Making a good clean and distorted amp????

[Satamax]

Hi everybody!

Well, i was wondering if it was feasible to build an amp with a good clean, ie. Fender twin, or hiwatt/sound city 120, and have the same amp perform a good distortion? Ie a sound city L100, or deluxe reverb, or a tweed deluxe. I like smooth creamy compressed dist as Garry Moore and a tad more grunty for blues. As well as the grit from ZZ top in el loco. I like the clash and toy dolls tight raspy grit. And pantera's or thrice heavy dist. AC/DC's sound too. Would you think it's possible to make an amp have all theses sounds, with great clean, be able to keep the atack or lose it a bit as in tweeds.

I think for the most part it's 6L6, or 6V6 xept for toy dolls, who uses marshalls. ZZ Top is runing deluxe reverb iirc, so 6V6, Clash was using boogie heads and cabs, but i can get the same sound using SC's.

I think mixing tubes, like 4 6L6 and two 6V6, the tubes being all parallel push pull all the time. The six tubes would be on all the time, for matching isues. But the signal could be fed just to the 6V6, or 6L6 pair or quad, and all of them if needed with seperate bias for each pair so there's no crosstalking.

What i'm puzzled about is the preamp, what should i study for finding inspiration??? I'm leading towards BF AAB763 for clean, but to have such a extended range in dist??? What am i looking for???

Thanks a lot and best regards.

Max.

[Richard]

I've been picking up schematics all over the web for a couple of months as I plan on building an amp soon. Schematic Heaven is a good place to start looking. From the schematics I've looked at everything is similar, but the high gain amps have more gain stages. Some of the voltages are different also. I think that you're on the right track with the mixed ouput tubes, I see the power amp as the make or break section. The right preamp without the proper power amp and speakers will not get the sound.

[Satamax]

Thanks a lot Richard.

Well, i know of most of teh sites where i can find info and schemos, i'm looking more for a lead to what preamp and PI can lead to the sound i'm looking for. It will be an old switchero, with most certainly two preamps. One for clean, one for crunch, and the clean feeding into the crunch for distortion.

[bob p]

you're obviously on the right track with the multiple preamp approach. the multichannel amps like the Boogies have made an industry outof using preamp switching to gain tonal variation. i have their Mk IV, which is probably as complicated a preamp switching monster as i can handle. the long and short of it though, is that preamp switching gives you a lot but it will only take you so far. the other half of the amp (the power amp) is something that can also be responsible for huge variations in tone.

as you mentioned, differences in output tubes can make a huge difference in tone. one thing you haven't mentioned, that i thought i'd throw out for discussion, is how variation in B+ voltage can change the character of the amp. higher B+ can give you dynamic and snappy, and lower B+ can give you darkness and compression. Mesa tried to do this with their "Modern" and "Tweed" B+ settings but imho they didn't make the differences dramatic enough.

like most individual variations, the subtleties in tonality are noticable but are typically not drastic. if you want marked variations in tone, you might have no choice but to go with two different circuits. at least i've never been able to find one circuit that does it all. that hasn't stopped me from trying, though.

have fun.

[Satamax]

like most individual variations, the subtleties in tonality are noticable but are typically not drastic. if you want marked variations in tone, you might have no choice but to go with two different circuits. at least i've never been able to find one circuit that does it all. that hasn't stopped me from trying, though.

have fun.

Hi Bob, thanks a lot for the reply. I think thta amp gonna be an old switchero. I was thinking of using that multiple feed for the output tubes grids, so i have one to three pairs useable, (i don't think you can get proper clean with 50 watts) and was thinking about doing switchable cathode bias on a pair of 6L6 and on the 6V6, and may be for lower gain, use the fixed and cathode bias in conjonction. Well, that's dreamin for the moment, as i'm waiting for a BF bandmaster to arive, which gonna be slightly modded (reversable) It gonna have 1 tube recto, i don't know if i'll make it switchable or not, obviously a variable NFB, and a switch which gonna send the vibrato chanel, which gonna be the one i plug in, into the normal chanel for distortion, and see how that works for dist. I'm looking for a bassman OT and an export super reverb PT for it. The amp isn' original anymore, there's already a power tube socket changed, and cap job done, it has 5881 sovtek in it (not the wafer bases which is a shame) Chassis straps, bolts are missing, back pannel too, and the switch is missing too as well as the cap pan

Nevermind, i'll manage.

Thanks again.

Max.

