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**tedmich** · 04-03-2009, 08:31 PM

Some of this is indeed "voodoo" modding companies are in the business of making money after all...

Peavey designs are often made the best way possible; they seldom cheap out on something which will make the amp shift from "good" to "bad". That being said there are ways to make the amp sound better to YOU.

Changing component materials (a ceramic cap to a silver mica) is unlikely to improve its sound markedly; especially if it begins to vibrate or you knock off something on the PCB trying to shoehorn the big mica cap in.

Similarly some film caps are more stable than others and some like the subtle sound difference they create but it is almost never that this "upgrade" can be detected in a blind test. Part of the effect is experimenter bias after the PITA of swapping out components; you can't objectively judge the sound after ~4h of hard labor (or 2 weeks at the mod shop)

Much can be done by changing component VALUES; this will definitely change sound in a reproducible way. Try changing tone stack values, cathode bias caps and possible beefing up the PS. These will do big things; with experimentation hopefully in ways that you like! Look at "Blueguitars" classic mods as a guide and older mod threads

oh and a better speaker! With a sealed cab! Oh and SED 6L6's and Ei 12ax7s help too!
my 0.02

**Enzo** · 04-04-2009, 12:20 AM

Nothing against Voodoo, but any company that makes its living doing amp mods is not going to tell you how to get out of paying them for the mods. And their advertising hype is going to be glowing. Look at McDonalds ads. They don't call their meal burgers and fries, they call it golden crispy Idaho potato french fries and a all-beef patty with special sauce grilled to perfection etc etc.

So naturally they are going to make your bargain budget entry level Peavey amp sound like a combination Fender Twin and Dumble amp. Don't read too much into it. All those descriptive phrases are subjective and vague, nothing specific.

AN amp is what it is, you can smooth out the rough parts and massage the tone, but it will always sound like what it is. Your Fender Twin will never sound like a Marshall Plexi and vice versa.

I don;t doubt subtle improvements can be made to that Peavey, certainly many guys have modified their Classic 30 amps and were very happy with the results. But don;t assume the parts are of low quality and that changing all of them will turn this amp into gold. Changing part values can alter the voicing of the amp and may improve what you hear. ANd some new caps might clear ti up a bit, yes. I am not so sure about replacing a lot of resistors. You can ranks resistor types in order of potential noisiness, but consider whether ther is a noise problem or not first.

And in fairness to Voodoo, when they charge $300, it is not just for a bag of parts, it is also for the labor, for the time and effort put into developing the whole mod program for that amp, and for having gathered everything needed for it and having it ready.

**tdkrause** · 04-04-2009, 04:57 AM

Well, perhaps I need to approach this from a different angle. The amp is severely lacking in clarity. There's a lot of mush that can't be dialed out with the eq section. It also has a harsh, grainy, solid-state quality to the distortion. How do I change this?

Now, here's where I'm a little lost. And I'm not trying to be argumentative. Maybe I'm just missing something. If there were no difference in the quality of tone produced by different capacitors, then why are Orange Drops and paper and oil caps still being made? Why do the best sounding amps have only the best components in them? If all 600V 220uf capacitors are the same, then why do so many amp manufacturers have theirs custom made? If I replace the speaker with a G12H30, over rate the transformer and put in NOS Siemens, RCA, GE, Mullard tubes, this amp will certainly sound better, but it won't sound like a $2000 amp.

I have to assume that the reason the amp was only $400.00 is not because of a poor design. Nobody's going to intentionally use component values that would result in a poor sounding amplifier. They didn't design it in an hour. If a company like Bogner or Matchless had built this amplifier, it certainly wouldn't live up to their reputation simply because of better tubes, trannys and speakers. Amps are always designed to sound the best they can at a certain price point, so the kind of capacitors used must make a difference, right?

**Enzo** · 04-04-2009, 06:05 AM

Not really. And i don;t take arguments persoanally, so argue all you like. I didn't say there was no difference in tonal quality between any parts. What I said was in response to your seeming assumption that shortcomings in the amp were due to cheap parts, and the implication that putting classier parts in there would cure that. I was suggesting that whatever subtle improvements classier parts may or may not make, the amp would still be what it is, and you may not find it sounding night and day better. Maybe you will, but I wouldn;t assume that.

orange drops and other caps are made because there is a market for them. Search some component threads here. recently it was pointed out in a thread about Sprague Atoms electrolytics caps - a name brand still sought after by many - that if you cut open one of these larger size caps, you will find a smaller cap inside. The larger Atoms container is just for show. Why does Sprague do this? Because there are still enough people willing to spend more on a cap because it is larger and says "Atom" on it.

Orange drop as a name has a certain quality connotation, but if you read the threads here, you will find a number of serious commercial builders who say that they don;t find them particularly special.

I was not aware the Valve King had any 600v 220uf caps. But as to why would "so many" amp makers have them custom made, I think the answer is: that is the only way they will find them. Try looking through a catalog for 600v lytics, and 220uf at that. Only way to get them is to custom order them. Of course amp makers already custom order controls, transformers, and other parts, even for cheap amps.

Peavey could have used all Mallory 150s or something in this amp, and it wouldn;t have increased the price much. Why is it only $400? Because they made it in their CHinese factory. Labor is dramatically lower if nothing else. That said, over 10,000 amps, saving $5 per amp is substantial. I don;t think taking on that extra expense will make a sales increase.

I am not suggesting you will hear no difference if you upgrade all your parts. But as you say, it will never sound like as $2000 amp. We are spending more time ironing out this point than it merits, I fear, but my only real point was suggesting that merely putting in fancier parts would not likely cure all the amps ills.

