Pass Headphone Amp

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dejanm

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Joined 2005
When Nelson Pass is going to make a headphone amp, either under the Pass Labs brand name or as the First Watt unit ?

I believe that there is a market for a such product and we haven't seen here many DIY works either. I can recall only one guy did an adaptation of Aleph circuit to make a headphone amp ...
 
qusp

qusp

Member
Joined 2009
I would have thought that a pass headphone amp would need carefully chosen headphones to work to satisfaction due to lower damping factor than most pure headphone amps. ive toyed with the idea myself on many occasions and figured the F4 for a good candidate
 
qusp

qusp

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Joined 2009
hmm not quite sure i'm with you jacco; i'm aware its an interaction between the 2, thus the need for carefully chosen headphone impedance to meet the higher than normal output impedance of an aleph headphone amp. myself i'm not even that convinced its a factor with most headphones, given a low enough outputZ and taking into account sufficiently electro-mechanically damped headphone construction, but last time i said that i got shot down. most references i have seen refer to grados

ahh i see where i created confusion, with the word 'factor' my apologies.
 
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6L6

6L6

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Joined 2010
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Damping Factor is the speaker's impedance divided by the amp output impedance. (Just like Jacco said)

Looking at the Firstwatt website, the Aleph J (The closest thing to a 'normal' Aleph) has an output impedance of 0.4ohm.

So that amp has a damping factor of 20 into an 8ohm load 8/.4=20

Into the low impedance Grado (32ohm) headphones it would have a Damping Factor of 80 32/.4=80

Into a 320 ohm headphone the DF would be a very good 800!
 
qusp

qusp

Member
Joined 2009
well actually i have to admit thats lower Z than i was expecting. the other pass inspired headphone amps i have seen however have not been that low. last time this came up, grados (i'm not a fan so cant really speak from experience with them) should be compared to lowthers and prefer current source 'amps' so in this case it would be said the output impedance is too low... its a complex conundrum and it seems everyone has an opinion

also headphone impedance is getting lower and lower, mine are under 10ohms at low frequencies. but i also have some 300r hd600
 
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qusp

qusp

Member
Joined 2009
fair enough, circular conversation really.

some swear the effect is profound with headphones, me i cant say ive ever had a problem with an amp i could attribute to it, so i cant say whether i have an opinion one way or the other. iam interested in the various viewpoints on the subject though, they are many and varied

K1000 jacco? nice one! bass heavy or bass light?
 
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qusp

qusp

Member
Joined 2009
EUVL's DAO? thats more of an evolution of ideas and concepts pulled from many sources (Erno for sure) isnt it rather than pass specifically?

its in there though on that page you linked. i found that in my travels a while ago too, some good stuff.
 
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dejanm

Member
Joined 2005
I found excellent article written by Mr. Pass about BA3 relatively late. It seemed to me that BA3 gain section is exactly what is needed for a good headphone amp. So I had to give it a try ...

I implemented it exactly as it is stated in the article:

http://www.diyaudio.com/forums/diyaudio-com-articles/194809-burning-amplifier-ba-3-a.html

I only removed the input and output resistors, succedded in getting low DC offset at the output and ... it works just fine with my Grados (32 Ohm) and AKG (60 Ohm). It has enough drive and the sound is OK.

DSC06951.jpg


I will go for it and try to build a preamp and headphone amp in the same enclosure, which will use the same pot.
 
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