B-Tech BT928 Headphone Amp

[Southall-1998]

Thinking about getting one for my bedroom.

Sorry for the rather foolish question. Will this amp have sufficient enough power, to drive 300 ohm Sennheiser HD600?

Thanks.

S.

 

[solderdude]

Max output voltage will be around 4.5V which is loud enough. The small value output capacitors (47uF) and 47 Ohm output R makes it really only suitable for high impedance, >250 Ohm, headphones which the HD600 is. Not really suited for low impedance headphones.
It does not have an on-off switch.

Expect the treble to be rolled-off even in the 'max treble' setting. (this is no 'common' +/- tone control)
You can actually make it 'flat' by removing the 2 capacitors in the red oval (marked 472) and by lowering the (enormous) gain.
This can be done by soldering 2 resistors (33kOhm) in parallel to the resistors in the blue rectangles.
You don't even have to remove the PCB for this. Just cut away the capacitors and solder the resistors on top of the ones already in there.

The amp can be modified so it can handle a larger range of headphones.
Those wanting to know can ask and I will explain. Requires removing the PCB.

 

[Bob-23]

Without severe reconstruction this amp is absolute BS. I saw it a year ago for 5 Euros at he local conrad store as a return good, and as I was in he mood for repairing, I picked it up. There was only a slight loose contact in one of the headphones' out which could easily be resoldered, and the amp was 'OK' again - if it were not such a misconstruction. The tone control is absolute rubbish: dull and muffled, I removed it and added a turn-on/off switch instead. The output capacitor is too low, as already solderdude pointed out. The vol pot is of the lowest quality, never have seen such imbalances, has to be exchanged, too. The 10 uf electro in the input is suboptimal, i put wima film caps there, instead. Added a larger filter cap, the power supply that comes with it is bad. Etc. Having done all the mods, you can use it. But I would strongly recommend looking for another amp. There's only one positive aspect of this 'B'(indeed)-Tech: the case is not bad.

 

[Bob-23]

If you've got a soldering iron there's also the possibility of getting an O2-kit:
http://www.headnhifi.com/diy-kits
(Expect ~10 Euro shipping costs).
Or get only the pcb (5,80 Euro) - it's a good quality! - and construct the rest as you like.
(The kit is quite easy to solder, though not necessarily an absolute beginner's project, a little bit of experience is useful.)

With regard to the B-Tech: These traditional amps can easily be reconstructed (no more possible today). So, if you've already got the amp - it can be made sounding acceptable, and solderdude offered you help how to do that. In addition to what solderdude proposed - and, yes, gain definitely has to be reduced - I would remove the tone control.