• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Any plans to build a 100W per channel power amp?

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Hello,

I am trying to build my own tube amp and looking for plans and parts source to build a 100W/CH power amp like the Music Reference RM-200 MK II or similar. My speakers, Aerial 10T, require a minimum of 100 watts.

Please advise.

Cheers,
 
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You can do PP 6GB5, or PPP 6GB5 for more. Still rather cheap at $5 each.
PP KT120 should get to 100 watts.

My speakers, Aerial 10T, require a minimum of 100 watts.

That doesn't make sense to me, you can, and usually will, put in a watt or less at normal listening levels. If you goto 100 watts too many times, the cops are gonna get you, and they have a habit of shooting first lately.
 
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If you can do the test linked in my sig line, you might have a better idea how much voltage (or power) output you really need. 100WPC isn't huge, but is getting big for tubes. You may not need that much. Or you may need more. ;) Always good to really know.
 
What is nominal impedance of the speakers? What does the impedance curve look like? Tube amps don't exhibit the gargantuan damping factors SS amps exhibit. Those speakers might need derating, if they are to be mated to tube power amplification.

Because of outrageous dips in the impedance curve, some speakers (like big Thiels) simply should not be used with tubed power amps.

FWIW, the KT88 data sheet gives some operating condition sets that yield 100 W. from a PP pair. Long service life is not to be expected when the tubes are worked that hard.
 
THE tube amp for those speakers is a Harman/Kardon Citation II that has been overhauled to the max., ala Jim McShane. Of course, the 4 Ω speaker taps are what get used.

A "McShaned" Cit. 2 will easily make 60 WPC continuously and will produce pulses well over 120 WPC. :) For a tube amp, the Cit. 2 has a huge damping factor. AR-3s and AR-9s are known to work well, mated to a "Deuce". :yes:

Yes, power is quite adequate, as tube amps can be taken right up to the point of clipping, which is something you don't do with "sand", lest the speakers' tweeters get damaged. Paul Joppa has provided the community with a useful rule of thumb. Joppa's Rule states that an amp/speaker combo should be capable of producing 102 dB. SPL peaks at 1 M. distance, inside a listening space of "typical" volume.
 
I think Patrick Turner said just treat them like the KT88 - use the same bias or perhaps a bit hotter bias, to get more class A output and/or longer tube life.

yes, read that one too.....
that is why am not so excited about these newer tubes....;)
what i would like to see is the tube maker to publish operating points
and guarantee their tubes can survive it....
 
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Joined 2011
Right, more bling like this one:

An externally hosted image should be here but it was not working when we last tested it.


or right out of the datasheet, the Genelec 100W UL amplifier, need about 560V on the plates:

Genelex100W.gif
 
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So far so good but I want to build my own from scratch. A Citation II is hard to find and totally overpriced. There is a fellow on Asylum Trader asking $2,500 for just a pair of power and output xfrms, is this insane? I wonder how much would cost a complete amp. Please bear in mind that I do not have the experience or knowledge than most of you have, maybe way over what I have.

I only built a Dynaco ST70 and two MKIII kits many years ago.
 
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How about this kit?

Triode USA Dynaco Mk3 Tube DIY Amp Kit

TUBE AMP KITS for DIY - ALL MADE IN USA TRANSFORMERS: Triode USA Dynaco Mk3 Tube DIY Amp Kit
[remove]

DriverBoard : TriodeUSAMk3
CapBoard : TriodeUSAMk3Cap
PowerTransformer : Standard 120VAC (P782)
OutputTransformer : A431
Choke : Standard C354
Caps : Solen (+$20)
Tubes : With Tubes (+$133)
Chassis : MK3 upgraded
Wire : Teflon (+$16.95)

Total: $729.90
 
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So far so good but I want to build my own from scratch. A Citation II is hard to find and totally overpriced. There is a fellow on Asylum Trader asking $2,500 for just a pair of power and output xfrms, is this insane? I wonder how much would cost a complete amp. Please bear in mind that I do not have the experience or knowledge than most of you have, maybe way over what I have.

I only built a Dynaco ST70 and two MKIII kits many years ago.

I agree with the assessment that the price asked for a set of "Deuce" transformers is nucking futz. :mad: A complete, unrefurbished, "core" should not cost that much.

The O/P transformers used in the Cit. 2 and the Heath W6M are very special and I don't know if satisfactory "clones" of either can be purchased. Good O/P "iron" is always EXPENSIVE. :bawling:

Maybe you could make something loosely based on the Heath W6M around the Plitron PAT-2100-SSCR O/P transformers, whose full power bandwidth is excellent. Even though the "finals" operate in UL mode, g2 B+ gets regulated for superior open loop linearity. Williamson style circuitry has plenty of NFB, for a decent damping factor. FWIW, I would use a "high" current/"low" plate voltage KT88 operating condition set, to compensate for the comparatively low primary impedance.

BTW, I would adjust the W6M's small signal tube lineup/circuit details to make the gain structure compatible with unattenuated 2 VRMS I/P signals and more linear.
 

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  • Heath W6M Schematic.jpg
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How about this kit?

Triode USA Dynaco Mk3 Tube DIY Amp Kit

TUBE AMP KITS for DIY - ALL MADE IN USA TRANSFORMERS: Triode USA Dynaco Mk3 Tube DIY Amp Kit
[remove]

DriverBoard : TriodeUSAMk3
CapBoard : TriodeUSAMk3Cap
PowerTransformer : Standard 120VAC (P782)
OutputTransformer : A431
Choke : Standard C354
Caps : Solen (+$20)
Tubes : With Tubes (+$133)
Chassis : MK3 upgraded
Wire : Teflon (+$16.95)

Total: $729.90

IMO, a Dyna MK3 knockoff is not remotely close to having the "stones" your speakers need.
 
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This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.