Looks like you have a ground loop through the Dac board. Disconnect the ground to the trafo neutral.
I assume all your jacks are isolated. Have you tried lifting your ground lift completely? I can't tell what you are using.
Next I would try separating the pre from the dac and shorting the pre inputs
Next I would try separating the pre from the dac and shorting the pre inputs
Yes the jacks are isolated.
The lift is anti parallel diodes, 10r resistor and 100nF cap. Pretty standard I believe.
I have removed power from the dac and and grounded the inputs to the pre. This is nice and quiet.
I'll try your other suggestions.
Thanks,
Pete
The lift is anti parallel diodes, 10r resistor and 100nF cap. Pretty standard I believe.
I have removed power from the dac and and grounded the inputs to the pre. This is nice and quiet.
I'll try your other suggestions.
Thanks,
Pete
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.
Do you know what dac board is better on this dac between cs4397, cs4398 or a pcm179x series??
i read so far that its pcm1798 which's what i decided to get.
has anyone actually tried the 20:1 transformers with the 1798 board? or any documentation on the x20 tube rectifier yet?
has anyone actually tried the 20:1 transformers with the 1798 board? or any documentation on the x20 tube rectifier yet?
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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One dual opamp does filtering for both channels, the other is a buffer for both channels. Do you have any pics?
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?
Hi Rich,
You shouldn't use Rs on both, try removing the 510s. I can't comment on the opamps, McGiver should be able to help there.
You shouldn't use Rs on both, try removing the 510s. I can't comment on the opamps, McGiver should be able to help there.
Nice One Bill, I'll try it now. Would you recommend keeping the filter caps in place across prim's and sec's?
Many thanks
Many thanks
I would keep them unless I could look with a scope to see what was coming out of the output. IOW, don't fry your amp.
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.