midrange and how to get it

[daz]

This has been maybe the most elusive thing for me. How to get my amp to produce that sustaining fluid midrange when the preamp is driven. There have been times it was closer than others but never have i had it to the degree i want. When an amp has this it takes very little drive to make a sustained note break into high harmonics, and it takes only a tiny bit of clean boost to produced the highest gain tones you could ever need.

I know there is no single thing that will make it happen. But does anyone have any tips on how to get closer to that tone? To those not familiar with the build i'm talking about, it's similar to a JCM 800 single channel amp but with a regular gain stage in place of the cold biased one in a JCM.

[chipaudette]

Sustaining mid range makes me think of Mesa Boogie Mark Series, not Marshall. Is the Boogie sound what you're talking about?

Chip

[daz]

I guess that just shows how different we all hear because i see it the exact opposite. But then i hear marshalls NOT thru celestion 4-12 cabs which tend to make them sound crunchy and buzzy. i play marshalls thru a 12" EV, and my fav marshalls have had that kind of mids. Boogies, at least the ones i had (MK2 and 3) sounded thin and not middy at all. I'm talking FLUID round mids like in the 500-700 Hz area, not upper mids. Thats 4-12 territory IMO. Anyways, back to the point....how?

[Enzo]

Defeat your tone stack. (open the ground connection) Now how does the overall tone of the amp sound?

[daz]

Defeat your tone stack. (open the ground connection) Now how does the overall tone of the amp sound?

It's kinda cool.....called a "raw control" by some, right? I've done this before tho and i have to turn the variable NFB i have all the way down to remove some of the highs and it's still a bit over the top. It has a more mid sound like i am looking for, but along with it comes the inability to adjust things as needed. I did have a thought tho....either add resistance where the ground connection was or maybe defeat it altogether and add a one knob tone like on some small simpler amps to soften the high end. i can see how that might work well, especially if i make it all switchable. thanks for the suggestion. I may look into this again, as when i've tried it in the past it was too bright and nasty and i didn't consider what i could do to make it work. Ahhh.....more things to play around with.....it never ends.

[Enzo]

My suggestion was not meant as a solution to your problem. I was trying to determine if the amp overall lacks the mids you want, or if it is the tone stack that is kicking them out. I don;t recommend having no tone stack. Just want to see if the stack is where we need to concentrate or elsewhere. Basically, with the tone stack out of the way, how does the rest of the amp sound. The stack can only take away from what is in the rest of the amp.


And of course, DUncan's Tone Stack Calculator is much fun to play with.

[daz]

It sounds fine w/o it but like any amp i've lifted the ground on in the TS it's too bright. But i really don't think this is where the answer lies. Its something to do with the way the preamp is biased or otherwise designed. I have as you no doubt know done about everything imaginable to this amp so i have had it where i DID get a lot of what i'm after. But in trying to rectify more serious issues it gets lost. at this point i've pretty much cured every ill it's had and got it sounding better than ever. And it DOES have some of that mid tone i'm talking about, but just not quite the way or as much as i'd like. I know it's a product of the OD and the way those first stages are setup because i've heard so many different tones come and go over the time i've been experimenting with the preamp on this poor amp.

[Chuck H]

Ahhh.....more things to play around with.....it never ends.

Nope.

There are a lot of things that can make an amp sound more middy. Lower plate voltages tend to soften attack and make an amp sound most dynamic in the mid freq's. If you're using a master volume you can probably get away with just lowering the preamp plate volts.

Narrowing the pass caps and filter systems is always a first go to for novice modders. Lower the values of coupling caps and remove high pass filters like the typical Marshall 470k/470p. There are also preamp cathode bypass caps and local NFB systems like the 47pf cap across the PI plates. Decreasing the size of bypass caps and increasing the size of the PI plate NFB resistor will have a similar effect. These kinds of mods would typically be followed by a gain boost since it is basically subtracting gain from the HF and LF leaving more mids in overall ratio, but not more mid gain.

