New PassDIY Headphone Amp (now available)

[Frazzled]

WOO HOO just purchased 2.
Thank you!

 

[wayne]

Thanks 6L6 for all your work on this. My gets used quite often.

 

[osscar]

Osscar - Wonderful! A beautiful construction!

Looking forward to hearing news of it's operation. Post more photos if you have them

Whammy is finally finished!
I turned to the dark side (with a blue LED of course):

internal part( There was a small hum on the left channel from the transformer - I made a mu-metal shield)

sounds very good, the bottom end is very fast!
Bias 100mA, Irfs, BB OPA 2604 (original), all 22uf non-polar+film caps.Rails: +-17V. heat sinks - 55 Celsius. offset - 1mV and 0,1mV

 

[6L6]

Beautiful! Thanks for the photos!

 

[osscar]

Thank you and others who are involved and made this project available to everyone.
I like the optocoupler bias circuit - no adjustments, it works from the first start !

 

[WalterW]

Wow! Nice work Osscar. Nice PCB's and chassis.

 

[osscar]

thank you, they are not as perfect as industrially produced, but it's DIY after all. (I decided at last to put parallel resistors in PSU CRC to reduce dissipation ..resistors are not parallel in - there was no pads for that )

 

[pelayostyle]

In the planning stages for this build and I really want to use an AD8620 I have laying around. Specs show max dual-supply voltage at 13V. It looks like its R35 and R36 need to be changed to drop the voltage a bit but not sure what values to try. Can anyone help? Thanks!

 

[wayne]

You could use a 15 volt transformer and 12 Volt regulators.
If you use 15 Volt regulators the resistors would need to be about 330 Ohms and I don't know if that is the best idea.

 

[nzlowie]

I've been looking for a really nice sound ding low power amp to drive my horn's, could I use something like this or would this struggle to drive 8 ohms?

Thanks

 

[wayne]

I can try running it into eight Ohms and see what happens. The bias is a bit low for class A into eight.

 

[alwineden]

I've been looking for a really nice sound ding low power amp to drive my horn's, could I use something like this or would this struggle to drive 8 ohms?

Thanks

I'm currently using 2.2R source resistors to drive 8R speakers and it works fine. Loading the schematic into Spice suggests 4R speakers will be poor unless you double up on the Fets.



TM

 

[wayne]

I tried it into 8 Ohms and the distortion goes up to about .15% at a couple of Watts. The harmonics are pretty high but it does work. Very efficient speakers recommended and like above smaller source resistors are better.

 

[Zen Mod]

I tried it .....

 

[alwineden]

Look, a clown.


TM

 

[mod_sonic]

Transformer Snubber C20

Hi 6L6,

Can you please point me to a suitable transformer snubber, C20 ? I am not sure what I am looking for, and there's no Mouser or other code in the BOM.

Thanks

Mark

 

[6L6]

Sure!

Kemet R46KN322000M1M


R46KN322000M1M KEMET | Mouser

 

[mod_sonic]

C20 and the Pot

6L6,

'Faster than a speeding bullet....' Thanks for a quick response on C20.

What can you tell me about the Pot value please. The schematic says 20-100K which is the first time I have ever seen a value range. Can you offer any guidance please ?

Thanks

Mark

 

[6L6]

Good potentiometers are getting progressively more difficult to source as all things march further and further towards becoming digital. And some people want to use stepped attenuators instead of pots. So our choice is somewhat limited.

The long story made short is that the value is not super critical, however if much lower than 20K the input impedance can get hard for some sources to drive, and if higher than 100K there can be interesting interactions with input capacitance. In either case, falling outside the range might make it difficult for your sources to drive.

 

[Zen Mod]

conclusion - just go with 600R attenuators

sources unable to drive that are for Sissies