Thank you ammel68 !
Do you sell the servo pcb and parts as a kit ? or do you have a BOM ?
Will order the transformer
Hey Ricren, the schematic of the dc servo is here (schematic, left down corner).
Source (rockgrotto proboards com): "JHL" headphone amp | Rock Grotto
Thanks a lot, Schiller.
The LT1169 is 8 dolars in Digikey ( almost half the price of the kit!) and difficult to get here. Could it be replaced with another, easier to get OP AMP?
The LT1169 is 8 dolars in Digikey ( almost half the price of the kit!) and difficult to get here. Could it be replaced with another, easier to get OP AMP?
Thanks Patrick, those OPAMS are easy to get, a have a few.
Any suggestion on how to modify the circuit ( increase filtering?) to reduce noise. I guess there's a trade off between capacitance and response time. But the difference is "that" audible?
Any suggestion on how to modify the circuit ( increase filtering?) to reduce noise. I guess there's a trade off between capacitance and response time. But the difference is "that" audible?
Of course that was not what i was asking. In case it was not clear, looking to modify the circuit to reduce the incidence of the opamp noise.
Yesterday I built the servo. I use a OPA2134PA. In Europe, available for 2,89 Euro (Conrad Electronic SE).
Start // DC_Offset: +38 mV
after 10 sec. // DC_Offset:. +0,02 mV
after 30 sec. // DC_Offset: +0,45 mV
after 1 min. // DC_Offset: +0,7 mV
after 10 min. // DC_Offset: +1 mV
after 12 min. // DC_Offset: +1,1 mV
after 30 min. // DC_Offset: +1,09 mV
after 50 min. // DC_Offset: +1,5 mV
after 60 min. // DC_Offset: +1,1 mV
That looks good. 🙂
A sound test still follows.
Regards
Schiller72
An externally hosted image should be here but it was not working when we last tested it.
Start // DC_Offset: +38 mV
after 10 sec. // DC_Offset:. +0,02 mV
after 30 sec. // DC_Offset: +0,45 mV
after 1 min. // DC_Offset: +0,7 mV
after 10 min. // DC_Offset: +1 mV
after 12 min. // DC_Offset: +1,1 mV
after 30 min. // DC_Offset: +1,09 mV
after 50 min. // DC_Offset: +1,5 mV
after 60 min. // DC_Offset: +1,1 mV
That looks good. 🙂
A sound test still follows.
Regards
Schiller72
Main signal is 1 kHz. The 50Hz is -80 dB:
Intermodulation distortion test: Two signals: 50 Hz and 1 kHz:
The intrusion of mains and mains harmonics is terrible.
I'm pretty sure you have a wiring error.
I'm pretty sure you have a wiring error.
Measurement setups involving looping a signal over an external amp with all unbalanced connections have this tendency of picking up mains hum due to the inherent ground loop. The amp on its own may be just fine, best confirmed by listening with sensitive headphones.
hi Alex74, if You have laptop with working battery power,use rmaa on pc as playback and on laptop as recording, You will get lot better results ,what interface is used for recording?
few people use emu0202 interface on my local forum with very good results but they use separate signal generator or laptop. i used behringer uca202 and creative usb card with ok results, but only when one was on battery powered laptop to cut ground loop.