Peavey Classic 50 Blue Guitar Mods

[ewd]

I'm doing Steve Ahola's Blue Guitar mod (Overdrive Channel mod, along with the tonestack mod) on a Peavey Classic 50-410 for a friend. Have a question for Steve, or anyone else who has done this mod. The owner absolutely hates the harsh buzziness of the amp, as manufactured. I understand about how increasing the C18 cap from 470pf to 820pf will allow more low freq signal from V1A through the OD channel. However, Steve mentions also possibly increasing the value of C24 (470pf), which bleeds off some of the highs to ground from the "Pre" gain pot wiper, but that he hadn't tried that change and thus could not recommend it (I'm paraphrasing Steve's mod descriptions). What I'm not understanding is that if C24 passes some of the high freq's to ground, would not increasing the value allow more of the lower freq's to be bled off to ground and defeating the purpose?

Thx,
Ed

[ewd]

Anybody?

[loudthud]

The schematic I found from Steve seems to indicate C24 should be removed and C18 should be changed to .022uF. If you could link or post the mods you are talking about, that would be preferable to having to hunt for it. I always take these kind of things to be a jumping off point, not something to be copied verbatim. There are many factors to be considered and I always like to make my own decisions.

http://el34world.com/charts/Schemati..._with_mods.pdf

[Enzo]

If we increase the value of C24, it will shunt to ground everything the original cap did, plus a little more down into the upper mids. Lows will not be affected. It is a rolloff curve, increasing the cap just slides is a little further down the frequency range.

C24 is a valid suggestion, he's just saying he can't say yes or no because he hadn't tried it. If the C18 trick worked, then no point in going further.

[Steve A.]

In my Classic 30 I wired up the equivalent of C47 to a trim pot replacing the stock 10k series resistor R68, treating it like a treble cut guitar tone control. Ignore suggestion to replace .015uf cap with 51pf. (I eventually replaced the 10k trim pot with a 3.9k or 4.7k fixed resistor.) This really helps cut down the brightness or fizziness of the OD channel.

BTW did Peavey ever come out with a C50 schem that just showed the basic circuit and not the interwiring between the various boards? I stll get a headache looking at it...

Steve Ahola

P.S. C18 increases low freqs going to input of OD channel, C47/R68 balances the brightness in the tone stack between the two channels.

P.P.S.Totally unrelated but back in the day I didn't notice that R20/2M2 and C11/.047uF comprised the same local feedback loop on 2nd gain stage of a Dumble ODS as shown on an early schematic. The 2M2 value adds a lot of compression; for a subtler effect you could use 22M, 33M or 44M. (This is most noticeable when using the Clean channel- it is the 4th gain stage for OD channel.)

[ewd]

Loudthud, the mods I was requested to install are the OD channel input mod, the tone cap mods, and the preamp tube board mods (not doing the shift circuit mod) as described @ http://www.blueguitar.org/new/articl...50_origmod.pdf . The owner really, really hates how the OD channel sounds.

Enzo, the owner wanted me to also incorporate the C24 cap value increase, along with the other mods at the same time, but as Steve could not speak for the actual results due to not actually trying that, I wanted to get input about the effect of increasing C24, as it seemed to possibly counter the overall desired results. Think I'm going to recommend to the owner that we be conservative and wait to see how increasing C18 works out before doing C24.

Thank you both for your responses.

[ewd]

Thx Steve. Every schematic I've seen for the classic 50 is the same one in your mods, even the faded-out component values for some of the components.

[Steve A.]

Thx Steve. Every schematic I've seen for the classic 50 is the same one in your mods, even the faded-out component values for some of the components.

Back in the day I was going to redraw it like a regular schematic with the eventual goal of rewiring a Basshead head to the C50 Tweed Bassman mod preamp circuit... (I've heard from about a dozen people who took Dremel to PCB to perform that mod.)

Steve Ahola

[Chuck H]

A little but the best mod I ever heard for a Peavey Classic 50 2x12 was changing the speakers to a pair of Eminence Private Jacks. It literally took a stock Classic 50 and made every tone useful. I have never before heard such a monumental improvement from a speaker change. And that's saying something because a speaker change is very often the best improvement you can make. I can honestly say that I probably wouldn't change another thing on the stock amp I put these speakers into. Just a perfect marriage of amp/cabinet resonant properties and speaker. Instant good. It was just another Peavey with that harsh glassy top end and "just alright" OD tone. After changing the speakers I couldn't stop playing through it! And the best part is that it sounded even better with the amp cranked up loud. A little expensive to change speakers, but if you can talk your guy into it he won't be sorry.

[Steve A.]

A little but the best mod I ever heard for a Peavey Classic 50 2x12 was changing the speakers to a pair of Eminence Private Jacks.

The Private Jacks are the Eminence Redcoat version of the Celestion Greenbacks. FWIW many people said the same thing about putting a Celestion Vintage 30 in their Classic 30.

I have a hunch that James Brown used Celestions when designing the Classic 50 and 30 amps since they do seem to be a match made in Heaven...

Steve Ahola

P.S. I had the 4x10 version so I was looking for more Fender-ish sounds like a Super Reverb or 5F6A.

[Chuck H]

I had the 4x10 version so I was looking for more Fender-ish sounds like a Super Reverb or 5F6A.

You've probably already worked things out for speakers but I'd be real tempted to try the Eminence Legend 1058/10516. A really good sounding speaker for the $$$ and I think it's been a starting point (or just a relabel) for several OEM models.

[Steve A.]

You've probably already worked things out for speakers but I'd be real tempted to try the Eminence Legend 1058/10516. A really good sounding speaker for the $$$ and I think it's been a starting point (or just a relabel) for several OEM models.

I've bought 6 of the 1058's in the past 2 or 3 years because they work so well replacing stock speakers in my various amps. I see that they are still $60, and with free Amazon Prime shipping if you are so inclined.

The Legend 1258's are also $60... any idea how well they work? (I'm a sucker for their Red, White and Blues!) I usually prefer the sound of vintage Jensens over Celestions...

Steve Ahola

P.S. Warehouse Guitar speakers have always been great choices for the price but their shipping charges were too rich for my blood. I see that GC and MF are selling them with free shipping... woohoo!

[Chuck H]

I seem to remember liking the 1258 in... Something. I tried them in a project once and they came up a little short. Too "boxy" and inefficient for the project I was onto. That doesn't mean they might not be perfect for a 4x12" cab with a Marshall 800 plugged into it. In fact that is what came to mind when I heard them.

[JCT Audio Designs]

Hello All, I know this is an old thread but I am looking for the Blue Guitar Mod for the Peavey Classic 50, the link that has been posted is dead. Does anyone have the pdf they can post?

[g1]

Hello All, I know this is an old thread but I am looking for the Blue Guitar Mod for the Peavey Classic 50, the link that has been posted is dead. Does anyone have the pdf they can post?

Try this: https://music-electronics-forum.com/...etch?id=860382