Upgraded Single Board PCM1794 NOS DDDAC

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B

Brumjam

Member
Joined 2012
emyeuoi (CCS x 2)
carlsor (CCS x 4)
juancho (CCS x 4)
crazyfrog (CCS x2)
mk57 (CCS x 8) + parts
SimonJ (CCS x 2) + parts
PET-240 CCS x 4 + parts
sterlingmck (CCS x 4) + parts
zz1969 (CCS x 8) + parts
kurand (CCS x 4) + parts
mbcoffman (CCS x 2) + parts
Myint67 (CSSx2)+ parts
tuyen (CCS x 8) + parts
Brumjam (CCS x 4) + parts

Total CCS= 58
Parts = 46
 
M

mr_whocares

Member
Joined 2005
emyeuoi (CCS x 2)
carlsor (CCS x 4)
juancho (CCS x 4)
crazyfrog (CCS x2)
mk57 (CCS x 8) + parts
SimonJ (CCS x 2) + parts
PET-240 CCS x 4 + parts
sterlingmck (CCS x 4) + parts
zz1969 (CCS x 8) + parts
kurand (CCS x 4) + parts
mbcoffman (CCS x 2) + parts
Myint67 (CSSx2)+ parts
tuyen (CCS x 8) + parts
Brumjam (CCS x 4) + parts
mr_whocares (CCS x 2) + parts

Total CCS= 60
Parts = 48
 
M

mr_whocares

Member
Joined 2005
emyeuoi (x1)
PET-240 x2 + 2 set JFETS + 2 set Susumu
Myint67x1+1sets JFETS + 1set susumu
Juancho x2 + 2 sets JFETS + 2 sets Susumu
Sterlingmck x2 + 2 set JFETS + 2 set Susumu
BDL x1 + 1 set JFETS + 1 set Susumu
mbcoffman x1 + 1 set JFETS + 1 set Susumu
carlsor x1
naimster x2
kurand x1 + 1 set JFETS + 1 set Susumu
brettlb x1
SimonJ x1 + 1 set JFETS + 1 set Susumu
JanGr. (x1)
ed linssen x1 + 1set JFETS + 1 set Susumu
tuyen x1 + 1 set JFETS + 1 set susumu
mr_whocares x1 + 1 set jfets + 1 set susumu

PCB= 20
Parts= 14
 
T

tods

Member
Joined 2013
emyeuoi (CCS x 2)
carlsor (CCS x 4)
juancho (CCS x 4)
crazyfrog (CCS x2)
mk57 (CCS x 8) + parts
SimonJ (CCS x 2) + parts
PET-240 CCS x 4 + parts
sterlingmck (CCS x 4) + parts
zz1969 (CCS x 8) + parts
kurand (CCS x 4) + parts
mbcoffman (CCS x 2) + parts
Myint67 (CSSx2)+ parts
tuyen (CCS x 8) + parts
Brumjam (CCS x 4) + parts
mr_whocares (CCS x 2) + parts
tods (CCS x 8) + parts

Total CCS= 68
Parts = 56
 
I

IanS1

Member
Joined 2012
emyeuoi (CCS x 2)
carlsor (CCS x 4)
juancho (CCS x 4)
crazyfrog (CCS x2)
mk57 (CCS x 8) + parts
SimonJ (CCS x 2) + parts
PET-240 CCS x 4 + parts
sterlingmck (CCS x 4) + parts
zz1969 (CCS x 8) + parts
kurand (CCS x 4) + parts
mbcoffman (CCS x 2) + parts
Myint67 (CSSx2)+ parts
tuyen (CCS x 8) + parts
Brumjam (CCS x 4) + parts
mr_whocares (CCS x 2) + parts
tods (CCS x 8) + parts
IanS1 (CCS x 4) + Parts

Total CCS= 72
Parts = 60
 
dwjames

dwjames

Member
Joined 2012
emyeuoi (CCS x 2)
carlsor (CCS x 4)
juancho (CCS x 4)
crazyfrog (CCS x2)
mk57 (CCS x 8) + parts
SimonJ (CCS x 2) + parts
PET-240 CCS x 4 + parts
sterlingmck (CCS x 4) + parts
zz1969 (CCS x 8) + parts
kurand (CCS x 4) + parts
mbcoffman (CCS x 2) + parts
Myint67 (CSSx2)+ parts
tuyen (CCS x 8) + parts
Brumjam (CCS x 4) + parts
mr_whocares (CCS x 2) + parts
tods (CCS x 8) + parts
IanS1 (CCS x 4) + Parts
dwjames (CCS x 2) + parts

