First I tried a simple grounded cathode gain stage
(ECC82/12AU7 both triodes paralleled) with the
transformer primaries in series as plate load,
and then a combination of a ECC82 grounded cathode
gain stage followed by a 6CG7 cathode follower
(both triodes paralleled), with the transformer
primaries in the cathode path.

The results in both cases were - ummm - interesting,
but far from being disappointing. I guess with some
further experimentation the results may even be quite
acceptable, if one does not expect the impossible from
such an unconventional, but simple setup.


With the two primaries avaliable, you could create a push-pull circuit.
Using a dual triode like the 12AU7. You'll need a phase splitter, though.

Hello Ian,

You might try distributed load...one winding on cathode and one on
anode,

Great idea, since there is no need for the splitter stage
as suggested for a micro p-p amp. On the other hand, there
is DC flowing thru that ungapped tranny and probably
core saturation is the reason for that "interesting" sound
I got with the tranny used eiter as a plate load or
cathode load.

And the symetrical windings/loads when using distributed
load are probably far from ideal, but what the heck, I'll
try it anyway :-)

But I'll try distributed load, of course.

assuming the insulation is up to it (perhaps not up to the
inter-winding voltage...but if you're having fun a bit of smoke and
ozone, and some of those fried enamel smells, might be a welcome
addition).

Yes, the safety aspect of tubed headphone amps shouldn't be
underestimated. I let the circuit work into a dummy load
resistor at least for 1/4 hour before plugging in the
headphone, which is convenient time to take some measurements,
too.

Up to now the little tranny survived and my brain isn't
cooked.

Also possibly PP/splitter combined.

Robert and Ronald suggested that too, and I tried it
already as a quick hack. This gave a large improvement
in sound, probably because the little cores didn't
saturate in p-p operation.

Tnx2u,

Tom

--
The large print giveth, the small print taketh away.
- Tom Waits

I used some small trannies parafed from an RC stage for my h'fon. amp:
http://webpages.charter.net/dawill/Images/WOT_Amp2.jpg
http://webpages.charter.net/dawill/Images/WOT_Amp1.jpg
http://webpages.charter.net/dawill/I...ones%20Amp.gif

Tim

--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms

"Tom Schlangen" wrote in message
...
Hi RATs,

just for the fun of it and to see (and hear) what
happens I tried some spare very little transformer
I intended to use in other projects for bias voltage
supply as micro-OPTs to drive a headphone.

The transformers have the following specs: Two
primary windings 110 volts, two secondary windings
9 volts; nominal max. secondary current being 50mA per
secondary. The primary ohmic resistance for each
winding measures ~1,6 kOhm, the secondaries are
at 20 ohms each. One transformer fits easily
into 1 cubic inch, there is a photo of it at
http://www.ndh.net/home/schlangen/ro...ansformer.html
at the bottom of that page. The origin of that type
is unknown; I bought (5) of them for 1 Euro on Ebay ...

When using primaries and secondaries in series, the
turns ratio is ~12, with my ~20 years old AKG K240
headphones (600 ohms studio version, this studio
version is quite different to what was/is sold as a
consumer version) this gives a reflected load of
~86,5 kOhms.

First I tried a simple grounded cathode gain stage
(ECC82/12AU7 both triodes paralleled) with the
transformer primaries in series as plate load,
and then a combination of a ECC82 grounded cathode
gain stage followed by a 6CG7 cathode follower
(both triodes paralleled), with the transformer
primaries in the cathode path.

The results in both cases were - ummm - interesting,
but far from being disappointing. I guess with some
further experimentation the results may even be quite
acceptable, if one does not expect the impossible from
such an unconventional, but simple setup.

Hey, toying around with tubes by try & error & improve
is fun :-)

Tom

--
Knowledge is power - knowledge shared is power lost.
-- A. Crowley

"Tim Williams" wrote in message
...
http://webpages.charter.net/dawill/I...hone%20Amp.gif

Oops... no plural on hfon's. Above link will woik..

Tim

--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms

Tim Williams wrote:

"Tim Williams" wrote in message
...


http://webpages.charter.net/dawill/I...hone%20Amp.gif





I did something similar, see:
http://home.netcom.com/~wa2ise/radio...t6112-8fq7.jpg
and http://home.netcom.com/~wa2ise/radios/tubedac.htm for
the commentary. About 3/4 the way down the page.