The DIY Electrostatic amp thread

[spritzer]

If you take care with the grease application and isolate the screw then it should be just fine. This is how Stax did it on the SRM-T2...

[pagan]

Thanks spritzer I have the larger heatsinks with the trannies pasted to them, temps hovering around 60 Degree C heatsinks are anodized so thats the insolation....

Adjusting balance and offset varies a few volt either way, might look at the led volts.

When adjusting the balance and offset, gather it's done with nothing connected, into or output, not even the input volume pot?

Also, I have 2 balanced stepped attenuators, one 50K the other 10K, does it matter with input resistance?

When using SE input, is the - input(unused) grounded or left floating?

[spritzer]

It's best to ground the input when adjusting offset and balance but in reality it makes little difference.  Just turn the volume down and you'll be fine. 

 

Input resistance doesn't matter for the amp and you always ground the - input for SE. 

[pagan]

Thanks spritzer

I have the kgss running now, put the esp950 on and was listening, very nice, 3 albums later I think it's time to do some tidying up.

Time flies while listening to electrostatics.

[spritzer]

It sure does. 

[eggil]

We want pictures!

[pagan]

We want pictures!

No problem..

I'll take some when the sun is out in the morning.

[pagan]

Ok

It's running, still need to tidy cable runs, but does sound good.

[Victor Chew]

Nice work pagan.

[eggil]

Congratulations! Nice and tidy.

[chinsettawong]

Very nice!

[spritzer]

I like that one, nice and straight.  Are you using plugs to ground the - input for RCA use as I can't spot a switch anywhere?

[pagan]

I like to keep it straight and simple...... just like me

I havn't wired up the rca's yet.

I'll probably make perf-board with relays to switch between the two.

It can sit between the two inputs on the back panel....

I'm using it balanced from a B3

Also

Just updated to a larger pic in that post (I was surprised I could modify it)

The better pic should show where I drilled holes in the pcb under the heatsinks..

I used flouro yellow nail varnish on the pcb holes for insulation..

And before anyone asks if the color of the nail varnish matters to the sound?

I have no comment:)

[dsavitsk]

Just to double check ...

 

This is looking into the front of the jack, and using the Amphenol part from Allied (78-S6S)

 

pin 1 is the bias

pin 5 is rt-

pin 4 is rt+

pin 3 is lt+ and is the one isolated from the rest

pin 2 is lt-

[Victor Chew]

I wire my amps in the same way as posted by you, which I believe is correct.

[spritzer]

I don't have any Amphenol jacks left to check but the picture is correct for the outside of a chassis.  I have one of those on my wall...

[jimmyb233]

Could someone point me in the direction of biasing instructions for a Blue Hawaii?  I own a BH built by Kerry.  Thanks.

[Kerry]

I will PM you.

[jimmyb233]

Thanks Kerry!

[mypasswordis]

I am trying to use the BATE boards I got from Birgir to make a BEA/baby Megatron, but have a couple of dumb questions first. Is it alright to use a separate transformer "stacked" onto the HV transformer to generate C- 430V? Also, any foreseeable problems with 10M90S cascode CCS on output tubes? What DC should I "float" the output tube heaters at. and what's the best place from which to derive this voltage? Finally, planning on using simple LM317 based circuit to power the input tube heaters, should I run this in current mode or voltage mode and do I bother with a soft start? TIA.

[kevin gilmore]

as long as the transformer has windings suitable for 400v isolation sure.

 

10m90s as current source, very popular with the stax mafia  (heat sinks obviously required)

 

output tube heaters can float or can be tied to -400

 

voltage mode for the input tubes.

Edited February 27, 2014 by kevin gilmore

[mypasswordis]

Great, thanks! I think that's all the info I need to start sourcing parts and begin this project. Will certainly have more questions along the way. Preliminary searching brought up something like this for the amp chassis/heatsinking the CCSes. http://www.ebay.com/itm/111110701287?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

 

A parts question, what circular connectors/sockets do you recommend? I think I'm going to need around 10 contacts. 400v, -400v, -430v, -15v, gnd, 580v bias, 230v bias, 6.3v heater x2, 12.6v heater, I think that's it?

[spritzer]

The -430V is generated on the psu board by stacking a TL783 supply "underneath" the -400V supply. 

 

No need to cascode the 10M90's, single units per tube are just fine. 

 

Heaters can just be left floating or take a voltage divider from the B- line.  Stax tied the heater directly to the B- line in the T2 so that would work here too. 

 

That chassis is similar to what I'm using for the small KGSSHV and they are nice to work with.  The umbilical connector can be something like this:

 

http://www.ebay.com/itm/1-Military-Gold-10-Pin-Twist-Male-Female-Connector-M10P-/300562711241?pt=LH_DefaultDomain_0&hash=item45faef02c9

 

Been using them for years and there is also a female version.  You can also just generate the normal bias from the B+ inside the amp chassis via a voltage divider. 

[mypasswordis]

Yes I know the supplies are stacked, just wanted to make sure two transformers can be stacked. Dumb question, but better safe than sorry.

 

I should go over the enormous T2 thread at some point, I'm sure I'd learn a lot. Leaving things actually floating seems a bit scary to me (obviously I did not grow up in the tubes era) so I will tie to B-. That way I can make sure the heater-cathode voltage is in spec.

 

Thanks, those connectors look really hardcore and are inexpensive to boot.

[justin]

are those the ones that dont come in both male/female versions?