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I have modded an B-Tech BT928 Headphone Amp

post #1 of 4
1/26/05 at 8:58am
Thread Starter 
Hi,

I modded this amp yesterday: B-Tech BT928 Headphone thanks to Rockgrotto http://www.rock-grotto.co.uk/B-tech.htm

The upgrades:
1. upgraded the resisters with the metal film type
2. upgraded the capacitors to Panasonic FC and ELNA capacitors
3. Upgraded the Op Amp to a OPA2134PA and added a 8 pin dip socket so i don't have to solder everytime i want to change the Op amp

It took me about 2 hours to do (my first soldering job for about 10 years)

My impressions:

Before the sound was kinda muddy, bass was strong, midrange was good and treble a little soft.

After the mod:

Wow! it sounds amazing. I used a Pair of Sennhieser HD200 and the sound has improved so much. I can hear more instruments than before and sounds seem to decay longer, its weird. Vocals are strong, Bass is awesome. Timely and with lots of oomph! I then tried my Grado SR-80 and things just get even better....the treble is details not harsh, midrange clear and bass is just awesome.

I cannot believe this sounds sooo good. I am shocked myself. The amp cost me £29.99 and the parts cost me £12 from RS. (so i have lots of left over parts too)

Has anyone else modded this amp? How was it for you?

Also, where now? Any ideas what else i could upgrade on this little beauty? I am using the 15v PSU that came with it. Would a better PSU help? Any recommendations?
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post #2 of 4
1/26/05 at 9:08am
Try using a (Ultra) low ESR cap like Panasonic FA, FC or FM instead of the 1000uF Cerafine. It should sound even better. Leave the other Cerafines alone as they're in the signal path and generally perform well there.
Socket the opamp and you can roll it. =) I'd recommend an OPA2227 if you like the current sonic characteristics. Otherwise, you can try the AD8620 instead.
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post #3 of 4
1/26/05 at 9:11am
Thread Starter 
Dreamslacker
Thanks for the advice.

I replaced the 1000uf cap with a Panasonic FC type

I will have a look at other op-amps. At the moment it sounds great, i guess once everything has burnt in, even better.
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post #4 of 4
10/2/05 at 11:07am
Any news with one the alternative op-amps ?

I would like to know how it sounds with AD8620.
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