Amps are always designed to sound the best they can at a certain price point

This is a slippery concept. Amps are designed to be made at a certain price point. And they are designed to sound like the designer wanted them to sound. best is a relative term. An amp designed to sound just killer with a Les Paul guitar might not sound so great when a strat is played through it, or vice versa. If you find that the amp sounds better with a 470pf treble cap instead of the 270 that is in there, they didn't put in the 270 because it cost less. the designer liked the sound with the 270 better. Same with the cathode bypass caps throughout. They affect gain and frequency response in the stages. They could use any values they wanted with no cost penalty. SO while you might find other values better, it had nothing to do with meeting a price point. Those values sounded the way the designer wanted them to sound.

And while I have no idea just who this amp is marketed to, if it is designed to appeal to the scooped middle death metal louder than hell kid, it probably won;t ever sound great to the blues player. Not unless you turn it into something else by making a ton of changes. Nothing wrong with making those changes, mind you, but they are about changing the nature of the amp, not overcoming price point.

By all means upgrade your parts, change values to suit, and experiment any way you can.

Have your tried a lower gain tube in a slot or two? SOmething like a 5751 or 12AY7? That tames many rough amps.

The peavey Classic 30 on the clean channel will start to rat out a little when th volume is over 4-5 on the knob. This is clipping in the phase inverter stage. I find a lower gain tube there improves headroom.

**tdkrause** · 04-04-2009, 09:52 AM

Okay then. I appreciate all this info. I think that pretty much settles the matter for me. And I'll give that V2 swap a try. As for the muddy tone, where should I start? Will a lower value cathode bypass cap clean it up or will it just be muddy with less mids?

**tedmich** · 04-04-2009, 05:35 PM

IMHO some high quality tubes and better speaker will de-muddy a great deal and is much easier than reworking the PCB

**jim5150** · 04-09-2009, 04:33 AM

I have found running a jumper cable in the effects loop also cures some muddiness. as well as a veteran 30 speaker from warehouse speakers

**jim5150** · 04-09-2009, 04:36 AM

I also installed a bias adjustment pot. really warmed and livened up the amp for just a difference of 5 ma

i also shorted r100 in the gain boost function which made the gain boost usable. I use the gain boost with the gain knob at about 9:00 oclock for a great classic marshall grind

**tedmich** · 04-09-2009, 05:07 AM

Originally posted by jim5150 View Post

I also installed a bias adjustment pot. really warmed and livened up the amp for just a difference of 5 ma

i also shorted r100 in the gain boost function which made the gain boost usable. I use the gain boost with the gain knob at about 9:00 oclock for a great classic marshall grind

you've recreated the earlier version of the dual diode "coring" noise gate: my Bravo just had the diodes, no 1Meg parallel...many swear that jumpering the diodes did wonders to the sound...but I haven't tested yet.

Why was the gain boost unusable originally? too much? too little?

**jim5150** · 04-09-2009, 10:56 PM

stock the gain boost sounds great for straight up rock with no semi clean parts.

I found in live playing situations (higher volume) the gain boost function,while tightening up the tone, did not clean up well when the guitar volume was turned down. It sounded like a torn speaker or nasty crossover distortion. shorting r100 with a resistor lead tamed it enough to use live and the fizz disappeared.

**CharlieP** · 05-20-2009, 06:11 PM

Originally posted by jim5150 View Post

I also installed a bias adjustment pot. really warmed and livened up the amp for just a difference of 5 ma

i also shorted r100 in the gain boost function which made the gain boost usable. I use the gain boost with the gain knob at about 9:00 oclock for a great classic marshall grind

Tell me how you installed the pot. Did you just take the 33K resistor out and put a pot in place or did you add a resistor to the pot somehow? I have some 25K Fender HRDx pots I was planning to use one with a 6.8K resistor but unsure how to arrange where to put the resistor or if the resistor needs a higher value. Should the resistor be soldered between one leg of the pot to the board?

**jim5150** · 05-22-2009, 12:42 AM

The 33k resistor was taken out and a 50k ceramic pot put in with a backup resistor of 33k put in in case the pot fails.

**CharlieP** · 05-22-2009, 02:11 AM

Originally posted by jim5150 View Post

The 33k resistor was taken out and a 50k ceramic pot put in with a backup resistor of 33k put in in case the pot fails.

So you can never adjust below the standard 33K. I don't see how that would work. If it were 1/2 that yes. Enzo says the resistor is not in case the pot fails. It should be there to ensure the pot is never turned to "0"k. You have to be able to go lower on resistance to bring up the ma. Failure of those pots is not likely. Many amps do not have resistors from the factory.

**Enzo** · 05-22-2009, 06:01 AM

The extra resistor is indeed there to make sure the pot never goes to zero.

But if the pot fails? Think about it. What happens if the pot opens?

We started with I don;t know, maybe -70v for the bias supply, then we established a voltage divider with a 12k over a 39k. The voltage divider tap is the bias feed. Starting with -70, that yields about -53v. I think my 70v guess was pretty close.

The pot replaces the 39k resistor. Varying that pot varies the voltage divider ratio and thus adjusts the bias feed voltage. If the pot opens, that would be the same as if the original 39k opened. That means no lower half to the voltage divider. it no longer divides. So the bias feed climbs to the same voltage as the supply, -70v.

The amp wouldn;t sound good, but it wouldn;t hurt a thing. The resistor is not there to protect a loss of the pot, it is only there to provide a lower limit to the bias feed voltage.

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