Hi Simon
Did you read this statement below by ecdesigns in the ' building the ulitmate NOS dac using TDA 1541A ' ?
OK, we're not NOS people but it's quite an eye opener anyway :
Originally Posted by -ecdesigns-
Tuning the capacitor is the easiest way for lowering DEM clock jitter amplitude, but jitter won't be as low as with an low jitter external DEM clock (DEM clock oscillator intrinsic jitter). So this modification improves sound quality over the 470 or 680pF, but still isn't optimal - unquote
So, another simple mod without doing DEM exists by getting a better lock to BCK using one of 9 values of cap outlined in the thread.
I'll be ordering the caps tomorrow - I'll let you know what happens if your interested.
I'm also itching to try the DEM mod .....but I want you to do it first....😀
Hope all is well
Andrew
Did you read this statement below by ecdesigns in the ' building the ulitmate NOS dac using TDA 1541A ' ?
OK, we're not NOS people but it's quite an eye opener anyway :
Originally Posted by -ecdesigns-
Tuning the capacitor is the easiest way for lowering DEM clock jitter amplitude, but jitter won't be as low as with an low jitter external DEM clock (DEM clock oscillator intrinsic jitter). So this modification improves sound quality over the 470 or 680pF, but still isn't optimal - unquote
So, another simple mod without doing DEM exists by getting a better lock to BCK using one of 9 values of cap outlined in the thread.
I'll be ordering the caps tomorrow - I'll let you know what happens if your interested.
I'm also itching to try the DEM mod .....but I want you to do it first....😀
Hope all is well
Andrew
Hi Andrew,
I recall reading about the optimal caps but thought it would be so hard to hear the difference I just left it alone... for now. I'm very interested in what you discover. I'll do the DEM re-clock at some point.
Simon
I recall reading about the optimal caps but thought it would be so hard to hear the difference I just left it alone... for now. I'm very interested in what you discover. I'll do the DEM re-clock at some point.
Simon
some more...
so instead of building the differential 352khz DEM clock (derived from masterclock) is it worth to try with only one 250 pF quality cap that will lock on 352.8 khz on DEM pins (16,17) ?
Answer was ' yes ' but not as good as proper DEM job - I'll bet you've read this already ?
Andrew
so instead of building the differential 352khz DEM clock (derived from masterclock) is it worth to try with only one 250 pF quality cap that will lock on 352.8 khz on DEM pins (16,17) ?
Answer was ' yes ' but not as good as proper DEM job - I'll bet you've read this already ?
Andrew
That's cool to know. Is that a readily available value or is it made up of 220pF + 22pF + 8pF or something mad like that??
No😀, actually straight 250pf exists in silver mica and styrene.
Though the guy insists low tolerance of 1% ......what ?
I've found mica's at 2% and I've asked him the question already - is it oK to use.
If I have to buy a bag full I'll send you some foc !!
Cheers
Andrew
Though the guy insists low tolerance of 1% ......what ?
I've found mica's at 2% and I've asked him the question already - is it oK to use.
If I have to buy a bag full I'll send you some foc !!
Cheers
Andrew
OK, I've got three 2% mica's coming - apparently that's fine.
Considering my styrene's were 10 % means 2% is a bit of a result !
I need two - the other one's yours.
Only one issue - the pitch is about 12 mm !
I'll give it a go anyway.
If you PM me your address I'll send it as soon as they arrive.
Andrew
Considering my styrene's were 10 % means 2% is a bit of a result !
I need two - the other one's yours.
Only one issue - the pitch is about 12 mm !
I'll give it a go anyway.
If you PM me your address I'll send it as soon as they arrive.
Andrew
Thanks Andrew, a PM has been sent your way.
12mm is very wide (typical silvered mica) but they usually come with long leads IIRC so it should be ok to fit.
12mm is very wide (typical silvered mica) but they usually come with long leads IIRC so it should be ok to fit.
They're here !
It's in the Alpha 5 now but it's too early for me to comment as I'm half way through a bottle of red - plus the 5 is completely different sounding to the Alpha
My poor Alpha 5 gets everything thrown at it first to see if it explodes and if it doesn't after a few hours I apply it to THE ' reference '
Hopefully tomorrow I can get it in and report back.
