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hi all

I started to deal with the vacuum-tube amplifiers
studied the subject, I decided to build an amplifier
with the following characteristics

1) single ended scheme
2) kt88 tubes
3) single ended Edcor output transformers

Who will advise me the construction of such properties

I found this scheme http://diyaudioprojects.com/Tubes/KT88/
Can I replace the James 6123H with a similar model from Edcor
if yes then what

You could use the Edcor GXSE15-8-5k outputs, and an XPWR010
power transformer. They would work fine in that circuit.

... tom

Another alternative to the James' outputs are Transcendar's. They are pricier than the Edcor's, however.

http://www.transcendar.com/2.html

5K with 40% Ultra Linear tap to 4 & 8 ohms, Frequency Response: 15 Hz to 75 kHz, Maximum DC Bias Current: 100 mA, Primary DC Resistance: 295 ohm, Part Number TT-119-OT $200 per pair.

You can also use a Clementine board with no mods with KT88s to do exactly what you would like. The 6SL7 would have plenty of drive for a KT88.

Shannon

What kind of power would we get out of KT-88's on a clementine board in Triode / UL?

separks wrote:You can also use a Clementine board with no mods with KT88s to do exactly what you would like. The 6SL7 would have plenty of drive for a KT88.

Shannon

I can set KT88 instead of 6L6 in this scheme http://www.diytube.com/clementine/clem6L6_schem.pdf
and it will work well with absolutely no modifications?

sergeykz wrote:

separks wrote:You can also use a Clementine board with no mods with KT88s to do exactly what you would like. The 6SL7 would have plenty of drive for a KT88.

Shannon

I can set KT88 instead of 6L6 in this scheme http://www.diytube.com/clementine/clem6L6_schem.pdf
and it will work well with absolutely no modifications?

Correct - it couldn't be easier. And if you jumper pins 1 & 8 you can basically tube roll *a lot* of different tubes (EL34s, 6L6s, KT88s, 6550s, etc.). You also could go with a stronger bias current using different resistors (use the >19W resistors in the bill of material).

Shannon

My first tube amp was a Tubelab Simple SE. It is a PC board with instructions. If you don't want to point to point wire, this is a fantastic option. http://www.tubelab.com/Simple_SE.htm

He has info on edcor transformers and the design is set up so you can use 6L6, EL34 or KT88

Cheers,

Chris

The aforementioned Deware cap coupled supressor grid mod is easily applicable to the Clementine board, just connect a 0.1 uF 400V cap between pins 1 and 8 on each of V2 and V3.
Has no efffect on tubes with the cathode internally connected to G3, butis an amprovement for any power tubes with a separate G3 pin.

/ed B

As I type this I'm listening to a Clementine fitted with a pair of JJ KT88's. NO mods.

Diana Krall on a 96/24 release. Delicious!

Would like to build a single-ended amp in the 22W range (mainly picked that figure because I want to build it into a stock Deluxe Reverb cabinet, and have it basically be a single-ended DR).

Figured a KT88 could come close (or maybe a KT120?)

After studying Valve Wizard's site, I thought I had a handle on the problem, but my first attempt badly miscalculated the OT value, HT voltages, and totally ignored the screen dissipation, so, before buying more inappropriate iron, figured I'd better bite the bullet and ask . . .

What would be the appropriate output transformer impedance, supply voltage, screen voltage, and so forth?

Thanks in advance!

Joe

Hugh's Wattwerx wrote:Would like to build a single-ended amp in the 22W range (mainly picked that figure because I want to build it into a stock Deluxe Reverb cabinet, and have it basically be a single-ended DR).

Figured a KT88 could come close (or maybe a KT120?)

After studying Valve Wizard's site, I thought I had a handle on the problem, but my first attempt badly miscalculated the OT value, HT voltages, and totally ignored the screen dissipation, so, before buying more inappropriate iron, figured I'd better bite the bullet and ask . . .

What would be the appropriate output transformer impedance, supply voltage, screen voltage, and so forth?

Thanks in advance!

Joe

A KT88 SE UL amp will yield about 12W audio output, no more. (Primary impedance = 2.5K Plate voltage = ~425V)

At 450V a KT120 SE UL amp is supposed to do no more than 15W. You would need to take the voltage beyond 500V for 20W. There are commercial amps which rate theirs at 24W, but I do not know what plate voltage is being used.

Parallel SE KT88s might achieve 20 watts, use an OPT with half the normal plate load impedance for a single tube.

The new KT-150 is "almost" equivalent to two paralleled KT88s.

Just a SWAG....

/ed B

Kind thanks to all! Much to digest.

Joe

EWBrown wrote:Parallel SE KT88s might achieve 20 watts, use an OPT with half the normal plate load impedance for a single tube.

The new KT-150 is "almost" equivalent to two paralleled KT88s.

Just a SWAG....

/ed B

And MUCH safer than the normal way of getting 25 to 35 Watts of SE Sound - An 845 at +1350 Volts (i'm finally tackling one of these
BUT
1) I've been an electonics apprentice => tech => engineer over 40 years
2) I've been designing and building tube gear for 20 of those years.
At these sort of voltages you can get caught out by something as simple as your multimeter probe wires not having enough voltage rating.

Parallel KT88 will cetainly get you well over 20 Watts, unfortunately none of teh dat sheets I've seen tell you anything except various modes of Push Pull Operation.
Parallel 6L6GC are reported to give 22 Watts. AN Ozzie electronics magazine did a parallel 6L6GC SE project - it was called teh "Mudlark" if you want to go looking for it. It used flourescent light balasts as choke loads on the output tubes and ran zero DC current in the output tranny.

Cheers,
Ian