Nope, no dummy load needed for any adjustment.  PSU works just fine without any load and the voltages should stay the same with a load. 

Some questions for the experts for the offboard 0.6 amp board.

 

For Q17 and Q18 the PCB shows A970 and ECB (with the flat side facing you).

 

This datasheet http://www.futurlec.com/Transistors/2SA970.shtml gives the orientation as BCE (with the flat side facing you).  I'm assuming the datasheet is wrong?

 

I'll be using MPSW56 as a sub for A970. This datasheet http://www.onsemi.com/pub_link/Collateral/MPSW55-D.PDF gives the orientation as EBC (with the flat side facing you).

 

So if I use MPSW56 I'll have to cross 2 of the legs, right?

 

 

Nope, no dummy load needed for any adjustment.  PSU works just fine without any load and the voltages should stay the same with a load. 

Thanks.

 

So it is safe to measure at the STAX socket without connecting the headphone?  Even with signal feeding to the input?

 

I want to make sure the amp is as close to 100% stable as possible, before connecting my headphone to it.

correct data sheet

 

http://gilmore.chem.northwestern.edu/2sa970.pdf

 

safe to measure the voltages at the stax socket.

but the bias will be the wrong voltage unless you have a very high impedance voltmeter.

Edited February 26, 201412 yr by kevin gilmore

Thanks Kevin.

 

So, it looks like I'll have to de-solder the MPSW56 and cross 2 of the legs.

Thanks.

 

So it is safe to measure at the STAX socket without connecting the headphone?  Even with signal feeding to the input?

 

I want to make sure the amp is as close to 100% stable as possible, before connecting my headphone to it.

 

Ditto what Kevin said  and it is perfectly fine to have the amp "playing" when testing it. 

Will this be the right tool to measure the bias voltage: http://www.fluke.com/fluke/auen/accessories/high-voltage-probes/80k-40.htm?PID=55357

No need for that, just measure before the ballast resistor i.e. the resistor next to the bias output. 

but that actually would work other than it divides by 1000 so

you have to put it on the millivolt range.

and you need to keep it away from steve

My only problem is the cost... 

One more question for you guys: what is min voltage rating for 5pF comp. cap, C1 & C2? Will 500V good enough?

needs to be 1kv

Guys,

Can someone tell me if Kevin's Current Domain Electrostatic Amp that appears on Headwize

is the same as what is known as the KGSS.

Les

yep

Thanks Kevin.

Can anyone enlighten me in regards to following behaviour of my KGSS. I built this back in

2000.

All supplies are stable and I carried out Kevin's setup.

Set the first pot for zero volts on meter between + and - Outputs.

Set second pot for zero output at + and Ground.

Reset these after running for 30mins.

After doing all of this I watched the both meters and meter between + and - varies between

-100mv and 500mv while the other one reads about 1.0v even though both of these were set initially

at 0.Both channels experience the same effects and both never get greater than 1 volt over 1 hour.

Is normal for the amplifier?. It sounds GREAT.

Appreciate any comments.

Thanks

Les

Edited March 4, 201412 yr by iwik

your amplifier is getting warm, very abnormal behavior

Yup, normal drift and warm up found in all circuits. 

Edited March 4, 201412 yr by spritzer

Got my off-board PCBs back from the fab.  Thank you Kerry for sharing your design.  I have made a few changes to go with my plan.  Actually, I'm making both on-board (standard) and off-board version of the amp.  One will stay at home, while the other one may go to my office.

 

 

Looks good

looking forward to seeing the final result.

Thanks all, nice to know all is normal.

Les

 

My only problem is the cost...

 

http://www.ebay.com.au/itm/New-High-Voltage-probe-40KV-DC-28KV-AC-1000Mohm-input-1000-1-4-multimeter-warran-/180775974394?pt=AU_B_I_Electrical_Test_Equipment&hash=item2a171675fa

Well this does seem to fit, if a bit cramped...

 

jeebus, that makes me want one. 

Well this does seem to fit, if a bit cramped...

 

I thought you liked cramped?

if you cased the transformer on top that would free up some space, not that you need it