifier. The Princeton Chorus is noisy by today's standards and is a little rough around the edges, but you know ... it tries really hard. Basically, the Princeton Chorus is simple, sturdy and has stood the test of time without ever failing ... and I do rather love that kind of gear.

Review Ratings:

• Ease of Use - 9 / 10
• Features - 7 / 10
• Power Amplifier - 6 / 10 (over-rated output specifications)
• Build Quality - 8 / 10 (could have been better, has some sloppy details)
• Durability & Reliability - 9 / 10
• Value for Money - 7 /10 (it is really only a 40W RMS guitar amp)
  
  
• Overall Average Score ... 7.6 / 10

Your Comments:
Please Note: Most of the significant comments, questions and answers have been incorporated into the main article above. If you would like a reply when sending comments, please include your email in the comment text. Stay well, stay happy!

241204 - (Excellent) Great review. I have a Princeton Chorus and it's my favorite amp.
Editor's Note: Thanks!


231129 - (Excellent) Thanks for this outstanding and comprehensive review. Not sure if you are based in Australia but the ownership of a Maton Mastersound suggests that you are! Was thinking about shipping one from FNQ to NSW South Coast and this review suggests that this might be a good purchase.

Editor's Note: Yep, I'm a climate refugee from the ever warming Victoria, who moved to Taswegia. The Maton MS500 Mastersound was indeed my fav axe (for close to 30 years) until I purchased the Godin xtSA, in 2019. While the MS500s don't appear to be all that common, they certainly have my recommendation. Though, given comments I've had from other players, you might want to try one out first and make sure you are good with the neck geometry. Best of luck!

230908 - (Excellent) Great work putting this together!
I've had the red knob model of this amp since 1989 and gigged with it a number of times. Never a problem. I seem to remember paying $900 for it new. I did swap out the power input for a more modern plug in type lead, and also have changed the speakers for a pair of Celestion Greenback 10" 25 watters a couple of years ago for a big improvement in sound quality.

Currently thinking about getting an extension speaker output to add a small 2 X 10" Hartke bass cabinet I own. Overkill perhaps, but I like flexibility and all the Princeton lacks sound wise is a bit more bottom end. Do you think it would handle this extension cab OK?

Again my thanks, JS

Editor's Note: An interesting question indeed John! ... and worthy idea ;-)

Because this is a stereo amplifier and the standard anticipated speaker load is 8Ω (per speaker), I would opt for a powered add on box, taking a line level output from either the mono send jack (fine if you are only after the bass frequencies anyway) or the stereo send jack if the additional speakers are intended to cover the full frequency range.

If one pairs each speaker with another 8Ω speaker in parallel, the resulting 4Ω load will mess with the power amps, which are already being pushed to deliver the 25W max per channel (and might reduce the power amp chip's life expectancy). Putting additional speakers in a series configuration will give 16Ω per channel and almost halve the possible output level ... which would be self-defeating.

Another option is to repurpose the stereo headphone jack, which currently (normally) disconnects the speakers when headphones are in use. This is still somewhat untidy electrically, but could provide a signal to amplify via another amp/speaker box.

My first suggested option is the cleaner/safer one, unless a dedicated line-out buffer amp is added to the circuitry (ideal ;-)

Hope that makes sense ... Cheers.

230904 - (Excellent) Super helpful and comprehensive review. Thank you for the considerable time and effort involved in compiling this. Yours gratefully, BK

Editor's Note: Totally welcome, thanks!


230705 - (Excellent) Hi, first I wanted to say thanks for your review of the Fender Princeton Chorus as it's the most comprehensive info I could find online about this amp, and it convinced me to buy one.

I did have a question though ... I noticed your review says plugging in headphones "typically" disconnects the output of the main speakers ... my amp is not doing this. When I plug the headphones in, I still get the output from the speakers.

Since you seemed to indicate this only works sometimes, is there something I'm missing? Or are there different versions of this amp floating around where some do this and some don't? Any info you have would be much appreciated as I have two young kids and would like to play through this while they're sleeping, thank you so much!!
- Chris (USA)

Editor's Note: No - the problem is that you have fallen into another dimension and gone utterly mad. Just kidding.

• You are in fact completely correct in expecting the speakers to be muted when headphones are plugged in. The switching headphone jack [J8], as shown in the circuit schematics (click to enlarge), should disconnect the speakers when a TRS plug is inserted.
  
