1st poweramp build. Suggestions wanted.

[nandrewjackson]

Hello,

I've built two rackmount preamps, here's one, http://www.el34world.com/Forum/index.php?topic=15609.0

I want to build a rackmount poweramp to go with it.

I've narrowed down the circuit to: one input, 4 6L6's, diode rectifier, one volume control, Presence control, multiple taps OT for different speaker cab configurations,

I used to own a single rectifier (mesaboogie) and I really liked the response of it when it was running 6L6's.
It had the ability to run el34 or 6l6.  It also had a diode rectifier only.

If anyone has any ideas of schematics to base this off of, i'm all ears.
Does anyone see any difficulties that may arise, again, this is my first tube poweramp build.
I do not own or have access to an OScope, is this OK?

[SILVERGUN]

My 2 cents....
The Mesa Boogie 50/50 is a pretty good solid design for 4 6L6:

http://www.el34world.com/charts/Schematics/files/boogie/boogie_5050.pdf

Just build one channel and add 2-6L6 if you only want a mono amp with one set of controls 

[nandrewjackson]

Cool.

Yeah, I was looking at Boogie.  The Dual Rectifier output section seems to be like the 50/50, double the tubes.
I was also looking at the Peavy EVH 5150 output section.  It looks a lot like the Boogie with slightly different values here and there.

[Ed_Chambley]

I would consider a fender twin power if you are looking for the ability to run 4 tubes either 6l6 or EL34.  Main reason is the Iron is much cheaper from classictone.  The main problem is the difference on the OT needed as el34 as opposed to 6l6.  The optimum OT for 6l6 is not optimum for el34 and vice-versa. 

A power section in the 100 watt range doesn't change very much tonewise.  It is rare the power tubes ever distort very much.  Many audiophiles use The Boogie 50/50 for their power amps since they are much cheaper than a McIntosh.  I have a Marshall 100/100 and really all it is is a very clean EL34 amp.  Put a JMP-1 in front of it and it rocks, but you can also plug a CD player in it and it sounds great and clean.

Ahh, but I do remember the days when we could dime a 100 watter.  There is another very cool power section and that is the Peavy Mace if that what you are looking for.  Stage amps for Lynyrd Skynyrd and Molly Hatchet back in the 70's.  You can find these amps cheap on craigslist from time to time because you cannot stand being near one when turned up to a good sounding volume, but you would have everything you need to build a amp with some nice parts left over.

[nandrewjackson]

Thanks for the heads-up on the OT, Ed_Chambley.  I was gonna order an OT for JCM 100 watt, but I'll rethink that now because those are EL34 amps.  I like the look of the Weber JCM 100 Watt OT because it has a lot of options for speaker impedences.

I've been looking at Mesa 50/50, Mesa Dual Recto, Peavey EVH 5150, and Twin Reverb power sections.

The main differences seem to be the feedback circuit.  The Twin just uses 820 Ohms from the OT secondary to the cathode circuit of the PI, while the Mesa's are using very different circuits for "Presence" control.  I'd like to use a "presence" control, but I'm not really sure which style I should use.  They are very different between Mesa 50/50, Dual Recto, and even different on the 90/90.  I even checked out the schematic for Soldano powersection presence controls and they are different too.

Well, they're not *TOO* different, just the way the control seems to be parallel to the PI cathode circuit in some, and in series with the PI cathode circuit (to ground) on others. 

It's gonna take me a while to acquire all the parts, so I've got some time to think about the circuit.

I really liked the Marshall rack stuff like the JMP-1 and the tube poweramps.  I even liked the Valvestate poweramp they had out around the same time.  Real cool stuff.