how to make use of all dac signal outputs

chokesrule · 24th September 2011, 08:32 AM

Hi, I am making my own dac using cs4397 dac cs8416 reciever chips....I have had a great result not using an output stage and just feeding the R minus and L minus analogue outputs thru a volume pot then 3.3uf output caps, straight to an amp. How can I make use of the R plus and L plus outputs this chip also provides?

Pano · 24th September 2011, 12:11 PM

Transformer. Easy, simple, good.

qusp · 24th September 2011, 06:30 PM

wouldnt it be best to have the caps before the pot so there isnt any DC on it? I wouldnt have thought having a pot at the output of the dac would be good for the next stage due to a large and constantly varying output impedance

Ken Newton · 06:59 PM

qusp:

Like many things in high-end audio, the issue is one of trading off the lessor of two evils in a given context. One could add an output buffer stage to isolate the impedance affects of having the volume pot. immediately at the output, but then one would also get the consequences of an additional active stage. There's no universally correct answer for it depends on the context presented by your system. In this case, the amplifier input impedance and interconnect capacitance.

Yes, the output cap. should be located so as to keep D.C. from flowing through the volume pot.

chokesrule · 24th September 2011, 07:16 PM

thanks for the tip, I will try this tomorrow. Can you tell me why it is bad to have DC going thru the vol pot?. The sound I am hearing now is very good....I was aware of the dc issue but I figured the cap after the vol pot would block any dc and I used this set up also because the 3.3uf's are in the amplifier and I have been told that a carbon/wiper volume pot generates dc itself so therefore needs a cap after it...Its a genuine question...I am not trying to be a smart ***..I am trying to learn...thanks alan

Ken Newton · 25th September 2011, 03:48 AM

Quote:

Originally Posted by chokesrule

thanks for the tip, I will try this tomorrow. Can you tell me why it is bad to have DC going thru the vol pot?. The sound I am hearing now is very good....I was aware of the dc issue but I figured the cap after the vol pot would block any dc and I used this set up also because the 3.3uf's are in the amplifier and I have been told that a carbon/wiper volume pot generates dc itself so therefore needs a cap after it...Its a genuine question...I am not trying to be a smart ***..I am trying to learn...thanks alan

A d.c. current through the volume pot. will produce a low frequency noise burst whenever the pot. is adjusted. You may have noticed this effect already.

Pano · 25th September 2011, 05:07 AM

The pot is putting a DC load on the chip. Maybe not much of a load, but it's not designed for that. The cap or transformer should go before the pot.

sandyK · 25th September 2011, 05:55 AM

Michael
Is that what you really meant to say ? There appears to be a contradiction there to me.
Regards
Alex

Pano · 25th September 2011, 02:11 PM

Between the DAC and the Pot. You want to block the DC from the DAC chip. You want it to be only AC coupled. A cap or transformer will do that.

Does that make more sense?

chokesrule · 26th February 2012, 07:58 PM

Hi, I put a cap before the volume pot as suggested but it never made any audable difference to be honest....but I went back to connecting the dac to a valve srpp obviously thru a cap to the grid....I was wrong...connecting a dac directly to a tripath does sound very very clear but it lacks punch...without the output stage its too weedy but the clarity is fantastic...I prefer the extra punch and dynamics of the valve...I have seen on the aikido website you can connect the differential outputs to the valve...negative thru the lower grid and positive thru the lower cathode...so that is the next plan I am not sure if the resistor values given to load the dac op amps will be the same for srpp but I just going to give it a try and see what happens..thanks Alan

24th September 2011, 08:32 AM	#1
chokesrule diyAudio Member Join Date: Jun 2010	how to make use of all dac signal outputs Hi, I am making my own dac using cs4397 dac cs8416 reciever chips....I have had a great result not using an output stage and just feeding the R minus and L minus analogue outputs thru a volume pot then 3.3uf output caps, straight to an amp. How can I make use of the R plus and L plus outputs this chip also provides?

24th September 2011, 06:47 PM	#4
Ken Newton diyAudio Member Join Date: Apr 2003 Location: Eastern Pennsylvania	qusp: Like many things in high-end audio, the issue is one of trading off the lessor of two evils in a given context. One could add an output buffer stage to isolate the impedance affects of having the volume pot. immediately at the output, but then one would also get the consequences of an additional active stage. There's no universally correct answer for it depends on the context presented by your system. In this case, the amplifier input impedance and interconnect capacitance. Yes, the output cap. should be located so as to keep D.C. from flowing through the volume pot. __________________ Ken Last edited by Ken Newton; 24th September 2011 at 06:59 PM.

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24th September 2011, 12:11 PM	#2
Pano diyAudio Moderator Join Date: Oct 2004 Location: North Carolina Blog Entries: 4	Transformer. Easy, simple, good.

24th September 2011, 06:30 PM	#3
qusp is choosing a less facetious title... diyAudio Member Join Date: Oct 2009 Location: Brisbane, Australia	wouldnt it be best to have the caps before the pot so there isnt any DC on it? I wouldnt have thought having a pot at the output of the dac would be good for the next stage due to a large and constantly varying output impedance

24th September 2011, 07:16 PM	#5
chokesrule diyAudio Member Join Date: Jun 2010	thanks for the tip, I will try this tomorrow. Can you tell me why it is bad to have DC going thru the vol pot?. The sound I am hearing now is very good....I was aware of the dc issue but I figured the cap after the vol pot would block any dc and I used this set up also because the 3.3uf's are in the amplifier and I have been told that a carbon/wiper volume pot generates dc itself so therefore needs a cap after it...Its a genuine question...I am not trying to be a smart ***..I am trying to learn...thanks alan

25th September 2011, 05:07 AM	#7
Pano diyAudio Moderator Join Date: Oct 2004 Location: North Carolina Blog Entries: 4	The pot is putting a DC load on the chip. Maybe not much of a load, but it's not designed for that. The cap or transformer should go before the pot.

25th September 2011, 05:55 AM	#8
sandyK diyAudio Member Join Date: Apr 2007 Location: Sydney	Michael Is that what you really meant to say ? There appears to be a contradiction there to me. Regards Alex

25th September 2011, 02:11 PM	#9
Pano diyAudio Moderator Join Date: Oct 2004 Location: North Carolina Blog Entries: 4	Between the DAC and the Pot. You want to block the DC from the DAC chip. You want it to be only AC coupled. A cap or transformer will do that. Does that make more sense?

26th February 2012, 07:58 PM	#10
chokesrule diyAudio Member Join Date: Jun 2010	Hi, I put a cap before the volume pot as suggested but it never made any audable difference to be honest....but I went back to connecting the dac to a valve srpp obviously thru a cap to the grid....I was wrong...connecting a dac directly to a tripath does sound very very clear but it lacks punch...without the output stage its too weedy but the clarity is fantastic...I prefer the extra punch and dynamics of the valve...I have seen on the aikido website you can connect the differential outputs to the valve...negative thru the lower grid and positive thru the lower cathode...so that is the next plan I am not sure if the resistor values given to load the dac op amps will be the same for srpp but I just going to give it a try and see what happens..thanks Alan