Mono Class A SE Schematics

[evancich]

I was wondering if somebody would point me in the direction of schematics for great sounding mono block SE amps? Schematics for a pre-amp would be groovy too.

I don’t need it to be stupid loud but I’m going to be driving a pair of Martin Logan electro-statics. I’m not afraid of building something that is difficult. I plan on doing the layout myself and designing the enclosure. My budget is around $1k, but cheaper is better.

I recently left my job where I built R&D prototypes and took a job where I’m reviewing requirements and overseeing projects. I miss being in the shop. I’ve always wanted to build a tube amp but I don’t know much about designing one (we spent maybe 10 minutes talking about tubes in my EE transistor class).

[Nanook]

I've been looking into various schematics lately. Do a search here at diyaudio.com. Also do some searches for Peter Millet, Gary Pimm, etc. Or do a "classic" design.

Is your budget for the amps and preamp? Do you need a phono stage in there as well?

[Eli Duttman]

ML hybrid 'stats are VERY power hungry. To drive them with a SE tube amp is going to need a transmitting type whose multi KV B+ requirements are DEADLY dangerous. That's not a good choice for a 1st project.

IMO, you should do the preamp 1st and get some experience under your belt. You have a fighting chance to survive a mistake at a couple of hundred Volts.

I've attached a schematic for a simple 12B4 based line stage. A few tweaks to that circuit and you have a low gain, low O/P impedance unit that can drive the nasty IHF "standard" of 10 KOhms. Use the SS power amplification you already own.

[jarthel]

Originally posted by evancich
I was wondering if somebody would point me in the direction of schematics for great sounding mono block SE amps?

one thing to note is that any design can be monoblock. it only means you have separate chassis and separate power supplies. So any circuit you see out there can be made into a monoblock.

Another thing to note with monoblocks is the cost. As mentioned above, you have 2 chassis and 2 power supplies and other (like binding post, rca jacks and etc) instead of one. So, you might have to rethink your budget.

[Nanook]

oops, didn't read into that.

an arc welder is usually needed to drive em. They are power hungry for sure.. Besides the lack of efficiency, they need current.

Although they can sound wonderfull.

If tubes required then big power AB tubes would be the way to go for the top, assuming you have an active sub-woofer built into them. for the bottom

[evancich]

Thanks for the tips.

Yep, my budget is everything: amps, psu, pre-amp.

I don't need a phono stage.

I feel pretty comfortable around high-voltage. I used to build MassSpec's that used 40kV. I spent time on Navy ships messing around with old radio and radar tubes.

I've friendly with a machine shop in my area and they will make the fab the enclosure for cost.

I always wanted seperates. When I was a kid reading stereophile, I dreamed about krell monoblocks and wilson speakers. That is totally out of my budget, but if I can build some tube monoblocks...

[Eli Duttman]

Forget about SE. O/P trafo costs alone will bust the budget.

Build a preamp 1st. That will get get your feet wet and position you for the monoblock project. The 12B4 circuit I previously posted has some gain. That gain would allow you to use the 12AT7 splitter/driver found in "El Cheapo" in front of PP KT88s. 60 honest WPC should provide decent listening levels in combination with your M/L speakers.

BTW, a set of Dyna MK3 reproduction trafos from Triode Electronics will cost about $250 per monoblock.

[Kent Smith]

I second the suggestion on push-pull KT88's... that's what I would build!

All in favor?.....

[Miles Prower]

Originally posted by evancich
I was wondering if somebody would point me in the direction of schematics for great sounding mono block SE amps? Schematics for a pre-amp would be groovy too.

I don’t need it to be stupid loud but I’m going to be driving a pair of Martin Logan electro-statics.

Single-enders won't work with those speeks. Most of your class A1 SE amps don't put out much more than five watts (and a great many not even that) and are used with high efficiency speeks with enough sensitivity to produce listenable volumes with very little power, sometimes under one watt.

Another big problem is SE OPTs. The more current they need to support, the more difficult to wind a really good one that can stand the DC core magnetization, maintain primary Xl at the low end, and have minimal stray capacitance and leakage inductance for good high end operation all at the same time. Unless you're gonna change the speeks, go with a PP amp.

I’ve always wanted to build a tube amp but I don’t know much about designing one (we spent maybe 10 minutes talking about tubes in my EE transistor class).

Most of what you learned in transistor class is transferable. Go Here, look in the "Downloads" section for "RDH4" and download that. It's well worth while to spend some time studying that before beginning anything.

[Klimon]

All in favor?

...okay then!

Or parallel PP as a less attractive alternative.

Simon