Imo line trannies are a quite fast option and at least as fast as changing the opamps design. Just my thoughts, im very glad about using the monacors, they sound clearly better than the opamp output stage 🙂
if u want to make some experiments i got the shematic here anyway:
Index of /lm_gigawork_dac3
i dont know who uploaded that files there, found this link in a forum somewhere
if u want to make some experiments i got the shematic here anyway:
Index of /lm_gigawork_dac3
i dont know who uploaded that files there, found this link in a forum somewhere
I am with the same thinking of the latest change in the analog section is causing the distortion.
Use post 229's diagram as a reference,
1. R13 and R14 are jumpers now vs 2 x 1K (not sure the exact value) resistors before
In the section between the 2 opamp's,
2. the middle resistors are not populated (47K??)
3. and the middle 2 caps are jumpers now (2.2uF?).
#1 and #3 are in series from the output of the first opamp into the input of the 2nd,
and #2 is from the 2nd opamp's input to ground.
In the present circuit, the 1st opamp is directly coupled into the 2nd which may increase the output which the NE5532 just can't tolerate.
What I plan to do are:
- Remove the jumps as in #1, this should decouple 2 opamps.
- Take the output to the RCA output directly.
- Connect the RCA's ground together and run a wire the the audio ground of
the onboard RCA output.
By doing so, we can avoid the newly modified circuit in the analog section and will
only use one opamp which should be an improvement.
Does anyone see anything wrong to do the above?
Use post 229's diagram as a reference,
1. R13 and R14 are jumpers now vs 2 x 1K (not sure the exact value) resistors before
In the section between the 2 opamp's,
2. the middle resistors are not populated (47K??)
3. and the middle 2 caps are jumpers now (2.2uF?).
#1 and #3 are in series from the output of the first opamp into the input of the 2nd,
and #2 is from the 2nd opamp's input to ground.
In the present circuit, the 1st opamp is directly coupled into the 2nd which may increase the output which the NE5532 just can't tolerate.
What I plan to do are:
- Remove the jumps as in #1, this should decouple 2 opamps.
- Take the output to the RCA output directly.
- Connect the RCA's ground together and run a wire the the audio ground of
the onboard RCA output.
By doing so, we can avoid the newly modified circuit in the analog section and will
only use one opamp which should be an improvement.
Does anyone see anything wrong to do the above?
A small update, I did exactly what I said in last post and effectively bypass the 2nd opamp. Unfortunately, it neither changes the symptom of the NE5532's nor reduces any gain.......
OK, a blast from the past...
Can anybody please clarify what this mod achieves?
Thanks
Can anybody please clarify what this mod achieves?
Thanks
I was asking myself the same question a while ago. Then, I can't remember why, but I read somewhere that this step is no longer necessary on newer versions of the DAC.
pcm1798
Hi everybody,
I saw that a PCM1798 could worth a try instead of the CS4398. McGyver did find some adaptor + chip in Poland but is there something available elsewhere?
(nothing against polish but...).
I would like to try that chip with my A-20s in a 600/50 ratio.
Hi everybody,
I saw that a PCM1798 could worth a try instead of the CS4398. McGyver did find some adaptor + chip in Poland but is there something available elsewhere?
(nothing against polish but...).
I would like to try that chip with my A-20s in a 600/50 ratio.
I asked Gigawork whether he had the PCM1798 dac board, not the big dac board. He first replied:
Then in a subsequent email when I asked to clarify that this PCB could drop in directly into the big dac board and how to buy, he said:
Given the state of my current big dac, it is not likely I will buy. I put in a LM4562 into the board, and I heard more distortion than the opa2134!! It wasn't as bad as the NE5532, not even close. However, I didn't expect any. This leads me to suspect there is something upstream not quite correct. I will find out as soon as I unload the Edcors from my Buffalo.
Not what I wanted to hear! I had pretty much convinced myself it had to be bad opamps... oh well. Let us know how the transformers work out.
thx for the link
on the schematic It Is shown that one 6VAC transformer winding feed two bridges to produce 2 x 5 Vdc and 2 x 3.3Vdc - Is this OK
how much hours burn In are needed LM4562 to start sing OK
Fred
I did not read all postings, but I notice your ongoing problem with crackling sound.