No probs though and no ' nasties '....meaning it's not worse for sure !
Yours will be with you Tuesday
Cheers
It's in the Alpha 5 now but it's too early for me to comment as I'm half way through a bottle of red - plus the 5 is completely different sounding to the Alpha
My poor Alpha 5 gets everything thrown at it first to see if it explodes and if it doesn't after a few hours I apply it to THE ' reference '
Hopefully tomorrow I can get it in and report back.
No probs though and no ' nasties '....meaning it's not worse for sure !
Yours will be with you Tuesday
Cheers
That's great Andrew! Any further comments on the sonics? Is a new cap in the reference machine yet?
Simon Hi
If jitter masks some upper mid and hf small detail then this has most certainly worked for me.
There's this track I listen to a lot which has some cymbal tapping going on in the background - you could just about hear it but it was never prominent.
Now, I can hear it quite clearly - that's not to mean it's gone bright or splashy ....just it's now part of the music as a whole - it's was quite surprising.
I'm really glad I did it and hope your findings are the same - see pic with the flat red Lemco.
The legs are not ' rods ' like resistors btw but instead are flat so you'll need to fold them with long nose pliers or something - very simple.
They still fit in the holes fine - no problem at all.
Btw.. the big Solens are now out - what a mistake they were. 10uf Box types are now in their place and don't move around.
As said, yours will leave tomorrow - good luck
Andrew
If jitter masks some upper mid and hf small detail then this has most certainly worked for me.
There's this track I listen to a lot which has some cymbal tapping going on in the background - you could just about hear it but it was never prominent.
Now, I can hear it quite clearly - that's not to mean it's gone bright or splashy ....just it's now part of the music as a whole - it's was quite surprising.
I'm really glad I did it and hope your findings are the same - see pic with the flat red Lemco.
The legs are not ' rods ' like resistors btw but instead are flat so you'll need to fold them with long nose pliers or something - very simple.
They still fit in the holes fine - no problem at all.
Btw.. the big Solens are now out - what a mistake they were. 10uf Box types are now in their place and don't move around.
As said, yours will leave tomorrow - good luck
Andrew
Attachments
Simon see below :
Quote: Also, is silver mica ok for the DEM cap in 2% tolerance ? You mentioned 1 % but they are hard to come by. unquote
Reply received today :
One could use a 220pF 2 ... 10% film cap in parallel with a 47pF film trimmer. This way the trimmer can be adjusted until the DEM clock locks on an exact multiple of the bit clock, this can be verified with a frequency counter or oscilloscope. The free running DEM clock can still lock to the bit clock because of on-chip crosstalk between both clock signals.
This is the latest received from ecdesigns - fyi
Quote: Also, is silver mica ok for the DEM cap in 2% tolerance ? You mentioned 1 % but they are hard to come by. unquote
Reply received today :
One could use a 220pF 2 ... 10% film cap in parallel with a 47pF film trimmer. This way the trimmer can be adjusted until the DEM clock locks on an exact multiple of the bit clock, this can be verified with a frequency counter or oscilloscope. The free running DEM clock can still lock to the bit clock because of on-chip crosstalk between both clock signals.
This is the latest received from ecdesigns - fyi
Hi Andrew,
I see why you installed that mica underneath, it's a pretty large and unwieldy-looking part.
I've not seen this other tweak, what's that all about then?
Simon
I see why you installed that mica underneath, it's a pretty large and unwieldy-looking part.
I've not seen this other tweak, what's that all about then?
Simon
Re 250PF silver Mica
Andrew,
Thanks for this tip. Do you merely remove the existing 860pf cap and replace with the sliver Mica?
I just got a bag of 1500pf 1000v silver mica from Russia. I suppose I could put 6 in series as an experiment. Talk about overkill!
Andrew,
Thanks for this tip. Do you merely remove the existing 860pf cap and replace with the sliver Mica?
I just got a bag of 1500pf 1000v silver mica from Russia. I suppose I could put 6 in series as an experiment. Talk about overkill!
Simon Hi
Underneath is the ONLY place I could fit it - probably same for you I'm guessing.