You can increase the size of the treble cap in the tone stack. Or add a parallel cap in series with a resistor to attenuate it's effect.



Your observation of the simpler "tone" knob filter is a good thing to keep in mind. Enzo's suggestion of bypassing the tone stack is as much a lesson as a suggetion. The tonestack eats mids for lunch. Especially low mids. Here's a trick I got from Dan Torres... Since the mid pot in your amp is basically variable resistor (well not exactly in the Marshall tone stack, but read on) you can measure the pot at whatever the lowest mid setting you use is and install a fixed resistor of that value on the grounded pot leg between the pot and ground. Now 0 is the same as whatever your lowest setting normally would be. Now use a bigger pot for the mids. In a Marshall amp a 50k audio pot would be a good start. Now as you adjust the pot you'll reach what use to be 10 at some lower number and everything beyond that number would be a boost over the original pot value. And 0 is like home base. The higher the mid setting the nearer you are to bypassing the tone stack altogether.

Using the right pickups for that kind of tone helps A LOT. Like Fat Strat type single coils, P-90's/100's, PAF replica humbuckers, etc. Vintage Fender type single coils and modern high output humbuckers usually don't do well for this sort of thing. With some exceptions.

If your guitar is one of those maple body, ebony fingerboard, Floyd Rose trem, high output humbuckers and strung up with a set of .009's then the battle is already lost. You gotta have some softer wood somewhere and the vibrating strings have to shake it a little through a solid bridge. The point being, guitar construction is an important part of this kind of sound too.

Observations

Chuck

[anson]

I wanted a really smooth mid sound out of my amp, someting high gain, but colorfull. So what did I do? I put a mid-scoop circuit in the global NFB loop, which ofcourse manifests as a mid-boost for our ears. Sounded really sweet. Basically I used the typical fender/marshall type tone stack, but replaced th treble pot with a fixed resistor, and completely removed the bass pot. I used a variable resistor between the shunt capacitor and ground. It worked and sounded great to my ears.

[daz]

Chuck.....i've had the V1 voltages as low as 100v before, but lately i'm liking them higher. I think low 200's seems to be where i've settled. I have a 16uf i'm thinking i'll try in place of the 22uf for the V1 node, as i have read low capacitance in the filters makes the amp more middy.

As to the torres idea, heres the thing. It's not just that i want more mids, it's that i want more mids of a certain type. That meaning a different range than the tone stack gives, and no amount of fiddling with cap values and the duncan calculator will give me that. like i told enzo, it's in the distortion generating stages where it either happens or doesn't. I've had the first stages configured a million different ways as you know, and i have heard the mids i like come and go to various degrees as i'm changing things in search of other things such as tigher bass, less harsh highs, etc etc etc. Now that those things are in order i'm now trying to see if i can find that mid tone to complete the picture. Lat nite i did find one thing that really helped. Nothing i haven't tried a million times before, but as you know the same tewak will work great with the amp in one configuration and like cr@p in another. In this one it worked nicely, tho again being a tone stack tweak it didn't do exactly what i wanted. I added a parallel .022 to the bass cap to simulate a larger cap. It really sweetened things up nicely in a middy sort of way like it never did in other incarnations of the amp's pre. I have also tried the larger treble cap as you suggested and liked that as an optional sound but i would never want it permanently.

So i think at this time i will have to play it for a while because i'm really digging the tone right now and i need some time to let it sink in and begin seeing it's faults. (you know how that is ) But i will tack in that 16uf filer at the V1 node tonite just to see how that sounds. Later if i feel i still feel the mids need to be different i will try lifting the TS and adding a single knob tone. Maybe breadbord it and clip it in so i can change to several different types quickly and easily. Oh, and it's not my strats because i've gotten the tone i'm after with them. and they are '62 style reissues, one with basswood one alder and bothe with van zandts and humbuckers in the bridge with the 5 way wired to split the bucker when in bridge/middle position. thanks much chuck.

anson.....do you happen to have a schematic of that?

