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Why Not An DHT SET amp?

post #1 of 6
Thread Starter 

Hello,

 

I am new to Head-Fi (2 weeks and counting) so forgive me if my question is not appropriate in this forum.

 

I am trying to understand as to why a typical SET audio amp cannot be use to power headphones as I have not read people using one.  For example, I see headphone amps with max power of 1.5W, transformer coupled.  If I use a preamp and an SET amp AC or DC heated with volume control also(say 71A at 750mW or a 45 at 1.5 W max output), why can't I use it as a headphone amp?  Let say if I use an auto former to make 4/8/16 ohms output of the amp to 30 ohms for example, will it work?  If the headphone is say an LCD-2 at 91dB/mW, 133dB at 15W, why can't it work?

 

Thank you very much for your inputs!

 

regards,

Abe

post #2 of 6
Thread Starter 

Any takers? ;)

post #3 of 6
Quote:
Originally Posted by amandarae View Post

Hello,

 

I am new to Head-Fi (2 weeks and counting) so forgive me if my question is not appropriate in this forum.

 

I am trying to understand as to why a typical SET audio amp cannot be use to power headphones as I have not read people using one.  For example, I see headphone amps with max power of 1.5W, transformer coupled.  If I use a preamp and an SET amp AC or DC heated with volume control also(say 71A at 750mW or a 45 at 1.5 W max output), why can't I use it as a headphone amp?  Let say if I use an auto former to make 4/8/16 ohms output of the amp to 30 ohms for example, will it work?  If the headphone is say an LCD-2 at 91dB/mW, 133dB at 15W, why can't it work?

 

Thank you very much for your inputs!

 

regards,

Abe

You can use direct heated triodes but the filament/cathode has to be run on DC or there will be to much hum. My headphone

amp is a 2A3 my preamp is a #26 of course all DC heated that is somewhat of a PITA but the SQ is worth it.

post #4 of 6
Thread Starter 
Quote:
Originally Posted by 2359glenn View Post

You can use direct heated triodes but the filament/cathode has to be run on DC or there will be to much hum. My headphone

amp is a 2A3 my preamp is a #26 of course all DC heated that is somewhat of a PITA but the SQ is worth it.

Thank you for your response!  A few more questions if you do not mind.

 

1.)  Is your amp PSU on a different chassis(with umbilical cord)?

2.)  What about the output transformer, do you use the 16 ohm taps on your amp or you have a custom one where in you have a higher output taps than 16 ohms and then connect a headphone out where their ground(0 taps) are common?

 

I am gathering parts to build a 45 amp (Tubelab circuit) which use DC heaters.  I already built the Simple SE from the same designer and it is very quiet.  The 45 should give me about 1.5 ~ 2W and should be plenty

 

Again, thank you very much for the response.

 

 

Abe

Abe

post #5 of 6

There are several commercial makers of headphone amps with DHT outputs. Eddie Current, Woo, and Donald North spring to mind, and there are probably others. However, most of the DHT activity is DIY. A search of the DIY forum would be a good place to start.

 

I drive an LCD-2 with a DIY 56/46 transformer coupled amp. I like the DHT/ortho combination a lot.

 

I use Electra-Print 7k:32 output transformers, but small 16 ohm speaker transformers would also work.

 

Separate power supplies are usually an advantage, but plenty of good DHT headphone amps have been built on a single chassis.

post #6 of 6
Thread Starter 
Quote:
Originally Posted by FrankCooter View Post

There are several commercial makers of headphone amps with DHT outputs. Eddie Current, Woo, and Donald North spring to mind, and there are probably others. However, most of the DHT activity is DIY. A search of the DIY forum would be a good place to start.

 

I drive an LCD-2 with a DIY 56/46 transformer coupled amp. I like the DHT/ortho combination a lot.

 

I use Electra-Print 7k:32 output transformers, but small 16 ohm speaker transformers would also work.

 

Separate power supplies are usually an advantage, but plenty of good DHT headphone amps have been built on a single chassis.

Thank you!  That helped a lot.  Umbilical cord it is.

 

Abe

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