I want to give thanks...

[Benjamin Ruffin]

I have only been a member on this forum here for a little while but I have read more than a few threads here for years now. I purchased a Peavey Classic 50 4/10 model in the late 90's and played through it bone stock for years. I inevitably got some complaints from band members over time about the piercing high treble at times while playing a strat or anything else that used single coils, even humbuckers would come across wrong. I
ran across some ideas for modifying this amp on Steve Ahola's great site. I got up the courage and a healthy respect for the danger of operating on a tube circuit and went to work. I did a little at a time to test the changes, etc. The pcb isn't ideal to work on (to say the least) but I got used to it.

One of the first things I did was the cathode follower mod. V2A has a 25v25mf cathode bypass cap around 820R instead of the smaller 1mf. I found that cap value retains a better bass/treble balance between 'channels' and no more icepicks at all, just sweet harmonics. I no longer fear switching channels! I approached V2a like it was an initial gain stage where you don't want to chop off all the bass in the signal. 100k plate resistors for V1 and V2 as per Steve A's recommendations gives much better headroom than stock which really wakes up the overall sound of this amp. I changed the load resistor on V2B to a lower value of 56k. I found some information on Valve Wizard's site regarding this little mod. It creates this really smooth compression that is so beautiful. The compression is buttery, almost like power supply sag. When you hit the input of the amp with a really hot signal it's really thick and harmonically rich in either channel. The amp is very near cut-off (I'm not sure where exactly but wow!) when driven hard both at low and high output volumes which is great. I put a Mu-Tron III in the chain right before the input and cranked the gain knob. Blast off!

I obviously had to mod the tone stack. That took the most experimentation to get right. I found the best combination to be 56k slope w/ .022mf orange drops for bass and mid was the best (the stock caps are garbage). The treble cap was the hardest to nail down. I tried 360pf sm first. Way to much hi mids (ouch). Dropped it to 250pf sm, still too bright (!). Dropped it further to 100pf and this was the ticket. This value seems to narrow the treble bandwidth just enough, but not too much. The treble pot is very useful now in combination with the mid pot. The bass center frequency is perfect. This amp is now the best sounding amplifier I have ever played. It is such a stealth amp now. It has the awesome Fender cleans and will absolutely roar when you kick in V2. I am absolutely hooked on this amp, the tone is stunning. All you need is the volume knob on the guitar. The stock speakers sound great now that the amp is dialed in. Honestly, I LOVE this amp. It can go from nice pristine clean with just the right amount of treble to full on Van Halenesque where every tube is in saturation. This is a desert island amp for certain.

I just want to thank the experts here that have shared their insight and ideas. I am here to tell you that the Peavey Classic 50 can be successfully modified into an amp that is just so seductive it's not even fair to other amps. I am proud to say I have the pleasure of owning the best sounding
amp I've ever heard. I didn't cover all the changes I made to this circuit so if anyone is interested and curious feel free to ask. I highly recommend
anyone performing these mods check out The Valve Wizard's site and blueguitar.org if you haven't already, great sites. I don't know how to upload sound clips here but I would like to if anyone is interested (have to learn how first). Thanks y'all from beautiful Atlanta! Excuse me while I plug into this amp!

Cheers, Ben

[Chuck H]

It's amazing to me what trouble people will go through to polish the tone of these amps. It's a sort of testament to how close to the mark they are out of the box. As in, it's hard to find something significantly better even at much higher prices, so let's just dial this amp in. Also amazing is how the name "classic" was used to sell the amps with their vinage look, but it seems like they'll be around long enough to live up to the moniker.

I hate to say it, but... My favorite mod for the Classic 50 is just a speaker change. It becomes more appearent to me all the time that pairing the right speaker with the right amp can make or break either. I absolutely HATED my personal amp with Emi Private Jack's. A friend has a Classic 50 and wanted to try them out, so I loaded them into it. All the ice pick highs went away. The tone remained defined, but not overly defined as Peavey's can sometimes be. And the EQ balance was a good match for the cab. The amp did sound like any other Classic 50 with the stock speakers in it. But with the Private Jack's it sounds embarrassingly good. Embarrassing because people pay sooo much for good tone and now this amp has it in spades.

