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Cheap hybrid amp for 45ohm headphones?

post #1 of 6
Thread Starter 
I suddenly feel the need to build something involving tubes, so are there any cheap tube/hybrid amps which could drive 45ohm headphones decently? smily_headphones1.gif A hybrid uses an opamp as the output-stage, so the gain could be set pretty low, right? I just can't find any suitable (and simple) design.

Btw. How much amplification does the output of a little usb DAC like the Hifimediy sabre need?

Thanks a lot!
post #2 of 6
Quote:
Originally Posted by UnknownAX View Post

I suddenly feel the need to build something involving tubes, so are there any cheap tube/hybrid amps which could drive 45ohm headphones decently? smily_headphones1.gif A hybrid uses an opamp as the output-stage, so the gain could be set pretty low, right? I just can't find any suitable (and simple) design.

Btw. How much amplification does the output of a little usb DAC like the Hifimediy sabre need?

Thanks a lot!

A hybrid amp is not necessarily a panacea for low-impedance headphones.  Almost every hybrid amp uses the tube(s) for the signal stage (amplification stage).  The buffer (which can be discrete instead of an opamp) is almost without fail, gain-neutral.  However, many tubes have gains in double digits - and those are the low ones.wink.gif  You may find some tubes with amplification factors down in the single digits - 7, 11, etc., but it obviously depends on the tube and circuit applied.

post #3 of 6
Thread Starter 
That's pretty much game over for me, then. I think I need something with a gain of 0-4.
How strong would the output of a "pure" usb DAC be?
post #4 of 6
Quote:
Originally Posted by UnknownAX View Post

How strong would the output of a "pure" usb DAC be?

 

How fast does a bicycle go? 

Its your DAC (I assume) measure it. 

 

In absence of measurements - They are all over the map, but the vast majority will work with just a buffer to drive low to medium impedance headphones.

post #5 of 6

Maybe a Millett minimax? change the output cap to larger size (680uf or larger), and use low-gain tubes. Should drive low ohm phones ok.

 

The minimax kits are pretty spendy but somehow completed amps are cheaper (have seen a few went for around $150 in the for-sale section lately, that was with tubes included). Not really a build, but modding is fun as well and the minimax is a proven design.

post #6 of 6
Thread Starter 
Well, I haven't bought the DAC yet so I can't measure it. I hope I can use it with a buffer, though.
Anyways, I have realized that tube amps aren't really ideal for me because I want all the opposite characteristics of a tube amp.(clear sound, low gain, low impedance headphones)...

Still thanks a lot for your recommendations!
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