A New Take on the Classic Pass Labs D1 with an ESS Dac - Page 2 - 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 14th November 2009, 12:30 AM   #11
ichiban is offline ichiban  United States
space charged
diyAudio Member
 
ichiban's Avatar
 
Join Date: Oct 2004
Location: Tonawanda
Quote:
Originally Posted by relder View Post
Given the DAC output is around ground potential you'll have DC above the MOSFET, you have to get rid of it, which is most easily done with a cap, sorry.
How about if the dc blocking cap were moved to the input of the B1 circuit and using Salas's symetric B1. Then a smaller(affordable) high quality cap could be used instead. I don't know if the input cap at that circuit point loads it too much?
__________________

  Reply With Quote
Old 20th November 2009, 12:35 PM   #12
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
Quote:
Originally Posted by opc View Post

......Anyone feel like helping with the digital side of the DAC?

Cheers,
Owen
awesome!!!! this is exactly the sort of thing I had in mind as one of the options. I had transformer coupling in mind too as another 'module' but I have been eyeing off the B1 buffer (what can I say; I like nice caps niot always, but I have a weakness) sio yes I think this and the acko dac would make great partners and I would be interested for sure; I think it easier to keep a wider pitch on the pin headers though, to keep it more flexible.

Quote:
Originally Posted by jkeny View Post
Owen, I have an idea to make a modular design between your pcb & ACKO's Sabre DAC board - here's my post from the Buffalo tweakers thread in response to qusp wishing that the tweakers board had something to plug into it by which I assumed he meant an output stage:

I have an idea about that - basically to allow output boards to be plugged in from the top into the tweakers board using standard (low impedance) pin connectors i.e a 3D design. I reckon this would give the shortest path to the output stage (probably shorter than the Buff with on-board o/p stage?) & would be stable with 8-10 pins on each side PLUS would make it modular - just plug in another IV stage or whatever as long as it has the correct standard socket I'll be floating this one with Acko & Owen

What do you think?
absolutely!!!

Quote:
Originally Posted by opc View Post
Hi jkeny,

That would probably be the best way to go if people want to be able to swap various stages. We would just need to come up with a standard pinout for the connector, and I think that should be optimized based on the DAC outputs. With good layout, you could probably keep those connections to less than half an inch which would be about as good as having it on the same board.
yep, I think its just as good as on the same board and much more flexible. that way you could have preregs and regs below and feed them from there, with the ability to try different regs without desoldering anything. seems ideal

Quote:
I'm guessing the standard 0.1" pitch inline connectors would be the best bet, but I'm open to suggestions. I have seem much more expensive and finer pitch connectors for video applications, but that might just complicate things for people.
yeah stay with 0.1" IMO, keeps more options open, less fiddly and as you say its cheaper.

Quote:
Maybe another two connectors one either side of the IV stage could be used for swapping regs for the +/- 18V. I'll look into it.

I should have the layout mostly finished by the end of this weekend so I'll post a preliminary version for comments.

Cheers,
Owen
cool will keep a look out for it; things are coming together. I like it
  Reply With Quote
Old 20th November 2009, 01:20 PM   #13
diyAudio Moderator Emeritus
 
jean-paul's Avatar
 
Join Date: Sep 2002
Location: Germany
Please add output series resistors just like the B1 and the Hypnotize/Mezemerize have. They are needed. When the B1 part would be fed symmetrically the output cap can be omitted. Even a ( very slow ) servo + "muting at power on" circuit can be added to adjust output offset.
__________________
It's only audio. Official member of the Norske Brillegeit Gang.

Last edited by jean-paul; 20th November 2009 at 01:26 PM.
  Reply With Quote
Old 20th November 2009, 03:54 PM   #14
opc is offline opc  Canada
diyAudio Member
 
opc's Avatar
 
Join Date: Oct 2004
Location: Ottawa, Ontario, Canada
Hi Guys,

Jean Paul,

Youíre absolutely correct; the circuit does need that 1k series resistor. I have it on my prototype, but it wasnít in my simulation, which is what I posted. There are a few other discrepancies, namely that the two resistors to set the voltage at the gate of the fets are not as shown. Iíll double check their values and re-post a proper schematic. The lower resistor (gate to ground) is actually a pot, but itís easier to just use a resistor for simulation. Also, the 1k on the output is a load, and should be the same 221k as the B1.

Ichiban,

As for the capacitor questions, itís not possible to do away with the output cap entirely since, as relder pointed out, the drain of each of the fets is at about 9VDC. The cap could be moved to the input, if the lower fet was tied to Ė18V instead of ground, but as Jean Paul mentioned, youíd likely need some form of pop/click suppression. Overall, I much prefer the cap on the output, but the other way could work as well.

By the way, the 22uF is just a suggested value. Iím using 4.7uF right now for testing, and it doesnít roll off by any meaningful amount in the bottom end. Take a look at the input impedance of what youíre driving and calculate it from there. If you have a 10K input impedance on the next stage, you can get away with a 1uF cap and your turnover frequency will be 16Hz.

