http://www.ampdesign.eu/pi4/pd73.htm

This one?

For that money, you can probably almost get a custom one from toroidy.pl with all secondaries you need.

 

We were talking about this one: http://www.antekinc.com/as-1t275-100va-275v-transformer/

http://www.ampdesign.eu/pi4/pd73.htm

This one?

Would this one also work?

http://www.antekinc.com/as-3t275-300va-275v-transformer/

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nope, you need 2 high voltage windings

Thanks, glad I asked

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This one would work with 500V capacitors (450V might be ok but we don't work well with "might") and larger heatsinks in the PSU.

 

http://www.antekinc.com/as-1t300-100va-300v-transformer/

It looks ok but I'd go for a single 30VCT@500ma winding instead of two separate windings.

Getting ready to send out for some quotes on a custom transformer. I tried to capture all the needs for a KGST in a single unit, using the out of stock Antek transformer and posted info here as a basis. For those that have more experience ordering custom transformers, do any of the following specs look too constraining or impractical?

KGST POWER TRANSFORMER SPECIFICATIONS:

120VA toroidal audio power transformer with:

-Static shield between primary and secondary coils.

-Heavier gauge wires than normal requirement to avoid the copper lost at full power.

-Magnetic shield around the outside to reduce the magnetic leakage.

-HiPot 3500V between primary and secondary coils.

-Approximate overall dimensions: 100mm diameter x 50mm height.

-Mechanically silent operation.

-45C maximum temperature in ambient 20C environment.

-Mounting hardware included.

-All wires out minimum 300mm long.

ELECTRICAL CHARACTERISTICS:

Power: 120VA

Inputs: 2X

Voltage-Hertz

117V-50/60hz

117V-50/60hz

Outputs: 5X

Voltage@Current

[email protected]

[email protected]

[email protected]

[email protected]

6.3V @1.5A

Thanks for any suggestions. I will send for quotes in a few days.

It looks ok but I'd go for a single 30VCT@500ma winding instead of two separate windings. 

This one would work with 500V capacitors (450V might be ok but we don't work well with "might") and larger heatsinks in the PSU.

 

http://www.antekinc.com/as-1t300-100va-300v-transformer/

does aavid make anything taller than 2.5 inch? I've got a bunch of those leftover from kgsshv parts binging- they seem like the only things that will fit...

It looks ok but I'd go for a single 30VCT@500ma winding instead of two separate windings.

Fixed.

The silk screening on the boards say 36VCT so anywhere in between 30VCT and 36VCT is okay?  Is there any point going higher than 30?

Not really, only more heat to dissipate.

Antek has a very nice transformer at 275V (i.e. close enough) and then you just need a 30VCT transformer for the +/-15V supply

In case anybody was wondering or didn't already know, the secondaries all of Antek's transformers have 2 individual coils which can be wired in series or parallel, so they can be used as center tapped transformers. In this case, this spritzer-selected transformer would serve the role of a 30VCT transformer perfectly :

http://www.antekinc.com/as-0515-50va-15v-transformer/

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In Birgir's and Kevin's photos of populated KGST boards there is a socket, for but no OP27 installed. Is the OP27 needed?

If you want the servo to work, then you need it ;-)

Deleted.

this is the cap you should use for the servo, fits the smaller holes

667-ECQ-E2105KF

I am waiting for the PCBs to build  the KGST but I am considering the option to duplicate, with the appropriate values, the set R20/VR2 for having separate adjustment for each valve and the possibility to correct some valve mismatch.

no, absolutely not. Output stage is a differential amplifier.

I believe that not all the valves evolve similarly, and although they are matched at the beginning it will not last for ever. For this reason, I prefer to substitute the need of matching with a procedure of measuring and adjusting a fundamental parameter in the response of the valve.

 

For example, in a power amplifier with a push-pull of EL34 the procedure is to measure the cathode current and to correct it adjusting the grid bias, but what is the procedure for a circuit such as the KGST, if any?

half of the differential gain comes at the output stage.

 

there is a offset and balance control. This takes care of everything.

Really!

Thanks Kevin. It is a excellent information.

@headinclouds:

 

Would be nice to read about the progress of the PCB order.

Regards

@headinclouds:

 

Would be nice to read about the progress of the PCB order.

Regards

Yes - good timing on that.  The pcbs will be with me Monday 11 Aug and I'll be posting out over Monday /Tuesday. 

Yes - good timing on that.  The pcbs will be with me Monday 11 Aug and I'll be posting out over Monday /Tuesday.

That sounds great Geoff. Many thanks for doing this group buy.

Kevin or Birger, what is the max P-P output voltage of the KGST with 350V rails? ~850-990V?

Also what is the KGST's gain?

I am trying to map out the gain structure of my system.

Thanks.