Did you ever measure all (supply-) voltages directly at the chips pins? I am not talking about the opamps, but the receiver, upsampler and DAC chips.
Franz
I did not read all postings, but I notice your ongoing problem with crackling sound.
Did you ever measure all (supply-) voltages directly at the chips pins? I am not talking about the opamps, but the receiver, upsampler and DAC chips.
Franz
Last edited:
Hi Franz,
No, I didn't measure the mentioned chips voltage. The upsampler is likely not the cause because it happens with or without the board. I will measure the receiver and the DAC tomorrow.
Thanks,
No, I didn't measure the mentioned chips voltage. The upsampler is likely not the cause because it happens with or without the board. I will measure the receiver and the DAC tomorrow.
Thanks,
As the distortion is still present if you take the feed from after the 1st (summing) opamp stage, I would suggest altering the values of the feedback and gnd resistors around this stage.
You should be able to lower the output and see if this resolves the distortion problem?
You should be able to lower the output and see if this resolves the distortion problem?
I remember I had a little crackling after I had removed and replaced the coax input jack. Probably be a good idea to reflow the top and bottom of all joints that can be gotten to
adaptor
Thanks Fred for your reply about PCM1798. I will ask to my seller. In the meantime, I will look for an adaptor that could fit on that board. I'll let you know guys.
Thanks Fred for your reply about PCM1798. I will ask to my seller. In the meantime, I will look for an adaptor that could fit on that board. I'll let you know guys.
Pin Lift
There was another pin lift mod, which I believe was for CS4397 only and not CS4398. This was to enable higher sample rates by lifting pin 2 on CS4397 DAC chip and connecting it to pin 16 on the CS8416 receiver chip.
I don't know what the pin 20 lift for CS8416 receiver chip achieves, let alone whether it applied to only CS4397 not CS4398. I tried reading the datasheet but was left baffled!
Cheers
There was another pin lift mod, which I believe was for CS4397 only and not CS4398. This was to enable higher sample rates by lifting pin 2 on CS4397 DAC chip and connecting it to pin 16 on the CS8416 receiver chip.
I don't know what the pin 20 lift for CS8416 receiver chip achieves, let alone whether it applied to only CS4397 not CS4398. I tried reading the datasheet but was left baffled!
Cheers
I remember the pin 20 lift was for using the reciever chip with sigma/delta dac chips, as both the CS chips are. I think pin 20 was grounded on the first few versions but they finally got it straightened out.
Hello everybody.
Looking for a little help, I use my apple tv for music playback - into this dac sounds fantastic (well getting there) but I also use the apple tv to feed my Cyrus AV8 for surround films etc (Tiptop)
So I've built and optical to coax converter that splits:- one feed to the AV8, one to the DAC.
Now when I send AC3 DTS to the AV8 alls good but also this DAC tries to playback and as you can Imagine its not nice.
So............
I'm looking for a way to detect AC3 DTS or anything it cant cope with and give me a signal out so I can disconnect the coax to the DAC with use of a relay.
Anyone point me in the right direction?
Looking for a little help, I use my apple tv for music playback - into this dac sounds fantastic (well getting there) but I also use the apple tv to feed my Cyrus AV8 for surround films etc (Tiptop)
So I've built and optical to coax converter that splits:- one feed to the AV8, one to the DAC.
Now when I send AC3 DTS to the AV8 alls good but also this DAC tries to playback and as you can Imagine its not nice.
So............
I'm looking for a way to detect AC3 DTS or anything it cant cope with and give me a signal out so I can disconnect the coax to the DAC with use of a relay.
Anyone point me in the right direction?
Thank Bill Fuss and McCrackers, I can take the pin lift mods off the list. Nearly there...!
I tried the optical input as well, same outcome. I am working backward towards the DAC. Hopefully, the issue is not originated from the digital circuit which I have absolutely no knowledge.
UV101's suggestion is good. I remember there were discussions on the LPF mods, and Kevin had one simple change that gave pretty good result.
You may ask why I bother doing this and not going to the transformer right the way. It is the stubborn side of me wants to know what cause the problem. After all, it is a good learning exercise to keep the brain working 😀