[bob p]

well, it really does sound like you've got the bases covered -- preamp switching/cascading, output tube switching, bias switching, variable NFB... i guess the only one of the standard tricks that i don't remember seeing in your post was triode/pentode switching.

my impression about all of this "multi-switch" stuff is that when we add all of these switches to an amp, we end up with something like boogie did with the MK IV. in that case, there's one amp that is very flexible and tonally enabled, but that has its upsides and its downsides.

on the one hand, the amp is a tweakers delight. i can get just about any tone that i want to get out of it -- if i am willing to spend the time tweaking. sometimes tweaking takes a long time. the downside is that there are some combinations of settings that sound truly dreadful, and it can often take quite a bit of time to dial in the tone that you're looking for.

having spent an awful lot of time with a complicated "do it all" amp like this, my preference has evolved to favor having more than one simple circuit at my disposal. sometimes i find it easier to just plug into a different amp that gives a different, good tone right out of the box.

having spent some time tweaking circuits with a soldering iron, my philosophical approach has changed a bit. instead of putting every conceivable mod into an amp, i'm at the point where i truly resent some of the functionality of my Mk IV, primarily because it offers some combinations of settings that sound truly bad. my pesonal philosophy is that no amp should offer a combination of settings that can make the amp sound bad, so some "flexibility" needs to be designed out intentionally. so instead of throwing the kitchen sink at the chassis, i try to limit what i include in an amp to those things that sound good together (at any setting). doing this may not result in an amp that is as flexible as it could be, but it keeps the focus on making the amp a musical instrument, and one that is easy to plug into and get good sound out of. there's always a trade-off.

just my$0.02.

[Satamax]

Thanks a lot for your reply Bob. I realy agree. But for this one i know what i want, and what i dont, one sparkly fender clean, and one heavy. Some friend said randall gets good reviews for heavy dist, so that's cathode biassed EL34. Well, nother option. I think i might stay with a pair of 6L6, which is smoother than EL34 imho. Cathode/fixed, no triode pentode, been there, done that, i don't hear much difference usualy. Variable nfb, that's for sure, switchable recto i like too. And i have that obsession of sending the signal out of the vibrato chanel into the input of the normal chanel of a BF fender That gonna be the first thing which will replace teh grounding switch of my soon ariving bandmaster. I might change plans then. I have a SC L100 stock and a L120 heavily moded. Don't have any boogie or fender left. Want tweed for experiencing new, may be one day some of the brown with viby. (i'll have to build that! can't afford it !) Realy the L100 might go soon, it's a one trick pony. The 120 is open to mods or going back to stock, it has the loveliest clean of all amps i've ever had. And i've been through few fenders and hiwatts. Realy, what i need to know, is what king of heavy metal preamp sounds good. A lead to schemos to study would be welcome, but i'd rather avoid browsing the whole schemoheaven.

Thanks again.

Max.

[bob p]

i'm not the right guy to answer your heavy metal preamp question, but i would think that any of the hot-rodded marshall designs would probably fit the bill. have you looked at the schems for the SLO-100? or maybe Mesa's dual recto?

[Steve Conner]

Hi Max

The Mesa Dual Rectifier or Marshall JMP-1 are supposed to be the kings of metal tone. (Not that most Ampagers would call it "tone" )

The formula for metal tone seems to be a preamp with loads of gain, combined with bass cut before the stages that distort, and then some bass boost and lower mid scoop after them. Some preamps also use tricks like two back-to-back diodes as a noise gate to tighten the sound up, or zeners to reduce blocking distortion. Then use a high-powered clean power section to stop it mushing out at high volume.

The Toaster was my take on the Boogie-style multi-channel-switching amps, with three different gain structures selectable by a switch, and a fancy EQ inspired by Mesa's graphic thing. It turned out to be very versatile. I recently added a noise-gate type circuit, loaded the power amp with 6550s, and fitted a Duncan Invader to my guitar. It now makes about the most OTT metal tone ever, IMHO but can still be dialed down clean enough to use as a bass amp.

I decided not to make two totally separate channels though, to keep the size and complexity down, so it's more or less impossible to switch tones on the fly. At the moment I'm experimenting with a 2-channel switching amp with a wussy 30 watt power section, that gives a choice of completely clean or blues-like distortion, combined with a tube driver pedal for the really nasty grinding sounds. But I've never got anything else to sound as ferocious as the Toaster does.

I think the problem you might come across, trying to make a "do everything amp", is that clean and metal distortion both want a high-powered clean output stage, but the blues tones want an underpowered one that squashes and mushes all over the place. Maybe you could experiment with lowering the voltage, or switching in an oversized screen resistor, on something like a 120 watt UL.

