New PassDIY Headphone Amp (now available)

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Jump to Latest
A

AndrewT

R.I.P.
Joined 2004
Gregje said:
.............The final question: I have -17mV offset on both channels. Regardless of the opamp. My supply is not exactly symmetric but I guess you cannot expect perfect symmetry with 7915/7815, can you? .......................
Click to expand...
An opamp does not mind whether the supply polarities are identical.
The only thing unequal supply rails affects is the early onset of clipping in one direction of the output.
 
G

Gregje

Member
Joined 2009
I have tried LM833 as suggested by 6L6. Indeed, it is very nice, not too bright, not too dark. Just about right amount of everything. The only problem I had with it was that the offset went to +22mV (so it is opamp dependent as it should be!). I am reluctant to run it for longer with such an offset though everything tells me that the heat in the coils of my Senn HD595 (50Ohm) is very very low... BTW found another OPA2134 in the drawer. Now I have +2mV and +5mV offset which is great! The only thing is that I am not sure whether OPA2134 is my favourite... Opamp rolling, very exciting!!!
 
A

alwineden

Member
Joined 2014
Nice Design. I made my own circuit boards which isolated the input circuit from the output. Drives my Fostex t20rp's beautifully. In the end I tested and compared the op-amp input with tubes. While they sounded virtually 'the same', I elected to use tubes. Russian 6j1p ev trioded has low gain and sounds superb with a small amount of feedback - just enough to linearize, Long story short everything fits into a small wooden antique tool caddy and I love it. I'm using 5r bias and driving a set of small 8r speakers ATM and it sounds superb! amazing bass response and 1.5w is enough for near field in my sailboats dodger. I only have 70v on the plates but still simulates well enough. The amp is totally hum free as far as I can tell and really sounds like a much more powerful unit - very dynamic. Working on a more powerful version with opto-bias and three pairs of fets!
>
BnHgMH2.jpg

>

WKhMCvu.jpg

Led biasing was replaced with resistors + caps.
TM
 
Last edited:
K

kalinowski

Member
Joined 2008
student.agh.edu.pl/mkali/
Just fired her up for the first time! The boards from Nisbeth call for a single opamp but I had only doubles - nothing a couple of jumpers and some IC legs cutting couldn't solve ;)

Now, the amp is dead quiet with inputs shorted to ground, but when I connect it to my laptop I hear a familiar mains hum. Did I mess up the grounding?

EDIT: uploaded a higher res photo
 

Attachments

  • IMG_2208.jpg
    IMG_2208.jpg
    705.8 KB · Views: 710
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Top Bottom