A New Take on the Classic Pass Labs D1 with an ESS Dac - Page 4 - 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 19th January 2010, 10:04 PM   #31
opc is offline opc  Canada
diyAudio Member
 
opc's Avatar
 
Join Date: Oct 2004
Location: Ottawa, Ontario, Canada
Hi Regal,

Sorry for the late response. I've attached a schematic that will work well with DAC's requiring 2.5V at the output.

Ignore the 33k3 value for R11 and R12, what you need there is a 50k pot. Start about midway (25K) and adjust to obtain 2.5VDC at the source of the fet. When that is set, you should see very close to 9VDC at the drain.

I'm not sure how much gain you need, but if you tell me what DAC and what configuration you plan to run, then I can dial in R1, R2, R3 and R4 to get you whatever you want voltage-wise at the output.

This project has been put aside for the past few months, but I should be getting back to it shortly.

Cheers,
Owen
Attached Images
File Type: jpg DAC.JPG (86.1 KB, 1725 views)
  Reply With Quote
Old 20th January 2010, 03:55 AM   #32
pidesd is offline pidesd  Canada
diyAudio Member
 
pidesd's Avatar
 
Join Date: Apr 2008
Location: montreal (cotes des neiges yo!)
looking foward to build one once it s complete! provided it works equally well with ess9008

keep the good work

Last edited by pidesd; 20th January 2010 at 04:04 AM.
  Reply With Quote
Old 20th January 2010, 06:06 PM   #33
opc is offline opc  Canada
diyAudio Member
 
opc's Avatar
 
Join Date: Oct 2004
Location: Ottawa, Ontario, Canada
Hi Guys,

I'm about to take a second run at the layout, and I have a general question about what people prefer as far as SMD and PTH components go.

I've been building with SMD parts for a while now, and I definitely prefer them, but I have noticed that people seem to prefer building with though-hole parts.

What is the general consensus on parts for a project like this? I've got some preferences of my own, and maybe people would like to comment:

Refer to the schematic attached above for designators.

R1, R2, R3, R4 - Panasonic 3W metal oxide or Caddock MP930 or 4x 1W thick film SMD (2512)

R5, R6, R7, R8, R9, R10, R13, R14 - Standard 1/4W PTH (300 spacing) or 0805 SMD

C3, C4 - 5mm spacing 10mm diameter solid polymer Nichicon - PTH

C1, C2, C7, C8 - 0805 SMD C0G/NP0 5% or PTH C0G/NP0 5% or PTH film

R11, R12 - Pots - standard 3-pin through-hole?

C5, C6 - Space for large film caps

J1, J2, J3, J4 - dual LSK170 SMD SOT123 or single LSK389 SMD SOIC

I could probably provide the boards with SMD parts pre-soldered for those who are afraid, but overall, it's easier than PTH to work with.

Any comments would be great!

Cheers,
Owen
  Reply With Quote
Old 20th January 2010, 06:47 PM   #34
pidesd is offline pidesd  Canada
diyAudio Member
 
pidesd's Avatar
 
Join Date: Apr 2008
Location: montreal (cotes des neiges yo!)
i guess PTH is easier to solder but if parts are not too close to each other then it might not be harder. also smd would be safer when desoldering.

availability of parts is also a concern, i dont know how it looks like from that perspective?
  Reply With Quote
Old 2nd February 2010, 10:30 AM   #35
diyAudio Member
 
Join Date: Nov 2002
Location: HK
Hi Owen,

I have search the forum and it seems you are the only guy who actually use a different mosfet with the original (almost) D1 circuit.
I order a few different mosfet to try as well (I can't find the RJK0305.
Is there any concern with the high input/output capacitance of this fet.
Also, I have notice that the transconductance drops lile a rock with low current for a lot of high transconductance device, how did u pick this one out from the bunch? Did u compare the sound between this and the original irf610? Thanks.

...chuck


Quote:
Originally Posted by opc View Post
Hi Guys,

..

I've combined the excellent transconductance of a power mosfet, with the low distortion of a JFET buffer to get to the circuit below. It's basically a low impedance D1, with a different mosfet, and a B1 buffer in place of the old mosfet based buffer. You could probably call it a D1B1.

..
Cheers,
Owen
  Reply With Quote
Old 6th February 2010, 05:51 AM   #36
pidesd is offline pidesd  Canada
diyAudio Member
 
pidesd's Avatar
 
Join Date: Apr 2008
Location: montreal (cotes des neiges yo!)
just did the half-d1b1(single end) and the sound is pretty good. really worth a try...

output cap is 2uf obbligato oil,
psu: dual sigma22
mosfet:irfz24n

thanks for sharing the design OPC
  Reply With Quote
Old 6th February 2010, 06:23 AM   #37
pidesd is offline pidesd  Canada
diyAudio Member
 
pidesd's Avatar
 
Join Date: Apr 2008
Location: montreal (cotes des neiges yo!)
stopped working...think the mosfet got too hot
  Reply With Quote
Old 6th February 2010, 01:25 PM   #38
opc is offline opc  Canada
diyAudio Member
 
opc's Avatar
 
Join Date: Oct 2004
Location: Ottawa, Ontario, Canada
Hi Pidesd,

I suppose both congrats and condolences are in order. Could you draw up exactly the circuit you were using, and what the voltages were at each of the fet nodes with respect to ground?

