Transformer

[davidwpack]

Hello. I'm in the process of designing/building a new amp using two KT66 tubes. Can anyone tell me if the 022855 OT is the suitable transformer for this build? Thanks!...Dave

[kagliostro]

You must specify B+ at which you want to use the KT66


also consider that the 022855 has one only secondary @ 2 ohm and primary 4.2K  (if I'm not wrong)


Franco

[DummyLoad]

KT66 and 6L6GC are near same characteristics. copy fender 40W-50W output stage and power supply. consult data sheets otherwise.


--pete

[davidwpack]

I'm using a 325-0-325 and a GZ34. It should be about 418 volts at pin 4... thanks

[davidwpack]

I downloaded the tube specs. I'm not certain what numbers to use. Is there a formula I need to apply to figure this out? Also, is the 018343 the likely transformer to use? Thanks... Dave

[Ed_Chambley]

Not a formula, but it has to do with what you are wanting.  A lot of people build the same as if you were going to build a 2 tube 6L6GC.  50 watt with somewhere around 4K reflected.  Doesn't mean you have to though.  I have a KT66 design I have been working on for a few years and it has had 4K/4,8,16 ohms and I have tried 3.4K.  Tried a 5k9


Right now it has 6.6K and I prefer it.  KT66's are lovely sounding and very round, but they are also sort of difficult to get a low volume sweet spot.  Best I have found tonally is to use the 6.6K with 430 plate voltage and I increased the screen resistors to 3.9k.  The increased screen resistors give it a little spongy feel without having to decrease filtration or use a Rectifier tube.


Yes, there is a way to calculate how to get the optimum power from the tube, but what is it you are wanting?  Optimum power with lots of headroom?

[PRR]

> It should be about 418 volts

It helps to "know" the classic designs.

Fender 5F6a (many of the large old Fenders) is 400-420V of B+, a 4KCT load, couple 6L6 or their heavy-duty kin 5881 and 6L6GC, makes 40+ Watts.

KT66 is very-near a European beefy 6L6, will do the same work.

So the plan is fine.

The only odd bit of this plan is the 2 Ohm-only OT; you can't run any common single speaker, you need two 4 Ohm or four 8 Ohm. I think that is restrictive. There is maybe a similar 40W 4KCT but with more secondary taps?

[Colas LeGrippa]

there is the Hammond no 1650N  , 4.3k, 4, 8 and 16 ohm, can handle up to 60watts , 20 to 20khz.
 I built many amps with them.


good luck !


Colas

[DummyLoad]

> It should be about 418 volts

It helps to "know" the classic designs.

Fender 5F6a (many of the large old Fenders) is 400-420V of B+, a 4KCT load, couple 6L6 or their heavy-duty kin 5881 and 6L6GC, makes 40+ Watts.

KT66 is very-near a European beefy 6L6, will do the same work.

So the plan is fine.

The only odd bit of this plan is the 2 Ohm-only OT; you can't run any common single speaker, you need two 4 Ohm or four 8 Ohm. I think that is restrictive. There is maybe a similar 40W 4KCT but with more secondary taps?

Tube Amp Transformers

Part number 018343


has 2 4 8 ohm secondary taps. i have used several - great sounding flexible OT. i have used that OT with 2 x EL34 and 2 x 6L6Gx and 4 x 6V6GT.


--pete

{EDIT -- forum software munged URL -- PRR}

[davidwpack]

Hey! Thanks for all the replies. The OT is pretty much the only hang up I've had so far. Also, thanks for the recommendations​. I believe I will get one with multiple taps. Thanks again...dave