I ended up settling on two amps and two guitars, one "Nice" and one "Nasty".

[Matt T.]

Bob and Steve both bring up great points. I've told myself "I know what I want" only to find out that it changed (or I never really knew) over time. The thing about building an amp like this is that ideally you'd want to build a prototype...use it for a while...mod it to hell and back...then build the amp (we'll call this one version 1a ). IMO it's best to not make the amp any more complex than it really needs to be.

I agree with Steve that it's not that difficult to get good pristine clean and good heavy distortion out of the same amp but all the 'in-between' tones are harder to get out of just one amp.

In any case, in addition to the SLO and Mesa DR you might consider the Bogner Ecstasy red channel. I built a one-off, custom-designed channel-switcher that sort of uses the SLO 'architecture' and switching but uses more Bogner-ish preamps. The PI/power amp are just Marshall all the way...big/stout power supply. The channels share the tone controls but that's surprisingly not much of an issue.

Others: Roccaforte HG100 (or is it HG1000?)...Engl (several)

[Satamax]

Hi everybody!

Bob, Steve and Matt, thanks a lot for your replies.

Matt, i mostly agree with you on the fact that an overly complicated amp is to be avoided, and with you and Steve on the mild distortions subject, but i think i have the way to do this, the 6V6 part with cathode bias. Realy the tric is to have both small squishy output tubes and big stiff ones all connected to the same ot, and have a way to select the signal going to them. I think i have that sorted, separate bias supply, and may be separate PI (which would isolate one from the other. as well!)

Thanks a lot guys!

Bye.

Max.

[Zoe_N_Iain]

Hi everybody!

Bob, Steve and Matt, thanks a lot for your replies.

Matt, i mostly agree with you on the fact that an overly complicated amp is to be avoided, and with you and Steve on the mild distortions subject, but i think i have the way to do this, the 6V6 part with cathode bias. Realy the tric is to have both small squishy output tubes and big stiff ones all connected to the same ot, and have a way to select the signal going to them. I think i have that sorted, separate bias supply, and may be separate PI (which would isolate one from the other. as well!)

Thanks a lot guys!

Bye.

Max.

That's the approach we're using with the amp we are currently poking with a stick. The poweramp is setup with seperate bias for all four valves, to enable it to run any four of 6V6,6K6,6EZ5,6L6,6L6GC,5881. Or a maximum of 4x6L6GCs or 2x6L6GC & 2xEL34/KT77.

The way we were thinking of is more or less this:

http://i49.photobucket.com/albums/f2...hpoweramp2.png

Though it might end up with 2 LTPIs instead of the cathodynes, haven't got that far yet The general approach will be pretty much the same, though.

At the moment, we're working on getting the power supply working properly in high and low voltage mode. 500v B+ and 350-380v, with a parallel supply for the preamp circuits.

[rathmann]

Here's what I did:

I have a remotely switchable power section in conjunction with a fairly typical switchable preamp.

The amp uses 6L6s which should provide the necessary headroom for powerful clean output. I opted not to do output tube switching since that introduced load issues I didn't really want to deal with (4 6v6s want the same load as a pair of 6l6s but I didn't really want 6 output tubes in the amp). I went with LTP For the Clean/Stiff setting the output section gets full voltage (420vdc) and utilizes grid bias set to a fairly cool AB range. There is a healthy amount of NFB. For compression/squishy setting I drop voltage with 70volt zener and switch the output to cathode bias. The nice thing about this setup is that the bias method switch allows for compensation of the mains voltage change. At close to 300volts I can bias the tubes fairly hot, pretty close to "spec" class A operation. This mode also opens up the NFB loop. The lower voltage also drop the headroom of all the preamps stages somewhat.

The whole switch can be done with a 4PDT relay. I use the other pole for syncing with the preamp relay.

There is a fairly complicated 3P4T rotary switch allowing for different methods of synchronization between the preamp and power amp with only a single footswitch, however there are separate relay switch inputs for individual control. But if all you want is a stiffer power supply for clean and a softer one for dirty the switching is remarkably uncomplicated.

steve

[Steve Conner]

Sounds neat, rathmann Have you got any more info or pictures of the setup online?

Steve

[rathmann]

I've got some pics. Take a look at http://share.shutterfly.com/action/w...d=9EYt2LRm1YQc

Funny. I'd forgotten that I also switch between silicon and tube rectifiers between the two modes. All my stuff has been in storage for almost a year since I had to demo my garage for an addition. It'll be fun to pull that thing out again.

I've got a schematic on my mac at home. I'll see if I can dig it up a bit later.