I had the good fortune recently to find an old Peavey Classic Series 60/60 tube power amp in good condition and at a reasonable price (thank you Mats!). I found that there was limited information available on the internet and decided to gather and collect what I can find and to photograph the inside of the unit and present it here.
It’s not uncommon to find these classic 3U rack amps in the small ad’s, ebay.com, reverb.com and the like. Weighing in at over 13.4 kg they were ruggedly built for touring musicians on the road. They were manufactured in three versions, a 50 watt, 60 watt and 120 watt units. Production started in 1989.
I think I’m right in saying that they were produced in either stereo, two-channel versions or in mono, single channel versions. Of course the stereo versions can be run in mono with a load resistor in the spare channel. More on that later. The unit I’m concentrating on here is the two-channel 60w version, the Peavey Classic 60/60. I use this amp in a studio environment for recording purposes.
Peavey Customer Support, Schematics and Spare Parts
I contacted Peavey Support to ask if they had the schematics for my unit and received a pdf copy the very next day. Gotta love that service. It would appear Peavey take customer support very seriously. They even have a site dedicated to supplying parts for both older, and newer amps. I’m confident they can help in locating or supplying parts for any Peavey Classic Series amp. Here’s some links:
Manual and Schematic Downloads
A Peek Under The Hood – Photo’s
Apart from the tubes everything looked original. Here’s some ‘under the hood’ photo’s of my unit manufactured on the 3rd of January 1990 according to a label inside.
Above you can see an aerial shot of all 7 tubes. The four larger tubes are the power tubes (Groove Tubes), two for each channel (L+R). Along the front edge you can see three ‘ECC83WA TAD Premium’ tubes from Tube Amp Doctor in Germany. These were obviously not the original Peavey tubes as supplied when the unit was shipped. Someone, at some time has changed them and I’m happy they did.
6L6’s are commonly found in amplifiers from USA. Historically, Fender amps have used 6L6’s since the 50’s. These tubes are renowned for their clarity, high headroom and punch. Here’s a close up.
ECC83WA TAD Premium tubes (close up below) are a 12AX7 style tube. Very common preamp tubes known for their low noise, warm tone and fat mid range.
Above: Another shot of the inside of the amp. Note the two enormous output transformers (top left) and the cooling fan, top right.
Output Transformers are the last stage in the audio path to the speaker and play a vital role in the tone of the amplifier. The transformers in the Peavey do not disappoint. They are big and beautiful. I don’t see any visible markings on them, hidden perhaps but I’m sure these are original parts. Large transformers are often associated with darker (duller) sounding amps. In fact I’ve read several forum post’s from people describing the Peavey 60/60 as ‘dark’ sounding. I’ve not noticed this myself but I generally use an EQ to tame the low-end anyway when dialing in guitar sounds for recording.
If you’d like to learn more about transformers in general, here’s a couple of links:
- Understanding your output transformer Part one by Mark Baier
- Legendary Tones- Guitar Output Transformers- The Overlooked Upgrade
Here we have an original Basler Electronic Co. power transformer with number 705-18705.
PCB Board And Cooling Fan
I’m researching a replacement fan for my unit because the newer fans are probably quieter. I’ll update here as and when I get more info.
2019-02-03 Updated Replacement Fan Information
Here’s some info from Enzo Campagnolo (big thanks Enzo), who found the perfect replacement fan for the unit. Looks like it can be ordered worldwide from mouser.com, see link below.
Orion Model: OA80AD-11-2 WD Available at Mouser Electronics, about 15.40€ https://www.mouser.com/ProductDetail/670-OA80AP112WB Its an exact drop in with slightly higher performance, quiet as a mouse!
Here’s the spec sheet (Orion Model: OA8OAD-11-2):
Click here to download the Spec sheet for the Orion fan
How To Use A Stereo Unit In Mono
At the risk of stating the obvious:
Never turn on a tube amp without a speaker connected. You can fry the transformers.
Secondly, my disclaimer. Do this at your own risk. I am not an electrician and cannot take responsibility for any damages to your amplifier. However, I can tell you that this method was given to me by a qualified professional and has worked flawlessly for a while now.
