Bias vary trem in 5F6A type amp?

tubeswell · 02-28-2009, 10:33 PM

My next build is going to be a 5F6A. (I have the trannies and the choke already.) I was wondering about putting in a bias-vary trem (because I really liked that in the 5G9 I built). So I add another 12AX7 (no problem for the PT). I understand (from my previous build when I tried subbing higher gain tubes in V1) that oscillator circuits can respond unexpectedly with 'chirps' and 'peeps' if the gain is different. Does anyone have an opinion on how well a 5G9 trem circuit would run in a 5F6A? (No doubt the values in the LFO circuit can be adjusted to compensate? - and I know I will have to get the plate voltage in the 12AX7 to a reasonable level)

Cheers

martin manning · 02-28-2009, 10:57 PM

Hi TW,

Why not just do as in a 6G16 (BrF '63 Vibroverb)?

MPM

MaBerY · 02-28-2009, 11:24 PM

Hi there!

I did that in my SF twin reverb because the opto coupler was dead.
It's totally different sounding IMHO.

When I build my Pro 5E5-A clone I added an extra 7 pin connector to supply the bias, B+, filament heaters and preamp in/out. This way I can hook up an external trem oscillator to bump the power tubes.

tubeswell · 02-28-2009, 11:40 PM

Quote:

Originally Posted by martin manning

Hi TW,

Why not just do as in a 6G16 (BrF '63 Vibroverb)?

MPM

Good suggestion thanks Martin. (The PT I have is tweed bassman spec (325-0-325 200mA), otherwise I could build a 6G16, but no reason why the Trem circuit from the 6G16 wouldn't be good in the (otherwise) tweed bassman I guess).

txstrat · 03-01-2009, 12:53 AM

Hi TW
I don't see any problems with the bias-vary trem in the 5F6A (just don't bias it too hot).
The 6G16 is one of my favorite amps of all time but if you go for the classic Bassman sound you should stick with the 5F6A. As you know they're totally different sounding.
I think Martin meant the same, like just to use the trem in the WAY of a 6G16.

02-28-2009, 10:33 PM	#1
tubeswell Supporting Member Join Date: Feb 2007 Location: Wellington NZ Posts: 2,639	Bias vary trem in 5F6A type amp? My next build is going to be a 5F6A. (I have the trannies and the choke already.) I was wondering about putting in a bias-vary trem (because I really liked that in the 5G9 I built). So I add another 12AX7 (no problem for the PT). I understand (from my previous build when I tried subbing higher gain tubes in V1) that oscillator circuits can respond unexpectedly with 'chirps' and 'peeps' if the gain is different. Does anyone have an opinion on how well a 5G9 trem circuit would run in a 5F6A? (No doubt the values in the LFO circuit can be adjusted to compensate? - and I know I will have to get the plate voltage in the 12AX7 to a reasonable level) Cheers __________________ Building a better world (one tube amp at a time)

02-28-2009, 11:24 PM	#3
MaBerY Junior Member Join Date: Feb 2008 Posts: 4	Done that, works nice Hi there! I did that in my SF twin reverb because the opto coupler was dead. It's totally different sounding IMHO. When I build my Pro 5E5-A clone I added an extra 7 pin connector to supply the bias, B+, filament heaters and preamp in/out. This way I can hook up an external trem oscillator to bump the power tubes.

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02-28-2009, 10:57 PM	#2
martin manning Senior Member Join Date: Mar 2008 Location: Cincinnati Posts: 147	Hi TW, Why not just do as in a 6G16 (BrF '63 Vibroverb)? MPM

03-01-2009, 12:53 AM	#5
txstrat Senior Member Join Date: Mar 2008 Location: Germany Posts: 724	Hi TW I don't see any problems with the bias-vary trem in the 5F6A (just don't bias it too hot). The 6G16 is one of my favorite amps of all time but if you go for the classic Bassman sound you should stick with the 5F6A. As you know they're totally different sounding. I think Martin meant the same, like just to use the trem in the WAY of a 6G16.

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