Coupling capacitor
I have now made 2 variations of this DAC. I have attached the schematics of one single channel B1 buffer that I use.
The DAC's built are equal down to C9, the coupling capacitor.
Version 1 have 3 cap's in parallell: 100uF electrolytic || 1.1uF Solen PA (metallized polypropylene) || Vishay MKP 1837
Version 2 have 2 cap's in parallell: 1.5uF unknown film cap || Vishay MKP 1837
The sound difference was bigger than expected. I have grown used to version 1. Version 2 were much more forward, the bass was harder and there was less space around the instruments and voices.
All of these film-caps were intentionally bought for passive crossover use. I have never really read any much about capacitor choice in active electronics, so my question here is: Could anyone point me in a direction here?
I have now made 2 variations of this DAC. I have attached the schematics of one single channel B1 buffer that I use.
The DAC's built are equal down to C9, the coupling capacitor.
Version 1 have 3 cap's in parallell: 100uF electrolytic || 1.1uF Solen PA (metallized polypropylene) || Vishay MKP 1837
Version 2 have 2 cap's in parallell: 1.5uF unknown film cap || Vishay MKP 1837
The sound difference was bigger than expected. I have grown used to version 1. Version 2 were much more forward, the bass was harder and there was less space around the instruments and voices.
All of these film-caps were intentionally bought for passive crossover use. I have never really read any much about capacitor choice in active electronics, so my question here is: Could anyone point me in a direction here?
Attachments
What i prefer? Don't know....well - I suppose that's matter of preference , and type of caps you prefer
With regards to passive crossover cap's I have found this page helpful: Humble Homemade Hifi
But I have not found any helpful pages with regards to cap's in active electronics. Have you?
as I said - just delete gate gnd resistors
in that case - made lowpass filter differentially on input , or blahlah on output .
without gate gnd resistors , each upper jfet will float up and sit where it feel comfortably
and - yeah - if you are lacking some drive from DAC , instead of double B1 - make Jfet BOSOZ , with all XCCSwhatever suffixes and prefixes ..... , and make it SUSY , what else ........
there are plenty of options .....
in that case - made lowpass filter differentially on input , or blahlah on output .
without gate gnd resistors , each upper jfet will float up and sit where it feel comfortably
and - yeah - if you are lacking some drive from DAC , instead of double B1 - make Jfet BOSOZ , with all XCCSwhatever suffixes and prefixes ..... , and make it SUSY , what else ........
there are plenty of options .....
Why do you need the input coupling cap? Is there DC at the
output of the DAC?
Nevermind - I see on your previous schematic.
Isn't it so that these DACs run off +5 V (and GND), hence each output is more or less midway between. (2.6 V is almost midway....) But as they have differential outputs (Aout+ and Aout-) all will be hunky dory. Or maybe I should have read the rest of the replies before writing... But I had this cup of damn good coffee in front of me and wanted to type something...
Yes, the outputs are at about 1/2 of the Vcc. With an dual opamp buffer on the outputs of the DAC chip, you just connect the 1/2Vcc (offset) to the + inputs of the opamps. The signal goes to the inverting (-) input. Normally you'd connect the + inputs to ground.
Don't know how that would work with the B1. Wish I knew what Z.M. was talking about, but he lost me, too! (Bozo, Susy, Xccs, kazzam!)
Don't know how that would work with the B1. Wish I knew what Z.M. was talking about, but he lost me, too! (Bozo, Susy, Xccs, kazzam!)
I'm lazy to type .......
anyway - here is diff buffer stage ;
point is that you don't need caps on input .....
you don't need them at all if you're gonna feed xformer with that buffer .... in which case you also don't need any type of diff Low Pass
with XCCSwhatever Jfet Bosoz I meant on BOSOZ variant - with cascoded Jfets , SUSY-ed , with CCS in LTP tail .
search ....... dunno where is it
edit - gate to gnd resistors are deleted ;
you can leave them in circuit , but referenced not to gnd but to Rf ( is that name of reference pin for all fluffy OPs after DAC , in datasheets ?)
anyway - here is diff buffer stage ;
point is that you don't need caps on input .....
you don't need them at all if you're gonna feed xformer with that buffer .... in which case you also don't need any type of diff Low Pass
with XCCSwhatever Jfet Bosoz I meant on BOSOZ variant - with cascoded Jfets , SUSY-ed , with CCS in LTP tail .
search ....... dunno where is it
edit - gate to gnd resistors are deleted ;
you can leave them in circuit , but referenced not to gnd but to Rf ( is that name of reference pin for all fluffy OPs after DAC , in datasheets ?)
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No caps, yes, that was my "hunky dory" statement
I'm going for my coffee mug now
naah ....... bad habit thinkin and drawing before coffee
I see that I drew one redundant cap multiplier , not redundant because of few parts , but because of possibility that extra part is really extra
I just drew similar thing for AR2 - intended between DCX DACs and Lundahls ,and off course that I put this time adequate number of cap multipliers in negative leg .......
this time you can't see LP blocks - they're not needed , most probably for his usage
I see that I drew one redundant cap multiplier , not redundant because of few parts , but because of possibility that extra part is really extra
I just drew similar thing for AR2 - intended between DCX DACs and Lundahls ,and off course that I put this time adequate number of cap multipliers in negative leg .......
this time you can't see LP blocks - they're not needed , most probably for his usage
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