Headphone Amp Build

[bcmatt]

I haven't started it yet or decided much about it yet. I want to see what I have for parts kicking around.
I bought a DAC for my desk stereo setup, But I need a way to drive my 250ohm DT990 headphones as well. It would also be nice to bring some tubes into a preamp situation for my old speakers. I can't afford a proper tube hi-fi build at this point in my life, but a preamp without an OT could be cheap and just what is needed to drive 250ohm headphones as well.

Anybody have some schematics or experience with this?
I'm looking at the Bottlehead Crack....

[Stevem]

With no OT you will need a lot of current pumping out of the output tubes you use for the build!

Maybe in terms of a 9 pin tube running a 12BH7 with its sections wired in parallel for each channel will do it.

Off the top of my head I think with such a set up you could get 5 watts with only some 250 volts on the plate.

For audio sake you would want a really good quality cap to decouple that plate voltage from your head phones!

[neskor]

Here is the schematic for Darkvoice

[neskor]

also please check zip folder for more tube OTL schematic

[bcmatt]

With no OT you will need a lot of current pumping out of the output tubes you use for the build!

Maybe in terms of a 9 pin tube running a 12BH7 with its sections wired in parallel for each channel will do it.

Off the top of my head I think with such a set up you could get 5 watts with only some 250 volts on the plate.

For audio sake you would want a really good quality cap to decouple that plate voltage from your head phones!

I don't know hardly anything yet, but it seems to me that these designs are running much lower plate voltages.... like maybe 125V B+
Honestly, I'm a little overwhelmed so far because this is something I've never looked at before and it's all new. I'm trying to wrap my head around it still, but this guy's overwhelming response to a what looks at first glance to be a very simple design got me really intrigued:
https://youtu.be/vnhjjPsm_Oo

[bcmatt]

Here is the schematic for Darkvoice

Awesome! This may very well be what I try. It seems to be the same idea as that xduo model.
Any idea on the Power Transformer?

[bcmatt]

also please check zip folder for more tube OTL schematic

I've been looking through them this morning trying to make sense of things and get an idea of this OTL world.
I'd totally be open to something with an OT down the road, but the potential low budget of the OTL idea, makes me motivated to try something now.

[TUBEDUDE]

Several designs are out there for the ECC99 as a headphone driver.

[bcmatt]

Several designs are out there for the ECC99 as a headphone driver.

Are yo referring to this one?:
http://www.pmillett.com/images/ECC99_SRPP_1.PDF
The versatility is intriguing, but I'd be looking at over $500 CDN just for the transformers plus shipping and taxes.
Or is it a OTL design you know of?

[bcmatt]

I'm trying to get a picture of an appropriate PT for this sort of build.
This other schematic (in that folder of OTL files) for a darkvoice variant shows +135VDC after the bridge rectifier, and +115VDC on the plate of that 6AS7 tube plates.

схема Dark Voise 336.JPG

[martin manning]

There is Hammond 369AXP, 250VAC CT and 6.3VAC @ 2A, similar in form (potted Hi-Fi type), but it doesn't even have enough heater current for the 6AS7, and anyway it's $300 from Mouser. Next closest is 269AAX, not potted, at 200V CT and 6.3VAC @ 2.5A. Only $84, but still short the 600mA for the 6SN7 heater. You might be better off finding separate plate and heater transformers.

[bcmatt]

There is Hammond 369AXP, 250VAC CT and 6.3VAC @ 2A, similar in form (potted Hi-Fi type), but it doesn't even have enough heater current for the 6AS7, and anyway it's $300 from Mouser. Next closest is 269AAX, not potted, at 200V CT and 6.3VAC @ 2.5A. Only $84, but still short the 600mA for the 6SN7 heater. You might be better off finding separate plate and heater transformers.

Yeah, Someone sent me a link to this, that looks to be the same idea but using a $30 Hammond 183J12 for heaters and a $20 Mean Well APC-35-500 constant current switching power supply (35W 0.5A 70Volt) for the B+:
https://lbhe.de/2023/08/07/kein-kalter-kaffee/

I plan to take a closer look at whether it is what I should try and what I maybe ought to tweak.

[martin manning]

How about Hammond 263AX (200VAC CT, 115 mA and 5V 2A) for the high voltage ($65), and Hammond 167N6 (6.3VAC, 4A) for the heaters ($40)?
Both are 115VAC primary, upright mount, enclosed, and would look nice on a HiFi style chassis.

[bcmatt]

I like how you are thinking... If I'm going to do it, I should probably do it right.
Thanks to the poor Canadian Dollar right now, it's more like $150 CDN. I'll see what else I would need to do it right and make the decision how fancy I want to go.

[neskor]

if you are patient enough you can find nice secondhand Darkvoice for $100-150