merlin,
What do you mean "passive I/V"? connect a resistor across the output? one resistor for the +V and one resistor for -V for each channel? Also, what value did you use?
I just powered mine and I connected it straight to the amp with no "I/V resistor" at all.
What do you mean "passive I/V"? connect a resistor across the output? one resistor for the +V and one resistor for -V for each channel? Also, what value did you use?
I just powered mine and I connected it straight to the amp with no "I/V resistor" at all.
Pretty nice! What do you call it? The Buffalo biscuit DAC?
I honestly hadn't given it much thought.
McVitie's Digital Assortment maybe? Tinned Buffalo? 😀
@glt
The Buffalo II is current output, but single supply so it has about 2.5V DC at the current output. If you use active conversion, then you will have a DC at the output of the I/V converter, and have to use a balanced-to-unbalanced converter to get rid of the DC.
200 ohms resistors between Vout+ to GND & Vout- to GND each channel giving 1VRMS audio at each phase as per manual:
"Each analog output at 0DBFS is equivalent to a voltage of approximately 92.4% of AVCC in series with 195. So given 3.3VDC AVCC it will be about 3.05Vpp across 195. The output will be DC biased at AVCC/2. This works out to about 16ma peak to peak at each output. The amount of bias current will depend of the voltage of the virtual ground."
The Buffalo II is current output, but single supply so it has about 2.5V DC at the current output. If you use active conversion, then you will have a DC at the output of the I/V converter, and have to use a balanced-to-unbalanced converter to get rid of the DC.
200 ohms resistors between Vout+ to GND & Vout- to GND each channel giving 1VRMS audio at each phase as per manual:
"Each analog output at 0DBFS is equivalent to a voltage of approximately 92.4% of AVCC in series with 195. So given 3.3VDC AVCC it will be about 3.05Vpp across 195. The output will be DC biased at AVCC/2. This works out to about 16ma peak to peak at each output. The amount of bias current will depend of the voltage of the virtual ground."
Really? With some active stages this may be the case, but certainly not all.
or AC couple the outputs (capacitors).
As Brian said this is most definitely not always true. Take for Example IVY-III. 🙂
Using a fully differential Opamp like the OPA1632 or THS4131 for active IV conversion, which has a Vcm input that sets the DC output level,
there will not be a DC offset even though the DAC currents ride on a DC level. The Vcm input is often used to set the common DC level for an ADC. Very elegant solution, IMHO.
Using normal OPamps for active IV conversion, however, will, AFAIK, leave a DC offset at the output, and that has to be taken care of with either a cap in series, adding DC voltage to the input, or do a balanced to single ended conversion (with a 3rd Opamp). Choose your poinson...
The DC output you do get from an OPA1632 is output voltage offset but that is generally just a few mV.
Just a note: I have experienced that the IV resistor (in the first OPA1632) - more than other resistor positions - affects sonics, and by changing it to other types one can tune sonics to one's own taste.
I highly recommend to simulate the IVY3. There you will see how it works, and note for ex that the LP filter -3dB frequency is not 27kHz but something higher.
Regards,
there will not be a DC offset even though the DAC currents ride on a DC level. The Vcm input is often used to set the common DC level for an ADC. Very elegant solution, IMHO.
Using normal OPamps for active IV conversion, however, will, AFAIK, leave a DC offset at the output, and that has to be taken care of with either a cap in series, adding DC voltage to the input, or do a balanced to single ended conversion (with a 3rd Opamp). Choose your poinson...
The DC output you do get from an OPA1632 is output voltage offset but that is generally just a few mV.
Just a note: I have experienced that the IV resistor (in the first OPA1632) - more than other resistor positions - affects sonics, and by changing it to other types one can tune sonics to one's own taste.
I highly recommend to simulate the IVY3. There you will see how it works, and note for ex that the LP filter -3dB frequency is not 27kHz but something higher.
Regards,
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So you confirm that there is DC.....I trust in Erno Borbely when said 2,5V DC but anyone can measure it.
Brian & you have to mind that exist others I/V on the market (not only the IVY III) so will be better instead not to bother clarify & help people to use well & get the maximum profit of your products independently I/V used.
One curiosity why IVY III have a separate single ended output?
I mind will be more useful have other kind of answer, like: you can use these types of I/V without any problem or never use these other type of I/V, will be more simple & clear to everybody.
Or use a servo DC?
The analog sections of the DAC are not powered by a 5V supply, so Erno was incorrect. I am sure he will tell you the same once he has his Buffalo. I don;t really think it is a point of contention.
I am not sure what you are trying to say here. We are fine with people using whatever output stages they want. The IVYIII is just one we offer that is highly tuned for the Bufflao. I was only trying to correct your statement so people didn't think the only way to have DC-free output was by using a passive resistor output.
Yes.
Flexibility. It allows you to set different gain levels for balanced and single-ended outputs when using them at the same time. Also, you get slightly better DNR for SE when you sum the differential outputs.
Not true, I never said.😡
Of course that I understand that it's not good for everybody to hear that exist another way to do a passive I/V instead to buy an expensive active I/V, it's all that matter?
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I want' to involve Erno in the discussion, he only tell me the information "as per your own manual". Because I own his I/V ask him how change the filter for your DAC, simple that. Erno told me that I use a passive I/V resistor while he got his BII to select the filter.
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It would be 2.5V if AVCC could be 5V(which it cannot that is far too high and would kill the DAC). 🙂
And yes of course there is DC bias at the output of the DAC. But there is none at the output of something like IVY-III even when you don't use the BAL/SE stage. 🙂 This is the really nice thing about fully differential amplifiers where you can set the output common mode voltage.
Cheers!
Russ
Is possible Erno don't read well your own manual "Errare humanum est"
I never said that there is DC at the ouput of the IVY III, remember I own one IVY III (opamps) purchased from you and sounds very good but I want to compare with Erno Borbely I/V (discrete) that I also own, when filter optimized for your DAC.
To be honest, I mind is not a good comparison because the prices of your products & Borbely products are not in the same range and in the I/V are using different components & topologies.
Just will see.
I never said that there is DC at the ouput of the IVY III, remember I own one IVY III (opamps) purchased from you and sounds very good but I want to compare with Erno Borbely I/V (discrete) that I also own, when filter optimized for your DAC.
To be honest, I mind is not a good comparison because the prices of your products & Borbely products are not in the same range and in the I/V are using different components & topologies.
Just will see.
He said that was shipped last monday, but still got it. I'm sure he will do something nice like you do with the IVY III.
Russ or Brian?
When you use the Volumite with the B-II, is the DC bias constant @ 1.65VDC?
I.e. only the signal is attenuated?
If so, could I use the 1.65VDC as bias for my buffer? Is it stable enough?
When you use the Volumite with the B-II, is the DC bias constant @ 1.65VDC?
I.e. only the signal is attenuated?
If so, could I use the 1.65VDC as bias for my buffer? Is it stable enough?
I just came across this tube output stage that someone is using and I was wondering if you guys might care to comment:
audio-talk :: View topic - Buffalo DAC output stage
Looks simple and effective, of course the transformer could be a different one 😉 Does it look OK or there are things that I don't see? Any input will be much appreciated.
audio-talk :: View topic - Buffalo DAC output stage
Looks simple and effective, of course the transformer could be a different one 😉 Does it look OK or there are things that I don't see? Any input will be much appreciated.
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