I'll have more on this below soon.
https://www.diyaudio.com/community/...s-input-nos-r-2r.354078/page-377#post-7497646
I notice quite some similary between circuit and PCB
So far, I have listened to a couple of CDs and it doesn't sound bad, quite deep bass with a lot of detail in the highs, nothing blurry, quite correct. The output voltage is 6.2Vp-p on a 10k load.
I still need to play a little with the operating points and the selection of transistors to see what this simple IV can do. This BJT IV is not yet close to the AD811 but who says it can't be so it will stay in my DAC for a while, at least until I make all the modifications.
Otherwise, I would recommend this BJT IV stage to anyone who doesn't want to invest in expensive op amps, tubes and transformers, it is capable of directly driving the output stage and it is sound correct and neutral.
I still need to play a little with the operating points and the selection of transistors to see what this simple IV can do. This BJT IV is not yet close to the AD811 but who says it can't be so it will stay in my DAC for a while, at least until I make all the modifications.
Otherwise, I would recommend this BJT IV stage to anyone who doesn't want to invest in expensive op amps, tubes and transformers, it is capable of directly driving the output stage and it is sound correct and neutral.
I am currently thinking about a completely new DAC with two PCM1794 and four AD811 for IV. I don't think that the AD811 will stay in that DAC forever, because I intend to go for a completely discrete IV (current conveyor) but much more complicated than what I presented today.
The show always goes on
Temperature of output transistors.
The show always goes on
Temperature of output transistors.
Attachments
1655/56 are really hard to beat. I am constantly torn between it and my transformer coupling. In dynamics, resolution, spacial representation the opamp has the upper hand. Natural timbre, fluidity go to the transformer. I have yet to try the suggest decoupling with 10uf Silmic II paralleled with 10uf X7R on the opa 1656.
Times are changing ten years ago I did not accept any opam in my chain.
Greets Klaus
Last weekend I made some small changes. Outputs are now 2SA1209/2SC2911 with slightly changed operating points. The current through each IV stage is now +/-40mA.
And the sound? Excellent considering that it has only 6 transistors that still work at slightly higher currents. Much much better than the first version. I hope that there will be further progress, however now comes the more difficult task which is to find output transistors(low cob, high ft, with good hfe) that are easily available at Mouser.
And the sound? Excellent considering that it has only 6 transistors that still work at slightly higher currents. Much much better than the first version. I hope that there will be further progress, however now comes the more difficult task which is to find output transistors(low cob, high ft, with good hfe) that are easily available at Mouser.
Attachments
Often it is about compensation. It sounds good in his whole setup but not sure it is for you. That must be tested to know.
As the 1655/56 . In my setup it sounded good but boring (ad1862 with dac board Miro V3) , after some dozen of work a good combination did work fine in my setup as a soundingresult with some old droptear red MKT or MKP (they are 80s' parts) and a particular resistor with the Panasonic FC as local decoupling smoothed by a R/Core with also a particular combination of caps. Here itr was much better than all my squared mkt mkp cap collection of 0.1uF caps I tested (have them all). I also prefer often acrylic/plastic smd to ceramic class II in analog decoupling. But one really should try it all to have the last spices perfums. And yeah, I am aware of inductance, etc.
This is all about compensation, therefor it is hard to give to others an universal receip. Anyway there are at least passive parts that works best than others whatever the good circuit. Good circuit however is needed first. I am sad not having time to try ad811 or listen to music theses days.
AD811 is TOP(for me at this moment
) , this discrete IV still can't evoke space like the AD811 although I can't say it's bad on the contrary someone may like it more than the AD811.It's worse in the bass and mids, highs and details are good, but the stage is more secluded and closed than with the AD811.