Headphone amp with 6P41S

[Pentium100]

Could anyone give me a schematic of a OTL headphone amp with one 6P41S as power amp. 6N2P (12AX7), 6N23P (ECC88) could be used in driver stage if needed . 6P41S could be connected in tetrode mode fore more power. I have 32ohm headphones. I know that I could build almost the same with SS transistors or MOSFETs. But I want tu build with tubes as I understand tube circuits better.

Anyone could help me?

Links to datasheets if you need:

6P41S - http://www.russiantubes.com/prop.php?t=12&p=273
6N2P - http://www.russiantubes.com/prop.php?t=12&p=196
6N23P - http://www.russiantubes.com/prop.php?t=12&p=226

6N23P is a clone of ECC88 as far as I know.

 

[Ansius]

u are right about ecc88 = 6n23p also 6n2p is REALY close to 12ax7, except heater pinout. I have used 6n2p in 12ax7 place (remembr to rewire) in may ax84 type guitar amp. sound good. Also 6n1p is really close to 6sn7. whay you wan use that powerful tube for headphones? (by the way it is not as linear as we would like, it is not ment for audio use, but TV). with standart catode fallower you can get min 120ohm resistance. (R_out [Kohm]=1/S [Steepness,mA/V]) The best way I know is to use 6n23p because it wil be way more liniar and give 80ohm. but it is up to you...

 

[Brian Donaldson]

Use one of the small twin triodes as a lont tail pair, and the big one as cathode follower and neg feedback to grid in LTP to reduce impeadance. Maybe choke load the follower to not exceed plate dissapation and still get the power you need.

 

[Pentium100]

u are right about ecc88 = 6n23p also 6n2p is REALY close to 12ax7, except heater pinout. I have used 6n2p in 12ax7 place (remembr to rewire) in may ax84 type guitar amp. sound good. Also 6n1p is really close to 6sn7. whay you wan use that powerful tube for headphones? (by the way it is not as linear as we would like, it is not ment for audio use, but TV). with standart catode fallower you can get min 120ohm resistance. (R_out [Kohm]=1/S [Steepness,mA/V]) The best way I know is to use 6n23p because it wil be way more liniar and give 80ohm. but it is up to you...

I have to learn and learn... I have always thought that if the tube can provide more current then it is more suitable for OTL amplifier. It seems that I was whong.

 

[Ansius]

If tube can provide more curent means its power abilities in optimum load. it is good that tube can source well, even in caode follower - it is important, but the outut resistance more depends on S(mA/V) and negative feadback. Therefore OTL designs use White catode follower, because of its low output resistance. 6n23p is good choice cos it is it can source well (15mA) and it S is 12mA/V so you can get some good power out. also if S is high - it means tube is quet (low hiss) and there for the first stage shouldn't be 12ax7 or 6n2p tube with high mu. the bst russian tube for Headphone amp at low prices is 6n23p. To be honest, I don't belive in OTL designs for tube dinamic headphone (below 200 ohms) amps - you have to drive tube hard to het small power for your headphones . but for the ones like 600 ohm ones it ROCKS. also you cant fing a good studio headphones with resistance below 200 ohms. only studio monitor ones, but with using thees there is no need for tube power amp, just use the input stage preamp, and then have some good MosFet stage. with carefull desig it will sound beter than hard driven tube to get needed power in to 32 ohms. or use output transformers. quality of them wouldn't matter that much cos you use below 1 watt of power, and the smalest ones what you can easy find are 5W ones. you could use even a power transformer (just add the gap) with appropriete ratio (that depends from tube). In this design there is a good and cheap russian tube ir 6f1p (triode + pentode). pentode optimal load is about 15K it gives then ratio 40:1 (110V:2.75V or 220V:5V). those are not that hard to find.