Non-CF Clipper?

[matt h]

Reel--thanks for that! It's nice to know I've got the seal of tardproval.

[sepulchre]

I agree completely with Miles. Matt does Rock!

Killing the noise was a combination of several things: the power supply changes (er, corrections) did a lot as did grounding the heater supply. But it was elevating the heater supply by connecting it to the power tube cathode that finally got it reasonably quiet. That raised it 18 volts. I checked the concertina cathode; it was 46 volts. The hum left in the amp can be dealt with but it's not dead quiet like my others. That's why I checked the PI with the thought of using that for the heater supply elevator.

I put 220K/220K voltage dividers on the two preamp stages. That made the first stage Much quieter, hum and noise wise. It took some of its gain too, of course. But there is still too much distortion; I have to turn the guitar's volume down to less than have to get a decent clean tone, and the two level controls are down close to minimum. And the distortion tone itself sounds to me like the coupling caps are too big. But they're relatively small (0.01uF) compared to most amps.

So this will be my first foray into actually voicing an amp. All I've done before was to adjust an existing design. So I'm going to lower the 200K Ra on stage 1 to 100K to start with. I may also lower the PI driver's Rk and maybe eliminate its bypass cap. There must be a way to clean up then sound without losing too much volume.

The voltages on this schematic are not accurate but the circuitry is. I'll have to take the voltages tomorrow.

[matt h]

Regarding that first coupling cap value (.01uF), to put into perspective how much range you have, the Vox top boost uses 500pF (.0005uF). A marshall's channel (either as a bright or first in three cascaded) tends to go four times larger, with a .0022uF. You're five times larger than a marshall.

You've got *plenty* of wiggle room... or shrinking room, if you want to look at it that way.

[roberto]

Why don't you simply make the 2nd stage bypassable by a switch?
Signal can be swtiched at the grid stoppers of 2nd and 3rd stages, giving the capability to send the signal directly from 1st to 3rd stage.

Then you can raise the first coupling cap to 22n to keep the bottom end of the clean and give more control on the tonestack, and lower the second coupling cap to 4n7 or something like that to avoid any muddiness.

Yes, I'd remove the bypass on the 3rd stage and lower to 1k5 or so.
2nd stage cathode bypass can be smaller to add brightness to the crunch.

I'd lower also the PI's caps down to 22n.

You can also supply the 1st stage by a 10k resistor and lower the 3k screen supply down to EG 1k.

[sepulchre]

I removed the Ck from the PI driver and replaced its Rk with 2.2K. It sounds much better, not so overblown. There's actually some usable cleans coming out.

The overdriven sound is still not there but I know the coupling caps need a visit. I'm thinking .0022uF after stage one and leaving the .01uF on stage two. If it's still too much I'll reduce that one to .0047uF or .0033uF or something like that. I will also reduce stage two's Ck to 1uF (it's currently 2.2uF).

Also the Volume pot between stage two and the PI driver is only usable up to about 9:00 o'clock. After that it not only gets very distorted but it loses highs. Maybe the coupling cap will help but it might need some other help.

One more thing - when the Drive pot between the first two stages is turn down it loses some highs so I might try a cap across it.

Roberto: I tried bypassing a stage on another amp. I had to jump through hoops to try and balance the output level to a reasonable usable ratio. Now it sounds pretty good but it lost some overall output level in the process, unless you crank its Master way up - like 85% on higher. This one is coming around and I think I can do something with load splitting for a switchable boost.
I put the 3K on the screens because that's all I had; trust me, I was searching for a 1K.

[sepulchre]

Here's a little clip. Pardon the sloppy playing - I was paying more attention to the H2's little meter than what I was doing so it wanders a bit. In the second half you can hear it going from overdriven to a cleaner tone easily with just the guitar controls. The amp does go more distorted but not in a very pleasing way. Right now I'm just happy it cleans up this much.

This is just my American Deluxe Strat with a little echo, no other effects.

[matt h]

If turning "up" a volume pot is causing you to lose highs, that's... odd. Especially since there isn't a bright cap in the equation. My guess is that you've got a bit of ultra-sonic oscillation going on, which, when turned up is enough to rob some of your signal. Not a ton, mind you, just a little. While some consider it a bandaid, I'd recommend tossing a small (like 47pF) cap across the first plate resistor and see where that gets you. If you don't like it there, try it again across the concertina output's (just like a fizz cap in a marshall) though I really suspect it needs to be further up the signal path than that.

If it's not quite that much of a robbing of high end, the other thing I'm going to say, nay, harp on, is that all EQ is relative. Really! So "losing highs" might actually be you're gaining too much in the mid-range and lows, causing it to seem duller. (I'm hearing plenty of highs in your clip, don't know what those settings were). Given that you're running a "cuts high end" type tone control as your only tone control, this doesn't really surprise me. Most guitar amp tones we're used to hearing run a decent mid-scoop to them and it may just be that you're missing hearing that scoop (relatively enhanced highs).

While you may want to voice the amp more to your taste, I'm going to go on record saying I thought (at least through these dumpy speakers) that sounded pretty damn good as it is!

[sepulchre]

Thanks Matt. Except for the really driven tones I'm pleased with it... okay, Very pleased. I think a little judicious cap adjustment should iron that out.

Did I fail to mention that I have opted for the Gibson style tone circuit? It's no longer a simple high roll off tone control, it has two caps. Check out a Gibson GA-8t.

Or, just look at this. Note: the voltages are not accurate. I'll need to fix that tomorrow if I get a chance. Also, there were coupling caps shown as .022uF. That was a mistake; all the couplers have been .01uF all along.

I think you might have something there about the parasitic oscillation. When I listen very closely I can hear what sounds like synthetic frequencies along with each note played. It wouldn't surprise me anyway considering the long signal wire runs in it. I'll try the little plate cap, or the fizz resistor if that doesn't do it. Otherwise I don't know how to fix it short of using coax which I want to avoid.

[matt h]

Yeah, I saw the tone control. It's like a fender tweed deluxe style. Essentially a variable bright cap across the volume pot that also dumps some bass. I was talking about a bridged-T, which gibson also used. I forget what amp model it is, but in some amp it's just simply a "tone" control rather than calling it a mid. Here's a recent discussion that brings up the issue: https://tubeamparchive.com/viewtopic.ph ... ight=notch

I'm not necessarily advocating replacing the kind you have in there now, just food for thought--or perhaps an experiment if you're up for it. As I stated in a PM, and will share back out here, the "carmen ghia" style tone control is very similar to this, but due to being wired a little bit differently, does act differently. Sort of a scoop/sweep combo that can be really useful.

[sepulchre]

I tried googling the carmen ghia but I got a variety of designs, one of which is just like what I'm using. I'll read the thread you linked and look again into the carmen.

[Reeltarded]

That clip sounds nice though!

[sepulchre]

Thanks, Miles!

[matt h]

The tone control I'm talking about can be seen here https://c2.staticflickr.com/8/7014/6687 ... 7a21_z.jpg for the CG style.

[sepulchre]

Okay, got it. It's similar to this one from a Gibson amp. When I get the chance this is another thing I want to try.

[roberto]

This is how to implement it directly on the pot.