kgst

[meeskees]

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

This one?

[insanity]

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?

[Mangler]

Would this one also work?

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

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[kevin gilmore]

nope, you need 2 high voltage windings

[Mangler]

Thanks, glad I asked

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[spritzer]

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/

[Laowei]

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.

[spritzer]

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

[nopants]

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...

[Laowei]

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

Fixed.

[chiguy]

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?

[Laowei]

Not really, only more heat to dissipate.

[Mangler]

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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[Laowei]

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

[insanity]

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

[Laowei]

Deleted.

[kevin gilmore]

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

667-ECQ-E2105KF

[Remolon]

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.

[kevin gilmore]

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

[Remolon]

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?

[kevin gilmore]

half of the differential gain comes at the output stage.

 

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

Really!

[Remolon]

Thanks Kevin. It is a excellent information.

[Remolon]

@headinclouds:

 

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

Regards

[headinclouds]

@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. 

[Laowei]

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.