closest 6L6 circuit to 5E3-like tone?

[tubeswell]

Maybe keep the preamp supply dropping resistor the same, but halve the screen node supply dropping resistor (seeing as how you’d have twice the number of screens, and therefore 2x the stock screen current draw).

[oldmica]

Thanks very much, that's really useful. I'm trying to get my head around calculating power supply resistor values.

[tubeswell]

The voltage dropped at each HT supply node is the product of the current drawn through the DC-resistance leading to each PS node.
(current x resistance = voltage)

E.g. take the last pre-amp dropper in the PS rail in the diagram below: there is 2mA through 4k7. 0.002 x 4700 = 9.4V. (352 - 343 = 9). Whereas the previous 4k7 dropper has a total of 4mA through it, so it drops twice as much voltage. Its that simple .

[oldmica]

^^ Thank you.

Thanks to everyone for their info and experience. Very much appreciated!

Now I have some thinking, parts ordering and soldering to do.

[oldmica]

Bad form to reply to myself, I know

Just a shout-out to my friend profusiac. Pm me if you see this post (TAG's email notification system is busted, so my reply might be delayed).

Back on track:

Going with a quad of 6V6 for certain. I have two donor chassis lined up. My brother gets one. I'll have a mirror for debugging & tweaking.

The design is undergoing feature creep:

5E3 parallel triode input, with a switch for the "most useful" channel jumper configurations, and a single input jack

CJ11 tone stack, with a 3 way voicing switch

A few switches to select cathode resistor/bypass cap values, including stock 5E3 or CJ11, boost, bass cut and so forth, for further voicing

Dumble/Tweedle Dee local feedback mod for the 5E3-style phase inverter, unless this removes mojo

A phase inverter balance pot, a la Tweedle Dee

Phase inverter is 12DW7 compatible (the 12AU7 section would be used for the phase splitter, if installed)

CJ11 (type 2/LarMar style?) post phase inverter master volume

GZ34. VVR with adjustable sag.

Two sets of power tube cathode resistors/bypass caps, a la TW Liverpool, unless this removes mojo

RobRob NFB 3-way switch


So this should play like a somewhat louder & a little more complex 5E3, when set appropriately. Almost everything above is configurable to be a stock 5E3, except for the Dumble PI mods (for tone), and the CJ11 bass/treble tone stack (for a little more versatility).

Then the player can dial it in, experiment, tweek for a particular song and go nuts.

If *that* flies:

a 5879 pentode (HoSo56), with it's own input jack, feeding the same CJ11 tone stack above. Compression pot and cathode voicing switch.

if chassis room, a parallel octal socket for the 2nd gain stage/phase inverter, to plug in a 6SL7 instead of a noval tube.

replaceable fuses in each of the power tube cathodes to guard against internal shorts.

if I have enough heater budget, and can figure out how to add 4 mosfet unity gain buffers: a tube driven spring reverb, that is fed from the PI and that has it's own, separate PI for the wet signal. That's going to be a bit of complicated work.

if there's further room, bias wiggle tremelo.

Whew.

[pompeiisneaks]

No it's not bad form, we love hearing the updates on any project

Good stuff!

~Phil

[fred.violleau]

Any update on the build ? Schematic to share, I am very interested in your project!

Fred.

[oldmica]

After visiting with my bro over Thanksgiving, and hearing his VHT 12/20 and what he wants, there are some changes. Current thinking (this is pretty much set in stone):

Triode input with bass cut -> 12/20 fixed tone stack -> 12/20 tone and volume controls -> possible cathode follower into external loop with recovery (a la 12/20) -> pentode with some kind of compression control -> cathode follower with tail adjustment -> 5e3-style phase inverter -> quad of 6v6 -> output transformer with 4 & 8 ohm taps. Either a GZ34, or solid state rectification, and a VVR, either 12/20 style or whole-amp setup. No NFB, separate pairs of cathode resistors/caps and depth control, texture control.

I promise a schematic, with voltages, and specs/part numbers on the transformers if they are on there (not 100% sure because I might be using some unknown organ iron), and some kind of a parts list. Can't promise a timeframe however - work is kicking my butt and I have a lot to learn - but I want to get this to him this winter. Going to do a parallel build because I want one myself

[rdh002]

The voltage dropped at each HT supply node is the product of the current drawn through the DC-resistance leading to each PS node.
(current x resistance = voltage)

E.g. take the last pre-amp dropper in the PS rail in the diagram below: there is 2mA through 4k7. 0.002 x 4700 = 9.4V. (352 - 343 = 9). Whereas the previous 4k7 dropper has a total of 4mA through it, so it drops twice as much voltage. Its that simple .

tubeswell, would you be kind enough to explain this? — I don’t understand how one of these droppers has 4ma and another has 2ma when they are all showing the same 2 x 1ma connections. Appreciate any clarification, so that I can learn.

Thanks

[Colossal]

I have an amp with 4x 6V6 or 2x 6L6.
I used an AC30 style OT w/ 4K primary.

Sorry for the slight topic detour, but Brewdude, how did you like that AC30 OT with the 5E3 topology?

[tubeswell]

The voltage dropped at each HT supply node is the product of the current drawn through the DC-resistance leading to each PS node.
(current x resistance = voltage)

E.g. take the last pre-amp dropper in the PS rail in the diagram below: there is 2mA through 4k7. 0.002 x 4700 = 9.4V. (352 - 343 = 9). Whereas the previous 4k7 dropper has a total of 4mA through it, so it drops twice as much voltage. Its that simple .

tubeswell, would you be kind enough to explain this? — I don’t understand how one of these droppers has 4ma and another has 2ma when they are all showing the same 2 x 1ma connections. Appreciate any clarification, so that I can learn.

Thanks

The dropping resistor for the last dual triode in the power rail is only carrying current for 2mA (1mA for each triode), but the resistor before that is carrying current for the that dual triode as well as the second to last dual triode, so that’s 4mA through that resistor, etc.

[brewdude]

I have an amp with 4x 6V6 or 2x 6L6.
I used an AC30 style OT w/ 4K primary.

Sorry for the slight topic detour, but Brewdude, how did you like that AC30 OT with the 5E3 topology?

Sorry to have mislead you, but this was not in a 5E3 style amp. It was just a cathode biased amp that used a 4 ohm OT with a choice of tube configurations.

[Colossal]

I have an amp with 4x 6V6 or 2x 6L6.
I used an AC30 style OT w/ 4K primary.

Sorry for the slight topic detour, but Brewdude, how did you like that AC30 OT with the 5E3 topology?

Sorry to have mislead you, but this was not in a 5E3 style amp. It was just a cathode biased amp that used a 4 ohm OT with a choice of tube configurations.

Ah, ok, thanks for clarifying.

[rogb]

Basically all you need to do is just build the stock 5E3 but use a PT and OT rated for 6L6s. You may be interested in this...

http://store.marshamps.com/product_info ... cts_id=492

or this...

http://www.ceriatone.com/american-classics-5x3/

Or just search for Neil Young 5E3. Lot's of info available.

Exactly!