Looks like you have a ground loop through the Dac board. Disconnect the ground to the trafo neutral.
This was originally not connected, however it actually made the hum quieter.
this thread's been an interesting read for me so far, even though i've only got to page 70 and not even sure of picking up this dac. because my primary desire is with TDA 1541 chip in NOS config. i'd like to know if anyone has an experience in comparing the modded form of the cirrus dac to a well implemented 1541 nos dac. the one trait that i want most in my next dac is- smoothness. and the other one is warmth- if that's possible to color in a dac. so i'd like to know what you gents think would be wiser choice when concerning with the above requirement. also, how does this dac look to you? a contender for the fully modded cirrius?
I really can't help with the opamp circuitry, I never powered it up on either of mine. You could try moving the star ground point to different locations, such as the output jacks, or the pre input ground, or the dac board output ground, etc.
one op amp for two channels?
Hello Bill,
hello everyone,
I hope you all doing well!
yesterday I tried replacing the OPA's that the dac came with, with pairs of OPA627. To mys surprise, the dac was working well and producing sound, with only one set of those OPA's (627) on channel A. Where is the trick?
Can anyone speculate why I would get stereo sound by using only one OPA, on one channel?
.-. are they not separate channels?
.-. is there a "bridge" sorting them somewhere?
later I changed back to the original NE (something) op amps, that the dac came with, and I was able to get music out of it, by using just one op amp at channel A...
only on channel A though..
...when I tried the same trick on channel B, I did not get any sound at all, it was mute...
thank you for your input
regards
angelo
Hello Bill,
hello everyone,
I hope you all doing well!
yesterday I tried replacing the OPA's that the dac came with, with pairs of OPA627. To mys surprise, the dac was working well and producing sound, with only one set of those OPA's (627) on channel A. Where is the trick?
Can anyone speculate why I would get stereo sound by using only one OPA, on one channel?
.-. are they not separate channels?
.-. is there a "bridge" sorting them somewhere?
later I changed back to the original NE (something) op amps, that the dac came with, and I was able to get music out of it, by using just one op amp at channel A...
only on channel A though..
...when I tried the same trick on channel B, I did not get any sound at all, it was mute...
thank you for your inputregards
angelo
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re
this is the kind of arrangement I use...
http://cgi.ebay.com/Dual-Mono-Opamp...72-OPA627-/260653081706?pt=LH_DefaultDomain_0
so do you say that it can work by just using one op amp? or a coupled as they work the OPA627's in my case?
pictures of the coupled OPA627BP's?
this is the kind of arrangement I use...
http://cgi.ebay.com/Dual-Mono-Opamp...72-OPA627-/260653081706?pt=LH_DefaultDomain_0
so do you say that it can work by just using one op amp? or a coupled as they work the OPA627's in my case?
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Look at the schematic. If you don't have it, email me and I'll send it.
It will work with no opamps if you tap the signal off the coupling caps. The dac chip puts out 2VRMS.
McGyver, that looks very nice.
I am trying the PCM1798 in my DAC now but have very low volume and hiss. It may be the UTC A-20's I am using, although I have them configured for 1:3 with 47R resistors on primaries and 510R across secondaries.
Did you remove the opamps under the PCM adapter? I think I may need them for adequate signal amplification. The spec calls for OPA2604 but I have some OPA2132 and OPA1642 I could try. I ordered blank adapter boards from snow and used some sample PCM1798 DAC chips. I have 56uF oscon and 10K resistor similar to your board in post #2854.
Any ideas?
I am trying the PCM1798 in my DAC now but have very low volume and hiss. It may be the UTC A-20's I am using, although I have them configured for 1:3 with 47R resistors on primaries and 510R across secondaries.
Did you remove the opamps under the PCM adapter? I think I may need them for adequate signal amplification. The spec calls for OPA2604 but I have some OPA2132 and OPA1642 I could try. I ordered blank adapter boards from snow and used some sample PCM1798 DAC chips. I have 56uF oscon and 10K resistor similar to your board in post #2854.
Any ideas?
Per Lunahal suggestion
Dear forumers,
I wrote an email to Per Lundhal. Based on the the data of the CS4398 and the input impedance of my preamp (47KOhms) he suggests to connect the trafo as in the picture with a 7k resistor between pins 10 and 9... as a first try I'll follow his suggestion... I guess he knows his stuffs!
Pietro
NOTE: Please notice that on the right hand side of the picture it should be "input impedance" and not "ouput impedance"
Dear forumers,
I wrote an email to Per Lundhal. Based on the the data of the CS4398 and the input impedance of my preamp (47KOhms) he suggests to connect the trafo as in the picture with a 7k resistor between pins 10 and 9... as a first try I'll follow his suggestion... I guess he knows his stuffs!
Pietro
NOTE: Please notice that on the right hand side of the picture it should be "input impedance" and not "ouput impedance"
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I'm using this board with opamps totally removed. I used it with 1:10 trafos followed by tube stage, but lately I removed trafos and the sound is better now.