The all DHT SET Headphone Amp

[Rod Coleman]

Could be a tap, though I should say that having its own trafo is not overdoing it! Even with CCS loading, the silence of the power supply is of top importance.

Shunt regulator is good value in a stage that only draws 7mA - the overall regulator dissipation can be modest.

[mogliaa]

I found 3A5 not that linear when swinging lots of voltages, good for low level signals though.
How many volts are you looking the 3A5 to swing?
Ale

[Pano]

The 4P1L has a gain of about 10 in my output stage, so take that as a starting point.

[mogliaa]

You can try it yourself. Here is the spice model I created for the pair of 3A5 triodes in parallel:

http://www.bartola.co.uk/valves/2013...dht-continued/

Don't want to be the bearer of bad news, but 3A5 is better suited for low signal (e.g. Preamps, etc.)

Ale

[iko]

I'm in agreement with Ale on this one. I've considered 3A5 for a long time for input duty, and it's excellent as long as you don't feed it too much swing. Plus, I don't see anything wrong with driving the 4P1L output with a triode connected 4P1L. Should work for most headphones at volumes that your ears will be sore. Different story for a power amp. Pano, which headphones exactly are you planning to use?

[45]

Originally Posted by mogliaa

I found 3A5 not that linear when swinging lots of voltages, good for low level signals though.
How many volts are you looking the 3A5 to swing?
Ale

Used as input in a 3 stage amp should be fine otherwise I tried to say this implicitly some posts ago talking about the ECC40.

[andyjevans]

The 3a5 is a very decent sounding DHT but not a great one. Another similar mu one is the 1J6 - it has a fuller and meatier sound. The sections are not usually too well balanced, however. It can sound good. But not in the class of the 26 and 4P1L to my ears. I've used all these.

[jpak]

Originally Posted by ikoflexer

Two stages, both with 4P1L would be just fine IMHO.

Pano says it has a gain of 10. IMO that is quite high for the very efficient Sennheisers. For reference I have a Beta22 here with voltage gain of 6, and with my 2vrms output DAC I am rarely past 10 o'clock on the volume.

I'm using Pete Millet's calculator to gauge output levels. It doesn't seem like I will need more than 300 mw of output, I'm trying to keep the transformers as small as possible and considering using custom wound Electra-Print or Sowter.

[Pano]

Originally Posted by ikoflexer

dphones at volumes that your ears will be sore. Different story for a power amp. Pano, which headphones exactly are you planning to use?

Sennheiser HD580. Nominally 300 ohms. I can drive them to quite satisfactory levels with a 25:1 OPT terminated with 8 ohms and the headphones. They won't knock your ears off, but for most materials it's plenty loud.

Some of my lower impedance cans, like JVC, don't get as loud at the same setting.

[iko]

And you want higher gain so that you can use your existing transformer into an 8R load?