audio-talk

Or even EL38

Here’s the latest headphone amp:
IMG_0617.jpeg
The output valves are driven by Brimar 6BR7 small-signal pentodes, which are a steal at £8 each from Langrex.
Screen voltage is set at 107V by an 0B2 set up as a shunt regulator. Rectification is by EZ81 and a Black Gate 2x220uF can cap is used in ...

Sad to read that veteran jazz funker and vibist, Roy Ayers has died aged 84.
https://www.theguardian.com/music/2025/ ... shine-dies

Several days ago, I went to a single 1626 per channel. The gain is reasonable for headphones, but could do with a slight boost.
I must say, I've been messing about with different headphone amps so much, that I'd forgotten how fecking superb these little transmitter triodes actually sound.

Pros ...

OK, so I've made up a chassis for a 45 headphone amp. I'm not going to make a new thread until I'm sure that's what I want to do.
I have the Rod Coleman V2.0 regs courtesy of Simon, but I need to try to work out how I am going to get 3 DC supplies inside the chassis with enough room for heatsinking ...

Last Friday I pulled the trigger on an AppleTV 4K streamer.
Unlike my old AppleTV HD, it'll stream lossless ALAC from the Apple Music app.
The sound is much improved over the 2016 HD model, regardless of the streaming quality, and the interface is about 50 times faster than my old AppleTV. Not bad ...

Paul Barker wrote: Sat Feb 08, 2025 6:53 am
…Might be nice to try fixed bias though.

Where the bloody hell I’d put a bias supply in there is the elephant in the room I’m afraid.

Beefed up the heatsink on the heater reg. The sink runs a bit cooler.

Everything squoze in Pin 1 needs strapping to pin 8 to use EL34s. I haven't got 'round to that yet. Just keeping an eye on the heat being put out by the reg before I go any further. It's not too bad after an hour. About 60 deg C

OK,
I changed the resistor on the reg board and using a couple of KT77, which have 1.4A heaters, they came up nicely to 6.3V after a bit of twiddling of the variable pot that sets the current through the reg.
In triode mode the KT77 has a mu of 11.5. This has given a useful boost to the gain, so ...

Hi Paul,
There’s no room in the case for EL34s. I did try a couple by loosening the bracket so they could be lashed up. Unfortunately the Rob Coleman regulator proved not to be set up for the heater current demanded by a pair of EL34 (3A) and it simply sulked when the amp was fired up with them in ...

I have a couple more octal sockets, so I'll make up a module using triode No2 in the 6DN7 over the weekend, slot that in and see how it sounds.

simon wrote: Thu Feb 06, 2025 1:12 pm I've got a couple of 6DN7s if you want to swap them for the 6EM7s Steve

Hi Simon
You loaned me both types.

I think the only problem for a headphone amp with the 6EM7 is the amplification factor of 5.4 on the low mu triode.
You'd be back to 2 stages with that.
OTOH the amplification factor of the low mu triode in the 6DN7 is 15.4. The gain will be knocked down a bit by the loadline so that might work ...

Cheers Paul.