Still no break-up. 2x 5F1's.

[Dave H]

That sounds good Dave H. I have a 470r 10w.. any good? I guess will act as a bigger 'heat sink' if thats the idea, but will its bigger size remove more V? My noggin say no.

I can remove the white wire from rec pin 8, leaving it from the the 1st filter cap, and switch it over to pin 7 of the rec (IE used as a junction only, to connect the OT as it is already here/ remove the link to pin 8 of course). Then put the R fatso in between 1st filter cap/ with the white wire as it is, and rec pin 8.

Is that sort of the right way of thinking to do such an addition?[/URL]

470R 10W is fine. There will be no extra V dropage.

Yes, good thinking, it will work exactly as you said. i.e. Switch the white wire from pin 8 to pin 7 and also remove the grey wire link between pin 7 and 8 then put the fatso 470R between the first filter cap/white wire and pin 8.

[Chuck H]

The 470r 10w is perfect. But only if you use it in a Pi filter. Added on it's own it may add too much sag (nitpickers may see note*)

As per the pic. Note that I removed the existing beige lead from the original. The cap would be a 22uf, 450V rated electrolytic. The cap can simply be zip tied to the other caps on the board. The resistor will generate heat, so keep it away from the caps somewhat.

NOTE* I know that a class A amp shouldn't "sag", but in the real world bias relationships shift when clipping as voltage rise on the cathode circuit. The amount of sag then induced by a large-ish resistor by itself may cause strange, pumping type compressions. The Pi filter arrangement will still drop 15 or 20V and also reduce hum.

[Dave H]

Chuck, I think the OT wire is still connected to 5Y3 pin 8 via the grey link to pin 7. It would have to be moved from pin 7 to the bottom left eyelet of the board.

[Chuck H]

Huh... Maybe I'm not following, but what's that circuit connected to pin 7?? Looks like there may be a black wire there as well. In any case, yes, isolate pin 8 from pin 7. Thanks for following up.

[Dave H]

I think the black wire on pin 7 goes to the OT.

[Sea Chief]

I think the black wire on pin 7 goes to the OT.

Yes the black (actually its dark blue) at rec pin 7, is going to the OT. It joins pin 8 via a bridge.

Ok so as Im just a bit confused, let me double check. If (for the mo) Im adding just the 10w fatso, am I adding it as per orig idea/ my way as it were that you concurred with in #211?


Best to be sure. (I do in fact have a VG f&t 22uf 450v I could use.. if needed for the other malarchy).

[Dave H]

Ok so as Im just a bit confused, let me double check. If (for the mo) Im adding just the 10w fatso, am I adding it as per orig idea/ my way as it were that you concurred with in #211?

Yes that's right. I didn't think you'd want to go to the trouble of the full Pi filter. If it hums too much you can try the Pi filter later. The Pi filter will need a higher value resistor to drop the same voltage (1k). The amp pulls about 50mA from B+ so 1k will drop 50V.

7 pages and still going strong

[Sea Chief]

Yes that's right. I didn't think you'd want to go to the trouble of the full Pi filter. If it hums too much you can try the Pi filter later. The Pi filter will need a higher value resistor to drop the same voltage (1k). The amp pulls about 50mA from B+ so 1k will drop 50V.

7 pages and still going strong

7 pages.. is nothing!

Ok done the 10w fatso: B+ tested (at usual point @ first filter cap+) and reads 378v. Previously 392v. So thats something, if not quite the jump I was hoping for.

In use it doesnt smell quite so toasty-tubey and amp slightly less hot. Before there was a distinct hot tube smell. Soundwise I cant at the mo whack it up full, or past 1/3rd on dial.. but sound is a little sweeter/ more grown up maybe? and could the sustain be slightly better too? not that any champ is a twin-reverb in this dept of course (sustain matters alot to me). Feels slightly more like a fender I think. Maybe a tad of bright taken off tho, which I liked for my gibson S-mud-G.

I put on a 22 uf 25v cap bypassing that resistor too. I guess the merits of this will only be noticed once vol turned up? added gain to preamp tube wasnt the idea?

[Dave H]

I put on a 22 uf 25v cap bypassing that resistor too. I guess the merits of this will only be noticed once vol turned up? added gain to preamp tube wasnt the idea?

Is that across the first 12AX7 cathode resistor?

[loudthud]

Is the feedback resistor connected to the 8 ohm tap of the output transformer? If it is, change the 22K to 33K.

[Sea Chief]

Is that across the first 12AX7 cathode resistor?

No that was already on. The addition was in the middle of the board, I think Chuck H recommended it/ circled it on a thumbnail of my pic as few posts back.

Will it all blow up?

[Sea Chief]

Is the feedback resistor connected to the 8 ohm tap of the output transformer? If it is, change the 22K to 33K.

No Im using the 4 ohm tap only, and it was 22k but now lifted a leg so now n/c.

[Dave H]

No that was already on. The addition was in the middle of the board, I think Chuck H recommended it/ circled it on a thumbnail of my pic as few posts back.

Will it all blow up?

If it's post #208 it won't blow up but it shorts out the negative feedback making the feedback resistor irrelevant (not that you have one at this point).

If the fatso 470R isn't dropping enough B+ volts change it to 1k.

[big_teee]

This one has the most potential, if you want more breakup.
http://el34world.com/charts/Schemati...a764_schem.pdf
It has a high and a low input.
All tube cathodes are bypassed, and ready to go.
Looks like a hotrod Champ!
You already have most of the components, just a little rewiring envolved.
Then tweak and tune it for tone.
T

[Sea Chief]

Ok I think I'll try a 1k fatty. if that say drops it another 16v ontop of the 470r dropped 14v, then Im down to 362 so only 20v above par. Maybe then I could try a NOS 5y3 which iirc might drop it another 10v or so when I know what to buy (if anyone has one suitable FS then that would help me scratching my head some more).

Job almost done I think!

Thanks, Sea Chief.