A New Take on the Classic Pass Labs D1 with an ESS Dac - Page 89 - diyAudio
Go Back   Home > Forums > Source & Line > Digital Line Level

Digital Line Level DACs, Digital Crossovers, Equalizers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 10th February 2012, 11:39 AM   #881
regal is offline regal  United States
diyAudio Member
 
Join Date: Jan 2004
Location: MD
Assume if one wanted to use these boards with the original PCM63k's, that their current output +-2.1 is not enough to use the new mofsets to get these lows THD results?

Would it be worth simulating with higher supply voltages ?

Also I believe I am down for a board, want to make sure that is good for stereo balanced, if not I need 2.

Last thanks in advance for putting up with a dac neanderthal's questions
  Reply With Quote
Old 10th February 2012, 12:20 PM   #882
diyAudio Member
 
Join Date: Dec 2009
Send a message via Yahoo to Lil Knight
Just wondering if this board would work with the AD1865? I have some spare DAC END 2 boards that I have no use. DAC End 2 - the AD1865N-K with single ended vacuum output stage
__________________

  Reply With Quote
Old 10th February 2012, 12:43 PM   #883
opc is offline opc  Canada
diyAudio Member
 
opc's Avatar
 
Join Date: Oct 2004
Location: Ottawa, Ontario, Canada
Hi Guys,

Generally speaking, I would say that it's probably not worthwhile to mate this with the AD1865 or the PCM63K. It can certainly be done, but with such low output current swing, the gain has to be adjusted way up which requires larger resistor values. This in turn drops the current, which drops the transconductance and the whole thing quickly spirals downhill. The output impedance also climbs up as those resistors are increased, and you'll soon find that you need a buffer or a second stage to lower the output impedance. This basically lands you right back at the original D1 circuit, which is really what you would want to build if you had the PCM63K.

The only viable option I see would be to just drop one of those dacs in as it is, and live with the very low output. You could always add your favorite voltage gain stage after this, and that would get you what you need.

Regal: indeed, one board does provide differential stereo output and all necessary power supplies. Just add transformers and a heatsink!

Cheers,
Owen
  Reply With Quote
Old 13th February 2012, 10:51 PM   #884
diyAudio Member
 
Algar_emi's Avatar
 
Join Date: Oct 2002
Location: Canada, Qc
Almost ready to test the FET into the actual circuit after a weekend spent in drilling and mounting into the recycled case. Everything is mounted on a sub plate of 1/8 aluminum for better heat dissipation and easier testing. All supplies tested ok. I'll mount the FET on the bottom plate near the heatsink for the test.
Attached Images
File Type: jpg Proto.jpg (191.3 KB, 417 views)
  Reply With Quote
Old 14th February 2012, 02:12 AM   #885
diyAudio Member
 
Algar_emi's Avatar
 
Join Date: Oct 2002
Location: Canada, Qc
To what value do I adjust the PCB pots? Is it for 3V at the pot as in the transconductance procedure? Then I measure the 200R Resistor Voltage? Thanks.
  Reply With Quote
Old 14th February 2012, 02:19 AM   #886
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
no, the pots on the PCB are a completely different purpose, simply to adjust gate bias to match AVCC/2 on your particular dac. so power up your buff and measure what the DC voltage from AVCC L/R reg to ground is and divide that by 2 (normally around 1.65-1.7vdc), note that down, power up the board with the dac not connected and adjust all the pots to match that voltage on each mosfet source ->G. power down and install the dac, power the lot up, measure each source to ground and readjust to match the voltage again as it will change a touch under load.


hope that makes sense

Last edited by wintermute; 19th February 2012 at 02:47 AM. Reason: fixed incorect procedure at the request of qusp.
  Reply With Quote
Old 14th February 2012, 07:04 AM   #887
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
the other operating points as set in the matching procedure, are already set by the fixed resistors given +/-45vdc input
  Reply With Quote
Old 14th February 2012, 09:30 PM   #888
diyAudio Member
 
Algar_emi's Avatar
 
Join Date: Oct 2002
Location: Canada, Qc
What is the AVCC L/R reg? Is it the analog Vcc regulators of the dac?
I have a Buffalo ESS ver 1 DAC. See the included schematic from the Buffalo. Is this the supply I need to measure to find the AVCC L/R? Thanks...
Attached Images
File Type: jpg AVCC_Schematic.jpg (11.0 KB, 368 views)
  Reply With Quote
Old 14th February 2012, 09:39 PM   #889
opc is offline opc  Canada
diyAudio Member
 
opc's Avatar
 
Join Date: Oct 2004
Location: Ottawa, Ontario, Canada
Hi Algar,

It is indeed this supply. It should be 3.3VDC so the pot should be adjusted for 1.65VDC on the source of the mosfet (where the DAC output connects). The DAC is happiest when its output is at exactly 1/2 AVCC.

Regards,
Owen
  Reply With Quote
Old 15th February 2012, 12:40 AM   #890
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
oops...., yes source, now that was a brain fart; i started thinking of matching too even after mentioning these were already set. its best to measure the reg rather than assuming 3.3/2 as the tp boys at least with the buf 2 onwards increased this voltage to 3.4 and even a touch higher on some modules. I have gone as far as 3.6v in my experiments; Dustin gives this tip to increase DNR; but i'm not sure if they were doing it back then; sorry i forgot you were using the V1 dac.

Last edited by qusp; 15th February 2012 at 12:50 AM.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pass Labs S/Ns ? dejanm Pass Labs 8 26th January 2007 07:35 AM
My opinion on Pass Labs and Mr. Pass (Nelson) himself b_online Pass Labs 11 21st May 2003 12:39 AM


New To Site? Need Help?

All times are GMT. The time now is 10:34 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2