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Fender Princeton Chorus 50Watt Guitar Amplifier
Review and Description
Fender Princeton Chorus Guitar Amplifier - Review and Description



Find a Fender Princeton Chorus  on Ebay






   


Fender Princeton Chorus Specifications


Inputs:
•  INPUT 1 only - 1 meg Ohm
•  INPUT 2 - 131k Ohm

Nominal Input Level:
•  INPUT 1 only - 100mv
•  INPUT 2 - 200mv

Tone Controls:
   Bass, Mid, Treble

Onboard Effects:
•  Overdrive: with Gain, Mid Boost (switched)
    Limiter and Presence control
•  Chorus - Analogue / MN3101 (BBD) (switched)
•  Reverb - 3 Spring / Mechanical

Footswitch for Overdrive and Chorus

Mono Effects Loop:
•  Nominal Level: -10dBv
•  Send Output Impedance: 1kΩ
•  Return Input Impedance: 25kΩ

Stereo Effects Loop:
•  Nominal Level: -10dBv.
•  Send Output Impedance: 1kΩ
•  Return Input Impedance: 150kΩ
Specifications are for each channel. 6mm Stereo Jack Wiring: Left on Tip, Right on Ring, Gnd on Sleeve.

Headphones Output:
•  Stereo 6mm (1/4") Phone Plug

Power Output:
   25.5 Watts RMS per channel
   or 51 Watts RMS total @ 5% THD
   (approximately 1% THD @ 20W RMS / Channel)

Rated Load Impedance:
   8Ω per channel

Speaker Compliment:
   2 x 8Ω Fender Special Design
   250mm (10") speakers (PN: 029753)

Power Requirements:
   AUS - 240VAC 50Hz
   US - 120VAC 60 Hz
   1.2 Amps Max., 145 Watts Max

Physical Dimensions:
•  Height: 44cm (17-1/2”)
•  Width: 57cm (22-3/8”)
•  Depth: 26 cm (10-3/16”)
•  Weight: 17.2 kg (38 lbs.)




Buying a Used Fender Princeton Chorus

As with any older guitar amplifier, finding a used Princeton Chorus that hasn't been beaten up over the years may be a challenge. The price at the time of original purchase was around AUD $1500 (RRP).

It's not unusual to see the Fender Princeton Chorus, in good condition, listed for between AUD $300 - $500. They are, not surprisingly, more common and appropriately cheaper in the USA at around USD $200 - $300.

And lastly, don't get sucked in by the hype and bullshit claims on eBay, like: "With its 2x10" speakers and it's built in chorus, this amp will even rival the vaunted Roland JC120". No it won't, at least not in this universe.

The JC120 can spit out a real and totally clean 120W RMS (60W per channel), about 3 times what the Princeton Chorus is capable of. There is no meaningful comparison or competition between the two amps other than they both have stereo chorus.

Another example from the same advert is a photo of the rear panel showing the input power, being 120 V @ 60Hz, followed on the next line by just 125W. Quite obviously trying to suggest (to those who don't know) that this is the amps output power. Again, no. The Princeton Chorus' max output is a very dirty 52W RMS (@ 5% THD). Running reasonably clean it can only manage 40W Total.

   

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Overall Rating: 7.6 (out of 10)

The Fender Princeton Chorus guitar amplifier is a versatile and well featured little all-rounder, proudly badged as 'Made in the USA'. 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 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 named Princeton Chorus. This article is about the one with black (not red) knobs, and without DSP - see the photo --->

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 tweak a 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 and 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.

Note however, that this particular amp is the all analogue version (read: no 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. That might not matter on stage, but it will in a recording studio. The Fender Princeton Chorus is definitely a work-horse amp and not a show pony.

For what it's worth, it would seem (based on comments from various forums) that most people who own a Princeton Chorus or have 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 External Link
•  Local File - Fender Princeton Chorus Circuit Schematic. It appears that the source I used to reference, 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.

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.


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).


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 ....

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, 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 quieter and more flexible (DSP).


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.

Further Details...
The actual reverb unit in use is an Accutronics Model: 8EB2C1B
  • Springs: 3
  • Input Impedance: 800Ω
  • Output Impedance: 2575Ω
  • Decay Time: Medium (1.75 to 3.0 sec)
  • Connectors: RCA - Input Insulated / Output Grounded
  • Mounting Plane: Horizontal - Open Side Down

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 stereo 6mm (1/4") jacks and a stereo cable. It would have been nice if Fender had included an additional Footswitch for the Reverb, but admittedly that would have complicated the switch cabling somewhat (quite possibly adding a second cable).

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 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 much over 1% 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 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 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.



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 still gets powered up on an almost daily basis. That's a lot of run-time hours, and I do occasionally also test its limits.

The build quality is perhaps a little less impressive than you would expect from an 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 'sloppy' workmanship.

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.

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Your Comments:


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" ;-) ... but, 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).


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 on condition 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 - $300.


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