View Full Version : Interstages Wanted

14-10-2008, 18:13
Anyone got a pair of 10:1 interstages primary 60ma or more, be better at around 100ma.

Currently using 19:1 that works well but looses too much umpf.

Anything from 4:1 to 10:1 would prob do.......

pure sound
15-10-2008, 10:46
What is the application? None of the usual suspects (Tango, Tamura or Hashimoto) make such high ratio transformers for interstage coupling, and especially not with such high standing current in the primary.

15-10-2008, 10:58
PX4 driving 833 in SE, currently using 2.5K 8R output transformers, i.e. using the speaker terminals to drive the 833 grids. Ratio 19:1 (step down)

Works exceptionally well, and the output is great, but could be higher with a lower ratio interstage to lower the current and increase the voltage fed to the 833 grid for a bit more umph. i.e more swing on the 833 grid.

Cap coupling simply doesn't work !! Not enough current and plenty of driving valve flashovers. Oh and blows speaker too.....:doh:

Of all the amps I've built (there have been many over the years) the 833 so far is my personal best.
It's sublime, punchy and just too involving for my own good. (once the record is on, work stops !!! ) :)

pure sound
15-10-2008, 15:18
You might be as well getting Sowter to make some custom jobs for that, or run the PX4 slightly less hard (30 mA) and get (ideally) some Tango NC-20's or, for less outlay, perhaps something like these. http://www.icl.co.jp/audio/english/RC20/RC20.htm

I suppose these might also do it
http://cgi.ebay.com/Vintage-UTC-driver-interstage-Transformer-x2-tube_W0QQitemZ360085485102QQcmdZViewItem?_trksid=p 3286.m20.l1116

Incidentally what drives the PX4? The same issues will apply to it and a choke loaded or transformer coupled driver stage might also yield benefits there.

15-10-2008, 15:50
It's a conundrum,

The R cores would have to be used in reverse at a lowly 1.8:1 ratio, even then the recommended driver max is a lowly 20ma.....so no good I'm afraid.

The ones on Ebay look better, but still low at 2.2:1

I have some lovely huge 1:1 interstages and they just won't drive the 833s hard enough.

I suppose what I need are some 16 Ohm secondary output trans, they should do it.
I can never understand why interstages cost so much?
I do have some, but they are the 833s output trans. Running the 833s at 140ma they are not going to be easy to replace either.

I do want to push the the 833s to 300ma sometime, but that's another story !!!

It's a MH41 driving the PX4, cap coupled.

Incidentally, the 833 stage has no caps or resistors in the circuit, I believe that's half the battle.

cheers Darren

15-11-2008, 15:35
There are some frighteningly expensive ones here: http://www.hificollective.co.uk/components/trans_driver_interstage.html


15-11-2008, 19:47
How's about these (http://cgi.ebay.co.uk/PARTRIDGE-SINGLE-ENDED-VALVE-AMP-OUTPUT-TRANSFORMERS_W0QQitemZ380081859065) or these (http://cgi.ebay.co.uk/PARTRIDGE-SINGLE-ENDED-VALVE-AMP-TRANSFORMERS-TRIODE_W0QQitemZ360107594446) ? 6k:15R