Looking for Supro Thunderbolt 6420 Build info

[Justin Thomas]

I think what most of us were arguing before (in the past) is that any changes in sound due to a tube change are real, but also adjustable by changing/tweaking the circuit to adapt to the different characteristics of the new tube. As you say, tge circuit didn't change, but how the tube and circuit interact with each other does. Stan & others would argue that any perceived sound changes could be reversed by slight tweaks to the circuit.

And the #1 sin of all was how vendors & internet hype say, "put these tubes in your amp & it will sound This Way & put those tubes in your amp & it will sound That Way. A more honest assessment would be "these tubes made our amp sound this way at this set if operating parameters (list them all) in this circuit. Your results may (and most likely will) be very different..."

Not arguing with anyone; I thunk we're all mostly saying the same things but from different angles... Now as far as relibility issues go, there might be more consensus. That Sovtek 5881WXTs are super-stout I think is pretty accepted in the guitar amp community.

Justin

[Helmholtz]

So what I am saying is that since each tube is going to have different values (i.e. different internal resistances and capacitances, different gain, input impedance, output impedance, etc.) then swapping one 6L6 tube for example into a circuit vs a different 6L6 tube will change the sound, and the circuit hasn't changed at all, except in how it interacts with the new tube and its different internal parameters. So the tube and all that entails as far as different internal values between tube types and the fact the tube is an active device has changed the sound as far as how it is reacting to the circuit. Simply saying that the tube changed the sound is probably not accurate since there are all these other variables involved, but saying that the sound did change when you swapped the tubes is accurate, and the tube itself had an impact on that sound change is also accurate.

Greg

Yes.

Where do we disagree regarding my original statement that tubes don't have a specific sound of their own?
And the sound of the same tube in a different circuit is not predictable.

BTW, the capacitances of power pentodes/tetrodes are too small to noticeably influence sound in the audio range.

[soundmasterg]

Yes.

Where do we disagree regarding my original statement that tubes don't have a specific sound of their own?
And the sound of the same tube in a different circuit is not predictable.

BTW, the capacitances of power pentodes/tetrodes are too small to noticeably influence sound in the audio range.

I guess in my original post where I said the Sovtek 5881 sounds great in the Tbolts, since I didn't say it was its interacting with the circuit and that was the reason for the sound difference between that tube and other tubes in this circuit, that you maybe assumed I was saying the tube's sound itself was the reason to sound good?

Greg

[Helmholtz]

I guess in my original post where I said the Sovtek 5881 sounds great in the Tbolts, since I didn't say it was its interacting with the circuit and that was the reason for the sound difference between that tube and other tubes in this circuit, that you maybe assumed I was saying the tube's sound itself was the reason to sound good?

Greg

I have absolutely no reason to doubt your positive experience with the Sovtek 5881s in the Tbolts. Quite the contrary - my comments were meant supportive.

[mikepukmel]

On a similar vein, Ive pretty much convinced myself (thanks to lots of your comments, suggestions) that the layout, e.g. point to point over terminal strips, vs a turret or eyelet board won't affect the tone, as long as one or the other isn't producing parasitic oscillation, or other odd effects due to wiring too long. So, Id like to take a shot at making a turret board for this project. Due to some great links you all posted, found a few starter layouts (for a board). Reading (a little knowledge is a dangerous thing), Merlin's book and MEF threads again on power supplies, and grounding, Id like to put the filter caps near where they are needed rather than way on one side of the amp, and running long wires.

The fender like designs have a bundle of wiring come through the chassis, from the power supply caps, on the opposite side of the board from the tube sockets. Is there a problem with running the 'power rail' for lack of a better term, on the tube side? I.e. supply filter cap for the preamp tube would have its + side pointing toward the tubes. A dropping resistor would go from there, on turrets, to the next cap up the chain, for the phase inverter, and so on. Would tube wiring running under, and perpendicular to the HV wire be a problem (noise, oscillation, etc)?

