Help looking for amp design using OPA627 & BUF634

[pho_boi]

Hello,

I tried searching the forums for a headphone amp design using the OPA627 and the BUF634. I have a few of these lieing around and just thought it would be a waste of money if there not be used.

Would it also be possible to build a MINT but using 2x OPA627 instead of a dual opamp?

Thanks.

 

[Nisbeth]

Google the datasheet for the BUF634 and look up figure 5 on page 9. For headphones, you should modify the 5k gain resistor to something like 1k (for a gain of 5)

/U.

 

[Francis_Vaughan]

Um, how about a Pimeta?

http://tangentsoft.net/audio/pimeta/

Seems to be tailor made for your residual components - so long as "few" means at least three. Otherwise a Mint is fine, you need an adaptor board, the Browdog 021001, which Tangent also sells, to mount two single op-amps in a dual design.

 

[evo_lution]

Try this:i built it and it sounds good, better than my Millet.

 

[~n00beR]

I did some work a while ago on a OPA627 and BUF634 design.

Looks the same as the above schematic.

It was primarily designed to be a preamp, but i know of one person who has used it as a headphone amp and enjoyed the sound.

It was heavily discussed over at diyaudio.com in this there is around 80+ pages of discussion, but not only of my board but others too.
There is plenty in there to give you ideas, and do a search for "opa627 buf634" and you will find plenty of other discussions, some relevant and some not.
Those who have read thru the topics will know what I mean.

Hope this helps you with ideas, or direction.

Cheers

n00beR

 

[1UP]

Here's one, pcbs available - description speaks of adjusting gain to drive headphones:

http://www.pha.inecnet.cz/macura/buffer_en.html

 

[~n00beR]

Quote:

Originally Posted by 1UP Here's one, pcbs available - description speaks of adjusting gain to drive headphones: http://www.pha.inecnet.cz/macura/buffer_en.html

The diesign in the above post is the schematic my design is based on.

If you look the gain is set at 1. as this design was used for a line driver.
I presume it was used for driving LONG lengths of cable.

My design is not disimilar, the ground channel is seperated from the ground plane , there is a noise reducing resistor on the output, has an option for a class a diode/resistor. There is pads on the pcb to join the ground channels together if this is so desired.

The design is single sided so i ran into a couple of problems witht the ground plane, therefor i added a jumper on the +V line to over come this.



As I have recently completed a couple of SMD projects, I feel i may look at this design again, and go double sided and look and using some or all smd.

thanks for the motivation, lol

n00ber

 

[pho_boi]

Quote:

Originally Posted by evo_lution Try this:i built it and it sounds good, better than my Millet.

I'm starting to build this design, and I was wondering what kind of caps I should be using, eg. the 100uf, 100nf and the 200pf.

Thanks

 

[evo_lution]

Quote:

Originally Posted by pho_boi I'm starting to build this design, and I was wondering what kind of caps I should be using, eg. the 100uf, 100nf and the 200pf. Thanks

Hi pho_boi,

Built mine using Elna Duorex caps and good quality polyprops(Wima), you may get better results from Cerafines, but any low ESR cap should be ok.
If you are gonna build this and not tweak, ie rolling op-amps, there may be a small performance increase from leaving out the sockets.
The PSU should be a trafo regulated for +15V/-15V for best results, but i used a wall-wart with a bit of filtering etc and it still sounds good.
Also its imperative the caps are as close to the op-amps as poss.

HTH
evo_lution

 

[~n00beR]

Quote:

Originally Posted by evo_lution Hi pho_boi, Built mine using Elna Duorex caps and good quality polyprops(Wima), you may get better results from Cerafines, but any low ESR cap should be ok. If you are gonna build this and not tweak, ie rolling op-amps, there may be a small performance increase from leaving out the sockets. The PSU should be a trafo regulated for +15V/-15V for best results, but i used a wall-wart with a bit of filtering etc and it still sounds good. Also its imperative the caps are as close to the op-amps as poss. HTH evo_lution

Hi there again.

I agree if you use the DIP8 version of the buf634 then +/-15V is going to be optimum and soemwhat the upper limit due to heat dissapation.
However my design uses the TO220 package, and with the aid of a heatsink, I belive the optimum voltage to be +/-18V for that little extra drive

n00beR