Total CCS= 74
Parts = 62
 
dwjames

dwjames

Member
Joined 2012
emyeuoi (x1)
PET-240 x2 + 2 set JFETS + 2 set Susumu
Myint67x1+1sets JFETS + 1set susumu
Juancho x2 + 2 sets JFETS + 2 sets Susumu
Sterlingmck x2 + 2 set JFETS + 2 set Susumu
BDL x1 + 1 set JFETS + 1 set Susumu
mbcoffman x1 + 1 set JFETS + 1 set Susumu
carlsor x1
naimster x2
kurand x1 + 1 set JFETS + 1 set Susumu
brettlb x1
SimonJ x1 + 1 set JFETS + 1 set Susumu
JanGr. (x1)
ed linssen x1 + 1set JFETS + 1 set Susumu
tuyen x1 + 1 set JFETS + 1 set susumu
mr_whocares x1 + 1 set jfets + 1 set susumu
dwjames x1 + 1 set jfets + 1 set susumu

PCB= 21
Parts= 15


Also, just to add, if people don't have a power supply in mind yet for their buffers, I think one of these would do the job well for low hassle and low cost
4.17uV Ultralow noise DAC power supply regulator +-12/15V 1A - DIYINHK
 
M

mr_whocares

Member
Joined 2005
E

ed linssen

Member
Joined 2004
emyeuoi said:
Dear All,

carlsor kindly highlight to me that the 2SK208, as per datasheet, need to be flipped.

Thanks carlsor to catch it :)

Attached the new layout of the CCS circuit.

Tomorrow I will close the GB and in few days I will send you a PM with the final amount including handling/shipping. Please reply to the PM with your paypal account and the exact shipping address.

Thanks and Happy New Years to all of you and your families.

Enrico
Click to expand...


Hi Enrico,

If you give this GB a few more days, I think you will easily pass the 100 piece price point?
Ed
 
C

carlsor

Member
Joined 2008
pdb Answer Re Volume Pot

Question: Could the buffer with psu's and a volume pot be used as a simple preamp with no gain? If yes, what would be the prefered impedance for the pot? Thanks. Per
__________________
pdb
Click to expand...

No. The buffer outputs are about 2.8V above DAC signal ground and are designed to drive a Transformer or capacitors. The audio signal to a volume control pot is usually at signal ground with no music playing. The Transformer does this conversion.
 
pdb

pdb

Member
Joined 2007
carlsor said:
No. The buffer outputs are about 2.8V above DAC signal ground and are designed to drive a Transformer or capacitors. The audio signal to a volume control pot is usually at signal ground with no music playing. The Transformer does this conversion.
Click to expand...
Thanks carlsor for your quick answer. Silly question: If I added in a pair of cinemags AND a volume pot - or a TVC w the buffer - would that make a preamp?
 
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E

ed linssen

Member
Joined 2004
emyeuoi (x1)
PET-240 x2 + 2 set JFETS + 2 set Susumu
Myint67x1+1sets JFETS + 1set susumu
Juancho x2 + 2 sets JFETS + 2 sets Susumu
Sterlingmck x2 + 2 set JFETS + 2 set Susumu
BDL x1 + 1 set JFETS + 1 set Susumu
mbcoffman x1 + 1 set JFETS + 1 set Susumu
carlsor x1
naimster x2
kurand x1 + 1 set JFETS + 1 set Susumu
brettlb x1
SimonJ x1 + 1 set JFETS + 1 set Susumu
JanGr. (x1)
ed linssen x1 + 1set JFETS + 1 set Susumu (+ 2 sets of CCS parts )
tuyen x1 + 1 set JFETS + 1 set susumu
mr_whocares x1 + 1 set jfets + 1 set susumu
dwjames x1 + 1 set jfets + 1 set susumu

PCB= 21
Parts= 15
 
dwjames

dwjames

Member
Joined 2012
carlsor said:
No. The buffer outputs are about 2.8V above DAC signal ground and are designed to drive a Transformer or capacitors. The audio signal to a volume control pot is usually at signal ground with no music playing. The Transformer does this conversion.
Click to expand...
I'm confused... There's a lot of guys running direct from the mainboard pos and neg outputs without caps or transformers with good results, how does this differ? The +2.7v dc offset of the pos and the -2.7v of the neg cancel out to give close to a dc offset of zero.

