Too much plate filtering in modern amps makes them sound stiff ?

[Iplayloud]

I'm looking at schematics of modern amps like a Marshall DSL 50 and they have two 330 uf caps in series on the plates. For a total of 160, is it just me or that is way to much filtering ? I remember doing alot of testing on 50 watts and my favorite was a 32+32 can on the plates just like a 50 watts plexi. Is there any reason in new amps why I sould not lower it ? I know I'm going to lose some low end but I was thinking of changing the deep switch for a Peavey 5150 style resonance pot which would bring back some nice low frequencies.

[Jazz P Bass]

You have to keep in mind that the reason the low value capacitors where used on the JTM 50 was because of the tube rectifier.

[jmaf]

It's a tendency for current day high gain amplifiers to have apparently excessively huge reservoir caps. The Orange Tiny Terror is an example, if there's one exagerated little bastard, it's got to be it.

While it may sound stiff for clean sounds, it's essential for the distorted output not to become a mushy soup when the amp is cranked. If you cover your ear and listen to a cranked amp that doesn't have well sized reservoir caps, you can hear all the ugly overtones and mushy notes.

[Gtr_tech]

Word. I *like* stiffly filter'd designs because they are so "immediate" sounding on the attack. Small amps like a Deluxe or something like that can benefit from poorly filter'd supplies if you want to plug straight in and dime the amp. I don't care for that approach myself....I think it sounds muddy and tubby without some kind of boost in front that has some low end rolloff. Kinda like what Brian May does.

I never have to run my amps balls out, so I don't care what it sounds like that way. But a better filter'd plate/screen supply means more headroom with minimal change in overall response if run hard.

[Iplayloud]

Well look at a Marshall 2203, a classic circuit, it has only 50 uf on the plates (two 50+50 cans in series) and that is plenty, it sounds big enough. Modern designs are chasing the big chugg like a Mesa Rectifier, it really annoys be. I like big filtering on the screens though, sounds big without being stiff. Anyway, I'll try it and report back... Filtering affects the amp in different ways along the way, it's worth spending some time to test that. For example just putting a 32+32 can in a JCM 800 preamp position usually makes the amp breather better IMO.

[diagrammatiks]

I mean the dsl sounds terrible and it's not the filtering that's to blame that do it.

The JTM45/bluesbreakers has a 50uf after the tube rec which is the most it can handle and then 50 throughout the rest of the amp with big dropping resistors. That's filtered better then most modern amps.

The 50 watt superleads are 50uf straight across as well.

The TSL/DSL has significantly less filtering after the plates with smaller dropping resistors. If anything it's under filtered.

[Iplayloud]

I don't mean that lowering the filtering on a DSL will make it a fantastic amp, I'm only talking about the precise sound of a stiff sounding over-filtered plate node.

About the JTM45, only the reissue has 50 uf cans, originals had one 32+32 can and two individual 16uf caps in the preamp.

You can see below a comparison showing how the DSL is packing ridiculous filtering at the plates:

32-32-16-16 (Original JTM 45)
50-50-50-50 (Reissue JTM 45)
100-50-50-50-50 (50 watt Marshalls from '70 to before JCM 900)
50-50-100-50-50 (100 watt Marshalls from '70 to before JCM 900)
165-50-22-22-22-10-10 (DSL 50 watts)

[Pedro Vecino]

Is there any reason in new amps why I sould not lower it ? I know I'm going to lose some low end but I was thinking of changing the deep switch for a Peavey 5150 style resonance pot which would bring back some nice low frequencies.

Filtering in DSL / TSL is high because they carry no choke transformer and the circuit is less effective. 50uF also work but with high volume behave worse. The effect of filtering on the lows is different to that produced by a depth circuit in the feedback loop. A high filtering does not create more lows by itself but it works to become more tense and tight keeping this effect with the volume. Typical depth circuit is capable of generating a "bass boost" but with a more loose and limp character. From my point of view may be useful in light overdrives but less with high overdrive.