That diagram is another DEM method allegedly and has been done with success on other machines.
Still some homework to do and some guidance from a guy whose done it already.
If I can do it and it works I'll post the pics for you and Walter to chew over - only if it works though !!!
Walter Hi
I think you may mean 680pf but the answer is yes - cap C223 is out and replaced with the silver mica.
Hey, if you can get six in series in there I want to see pics please 😉 !!!
Andrew
Underneath is the ONLY place I could fit it - probably same for you I'm guessing.
That diagram is another DEM method allegedly and has been done with success on other machines.
Still some homework to do and some guidance from a guy whose done it already.
If I can do it and it works I'll post the pics for you and Walter to chew over - only if it works though !!!
Walter Hi
I think you may mean 680pf but the answer is yes - cap C223 is out and replaced with the silver mica.
Hey, if you can get six in series in there I want to see pics please 😉 !!!
Andrew
Guys
Thorsten Loesch just sent this to me :
In this case make sure your layout for decoupling around the TDA1541 (including ground) will not cause excessive problems at 2.8MHz. Just look at the various traces and capacitor dimensions (Datasheets for capacitors even better) ad have a reasonable guess at inductance. Then decide if you want to go as high as 2.8MHz. The logic will work this high, I seem to remember.
Using 4 * Fs (which in your case would 705.6KHz for 4 * OS) gives you more margin for layout issues etc, and still has four full DEM cycles per sample, which suffices if this stuff works at all... ;-)
This means ( with 705.6khz instead ) we can go for 122pf for a lock to BCK for 4x os too.
Walter, have you got 122pf ?
I'm getting into this now - DEM re clocking is definitely on the cards soon.
Just a few more questions to ask ......
I'll let you both know.....wtf....do the cap mod first, apologies for my new enthusiasm
Andrew
Thorsten Loesch just sent this to me :
In this case make sure your layout for decoupling around the TDA1541 (including ground) will not cause excessive problems at 2.8MHz. Just look at the various traces and capacitor dimensions (Datasheets for capacitors even better) ad have a reasonable guess at inductance. Then decide if you want to go as high as 2.8MHz. The logic will work this high, I seem to remember.
Using 4 * Fs (which in your case would 705.6KHz for 4 * OS) gives you more margin for layout issues etc, and still has four full DEM cycles per sample, which suffices if this stuff works at all... ;-)
This means ( with 705.6khz instead ) we can go for 122pf for a lock to BCK for 4x os too.
Walter, have you got 122pf ?
I'm getting into this now - DEM re clocking is definitely on the cards soon.
Just a few more questions to ask ......
I'll let you both know.....wtf....do the cap mod first, apologies for my new enthusiasm
Andrew
and finally :
....new (more stable) external DEM clock circuit. It consists of a differential TTL-level clock source (352.8 or 705.6 KHz), and 4 resistors. each DEM clock pin (16 & 17) is connected to -15V through a 2K2 resistor. The TTL-level clock signals are connected to pin 16 & 17 using 10K Ohm series resistors. The resistors will provide bias voltage (prevents the internal DEM clock from oscillating), attenuation and level conversion. This is the best performing DEM clock circuit so far.
Off to the post office😉
....new (more stable) external DEM clock circuit. It consists of a differential TTL-level clock source (352.8 or 705.6 KHz), and 4 resistors. each DEM clock pin (16 & 17) is connected to -15V through a 2K2 resistor. The TTL-level clock signals are connected to pin 16 & 17 using 10K Ohm series resistors. The resistors will provide bias voltage (prevents the internal DEM clock from oscillating), attenuation and level conversion. This is the best performing DEM clock circuit so far.
Off to the post office😉
Ah yes, I have read about that one, now I remember!
And Mr Loesch is a very helpful man indeed. He once e-mailed me to offer advice (on horns, waveguides, bass loading and foam usage) when I was designing my 3-way open baffle speakers, which really sing thanks to such expert tips 😉
And Mr Loesch is a very helpful man indeed. He once e-mailed me to offer advice (on horns, waveguides, bass loading and foam usage) when I was designing my 3-way open baffle speakers, which really sing thanks to such expert tips 😉
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