New PassDIY Headphone Amp (now available)

[6L6]

I'm 99.5% sure it's oscillating. Change in noise with movement of volume pot is the giveaway.

Try the feedback loop caps, see it it helps.

Other than that, enjoy with the LM4562

I got my Burson V5i today and it sounds TERRIBLE! Turn-on noise, turn-off noise, hum and noise with no source playing. The noise increases with volume until about 1/3 volume then levels off. The ODD thing is that the noise increases faster in the L vs R until 1/3 then L noise drops to match R until about 3/4 volume then R increases until full as I slowly turn the volume up and down.

...

To throw a wrench in it, the amp works FLAWLESSLY with NO noise using an LM4562 with a normal linear volume response as it is turned up and down. I have also tried an Analog Devices op-amp that also behaved fine.

FWIW, I did install the optional stabilization caps on the feedback loop.

... Am I oscillating? ...

 

[nicusim]

I'm interested in 1 board as well.

 

[craigtone]

I'm 99.5% sure it's oscillating. Change in noise with movement of volume pot is the giveaway.

Try the feedback loop caps, see it it helps.

Other than that, enjoy with the LM4562

I already have the feedback loop caps installed ... I'm assuming taking them out would not help. Is everyone that built one to date running the caps and the value in the schematic?

 

[ammel68]

I chalked it up to a bad op-amp but now I am not so sure.

Not likely to be a bad op-amp unless you did something really dumb to damage one of the OPA627s.

Try it in another application to verify if that OPA627 is bad, or not.

Sounds like the Burson may be a no-go in this circuit as well?

 

[meldano]

I build a HPA with the Feedback Caps and part values from Waynes shematic.
No trouble with OPA627,604,134,132, AD8610.
No osc. trouble.

Daniel

 

[wayne]

Boards should be ready end of next week. They will be green with white silk and 2 ounce copper.

 

[6L6]

Great news!

 

[kffern]

Boards should be ready end of next week. They will be green with white silk and 2 ounce copper.

I would like one.
Is there a list i need to put my name on?
Kffern

 

[wayne]

I would like one.
Is there a list i need to put my name on?
Kffern

I will just post when they come in and people can PM me.

 

[gwrskien]

Has anyone bought FQP3`s from Mouser, and know a good number to buy to get some good matches?

 

[wayne]

The MOSFETS don't need to be matched for this project. But the best way to order them is a full tube they seem to come off from adjacent spots on the die.

 

[kevinr]

Thanks Wayne, I'm looking forward to it becoming available.

a noob question , will any 1N4004 Diode be preferable ?
I put that term in for my cart at Digi-key and lots of choices under that category .

Someone kindly created a BOM file many pages back here showing C 3,4,10, and 28, but entering the part number it is a 25 or 35 volt cap .
The pcb layout shows 50 volt for those caps

 

[wayne]

I built it with 220uF/ 50V because we stock them and they fit but anything 25 Volts and above will be safe. Diodes inc is the brand I have and they work fine now also owners of Zetex.

 

[marktd]

What is the procedure for ordering a board?

 

[kevinr]

thanks Wayne ,
any voltage preference for the diodes or is 50volts okay ?

thanks

 

[wayne]

thanks Wayne ,
any voltage preference for the diodes or is 50volts okay ?

thanks

4004 are just fine. Tried fancy diodes and the 4004 seem to give the best results balance wise but fairly subtle. on our power amps the high speed fast recovery work well but on small current draw good old 1N4004 with a snubber cap work very well.

The boards are supposed to arrive early next week. I ordered these myself so if anybody wants one just send me a PM.

 

[Morde]

^PM sent, thank you so much for making this happen!

 

[Russellc]

Yes, I am excited to build this headphone amp!

Russellc

 

[gwrskien]

@ Craigtone did you find/fix the problem? What was it?

 

[craigtone]

@ Craigtone did you find/fix the problem? What was it?

Not yet. I talked with Burson and they said the op-amp is very fast with a lot of bandwidth so they want me to add some 0.1uF MKP films across the supply rails at the op-amp. I'm going to try that tomorrow.