There are a lot of good and relevant mods for the Classic 50 to be sure. I just stumbled on the ideal speaker for the stock circuit though.

[Enzo]

Yep, speaker is THE one thing that will change the sound of an amp more than anything else.

And ears matter. MY friend Scott comes up to the shop now and then and we build some little amplifier or stomp box. COnsistently he likes a much "darker" tone than I do. I don't like screech, but I do like the bright switch ON in my Fenders. We don;t seem to prefer the same tone. I tend to relate that to our hearing as much as to taste. As I age, the top end diminishes. I sure cannot hear 15kHz. Perhaps his younger ears hear more top end than mine, so his tones are thus darker than mine. Mine need to be brighter to come through to my ears.

[JoeM]

Yep, speaker is THE one thing that will change the sound of an amp more than anything else...

I couldn't agree more with this statement.

[log1982]

Ben, your mods sound great. Is there a chance that you could post a schematic that shows your modifications? Thanks. Joe.

[dmartn149]

Some of the contributors to this forum are incredibly knowledgeable, and super generous with that knowledge. They helped me fix a dead fender, and mod my Acoustic g60t. My band mates just LOVE the sound of this modded amp. (so do I) and we are all pretty old and have heard/owned lots of great amps. Anyway, let me add my thanks.

[Benjamin Ruffin]

This is the schematic that I worked from along with the factory schematic, both are available at blueguitar.org.
I will go through the component values I used as I haven't redrawn this schematic to include them. I used most of the values you see on Steve A's attached schematic. I'm simply listing my changes, here we go.
C5 is 3.3uf for less bass roll-off.
C6 is 25uf25v-easily the most important change I made! This cap keeps more of the body of the guitar signal intact. Very important because I look at the OD of this amp is really just an extension of the work V1 is doing (obviously). I tried leaving this cap out (unbypassed) and it allowed the OD circuit to oscillate at high frequencies on higher gain settings. I recommend having at least 2.2uf value here.
R10 is 56k as part of the DC coupled pair. This resistor can be adjusted to taste. 100k is less compressed and more punchy, 56k has a very smooth, buttery attack, almost like sag like I said earlier. I wouldn't go much lower than 56k but you could to say 47k. That value might remove all the attack though. I really like the sound this change produces so feel free to experiment. 68k would sound pretty awesome too.
C47 is 360pf- I believe the idea behind this cap is to bleed some highs to ground, this value sounded better than a very low value of 51pf. I haven't tried a value larger than this so if you try something larger let me know the effects.

I replaced the coupling caps post P.I. and the others for that matter with orange drops at the same value (not shown on Steve A.'s schematic). I also had to replace the ribbon cables between the the main board and the preamp tube board. I used stranded 18 ga. wire which worked very well.

I didn't add the switched mid boost on the tone stack. I did go with a lower value for C14 at 100pf. I believe this value is critical because it handles
frequencies above 3 khz for boost or cut rather than 1.5-3 khz boost or cut. I don't know the exact frequencies, I'm just going by ear here. This cap makes all the difference in the world. The other caps are .022 orange drops.

I began these mods with the idea of keeping everything around the circuit stock, pots, switches, and speakers. I had to know if this amp could
sound like I hoped it would with just a little work and very little expense. These changes aren't expensive at all unlike replacing all the speakers.
I am a cheap bastard to be sure, but I simply can't put a value on this amp. I will never part with it, no matter what. I would love to hear what it sounds like with V30's or greenbacks though.

I have yet to mic it up and record it but I will post here soon with the finished product. I hope this helps anyone who wants to make their amp a
real keeper. I had the pleasure of A/B-ing this C50 with a JMP 50 watt the other day and I felt really bad for the JMP. The JMP wasn't bad, it just didn't compare tone wise. The lowly Peavey C50 actually showed up a Marshall, and how. I felt strangely embarrassed.

