PMA, can the circuit be biased to drive 50 mW class-A (1.225 V RMS, 58 mA peak) into 30 Ohms with very low distortion ?
Thank you,
J.
Thank you,
J.
Hi Jen,
yes, it is possible even with standard idle current setup (40mA), that is class A up to 80mA.
I have just measured distortion into 75ohm at 1Vrms, and it is below 0.001% both THD and CCIF IMD 19+20kHz (with JFET's with Idss = 8.5mA matched within several 0.1mA). No high harmonics visible (re my measurement resolution)
I have also added technical parameters to Dispre 2 -
Best regards,
yes, it is possible even with standard idle current setup (40mA), that is class A up to 80mA.
I have just measured distortion into 75ohm at 1Vrms, and it is below 0.001% both THD and CCIF IMD 19+20kHz (with JFET's with Idss = 8.5mA matched within several 0.1mA). No high harmonics visible (re my measurement resolution)
I have also added technical parameters to Dispre 2 -
Best regards,
Last edited:
I am preparing a fully balanced version of this preamplifier. It will have true balanced inputs and true balanced outputs. Quad Alps as a volume control. The prototype PCB is already being produced.
Hi PMA,
A balanced version is a nice idea, but... that balanced Alps may be a problem for you...
I've measured several two-channel Alps RK27 and the mismatch at low rotation (approx. 0 - 30°) was relatively poor, and if that error is repeated in a balanced configuration that might be a significant problem.
I think in balanced configuration you may need to consider a stepped attenuator?
A balanced version is a nice idea, but... that balanced Alps may be a problem for you...
I've measured several two-channel Alps RK27 and the mismatch at low rotation (approx. 0 - 30°) was relatively poor, and if that error is repeated in a balanced configuration that might be a significant problem.
I think in balanced configuration you may need to consider a stepped attenuator?
The boards are sold out at the moment, but I will order new production on Monday 12th and the boards should be produced on 26th July.
Sorry for later answers to all who have also contacted me by e-mail, I have just returned from my holiday trip.
Regards,
Sorry for later answers to all who have also contacted me by e-mail, I have just returned from my holiday trip.
Regards,
It is possible to connect an unbalanced sourced, but you would get an unbalanced output then (hot, ground).
Yes you are right, the relay or stepped attenuator would be more precise, but you can certainly connect it by wires into the pads of the quad Alps position.
Regards,
Hi Mike,
boards for single ended version are in stock or being produced when stock is empty.
Sale of boards for balanced, symmetrical version has not started yet.
Regards,
boards for single ended version are in stock or being produced when stock is empty.
Sale of boards for balanced, symmetrical version has not started yet.
Regards,
Finalized components and values
PMA have you finalized all the components and values for the single ended version yet? I have not seen you post them in this thread. Maybe I just missed it!
Don S
PMA have you finalized all the components and values for the single ended version yet? I have not seen you post them in this thread. Maybe I just missed it!
Don S
No, you have not missed it. The documentation is not free, it is sold with PCBs as a kit. More in
http://www.diyaudio.com/forums/vendors-bazaar/166049-dispre-ii-pcbs-available-2.html#post2186715
http://www.diyaudio.com/forums/vendors-bazaar/166049-dispre-ii-pcbs-available-2.html#post2186715
I am definitely interested in the balanced version. when do you expect to have PCB finished? will it drive 28 ohms headphone load balanced? or do I need to add a buffer? this is excellent as I just ordered a heap of LSK170 and LSK389. I ordered at 8ma, is this suitable for all positions, or should I get some other idss values too?
build will not be reasonably priced for me as I do not use analogue pot, this will be tacked onto a dac with digital volume. I will have my DCB1 buffer in external box for driving cables to active monitors.
build will not be reasonably priced for me as I do not use analogue pot, this will be tacked onto a dac with digital volume. I will have my DCB1 buffer in external box for driving cables to active monitors.
Last edited:
I meant to say board will be VERY reasonably priced for me above, there is an errant 'not' there
Hello qusp,
that's it. Till now, just one complete symmetrical preamp was built, on a special purchase order. That means, the PCB was very, very expensive. Untill there is not a production of at least small series, the price is not reasonable.
Regards,
that's it. Till now, just one complete symmetrical preamp was built, on a special purchase order. That means, the PCB was very, very expensive. Untill there is not a production of at least small series, the price is not reasonable.
Regards,
Hi Pavel, ahh I see, so there was not enough interest in the balanced version? I guess I would just have to build 2 boards, but I much prefer actual balanced operation to the brute force dual mono, cheaper to build too. I guess I will wait and see. I am getting some other PCBs made for myself, would you consider a one off sale of a gerber to put in the panel with them for single personal use? I am getting some small reg PCBs done (just one board panelized) I would just get a couple of them, but need to fill the panel with something so could place one copy of the dispre on the board.
an unusual request I know, I totally understand if you would rather not. in which case I will wait in the wings for a while and see what happens
an unusual request I know, I totally understand if you would rather not. in which case I will wait in the wings for a while and see what happens
Last edited:
I would also be interested in a balanced board, though I might just build the SE version while waiting.