[J M Fahey]

Maybe the solution is to use *always* EV speakers, although I trust V30s too for that midrangey sound.
Not sure that a purely electronic solution will do, if you do not take care of the acoustic part too.

[daz]

I've used nothing but EV for years and gotten that nid sound with them and other amps many times. It's not the speaker.

[Chuck H]

Chuck.....i've had the V1 voltages as low as 100v before, but lately i'm liking them higher. I think low 200's seems to be where i've settled.

180 to about 210 seems to be where I live. But some of those old tweed era amps sound really good lower. That's not the kind of amp I'm building though. And I don't expect my amps to be able to do the "tweed" sound as well as what they already do either.

I have a 16uf i'm thinking i'll try in place of the 22uf for the V1 node, as i have read low capacitance in the filters makes the amp more middy.

Considering the +/- tolerance on those parts you'll be lucky to hear a difference. It'll be sooo subtle that you'll wonder if your imagining it. Try a 10uf or even an 8uf instead. Still a really subtle difference in tone. But the feel of the amp changes a little too. You may like it.

I added a parallel .022 to the bass cap to simulate a larger cap. It really sweetened things up nicely in a middy sort of way like it never did in other incarnations of the amp's pre.

Hmmm?

I have also tried the larger treble cap as you suggested and liked that as an optional sound but i would never want it permanently.

Agreed. I have one on one of my amps on a switch. If it were permanent the amp would be more of a novelty toy and lack versitility. I only use it for those lively mid heavy OD tones... Hmmm?

You could experiment with a series resistor on a parallel cap to limit the effect so it doesn't limit the amps versitility soo much. Jus kind of nudges a middy suggestion into your ear.

Oh, and it's not my strats because i've gotten the tone i'm after with them. and they are '62 style reissues, one with basswood one alder and bothe with van zandts and humbuckers in the bridge with the 5 way wired to split the bucker when in bridge/middle position.

Very similar to my own strat. Alder and van zandts with a humbucker in the bridge. I have the standard strat type bridge tightened against the body. If yours sounds like mine it's not the guitars.

Chuck

[daz]

yeah, definately not the guitar or speaker. And i also have my bridge tightened to the top.
i was just thinking about my question and it occurred to me that it's not just the particular frequency in the mid range i'm trying to get, but more the way it sounds. It's a mid thats very fluid and light feeling on the fingers yet very very focused w/o sounding thin. many solid state amps can do this tone with ease, or at least they used to. Not so sure about the ones today. But a good example of the tone i'm looking for is a tech 21 trademark 60, second channel with the drive way up and the growl knob fully clockwise with the EQ set with bass and treble as far up as they can go before it gets thin or muddy. That tone is very close to what i'm after. But don't tell me to buy one because i've done far too many gigs with far too many amps to not be very educated as to what happens to SS amps in a band mix !

[daz]

Hey Chuck, if you were right about 16uf vs 22uf making little to no difference, then i realized something i never knew tonite. I always heard filter caps make no difference as brands go. but i now know thats as wrong as can be. It makes sense too because i gave a buddy the 1st amp like this i built and the only difference between them is the filters. I have F&T 22uf and he has atom 20uf and the amps sound very different in that his is darker and smooth while mine is brighter and crispier, even after i have tried to make them exactly the same with all the same components except the filters. (same main cap can tho) Tonite i stuck a 16uf atom in the v1 node and man, it sounds way different ! Then an atom 20uf, same thing tho slightly less. Sounds like his amp with them! So i'm now thinking i can tame any high end with these in any stages that need it. of course this means..............gulp............more experimenting ! something as you know i am very unfamiliar with ! Why does everyone say filters have no tonal difference?! Maybe it's just that atoms are very different than most others?