New amp project coming. Does my plans sound worth doing?

[Dingleberry]

Hi.

I scored an old swedish school PA-amp during summer for very cheap.
I'm now starting to convert it to guitar amp. It has only 50V line output in the original output transformer, so it will be replaced.

I have two options on my hand. Old Drake from 50W marshall and old Dynacord eminent 2T iron. Both are designed for 2xEL34 power amp, but the dynacord is rated for 80W (it's really huge!). I'm planning to use EL34 or KT66 tubes in it. What are the benefits to use overrated power transformers?
Of course it won't probably never burn out but are there any sonic reasons?

I was also thinking to make it "dual clean channel amp".
I even might do the channel switching with relays if I decide to make it just one input amp.

Channel 2 will be some kind of R...66 variant with EF86. Vol. treble and bass.

First channel I would like to make as simple as possible and I was thinking something alá 18W liteII.
Just one paralleled triode. Volume and tone. Beautiful, simple, classic.
My question is: Will there be enough gain with that arrangement?
I know that one paralleled stage is enough to drive EL84's but how it will work with EL34's or KT66's? Anyone tried?

Hope you got some picture what I'm planning. Any info welcome.

-T

[Structo]

Well certainly it won't hurt anything to have a large PT, some would call it desirable because it will run cooler with less demand.

To me the important consideration would be what kind of voltage does it supply and how stout is the current supply at that voltage.
Some PT's will sag quite a bit in voltage when a large demand is put on them.
So it would be good if you knew what kind of ratings it had.
Now, some guys like that power to sag as that gives them that old school compression effect that some amps have
So I guess that is a sonic effect of the PT.
Do you plan on using a tube rectifier or solid state diodes?

You will need to add up the heater current of all the tubes you plan on using to see if the 6.3vac side of the transformer can handle that load as well.

I think if it were me, I would look into the Rocket for a cleanish type preamp on one side then you can have your EF86 type on the other side.

[Dingleberry]

Well I was thinking going for that dynacord output transformer 'cause I certainly will use it as my main gigging amp and when the amp runs cooler the reliable it will be.
I'm gonna use the original power transformer from that amp. It is huge and very sturdy looking. I haven't measured the voltages yet but I'm quite sure that it will suit my plans very well.
There is 2xEF86, 1xECC82 and 1xECC83 in the preamp and 2xEL34 in the power amp. I planning to use one EF86 less so there will be little extra left on the power tranny also. Not a bad thing either I think.
I willl go for diode rectification because the power transformer is designed for that.

The reason why I want only volume and tone controls for the clean channel is that I don't want to screw the original looks of that amp. It has five potentiometers and three of them I will use for the EF86 channel so I have only two more left.
Any ideas for great sounding preamp with just two controls besides Champ-type setup?

-T

[Dr-Joned]

You could use concentric treble/bass controls like the old Standel amps had. That is the stacked pots with seperate controls. It sounds like the power tranny should be able to handle what you want to do. Looks like it could have some interesting results.

[Dingleberry]

That's a good point Dr-Joned. I actually happen to have some dual concentric pots that I have gutted from old tube radios and they are in very good working condition. But... As you can see from the attachment I'll then have to give up using those cool looking knobs. And I dont think I'm ready for that. I would really love to keep the front panel as original looking as possible. Of course never say never, but now I think that I'll stay with the original looks.

The mic. input vol. 1 will be the clean channel volume and mic. input vol. 2 will be clean channel tone.
Turntable input vol. will be channel 2 volume and the bass and treble controls will be bass and treble controls for channel 2. That's my current plan at the moment.

I was also thinking to add cathode bias/fixed bias switch to it just to add little versatility and there are some holes ready in the back panel that will be empty.

I'll just have to decide what kind of 12AX7 preamp with only volume and tone to do for the clean channel.
Still any Ideas welcome and thaks to all of you already suggested.

-T

[rsalinger]

Any ideas for great sounding preamp with just two controls besides Champ-type setup?

-T

The Dr. Z Mazerati GT and Carmen Ghia are excellent examples of "less is more".

Cheers,
Rob

[tubeswell]

Any ideas for great sounding preamp with just two controls besides Champ-type setup?

-T

The Dr. Z Mazerati GT and Carmen Ghia are excellent examples of "less is more".

Cheers,
Rob

There's a heap of tone stack options here (if you are just looking for some net-based info)

http://amps.zugster.net/articles/tone-stacks

[Drumslinger]

The Ghia is a cool little project.