The buffer uses the pos and neg as inputs and the dc offset that comes out of the buffer is tweakable to be zero via the trimpot.

Is it just a safety thing, that if something goes wrong you could feed a 2.7v dc offset into your amp that's the issue?

Not having a go, just curious :)

James
 
C

carlsor

Member
Joined 2008
Direct Feed

All four of the differential outputs from the DAC outputs are about +2.7V above DAC signal ground into Rload resistors. The Pos and Neg outputs of each side are both +2.7V. There is no such thing as a +2.7V pos cancelling a -2.7V neg. The differential between these two is usually less than 2.0mv. With the buffer this difference can be adjusted close to 0.0mv, but is still about 2.8v above DAC signal ground. It is a little higher than 2.7V because the Buffer JFETS are operating at 70-80% of Idss.

Doede's DAC and the buffer are designed to feed output transformers or output capacitors. Direct feed to preamps or amps may or may not cause problems depending on the equipment and how they are connected. Differential connections have the best chance of success. It depends on how the down stream equipment deals with the +2.7V output signals. My guess is that the DAC ground is not even connected. No one explains exactly how they directly connect the DAC to equipment. I wish these were explained in the forum. A TVC volume control might be able to function like an output transformer as long as it is not putting 2.7V through it to ground.

I recommend that the buffer NOT be used to directly feed equipment. Do this at your risk. If a Buffer JFET blows up then the output becomes a 12-15ma current sink limited by the constant voltage transistor operating at about -2.75V. I can always supply more JFETS. If someone insists of using the Buffer to directly feed something then put at least 470 ohms in series between the buffer outputs and the direct feed as a test that might not blow up anything. Usually an input transistor or input tube is an easier load to drive than an output transformer so a buffer wouldn't be much benefit.
 
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pdb

pdb

Member
Joined 2007
carlsor said:
All four of the differential outputs from the DAC outputs are about +2.7V above DAC signal ground into Rload resistors.....
Click to expand...
Thanks carlsor - even though this answer was not directed at me (I think) My question was IF the buffer could be transferred into a (safe) preamp - with trafos, caps or other means. I have always felt that no (or very little) DC on the input of DC coupled amp(setup) has to be no or little DC under ANY CIRCUMSTANCES. Sorry for any off topic confusion. Back to the group buy listings...
 
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dwjames

dwjames

Member
Joined 2012
carlsor said:
All four of the differential outputs from the DAC outputs are about +2.7V above DAC signal ground into Rload resistors.

No one explains exactly how they directly connect the DAC to equipment. I wish these were explained in the forum.
Click to expand...
Sorry yes, my bad... the DC offsets for pos and neg are both +2.7v or thereabouts, So the DC offset between pos and neg is minimal. Usually only a couple of mv, depending on how accurately matched the I/V resistors are I believe.
The audio signals on pos and neg are the same, but opposite phased.

So what some people have been doing is ignoring the common (dac gnd), and just using pos and neg as a single ended output with almost no DC offset and not using any caps or transformers on this output. Neg becomes RCA gnd. Obviously it's not the recommended route (and I wouldn't be happy doing it on an amp without some form of coupling capacitors or transformers before the power stage) but some have found this works well for them.
 
T

titus2002

Member
Joined 2009
emyeuoi (x1)
PET-240 x2 + 2 set JFETS + 2 set Susumu
Myint67x1+1sets JFETS + 1set susumu
Juancho x2 + 2 sets JFETS + 2 sets Susumu
Sterlingmck x2 + 2 set JFETS + 2 set Susumu
BDL x1 + 1 set JFETS + 1 set Susumu
mbcoffman x1 + 1 set JFETS + 1 set Susumu
carlsor x1
naimster x2
kurand x1 + 1 set JFETS + 1 set Susumu
brettlb x1
SimonJ x1 + 1 set JFETS + 1 set Susumu
JanGr. (x1)
ed linssen x1 + 1set JFETS + 1 set Susumu (+ 2 sets of CCS parts )
tuyen x1 + 1 set JFETS + 1 set susumu
mr_whocares x1 + 1 set jfets + 1 set susumu
dwjames x1 + 1 set jfets + 1 set susumu
titus2002 x1 + 1 set jfets + 1 set susumu

PCB= 22
Parts= 16
 
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