  
• Unless ... J8 failed at some point and was replaced with a non-switching jack, resulting in the speakers being hardwired to always be connected.
  
  
• Or ... J8 became faulty, perhaps causing those annoying intermittent drop-outs (most often due to oxidation and/or corrosion of the switching contacts), and was electrically bypassed to once again keep the speakers always connected (a.k.a. the quick fix).

These are just the most likely reasons.

A potential (and simple) solution is to plug your headphones into the Send jack of the Stereo Effects Loop, then plug a dummy TRS jack into the Stereo Effects Return socket. This should (if the amp is properly wired) disconnect the stereo signal just before the power amplifier stages ... you win, kids sleep, everybody happy!

230502 - (Excellent) I got mine a few years ago, used of course.  I also noticed my Princeton Chorus badge is not crooked.  I have used mine with a drum machine, and now with a Duo Sonic.  It really does sound great.  I think some people knock it because it is solid state.

Editor's Note: Having spent most of my life (and very happily) with Solid State amps (I was only gifted a boutique Ceriatone 20W all valve head in 2017), to me the whole Valve vs Solid State argument sounds farcical. When I was a 'Biker' (late 70s) it was Harley (or similar) vs Jap Crap. Of course, I rode a very nimble Yamaha TX500 café racer (never was a joiner). Today they're even still beating the vinyl verses digital thing to death, despite all the testing and evidence that clearly settles all points.

I believe that some people are just not happy unless they have something or someone to put down. Sometimes people get all agro on these pages when they don't like (or perhaps don't understand) what they read. Because of that I'm systematically decommissioning these Rate My Page sections. I honestly can't be bothered with people who want to kick you in the balls for being helpful.

Hope you continue to enjoy your very solid state, but very wonderful Fender Princeton Chorus amp!

230330 - (Excellent) Excellent.
Editor's Note:

230330 - (Excellent) very practical and helpful. thanks.
Editor's Note:


230305 - (Excellent) Interessant als referentie
(Dutch: "interesting as a reference").


230305 - (Excellent) Very informative and helpful.


230126 - (Excellent) Thank you that helped a lot, it has been everything you said it is and it sure was better than dragging my Marshall and stack around. Hope to pass it on to my grand daughter someday, and the Marshall - MAHALO.

Editor's Note: Well, I think it's really cool that you have someone to leave it to. Seems the only person interested in my gear is my X-wife (to be clear, not in a bad way) ... and thanks!

220725 - (Excellent) Totally helpful and I agree on everything. My 1988 PC was finished on May 16th 1988 and the board doesn't even have the copyright date yet and is hand signed by 2 people on 2 different dates. I will never part with it. I was also the very first person to pull out the board to clean the pots. My sample was hand assembled, easily seen by the odd lengths of the components legs through the PCB board and all the caps have perfectly level tops. For $279 CND it is a total keeper - Buddy.

Editor's Note: Thanks for the info. Glad to hear you're another happy owner.


220325 - (Excellent) Well written. Much enjoyed reading. Most helpful.
Good work. Thank you.

Editor's Note: Many thanks, glad you enjoyed it.

211008 - (Excellent) Hi - I'm the guy with the Vintage 10s in my Princeton Chorus. I just wanted to mention a quick correction to your excellent article: The footswitch uses a mono cable rather than a three wire. The footswitch has diodes wired so the amp "knows" which switch is being depressed. My amp didn't come with the switch, so I ordered a Fender OEM. Seeing the provided 2 conductor cable, I got curious. Very clever design, works flawlessly.

Editor's Note: Many thanks for the correction. This page has now been updated and also includes a link to a DIY project, just in case any one else has a missing footswitch. Your assistance in maintaining the accuracy of this page is greatly appreciated! See also: Fender Princeton Chorus Footswitch Pedal DIY page


210728 - (Excellent) Excellent review, fair and accurate.  I switched out the stock speakers in mine for two Eminence Ragin Cajuns.  It increased the power levels dramatically, and the lows are positively thunderous.  I strongly suggest this mod. In my opinion, this is the best solid-state amp Fender has produced to date.