[Chuck H]

The things that seem most obvious to me are that earlier designs either used, or sprung from tube rectified power supplies. That also means that the commonly available part values that were still cheap for MFG were akin to this thinking. Then there's the fact that most of these old amps were not intended to be cranked into heavy distortion. Design innovations take a lot longer to evolve than playing trends. I think that designs are just starting to catch up to what's been going on for the last thirty years. The easy availability of higher value caps in smaller packages helped.

Some guys like the feel of an amp with smaller filters. That's how they were all made for a long time and many great recordings have been made with amps built this way. There's inertia to these tone familiarities.

I like bigger main filters for two reasons. Under heavy OD smaller filters ripple like a slinky. I hate ripple and the ghost notes it imparts. Bigger filters help a lot with this. I also like the tighter, more contemporary OD tone of bigger filters when an amp is cranked. As noted, the change to the clean tones isn't all that much. The difference becomes more clear as an amp draws more current through the power supply. So it becomes a matter of preference in the OD tone/feel.

FWIW it's entirely possible to get the "sag" and 'fold up on the bass' tones of yesteryear by adding resistance to the power supply. Bigger filters can't help if an amp can't supply the current in the frst place. So I don't see any reason to put up the ripple caused by smaller filters.

You can still get a "tighter" sound with smaller value caps down stream of the main filters. But big main filters don't seem to change the tone all that much by themselves, and they sure help elminate ripple.

All this AND... IMHO new caps (while supposedly better in general) don't seem to be as good at filtering ripple as the older caps. More UF's seems to help.

JM2C

[tedmich]

older amps had as much filtering as they thought necessary for their price point, and they sound "different" than modern amps which use MUCH more filtering, largely because they demand a lower noise floor and/or have higher overall gain (and the price of filtering has dropped quite a bit!)
its simple, if you like old amp sounds, play old amps and make old amp designs...

its the "I want an original Bassman sound with a modern PS" crowd which runs into problems, its like trying to sound like BBKing with EMGs...IMHO

[diagrammatiks]

i agree with ted but at the same time I think there is a way to compromise...
a carr doesn't sound exactly like a vintage amp but I feel like they don't suffer from an overly modern sound.

of course...the amount of capacitance is really only skimming the surface of the power supplies relation to the sound of the amp too...

[melvin]

At first, ghost notes bothered me; they seemed to be symptoms of a problem that I needed to fix. But now I have developed an appreciation for them and if the amp is actually operating properly, they add a certain character to the sound. Very musical in my opinion. One of the most interesting things about guitar amplifiers is how they sound when pushed beyond their limits. Under-designing can be an art, I guess...

[Chuck H]

At first, ghost notes bothered me; they seemed to be symptoms of a problem that I needed to fix. But now I have developed an appreciation for them and if the amp is actually operating properly, they add a certain character to the sound. Very musical in my opinion. One of the most interesting things about guitar amplifiers is how they sound when pushed beyond their limits. Under-designing can be an art, I guess...

But how many players would subscribe to the idea of using an amp with an unstable power supply as part of the art of musicianship??? It's a double edged sword. Yes, there are musical tones to be had. But... I don't know of many recordings that exemplify ghost notes. In the end I think it just complicates things too much to make the amplifier (which is an instrument of itself) too finicky. I've never used ghost notes intentionally. But I have an aversion to them. I suppose that any great player could make something musical happen with a ghosty amp. That's what the great ones do. They find something musical about everything they touch. This is part of the reason there's no definition for "good tone".

[kg]

hell, i like playing an amp with microphonic tubes.

[tedmich]

i agree with ted but at the same time I think there is a way to compromise...
a carr doesn't sound exactly like a vintage amp but I feel like they don't suffer from an overly modern sound.

of course...the amount of capacitance is really only skimming the surface of the power supplies relation to the sound of the amp too...

Hey check the gut shot of a Carr Vincent on p3 of this GP article
http://www.carramps.com/press/gp_200712.pdf
its using PP film Solen caps in the PS with maybe 70 TOTAL uF of filtering!!!? Expensive AND loose!