I think I need an attenuator, or preamp, or something like that.
The way it goes is like that: PC -> USB-SPIDF using tascam 144 asio driver-> gigawork DAC -> KRK rokit 8 monitors. It sounds good, but too loud when using BIT PERFECT streaming, and there is no way to control the output level.
Maybe something like this will do the job?
Tube preamplifier Matisse Atom w/transformer 110V/220V - eBay (item 120577760515 end time Aug-30-10 08:42:22 PDT)
By the way, I have now two Tamuras Ga80080 form Ebay for the trafo mod. I will buy Takman Carbon Film, Polystyrene Film capacitors for the RC filter and Cardas RCA connectors.
Thank you in advance
Is this upsampling problem occur to previous version boards like v6 and v7?
A 10k ohm pot or stepped attenuator will work fine with the opamp outputs.
I am not sure, but I think you are right, I know one of the previous version board can receive ony 48K signal in non-upsampling mode.
Anybody who is interesting in this DAC board and need 192K signal receiving, you must purchase V10, if 192K signal receiving is not important to you, please do choose DIR9001 as receiving chip instead of CS8416.
I just talk to the orginal designer Mr.Liu-Sheng on-line yesterday, I will ask your question to him, to see if he has any solution.
I have asked the designer about the noise, he told me that human ear can not hear the 5mv noise, only machine can test it, so it's meaningless.
Hi Jeffery, thank you very much for asking!
But 5 milliVolt equals about -60dB. Maybe the designer thought I meant 5 microVolt, which, I agree, can't be heard. This 5 mV however is very much noisier than my other pre amp inputs, so I would like to get rid of it.
Kind regards
Piet
Hi Piet,
The desinger ask you to swap op-amp, and he is very interesting in how did you find the 5 milivolt noise?
Jeffery
The desinger ask you to swap op-amp, and he is very interesting in how did you find the 5 milivolt noise?
Jeffery
I did swap op amps, but same result. I also tried another power supply. Even tried disconnecting the power supply for the digital sections.
I use an oscilloscope connected to the output of the DAC and of course my ears ;-).
I use an oscilloscope connected to the output of the DAC and of course my ears ;-).
In my second system I had a similar problem. I used a tube buffer. Actually I bought a musical fidelity X-10 clone. It's buffer with two ECC88/6dj8/6922 tube with 1db of gain. That one with a pot does a really great job. Actually I bought two of these buffers with power supply and one is unused, so if you what to buy it second hand just write me a message.
Best
Pietro
Hello Bill
I found a very good 400pF silver mica cap. The problem is the 7KOhms resistor which goes in series with cap (and parallel to output) It's hard to find a good combination. Do you thing 6.8KOhm or 7.1KOhm (1/2W) makes much difference? How much it is important to have precisely matched values in this place?
Thanks for your valuable help... I am pretty ignorant about signal transformers!
Pietro
Hi Pietro,
I would say that 7.1K is plenty close for correct operation. The filter's F3 will be very slightly higher than the design. Likewise, the 6.8K would lower the F3 slightly below the design.
I would say that 7.1K is plenty close for correct operation. The filter's F3 will be very slightly higher than the design. Likewise, the 6.8K would lower the F3 slightly below the design.
I'm having trouble with a hum on the output of my dac.
DSC01216.jpg picture by repeet_photos - Photobucket
The boards on the left are Ska Audio SkPre amps, and on the bottom left is a Ska Optivol.
All grounds are star connected with a ground lift circuit.
If I disconnect the inputs to the SKpre the hum goes away.
Any thoughts for the cause of the hum would be appreciated.
Pete.
DSC01216.jpg picture by repeet_photos - Photobucket
The boards on the left are Ska Audio SkPre amps, and on the bottom left is a Ska Optivol.
All grounds are star connected with a ground lift circuit.
If I disconnect the inputs to the SKpre the hum goes away.
Any thoughts for the cause of the hum would be appreciated.
Pete.