To use a stereo unit in mono I advise the use of a resistor, or a dummy load as it’s often referred to. These can be purchased cheaply from ebay. For my 60w unit I used a 100w 8ohm resistor. The resistors positive and negative lugs are soldered to a standard 1/4” tele plug (a guitar cable plug) via a suitable ’copper speaker cable’. The resistor can then be connected to an ’Input’ jack on the rear of the unit. I chose to use input channel 2, leaving input channel 1 free to use as a mono guitar input. Turn down the ’Sensitivity’ knob to zero on the channel with the dummy load. Here’s an image of the resistor mounted on the inside wall of the enclosure.
As you can see in the image above, I took the precaution of placing the dummy load resistor (the orange block) behind a piece of plastic to reduce the risk of shocks.
I did read somewhere on the web that these units use ’Flyback Diode Protection’ so its possible to run a single channel in mono and simply turn down the ’Sensitivity’ knob to zero on the other, without the use of a dummy load. I don’t know that is the case and I’m not going to risk losing a transformer so I use a dummy load. Simple.
The Controls – Back Of The Unit
The controls on the rear of the unit are pretty straight forward, let’s start with a picture.
So, there’s two of everything. It’s a stereo unit.
- SPEAKER OUTPUTS: Connect your speakers here.
- LINE OUT: Take a lined signal here directly to your mixing desk, audio device, outboard FX etc. Note the two XLR outputs which deliver a transformer balanced output. Handy. Also there are two pots to control the outgoing signal.
- INPUT: Here you could connect a guitar signal from a guitar preamp. Also, this input could facilitate the dummy load resistor mentioned previously. The ‘Sensitivity’ knob, think of this as a volume pot for the input signal. I leave these on 10. I’m told that the two XLR inputs are balanced but cannot confirm that at this point. The manual does not state that this is the case. It would certainly make sense though, being XLR’s.
2019-04-14 Updated Bios info. See below:
These units are ‘Fixed Bias’. As Barry Tyler pointed out to me, this can be misleading. Here’s Barry’s text:
Fixed bias does not mean it cannot be adjusted, Quite the opposite. Although the term is extremely misleading, fixed bias means that it CAN be adjusted.It just needs to be biased to a fixed value. I know that at face value that makes no sense but that is the reality. Only cathode biased amps cannot be adjusted or rather, they do not need to be.
Secondly there is no connection between the matching of a pair of valves and the fact that they need to be biased. Yes you always need a pair of matched valves but this does not in any way help you with the biasing of the valves.It merely ensures they are pushing and pulling with equal measure and so all power valves must be purchased as a matched set.
I have 30 years of experience with amp repairs so trust me this is correct although I am sure you will want to check it out. I just thought it was a shame to spoil such an excellent review with one incorrect line.
Some Good Advice From ‘Enorbet2’ on Gearslutz
Whilst researching the amp I had the good fortune of getting some good info from Enorbet2 on the Gearslutz forum. See below:
“I suspect that date of 1989 for the manual was a record of a revision since I am certain the 60/60 rack unit existed as early as 1985-6. I was employed by a large retail Musical Instrument outlet and saw those amps then and a few, very few I should add, came across my bench. It was and is a decent amp and came from a time when savvy ol’ Hartley was finally beginning to lose his well-documented bias against tube amps. Nevertheless he, being the salt of the earth savvy gent that he is, was swayed by his Sales Department which while partly responsible for the evolution into understanding that tubes do indeed offer something SS can’t also made him push design to deliver hot bullet points like wattage numbers pushed high by skirting the very boundary of Class B where things get nasty.
As a result I think the 60/60 would benefit greatly from a qualified tech either adjusting the bias for a warmer, more dynamic sound either by resistor substitution or better, by altering the amp for adjustable bias especially considering the difference in available tube quality from 30 years ago.”
Enzo Campagnola’s 60/60 Restoration project update
2019-02-24 Updated Enzo’s list. See below:
Enzo has given us permission to make available his restoration list from his recent 60/60 overhaul. Click the link below to view the document.
I can’t say enough good things about this amp. Just the smell of the tubes does it for me. There’s ample headroom, a warm, round tone, rich in harmonics and a great dynamic response. For those of us that cannot afford a Fryette Power Station, this is a great tool to have in the studio. The only qualm I have with my unit is the fan noise. However, fans are inexpensive and easy to replace so I will be looking into that.
If anyone has any more information they can share with me I’d be grateful. Contact me here .
Other mooselander links:
or visit Peavey by clicking the logo below.