Editor's Note: Thanks for the input and speaker mod suggestion. A few dB of extra grunt could really transform this little amp. Firstly though - I've learned not to get too excited over modding my gear or emails about the same. Often they're just paid promoters pretending to be reader feedback ... not that I'm saying that's what this is ...

For those interested ... the Eminence Ragin Cajun speakers retail for around AUD $205 each, so this upgrade could be considered as 'very substantial'. If however the original speakers were starting to perish and/or show signs of cone deterioration, this could be a very cool upgrade.

The Eminence Ragin Cajun speakers are rated at 75W into 8ohm (so a pair of these is major overkill), with an SPL of around 100.5dB (something like 4 to possibly 6dB more than the standard Fender Special Design - that is, on paper - these should sound almost twice as loud). The price of this upgrade would be close to the value of a used Princeton Chorus amp in very good condition. So, the original speakers would need to be badly worn or you would have to really like (nah, love) this amp to commit to this mod - or of course, you could just be a little bit crazy (like the rest of us).

More on Speaker Replacements / Upgrades:
There are also some Australia Made speaker options from Lorantz worthy of investigating (prices include shipping):.
LORANTZ 10"  30W RMS, 8 Ohm Guitar Speaker - Vintage U.K. Greenback Clone - SPL 102dB at around AUD $185 ea.
LORANTZ 10" 100W RMS, 8 Ohm Multi-Purpose Speaker - SPL 98dB at around AUD $220 ea. (a full range speaker that might be useful if the amp where also used for keyboards).
Can be found on eeebaay, or from the Melbourne Music Centre / Lorantz web site. That's a free plug, by the way ... just supporting a local business.


210605 - (Excellent) Excellent !!!!!

Editor's Note: Thanks ;-)


210426 - (Excellent) Thank you.

Editor's Note: You're welcome ;-)


210417 - (Excellent) "I'm currently awaiting the arrival of my latest upgrade (in transit as I write), which is a shiny new AXE-FX III Mk2" [Snippage] - "It may even see the Fender Princeton Chorus and a few other bits of gear eventually heading to new homes."

I have a NUX MG-30 on preorder, and I'm wondering about running the MG-30 modeler into the FX return, turning the Princeton into a stereo pedal platform. It definitely won't be a flat response through the Celestions I have in there, but it's worth a try. By the way, any thoughts on how the Axe FX works for you?

Editor's Note: Absolutely worth trying as a stereo amp. I used the Princeton Chorus that way (stereo) with the Zoom G9.2tt Console, worked fine with some EQ adjustments. Once I started putting my guitar through synths though, the lack of crisp highs and booming lows became an issue fairly quickly. So for now my amp is actually a JBL EON-612 pair. At least until I find something better and/or more compact (update: 2023 Yamaha HS-8 pair).

I have begun a write-up of the AXE-FX III, mentioned above (not ready for publication). The thing really is a world unto itself. When I'm done moving house and properly relocated with my gear set up again, I will explore that beast in greater depth and detail. For now I can only say, it's awesome. The quality and clarity of the audio that comes out of the AXE-FX III will raise the hair on the back of your neck. All the factory presets are meticulously refined to work straight out of the box. Do I sound impressed?


210227 - (Excellent) I bought this amp at a thrift store and knew nothing about it. My arch top and J200 both sound decent with just a bit of reverb and chorus. It seems like it is a pretty decent little amp for $80.Thanks.

Channel 1 does not work on my amp and I was considering having it repaired but after reading that both inputs are the same I won't bother. The amp only cost $80 and I can't see getting out of a repair shop for less than $100. So it's a no brainer now that I know repairing it woudln't make any difference to the sound .

Editor's Note: As far as guitar amps go, the Princeton Chorus has a really nice range of sounds for a relatively small package. It should serve you well as long as you don't need a stage amp.

I suspect you've probably nailed it there with the channel one problem. A faulty jack and/or soldering at the jack will quite likely be the culprit. Catch is that opening it up to get to that jack, for a 5 minute repair and then reassembling, will probably take good half an hour. The jack is multi-tapped switching jack, so that won't be cheap either. So unless you can DIY, you would be right in thinking that a $100 repair would be somewhat optimistic ;-)


210205 - (Excellent) Re: the tone controls, and why they're not inside an amplifier feedback loop.

