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need help/schematics for a tube amp project

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I have four 2-way speakers with 93 dB sensitivities, rated at 75 watts RMS, 375 watts max into 8 ohms. As of now, I have no amp for these, since it was an impulse buy that set me back a little money. I have begun looking at the DIY portion of things and think it could be both fun and a good learning experience. Not to mention probably cheaper. :)

So, given the specs I listed, what kind of amp am I looking at? Lets just go with about a 50-100 watt output level @ 8 ohms. Schematics for this are required, since I know background info on building an amp, but I am not near being perfect at it. Also, try to keep it fairly simple, but not too simple. Sound quality is a must. Thanks
 
Settle for 30 watts and bigger caps to back them up and you can stay in the 6L6 family which gives you a wider range of tubes some of which are being made today. The iron will be easier and cheaper to get as well because it was and is produced in mass quanities.
As for schematics etc if you can get the iron cheap enough a good one is the Eico ST 70 and if you can get by with a bit less power the Eico ST 40. Nice thing about kits is the contruction manuals are such a big help. By the way I own neither and have listened to both.
David Thatcher
 
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I'm with Thatch_Ear here. 30-35W is a practical maximum, especially if you are a beginner with a budget. With 93 dB sensitive speakers you could even consider a small SE amp (i've been using 4 W EL84 on my 91 dB speakers).

Forget the speakers power ratings, they are almost meaningless, but do give us some more info. Impedance. Brand.

There was also just a very recent thread you should look up (and i think an older one too) that covered off this same topic. The fellow ended up ordering one of Gabvee's PP kits.

dave
 
They are Klispch spekers- 8 ohm impedence. I am on a budget, and found a place to buy tubes and most things I needed so I could avoid getting ripped off by a package deal-- of course, it may be betetr pricing than I could get individually. It just depends.

I don't know much if anything about tube amps. I can understand and build according to a schematic, but I need to know where to find one and a parts list... or a good quality but cheap kit.
 
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trespasser_guy said:
This one looks fairly simple, but does not haev scematics... how would I go about building a nice simple organized one like this? Minus the PC board, of course.

http://www.tubeaudio.com/page23.html

Reviews of this amp have been favourable.

This uses 4 - 11MS8. The 11MS8 is a triode/pentode. Each channel uses 2 of the pentodes in an 8-10W PP output stage with one triode for a gain stage & the other as phase splitter. In terms of topology it is the same as the ASL WAVE 8 amp (which uses 6BM8s & costs $200 for a pr of monoblocs). I have also seen an 11BM8 amp kit (11 volt heater version of the 6BM8) that is available in stereo or mono blocs (but can't find the ref).

Go looking for 6BM8./ECL82/ECL86 amps.

dave
 
A very good design for a 6BM8 PP is the Calrad AP-15. 1 12AX7, 2 6BM8 per channel( these are mono blocks and there is a Sam's Photo Fact on the AP-15).
What Klipsch, if they are new multi driver towers the crossovers could be power hungry no matter the factory given SPL and need the 30 watts to crank them.
 
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Thatch_Ear said:
A very good design for a 6BM8 PP is the Calrad AP-15. 1 12AX7, 2 6BM8 per channel( these are mono blocks and there is a Sam's Photo Fact on the AP-15).
What Klipsch, if they are new multi driver towers the crossovers could be power hungry no matter the factory given SPL and need the 30 watts to crank them.

Is the 12AX7 there to drive the tone controls, because in a set of monobloc poweramps it is sort of an extraneous stage. Got a schema?

I have a little Carad SE 6BM8 that is quite nice.

dave
 
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Thatch_Ear said:
Kind of interesting in that 1/2 of 12AX7 is for phono stage and the other for tone, volume. The amp itself is all 6BM8, notice the feedback circuit.

If you didn't need the tone you could use the 2nd 1/2 of the AX7 as the 2nd stage of a passive RIAA. For a power amp you could just start at the 1st part of the 6BM8.

Any chance of mailing me a larger readable gif of that circuit?



dave
 
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Re: Email me

Thatch_Ear said:
And I will send you the whole photofact. They are nice little amps, and sell for low prices, but have only recieved 2 out of 5 worth paying for.(Ebay)
Thatch

Done... i have only ever gotten three old amps that came in enuff working order to use on a regular basis -- and 2 of those died and the little calrad is developing a little hum, so i expect to have to rebuild whatever i get (and i'm sitting on some 30+ amps right now -- monsoons are coming maybe i'll be able to get at them :^)

dave
 
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