I've only tried the one mosfet so far, but I took the time to simulate several of them, and there wasn't much difference between them other than the voltage required at the gate to adjust the circuit.

I should be clear about power dissipation and requirements:

- R3 and R4 dissipate just under 1/2 watt each. Use at least 1W resistors.
- R1 and R2 dissipate just under 1 watt each, use at least 2W but 3W is better.
- Each mosfet dissipates a little over 1/3 of a watt, so it will be toasty.
- All other parts can be anything you want.

If you're uncomfortable running the fet that hot, then either add a little heatsink (the small tab mount TO-220 should do the trick) or use SMD parts and add some copper area to the PCB.

I'm glad you took the time to build it, and if you post your schematic, I'm sure we can figure it out!


Chuck,

You are absolutely correct about the transconductance of the fet dropping drastically at low current, and after quite a few simulations, it looks like the fet plays a smaller role than I initially assumed. I need to verify this with real tests, so I'll be doing that over next week. If anyone has any favorites, let me know and I'll include them in the test. Here's the short list:

IRF510
IRF610
IRF640
FQA19N20C
FDP030N06

As for input capacitance, I don't think it will have much of an effect, since the gate doesn't swing in this application. High Coss and Crss might have a negative impact, but I doubt it. I'll have to check. Keep in mind the conditions for all these specs in the datasheet, and that they are quite a bit different from what we're doing with it. We're running it at 50mA with only 7.3Vds. The swing at the source is less than a few mV and at the drain it's only a few volts.

Also, remember that the distortion and other performance specs on page 1 were obtained with the little Renesas fet, which is the only fet I've tested. I'll test the others mentioned above and post a comparison.

Cheers,
Owen

Last edited by opc; 6th February 2010 at 01:48 PM. Reason: Forgot to answer ChuckT
  Reply With Quote
Old 6th February 2010, 01:36 PM   #39
regal is offline regal  United States
diyAudio Member
 
Join Date: Jan 2004
Location: MD
Quote:
Originally Posted by opc View Post
Hi Regal,

Sorry for the late response. I've attached a schematic that will work well with DAC's requiring 2.5V at the output.

Ignore the 33k3 value for R11 and R12, what you need there is a 50k pot. Start about midway (25K) and adjust to obtain 2.5VDC at the source of the fet. When that is set, you should see very close to 9VDC at the drain.

I'm not sure how much gain you need, but if you tell me what DAC and what configuration you plan to run, then I can dial in R1, R2, R3 and R4 to get you whatever you want voltage-wise at the output.

This project has been put aside for the past few months, but I should be getting back to it shortly.

Cheers,
Owen
Thankyou, probably would be the TI PCM 1794, 7.8 ma p-p
  Reply With Quote
Old 6th February 2010, 02:29 PM   #40
opc is offline opc  Canada
diyAudio Member
 
opc's Avatar
 
Join Date: Oct 2004
Location: Ottawa, Ontario, Canada
I forgot to give the update on the layout... everything is pretty much done, and I'm about to send it off to Acko to check against his PCB. There are some differences, but I'm going to see where he can give a little, and where I can.

As you can see, it's not a lot of space (100mm x 72mm), but everything seems to fit. I've crammed the +/- 18V regulators on the board, but it's a very tight fit, and I'm not sure if people would rather have the regs off-board. Any opinions are welcome at this point. I personally would rather have them on the board, and I can provide tie-points for bypassing them if you want to use your own off-board regs.

I still need to talk to Acko about running the board wider than his DAC, which I don't think will be a problem. If that's a go, then I can layout the regs in a more optimal manner.

The board is two layer, ground plane on the bottom, signal and power on the top. I'll be splitting the ground plane in the middle of the board, so each channel has it's own plane. I'll provide multiple tie points for grounds, giving the user the option of tying the grounds at the DAC, at the PSU, or on this board itself.

The only other issue is output coupling caps. I've left space for 27.5mm spaced radial caps, that are 18mm wide and 31mm long. I'll be using 8.2uF Epcos polypropylenes (B32674D3825K) but others may want to use their favorite caps. As you can see, I've already given up over half the board area to caps, and I can't afford any more. I can provide pads for smaller caps, as well as electrolytics if people would like, but you're not going to be able to put monster sized films in those spots unless you mount them off-board and wire them over with flying leads.

Check it out and let me know if there are any comments!

Cheers,
Owen
Attached Images
File Type: jpg D1B1.jpg (132.9 KB, 1524 views)
Attached Files
File Type: pdf D1B1.pdf (15.0 KB, 314 views)
  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 02:15 PM.


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