Compare/contrast Tremolux 6G9 to Bassman 5F6...

[Lizard King]

I have been working on a power amp project based on the Bassman 5F6-A circuit.  I was toying around with the idea of adding vibrato/tremolo.  I looked first at the Princeton AA1164 and was thinking about grafting that vibrato onto a bassman power amp section - along with Doug's bias adjust circuit.  Then I saw the Tremolux 6G9-A. 

The Tremolux looks similar, operating at lower voltages.  I'm never played a Tremolux.  What will be the major differences in sound coloration between it and a Bassman?  I'm not overly concerned with volume as I have a nice chassis with two output transformers so I'm probably going to build a stereo power amp.

I'm starting with a 350-0-350 power transformer so I'd have to drop voltage for either circuit.

Thoughts?  Suggestions?

Thanks as always...

[sluckey]

Grafting the 6G9 trem and Doug's adjustable bias mod into a 5F6A should work fine and be fairly easy to do. The 5F6A and 6G9A power amp circuits are so similar that I'd expect the power amps to sound very similar, especially if using the same iron and speaker cab for both.

If that 350-0-350 PT is not too heavy duty, the 6L6s may load the B+ down enough to not worry about.

[Lizard King]

Grafting the 6G9 trem and Doug's adjustable bias mod into a 5F6A should work fine and be fairly easy to do.

When adding an adjustable bias, would I keep the resistor/diode/cap-res to ground that sits between the PT & the tremolo intensity pot or run the PT right into the tremolo; add Doug's bias adjust after the intensity control.

The 5F6A and 6G9A power amp circuits are so similar that I'd expect the power amps to sound very similar, especially if using the same iron and speaker cab for both.

If that 350-0-350 PT is not too heavy duty, the 6L6s may load the B+ down enough to not worry about.

I see the circuits are almost the same, the only difference being the 6G9A operats at nearly 100 volts lower.  I was wondering what that would do to the sound, if anything?  I suppose I could switch in a 10W resistor and have it either way...


Thanks.

[sluckey]

Here's a schematic of Doug's bias circuit and a 6G16 vibrato circuit. Wire your vibrato and bias circuit exactly like this...

http://home.comcast.net/~seluckey/Hoffman_AB763.pdf

I've not sure what effect the lower B+ would have on just the power amps of either of those. I know that lower B+ is usually associated with twead and brownface amps and that those amps have a very different sound compared to the later blackface models. I'm sure that the power amps are a factor in the sound, but I believe the preamps and speakers probably have more of an impact on the sound. Maybe someone with good ears and some experience with these amps can offer a more informed opinion.

But if you build both the 5F6A and 6G6A power amp only, AND use the same PT, OT, and speaker, AND drive the PA with the same preamp, both should sound about the same.

[Lizard King]

OK.  That's easier...I was looking at Doug's bias mod for the Princeton that was far more complex and wasn't sure where to integrate it with the tremolo.  

This is pretty close to the bassman 5F6A...only difference I can see is a 1500 ohm resistor coupling resistor....might just build this as is.

Thanks again!  Love this board.

PS....one last question (I hope )
If you were going to build two of these pwr amps in a stereo unit, would you build two spearate tremolo/bias circuits or build one tremolo and feed two bias circuits or build one tremolo/bias circuit and bias both pwr amps the same?

[sluckey]

If I was gonna build only one B+ rail, then I'd only build one bias supply. But I would use two separate bias pots, each with it's own separate filter cap, to feed each power amp. I don't care much for tremolo.

[Lizard King]

Hence my delima....I kinda like old school tremolo...can't really duplicate it with a pedal....decisions, decisions.....

My Silvertone has a similar bias tremolo but it doesn't work and I can't find a schematic for it.....

[sluckey]

I'd just build two complete trem circuits and two complete bias circuits.

Which Silvertone? There are many schematics over at Schematic Heaven.

[Lizard King]

Of course if I build two tremolo's I'd need to find a dual 3M speed pot.....can't seem to find any of those.....it's never easy.


My Silvertone is 1494 twin 12 combo amp.  Sounds great but the amp tech who looked at it couldn't get the tremolo to work.  We downloaded a couple schematics and either someone heavily modded my amp or the schematics aren't correct.

Thanks for your help!

[tubeswell]

The 6G9A/6G9B trem would sound a lot better than the AA1164 trem. (In fact it looks the trem that the modified 'Hoffman' trem is based on??). I think the Ventures played with BF/blonde tremolux/vibrolux on some of their records

From what I can make out the PT for a BF Tremolux (or for that matter vibrolux) is 280-0-280 @ 180-200mA with heater (4-5A), recto and bias (50v) windings. The lower plate voltages in these amps allows a lower bias voltage (which you can see by looking at the size of the bias resistor compared with what is in the 6G6A/B bassman and other higher-voltage amps). I'd use maybe a 35W OT (4k PrZ)

[Lizard King]

Love that "wet" sound the Ventures use to get.

My PT is 350-0-350 and my outputs are probably 50 pr 60 watts.  I was going to stick a 10W resistor after the recto to drop the voltage....drop it all the way down to Tremolus levels or just to Bassman levels...that's my quandry....might put in a switch to drop to either level....still working on a schematic.

Thanks for the input...

[sluckey]

Of course if I build two tremolo's I'd need to find a dual 3M speed pot

Why? Separate pots work very well.

My Silvertone is 1494 twin 12 combo amp.

Never heard of that one. I once owned a 1484 Twin Twelve. The head stowed into the bottom of the speaker cab.

[Lizard King]

Why? Separate pots work very well.

I have a chasis and face plate with 4 holes drilled.  The face plate is heavy chrome plated.  I don't want to mess it up drilling more holes...though I suppose I could.  wonder what different speed/intensity levels on a stero output would sound like?

Never heard of that one. I once owned a 1484 Twin Twelve. The head stowed into the bottom of the speaker cab.

I think the 1494 is similar in a combo package.  It has two output transformers, one for each speaker.  Has the preamp section on top and the power amp section at the bottom of the cabinet.  Adds to the confusion making it harder to trace wires...SOUNDS WONDERFUL, though I don't take it out much any more....

[Fresh_Start]

A dual concentric pot would work (awkwardly?), but a 3.3meg RA is probably un-obtainium.

There was a recent discussion here about Fender's 1990s Vibroverb reissue.  Here's the schematic:  http://www.prowessamplifiers.com/schematics/images/63RI%20Vibroverb.pdf  Note that the Speed pot is a 1 meg, not 3.3 meg, but still reverse audio taper.  I do NOT know how that tremolo sounds - the circuit is different from other Fenders.  It is designed to diddle 6L6 power tubes which should help.  Dual 250K pots for the Intensity shouldn't be a problem to find though - one wobbler circuit feeding two isolated Intensity pots???

Cheers,

Chip

[sluckey]

I have a chasis and face plate with 4 holes drilled.  The face plate is heavy chrome plated.  I don't want to mess it up drilling more holes.

You want to put a stereo amp with tremolo into a chassis with only 4 holes in the front panel? That's a severely limiting constraint to put on an amp of the caliber you're talking about.

[Lizard King]

I have a chasis and face plate with 4 holes drilled.  The face plate is heavy chrome plated.  I don't want to mess it up drilling more holes.

You want to put a stereo amp with tremolo into a chassis with only 4 holes in the front panel? That's a severely limiting constraint to put on an amp of the caliber you're talking about.

It was a Carvin TS-100: 2 vol & 2 presence controls.  I was going to go with 2 vol, intensity, & speed.  Guess I could add some controls to the back as in reality, I probably won't use the tremolo all that much.  Maybe I'll leave it off.