5F6A Tweed Bassman Kit

[jibe]

I don't think I'll replace the OT, not in the near future anyways.
But tubes and caps has been on the wish list from day one, if not for anything else
than actually finding out if it makes a difference. I'm planning on playing "stock" and
then switch to see if I can hear it. If i'm one of "them".
What about 12AY7? Lower gain? What does it do soundwise? Why would I wan't to lower
the first gain stage? Apart from the fact that the original 5F6A had a 12AY7.

I don't seem to have problem with my presence pot, if it ain't broke, dont fix it!!!?
I had a ton of other problems, (or just one really, my broken RCA jacks), but I haven't had problem with oscillation, yet. I guess I can skip grid stoppers for now and concentrate on the bias of my tubes and getting my replacements.

What's the difference of 5881 and 6L6, know any good webshop for getting tubes? Found a matched pair of new production Tung-sol 5881 for 39.95$ at Tubedepot.

Power filter caps, does that affect sound as well?


//Jibe

[tubeswell]

What about 12AY7? Lower gain? What does it do soundwise? Why would I wan't to lower
the first gain stage? Apart from the fact that the original 5F6A had a 12AY7.

You might not want to. Fender did it because it was cleaner that way. A 12AY7 also has a nice fat tone. The EH 12AY7 is surprisingly nice sounding

What's the difference of 5881 and 6L6, know any good webshop for getting tubes? Found a matched pair of new production Tung-sol 5881 for 39.95$ at Tubedepot.

5881 = 6L6GB same tube, same rating

(However a 6L6CG has a more powerful rating)

Power filter caps, does that affect sound as well?
//Jibe

The size of the cap will impact on the quality of the filtering. That's why lotsa peeps like Sprague Atoms (including myself)

[Diablo]

The 5881 tube should break up at a little lower volume than a 6L6GC, and the original Bassmans used the 5881 tubes. My main filter caps are two 100mfd in series, so that's 50mfd vs the standard 40 mfd. Maybe it makes the bass a little tighter, maybe no one can hear the difference.... Original cap ratings are + or - 20%, so that's close enough. If you want to make the amp grind, get a y-cord and use both channels, so you use both triodes of the 12AY7. The Y cord doesn't dull the tone like normal channel jumpering.

[jibe]

I do get a little less output from the 5881, right? Do I need to make other changes in order to use 5881 instead of 6L6? It's not rated for a high plate voltage as the 6L6 and the plate voltage on mine is around 420-470v, I read somewhere that 5881 is rated for 400v. Maybe the plate voltage changes when biasing?

The use of OT taps, does the use of either 8, 4 or 2 ohm tap change the output of the amp? I used the 8 ohm tap when I bypassed my broken RCA connector, the cab I have is a 8 ohm Cabinet. I saw a post the other day when someone stated to have 36w@4ohm and 25w@8ohm.

Sorry for hijacking your thread but your mods made me come up with tons of questions



//Jibe

[tubeswell]

Like I said a 6L6GB is a straight swap for a 5881.
If you want to put 6L6GCs in, you want to up the B+ and rebias. 6L6GCs can take more heat (in fact they sound good when they're hotter).

[MWJB]

"My main filter caps are two 100mfd in series, so that's 50mfd vs the standard 40 mfd. Maybe it makes the bass a little tighter, maybe no one can hear the difference...." I have had customers comment, unpromted, on the difference between the parallel 500v caps and the series wired caps. I can hear it, so did they. Yes, the series wiring makes for a tighter sound.

[jibe]

Chinease 6L6GC is what's supplied with the kit, that's what makes me wonder if I have to lower B+ in order to switch to 5881. Thinking of getting the Tung-sol 5881.


//Jibe

[MWJB]

5881 will happily take your 470vdc, no need to lower B+.

[Diablo]

The use of 2, 4, or 8 ohms doesn't change the power output. But, is only used to match the speaker load through the transformer turns ratio to the power tubes. As has already been posted, the 5881 tubes can handle 460V without a problem, but don't bias them up as hot as 6L6GC tubes, since they can only handle 23 Watts max. I suggest around 35 mA per tube for idle bias.