These mods aren't hard to do, just a little time consuming. If you're new to working with tube circuits you should learn the steps to take to keep
from killing yourself. You have to understand the danger of different voltage potentials and learn how to discharge electrolytic capacitors safely.
Never work on energized equipment.

Once again, thanks to all you guys.

[Benjamin Ruffin]

I just put up a post but I don't think the attachment went up right. Go here:The Blue Guitar
He has a link to all files, go there and look around some. There's all kinds of cool stuff there. Find the Classic 50 tweed bassman mod schematic, that's what I was trying to attach earlier. The mods are very worth the effort, you won't believe the wide range of tones you can get after the mods.

[Benjamin Ruffin]

It's amazing to me what trouble people will go through to polish the tone of these amps. It's a sort of testament to how close to the mark they are out of the box. As in, it's hard to find something significantly better even at much higher prices, so let's just dial this amp in. Also amazing is how the name "classic" was used to sell the amps with their vinage look, but it seems like they'll be around long enough to live up to the moniker.

I hate to say it, but... My favorite mod for the Classic 50 is just a speaker change. It becomes more appearent to me all the time that pairing the right speaker with the right amp can make or break either. I absolutely HATED my personal amp with Emi Private Jack's. A friend has a Classic 50 and wanted to try them out, so I loaded them into it. All the ice pick highs went away. The tone remained defined, but not overly defined as Peavey's can sometimes be. And the EQ balance was a good match for the cab. The amp did sound like any other Classic 50 with the stock speakers in it. But with the Private Jack's it sounds embarrassingly good. Embarrassing because people pay sooo much for good tone and now this amp has it in spades.

There are a lot of good and relevant mods for the Classic 50 to be sure. I just stumbled on the ideal speaker for the stock circuit though.

I believe once you get this amp dialed in the speakers are fine really. You would be surprised how very very good they sound actually. The stock circuit simply dumps the meat of the signal to ground, Rk's are the biggest culprits I think. I just wasn't willing to spend $200-500 or more for speakers when I only paid $400 for the amp to begin with. I hope the values I listed will give similar results in a similar amp, they should. I am getting ready to perform these same mods on my best
friend's 2x12 C50. I will post after completion with a follow up in case of any discrepancy. My next purchase will be a C30 which will be modded along these same lines. The C50 is louder than hell beyond 3, I'm serious, almost too loud.

[Chuck H]

+1
Absolutely understood. There are two ways it CAN go. Match the speakers to the amp OR match the amp to the speakers. One costs a lot less than the other. So if you already have a mod formula...

[Benjamin Ruffin]

It is inspiring to play through an amp that plays itself, so much so that I find it very difficult to turn it off. My band mates call it 'Nestle Crunch tone'. The clean tones I get are so good I can't explain. Hitting this amp with a hot input signal is pure magic and I highly recommend it.

[imaradiostar]

For years I've enjoyed a thick midrangy lead tone. I have some ancient beat-to-death 25 watt celestions and a marshall style amp and a few pedals and it does that whole Eric Johnson thing really well. It's lots of fun and I love to play with it! But that's just me enjoying what I like.

Every once in a while I'd lend some equipment to some studio friends and they'd all whine and complain about how trashed my celestions are. I'd lend them my ported 1x12 with a 100 watt celestion and they'd go on about how much better it sounds than my old closed back 2x12 with the greenbacks. Then I'd go to the studio and listen to the tracks they're recording and it's all modern rock thunk thunk and pop stuff with bright DC30 tones- which leads me to believe I should have given them my G12-75's!

Maybe it's more than our ears, too. It's picking the speakers that serve the tonal goal. Though I've tried there really is no one "do it all" amp. I love strats and marshalls and blackface fenders but when I'm playing church/worship gigs it's a pentode preamp cathode biased 7591 amp and a PRS hollowbody that get used most. The other stuff just gets lost in the mix!

jamie