[mikepukmel]

e.g. something like this:

The crummy hand modified (using paint) layout is missing some jumpers, maybe to go under the board to connect the power supply.

Another trial at hand/MSPaint drawing. I think this is a little closer. The Fender amps twist the pair going from the PI to the output tubes. Can't draw that.

[eschertron]

Just one thought I had (late in the week, running low on thought power) is to make sure the lead to V2's first grid is shielded - pretty low level on that signal wire.

edit: OK, a couple more thoughts. Don't be afraid to put a 10k grid stopper on the first couple stages. And related to that, what's the function of the 47k resistor from the input? If it's a grid stop, then put it right on the socket. The cap after it confuses me as to its intended purpose.

[mikepukmel]

Just one thought I had (late in the week, running low on thought power) is to make sure the lead to V2's first grid is shielded - pretty low level on that signal wire.

edit: OK, a couple more thoughts. Don't be afraid to put a 10k grid stopper on the first couple stages. And related to that, what's the function of the 47k resistor from the input? If it's a grid stop, then put it right on the socket. The cap after it confuses me as to its intended purpose.

Hi Eschertron, Thanks for the tips! Yeah, will definitely put grid stops on the input tube pin, and also use shielded wire there. And, as to the 47k resistor and cap, oh man I tore my hair out (OK not quite tore my hair out), but thought deeply with a stern look on my face, no idea what that cap on the input is for. The schematics Ive been able to find, and also images of the chassis, they did put 47k near the input jacks (one per input jack). The wierd thing is that they did not put them right on the jack, like Fender did, they're on a terminal strip, after a wire a few inches long. And they both feed into a 0.005uf ceramic cap.

[eschertron]

I can see putting the cap in that order IF the grid stops are on the jack, a la Fender. Otherwise, I'm confused too. I can't actually tear my hair out, not enough left to grasp!

[mikepukmel]

I just hope it doesn't blow up when I run it on 10.

[nosaj]

I just hope it doesn't blow up when I run it on 10.

Put an 11 on there then you'll be ok

nosaj

[eschertron]

Please let us know how it sounds! I'm curious about the paraphase phase splitter.

Record some clips before it blows up

[Helmholtz]

Hi Eschertron, Thanks for the tips! Yeah, will definitely put grid stops on the input tube pin, and also use shielded wire there. And, as to the 47k resistor and cap, oh man I tore my hair out (OK not quite tore my hair out), but thought deeply with a stern look on my face, no idea what that cap on the input is for. The schematics Ive been able to find, and also images of the chassis, they did put 47k near the input jacks (one per input jack). The wierd thing is that they did not put them right on the jack, like Fender did, they're on a terminal strip, after a wire a few inches long. And they both feed into a 0.005uf ceramic cap.

[ATTACH=CONFIG]51899[/ATTACH]

The two 47k input resistors shown in the schematic are for mixing and decoupling 2 instruments when used simultaneously. They also act as grid stoppers, producing a low pass effect together with the input capacitance (mostly Miller) of the input triode. Mounting grid stoppers directly to the tube socket only makes a difference in the MHz range.

[mikepukmel]

The two 47k input resistors shown in the schematic are for mixing and decoupling 2 instruments when used simultaneously. They also act as grid stoppers, producing a low pass effect together with the input capacitance (mostly Miller) of the input triode. Mounting grid stoppers directly to the tube socket only makes a difference in the MHz range.

Cool, thanks Helmholtz.

[mikepukmel]

Please let us know how it sounds! I'm curious about the paraphase phase splitter.

Record some clips before it blows up

Me too, will do. Ive heard raves about the overdrive tone, but haven't found anyone who has one to try out. Will get the old Nikon warmed up and recording before I dime it! This is the absolute last amp build for me. No more. Probably. Most likely one of the last ones I'll build. Getting near the end of the builds. Unless something spectacular comes along.