I assume this is to preserve the "Fender sound". The schematic posted looks very much like the passive TMB tone stack (Treble Mid Bass - ed.) you'd see in any old Fender (or Marshall, etc.) tube amp. This circuit will produce a "mid scoop", which you can't fully eliminate regardless of knob settings. This is the sound many guitarists like and expect.

Given the opamps already in the circuit, it wouldn't be that hard to redesign the tone controls to a "Baxandall" (Search w Duck Duck Go) configuration, which would give you true boost and cut on each control, with flat response at the midpoint. Much more versatile, preferred in my book -- but not the "classic Fender sound", at least, not unless you set the controls that way.

Alternatively, you could put a switch that disconnects the mid pot from ground, aka "raw" switch: this will pretty much disable the internal tone stack, eliminating that baked-in mid scoop, and you could then use an external EQ of some kind via pedals or the effect loops.

Editor's Note: Many thanks for your excellent and informative suggestions about the Princeton Chorus tone section circuitry. Very nice to have a little tech input. They are the sort of mods I would have been all over in my younger daze ;-)  In fact, after a suggestion from a visitor, I purchased a full set of the much quieter specification OPA2107 op amps to replace the standard TL072 op amps used throughout the Princeton Chorus. Fact is, I've never found the time (and/or inclination) to make the mod.

Another part of the problem (aside from age induced laziness), is that I have learned that the value of stuff can diminish in direct proportion (or worse) to the amount of mods done to it. For example: I have some classic old guitar effects that would be highly collectible and worth many times what I paid for them - if hadn't modded them and tossed out their cases. Current collective value = nil. Just to say - caution is advised before modding perfectly functional gear - or - if it ain't broke, don't fix it.

If on the other hand the amp is already a repair job - then, go for it!

I'm currently awaiting the arrival of my latest upgrade (in transit as I write), which is a shiny new AXE-FX III Mk2. This will make worrying about and/or tinkering with the tone control circuitry of any one amp, well, pretty much a thing of the past. It may even see the Fender Princeton Chorus and a few other bits of gear eventually heading to new homes.

201223 - (Excellent) Hi. I was told by a very knowledgeable shop owner that the speakers are actually Celestion made for Fender. I have just started using this amp again after years of using a Princeton Reverb. I'm finding it to be very good.

Editor's Note: Well that's an interesting insight. Fender have released re-issue amps (apparently) with Celestion speakers (e.g. FSR ’65 Deluxe Reverb reissue with a Celestion Redback), so it's plausible that there is a working relationship between the two companies. Also Celestions are probably the most commonly recommended replacement for Fender speakers. However, this is supposition, not proof ;-)


201117 - (Excellent) Thank you for some useful info. I own one of these. I needed to refresh my memory of some technical details. My experience of the amp is the same as the review.

Editor's Note: Thanks for leaving a comment.


200826 - (Excellent) If, as many people online claim, that the speaker is a Fender-branded Eminence Legend 1058, the stock speaker is a bit more efficient than the Vintage 10 inch: 98.7 dB for the "Fender" vs. 97 for the Vintage. That claim may be a big "if"... Fender may not have ordered that exact driver to put in the PC amp. The amp sure does sound nice with the Celestions though.
Added later:
One other thing to note is the unusual behavior of the tone circuit: in my experience, with all three controls at zero, no signal will pass through. Kind of odd, but if you are aware of it, it can help with both getting a good tone and more volume from the amp.

Editor's Note: Interesting! Picking the difference between two speakers with a 1dB SPL difference will completely come down to tonality, because the actual perceived loudness would be too small for most of us to differentiate. For what it's worth, I'm not a fan of the 'Fender Special Design' speakers in any of their incarnations (10" or 12"). They have a particular sound, they do a job, and I'm guessing for Fender, they are at a price-point that they like for keeping their costs down. And to be honest, I find the stated 98.7dB SPL claim a little difficult to believe.

I've got an old (actually, not that old) 100 Watt Fender Frontman in need of repair (a totally crap piece of electronics), but everyone loves the sound. And that sound is the speakers! Sadly, both of the two 12s are showing radial cracking of their cones around the edges and are essentially in need of a recone. With the output power stage blown, It's simply more trouble and cost than the amp is worth.

Re: Fender Princeton Chorus Tone Control Design - A look at the circuit diagram (shown at right) confirms that zero output would indeed happen with all tone controls set to zero, where the signal is essentially shunted straight to ground.

