I am using a CS4397 DAC, and before I was running directly from the DAC chip into my Gainclone amplifier.
I added one Dale 1kohm CMF55 to each of the differential outputs on the DAC to load it, and it now sounds more detailed, but I get an awful 60hz buzz now. It was silent before.
Is there anything I should add, change or take away? Thanks. I don't understand some aspects of circuit design yet.
I added one Dale 1kohm CMF55 to each of the differential outputs on the DAC to load it, and it now sounds more detailed, but I get an awful 60hz buzz now. It was silent before.
Is there anything I should add, change or take away? Thanks. I don't understand some aspects of circuit design yet.
Not too many people would use the direct OP without at least some filtering. Post a drawing of what you have done and you might get some posts. Have you considered using OP trafos.
Best, Bill
Best, Bill
Since you're evidently not using a balanced input amp, the resistors to the ground side of each RCA jack is simply creating a ground loop. To do what you intended to do here, you either need a balanced input amp(so that you have a ground line separate from the + & - signal lines, or you need output transformers to acccomplish basically the same thing.
Excellent, thanks.
1. Where should I pull the ground from instead?
2. Also, why was it completely silent before?
3. Will using output transformers dramatically change the sound?
1. Where should I pull the ground from instead?
2. Also, why was it completely silent before?
3. Will using output transformers dramatically change the sound?
Another issue you are going to have doing this is that you are not filtering the output of the DAC and so you will have all of the DAC high frequency artifacts on the output.
Again, an output transformer (with or without an RC filter on the secondaries) will accomplish this for you). Here's one that will work that isn't terribly expensive. http://www.edcorusa.com/Products/ShowProduct.aspx?ID=327
Again, an output transformer (with or without an RC filter on the secondaries) will accomplish this for you). Here's one that will work that isn't terribly expensive. http://www.edcorusa.com/Products/ShowProduct.aspx?ID=327
good idea, bill
here is a picture. before, it was exactly the same, just without the resistors.
The Rs are really not serving any useful purpose. The jumper across the RCAs might be the thing that is creating the hum, it makes a path for current to circulate through the interconnect shields, a ground loop. The Rs just complicate the situation.
You should either use 4 coupling caps or trafos to feed the RCAs. You only have about 0.5vrms output, I would use 1/2 step up trafos. There are a couple threads about using OP trafos with Vout dac chips on this forum.
thanks guys, it's back to being dead-silent! I just grounded the RCAs.
So what will that output transformer do if it's already silent? I thought it was best to have as few things as possible in the signal path?
So what will that output transformer do if it's already silent? I thought it was best to have as few things as possible in the signal path?
There isn't a jumper in that pic, but I just put in a jumper and put the RCA shields on a real ground. It works without hum now.
It sounds better with the resistors -- it retrieves more detail and improves bass. Would it sound better with a OP trafo instead? I have caps further up the signal path.
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Well, this IS diy, and if you are happy with the results I,m not going to criticise. What did you ground the RCAs to.
hmmm... actually now that I can listen without buzz... the treble sounds a bit too forward. Maybe I should look into these OP transformers.
EDIT: I put it on the analog ground pin that came off of the op-amp output connector. That section still has power, but just isnt used.
EDIT: I put it on the analog ground pin that came off of the op-amp output connector. That section still has power, but just isnt used.
I just looked at the pic again, you have the L- and R+ running to one RCA and the L+ and R- running to the other, unless the pic is fooling me.
haha WOW...i must have mixed them up when i put the resistors in...wow. Oh well, theyre normal now.
So should the OP transformer sound better than the resistors?
I have not tried direct so I cannot comment. To my ears good trafos are better than any opamp circuit anyone has come up with. They just sound right.
With your present arrangement you are shunting the minus outputs to ground through a 1k R, and the plus outputs are shunted to ground through the downstream equipment input circuitry. That is not an ideal situation, different loading on each half of the signal.
With your present arrangement you are shunting the minus outputs to ground through a 1k R, and the plus outputs are shunted to ground through the downstream equipment input circuitry. That is not an ideal situation, different loading on each half of the signal.
The resistors do serve a purpose. They protect your DAC outputs from being shorted together accidentally.
An output transformer is the "right" way to do the minimal output stage that you are going for. But like someone else said, if it sounds good to you, I won't complain.
An output transformer is the "right" way to do the minimal output stage that you are going for. But like someone else said, if it sounds good to you, I won't complain.
Yes, I agree with your thoughts on op-amp output. It just doesnt sound right.
The minus outputs are currently not connected to anything, it's just the plus outputs and the downstream ground.
How would you ground it?
So you're just using the pluses and the ground plane of the board. If it works, it works, but remember you have a DC component on the output. Dont connect it to a DC coupled amp.
I can't advise you on grounding, if it's quiet now that's all you could hope for.
I am a totally convinced convert to the trafo output, I would never try what you are doing, but it is DIY after all.
Best, Bill
I can't advise you on grounding, if it's quiet now that's all you could hope for.
I am a totally convinced convert to the trafo output, I would never try what you are doing, but it is DIY after all.
Best, Bill
Thanks Bill, I will try transformer output as well, it sounds promising. Do you think the Edcor XSM 600/600 is an OK choice?
I haven't heard any feedback from people that tried them, they might be OK. If I was to buy more trafos I would take a chance on a pair of Cinemags for around $60 a piece, and dual secondaries would double your output voltage if wired in series. I've tried a bunch with a cs4398, but they have a 5vpp output. Check out the thread, (Experience with this diy dac), start around page 15 or so.
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