Usually the Tone Controls would be located within the feedback loop of an amplifier. An approach which keeps the output level more or less constant, regardless of tone settings, but may introduce some noise (dependant on the quality/spec of the operational amplifier used). The TL072 op-amps used throughout the Fender Princeton Chorus have great slew rate but fairly ordinary noise specs. But I'm not going to pretend to understand the thinking behind this little quirk.

Master Volume: I actually used the stereo send/return ports (conveniently side by side on the front) to create a Master Volume control. Two stereo 6mm (1/4") jacks soldered directly to a Stereo 50K B potentiometer (pot ;-) Works a treat! Means you can crank up the front end but keep the output level tame. Of course you won't get the benefit of the max'd-out power amp distortion - if that's what you like ;-)


200825 - (Excellent) Thank you for the fine explanation of the signal flow and the circuitry that impacts it. I was recently given a red knob version of the amp, loaded with Celestion Vintage 10 speakers, by a friend of mine before he moved away. This page has been a great insight into the inner workings of this great little amp.

Editor's Note: Hmm, the Celestion upgrade sounds like a good idea. A few extra dB of SPL could take the humble Fender Princeton Chorus to a whole new level. I might have to look into that - thanks!


200719 - (Excellent) Thanks for the excellent review and circuit w IC details! I made a compressor with a similar "opto isolator" from the Craig Anderton Electronics for Musicians as well as a bunch of other circuits from that book. I liked the compression characteristic more than the Boss and other brands of the mid 80's when i used these effects as my rig in a cover band.

Editor's Note: Ah yes! I still have the old Electronics for Musicians in my archives (along with plenty of other dinosaur brain food). Like you I also built several of Craig's circuits - and - some where much better than others. After which, seeing the Princeton Chorus schematic, that opto isolator compressor really stands out. So - greetings fellow dinosaur! ;-)


200610 - (Excellent) Very nice amp! Great sound, easy to use and ALL ANALOG! I definitely like it, a lot!


200407 - (Excellent) I own one, and like it.


190913 - (Excellent) I just won one of these in a raffle, this is fantastic detailed background of what I have.

Editor's Note: I hope the Princeton Chorus serves you well ;-)


190830 - (Excellent) Clear, thorough info all in one place!


190822 - (Excellent) This helps a lot. I wish it had a little more highs when using the overdrive.

Editor's Note: That's why I think it's not fair to call it a 50W amplifier. That last 10W is at the expense of frequency response, particularly higher frequencies.


190130 - (Useful) Aha, a schematic. Had trouble finding that. I think it's a decent amp, and can be had at reasonable prices here in the States. I should point out that the red knob versions are the same circuitry, just a few years older (first issued in 1988, black knobs appear in 1990).

Editor's Note: Well, thanks for your almost useful comment. It would be nice if that information could be verified (which it can't;-)
From Wikipedia : "The Red Knob amplifiers were produced from 1987 until 1993".

180810 - (Excellent) This amp is very pleasing to use at rehearsals, though I am tempted to overclock it for gigs - Jack.

Editor's Note: I took the Fender Princeton Chorus to a rehearsal with a drummer, 100W bass amp and 100W Fender Frontman amp in use. Put simply, you could not hear the Fender Princeton Chorus unless everybody else stopped playing. For any serious rehearsal or on-stage use it will need to be mic'd up.


180517 - (Comment Only) Your comment about the power amp IC are not really much help to anyone. 5% THD is rather good and superior to most valve/tube amps... even boutique! I rate your comments as just another dig at SS guitar amps. Check out these: advertising link deleted. They are superb and 100% SS!

Editor's Note: What a load of utter bullshit!
Firstly, I love Solid State amps. The only valve amp that I own was given to me (and it is actually a gorgeous little boutique 20W (Ceriatone Lunchbox) amp ;-)

There was a time when I owned the Class A, stereo, Sansui BA5000 (a 48kg rackmount brute of a PA amp). It's specs included: 300W RMS (both channels driven) at 0.0015% THD (Total Harmonic Distortion). But - what was really impressive about this amp was that, though it was rated at 300W RMS, the distortion spec only degraded to 0.01% THD at 600W RMS!! That's a very real, very clean 1200W RMS total when the power amps are bang'n the rails. Each unit came with it's own signed spec sheet. Ok, that is overkill.

Even in this age of lazy amp design (amps on a chip), where designers will sometimes take the same Class D amplifier chips used to drive car speakers to build what I would call "practice amps", a result of 5% THD is rather shoddy. Certainly nothing to brag about or any kind of a target for excellence. Admittedly, most non-professional guitarists and bassists probably wouldn't be too fussed about it. It just happens that I am.

And just for the record, that puts me in the 'middle ground'. I had a dear friend who was a true audiophile for many decades, who wouldn't even look at buying audio gear with a THD greater than 0.01% (high end cassette decks like the Nakamichi at around 1% THD, excepted - what are those again?).

(Bang'n the Rails = Old electronics parlance for an amp that is running at the full capacity of the available power supply, i.e.: the +ve and -ve supply rails).

And just, finally - No matter how far we and our technologies evolve, mediocre will never equal excellent nor 'superb' (at least in my universe) ... and if you want to do advertising on any of my pages, pay me first ;-)

170401 - (Excellent) I notice a volume drop with my FPC, do you know what the culprit may be for this? Thanks.

Editor's Note: That's a little like asking "how long is a piece of string" ;-)

Check the Tone Control settings - These can effect the output level.

Then ... since it is a stereo amplifier, I would first check that both channels are still working.

Connect a signal to the Stereo Effects Return with a stereo jack and check that each channel has output. If not, check that the speaker of the failed channel is good. If the speaker is good, then it may be the power amp. Since both channels are on the same power amp chip, this would require professional repairing/replacement.

It could also be a faulty jack or damaged input pre-amplifier. So if you don't know your way around the guts of electronic equipment, please take it to a qualified repairer.


170102 - (Excellent) I like it ... Very good.

Editor's Note: Thanks and all the best for the new year.


160519 - (Excellent) My friend and fellow band mate has had this amp since brand new in the nineties and it just now needed a pot cleaning which wasn't that dirty in the first place. Now it sounds smooth and clean like new. I like the fact it was a USA made amp and how easy it is to operate the controls. I myself have a 1965 Bandmaster with all original parts and I'm it's first owner and it still sounds amazing. I bias my own amp when needed and do the electronics myself if needed. Fender had some great techs working for him.

Editor's Note: It's good to hear about equipment that lasts and that there are still some 'tech savvy' musicians around. Sadly, with the manufacturing technology currently in place, everything is being built to achieve finer tolerances and lower costs. One outcome of this is an increasing tendency to creating ever more fragile products ... or simply put ... stuff doesn't last like it used to.


160519 - (Excellent) I'm agree with most of things said. I own a red knob one and I'm satisfied for what it is.

Editor's Note: I have never encountered/used the model with red knobs, so I have no idea if there are any meaningful performance differences and/or improvements. One might expect (or perhaps at least hope ;-) that the differences do go beyond just the colour of the control knobs.


160403 - (Excellent) Wow! I REALLY appreciate all the information! Unless I missed it, I would like to know when the Princeton Chorus first appeared on the scene?

Editor's Note: I've tried to get a specific date on several occasions, but the best I've come up with so far is ... the early ones were made in the 80's and have red knobs, the later ones made through to the mid 90's have black knobs. For some reason the Princeton Chorus doesn't rate a WikiPedia entry (or even mention).[Since then ... Wikipedia : "]


160226 - (Excellent) Straight forward, very objective, that's what helps people interested in buying one. Thanks.

160122 - (Excellent) Nice work. Thank you!



150817 - (Very Good) I purchased my Princeton Chorus used for $99.00 and all was well until I got it home and now the reverb is not working, but I still really like the sound.

Editor's Note: The reverb spring unit is mounted on the floor of the speaker box and is connected to the electronics by a pair of leads with RCA connectors. These may have become disconnected during transport. Glad you like your new 'old' amp ;-)

150816 - (Very Good) I have found the info very useful because I am planning to buy a used one, if I can find one. What would be a good price for one?

Editor's Note: Value will depend ondition and availability (rarity), in Australia expect to pay AUD $300 - $500. They are more common and possibly a little cheaper in the US, USD $200 - con$300.




Incept Date: Wizard - 140331
Last Update: Wizard - 241204