I still havenít had a chance to fire up the AP and measure the single-ended performance, but Iíll hopefully get around to it this weekend. Iím still working on the layout, but itís not quite there yet.

Iíll post an update with a final schematic (identical to my prototype) and the layout when I get some spare time.

Can someone post a direct link to Acko's most up to date schematic?

Cheers,
Owen
  Reply With Quote
Old 20th November 2009, 05:23 PM   #15
jkeny is offline jkeny  Ireland
Banned
 
Join Date: Feb 2007
Location: Dublin
Hi Owen,
Acko isn't going to post a schematic but I believe he emailed you to collaborate on the plug & socket arrangement between boards. Drop him an email!
  Reply With Quote
Old 20th November 2009, 06:33 PM   #16
acko is offline acko  Australia
diyAudio Member
 
Join Date: Jan 2008
Location: Sydney, Australia
Hi Owen,

I have sent a PM to you. Please contact me for details of the ackoDAC interface.
Hope to hear from you soon. Regards, Acko
  Reply With Quote
Old 20th November 2009, 07:48 PM   #17
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
Quote:
Originally Posted by opc View Post
Hi Guys,

Jean Paul,

You’re absolutely correct; the circuit does need that 1k series resistor. I have it on my prototype, but it wasn’t in my simulation, which is what I posted. There are a few other discrepancies, namely that the two resistors to set the voltage at the gate of the fets are not as shown. I’ll double check their values and re-post a proper schematic. The lower resistor (gate to ground) is actually a pot, but it’s easier to just use a resistor for simulation. Also, the 1k on the output is a load, and should be the same 221k as the B1.

Ichiban,

As for the capacitor questions, it’s not possible to do away with the output cap entirely since, as relder pointed out, the drain of each of the fets is at about 9VDC. The cap could be moved to the input, if the lower fet was tied to –18V instead of ground, but as Jean Paul mentioned, you’d likely need some form of pop/click suppression. Overall, I much prefer the cap on the output, but the other way could work as well.

By the way, the 22uF is just a suggested value. I’m using 4.7uF right now for testing, and it doesn’t roll off by any meaningful amount in the bottom end. Take a look at the input impedance of what you’re driving and calculate it from there. If you have a 10K input impedance on the next stage, you can get away with a 1uF cap and your turnover frequency will be 16Hz.

I still haven’t had a chance to fire up the AP and measure the single-ended performance, but I’ll hopefully get around to it this weekend. I’m still working on the layout, but it’s not quite there yet.

I’ll post an update with a final schematic (identical to my prototype) and the layout when I get some spare time.

Can someone post a direct link to Acko's most up to date schematic?

Cheers,
Owen
only problm with that is if 1k is added in series with the sabre output, it will no-longer operate in current output, will become voltage. the sabre needs to see around 680-700R output impedance or under to remain a current output dac. now whether that is at all meaningful now, with the possible implementation of the D1B1 is another thing. I just prefer current output dacs thats all

Last edited by qusp; 20th November 2009 at 08:02 PM.
  Reply With Quote
Old 20th November 2009, 08:19 PM   #18
opc is offline opc  Canada
diyAudio Member
 
opc's Avatar
 
Join Date: Oct 2004
Location: Ottawa, Ontario, Canada
Hi qusp,

The 1k resistor goes on the output of the I/V stage. The input impedance to the IV stage is very very low. With 30mA p-p of input current, I see less than 18.5mV p-p of swing at the DAC output. Thatís an effective impedance of less than 1 ohm. Itís part of the reason this circuit is so nice. It really lets the DAC operate at its best.

Hope this helps.

Cheers,
Owen
  Reply With Quote
Old 20th November 2009, 08:41 PM   #19
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
well that sounds perfect, sorry I had thought you were talking about the entrance to this circuit, not the output of this; input to the next amp stage. NICE!!

also, with the possible implementation of a digital volume control with the micro, will the buffer have enough drive to feed 300ohm balanced headphones directly like I can/could with my buffalo32 if I wish?? and also lower Z cans with the addition of an optional load resistor on the output of the buffer?? this is how I had by buffalo set up, I used an otto (relay) to switch TX2575 650R resistors into the signal for low z cans and remove them for less efficient cans and driving my active monitors and amp directly. I really liked this flexibilty. no biggie if not, but would be cool if that was still an option.

Last edited by qusp; 20th November 2009 at 09:03 PM.
  Reply With Quote
Old 21st November 2009, 02:14 AM   #20
opc is offline opc  Canada
diyAudio Member
 
opc's Avatar
 
Join Date: Oct 2004
Location: Ottawa, Ontario, Canada
Hi Guys,

I started a discussion with Acko, and it looks like everything should be a go! Once I get details on how the output section of his DAC is setup (layout, size, pinouts, etc...) then I can lay out the I/V stage and get boards made that will fit like a glove with the DAC.

In the meantime I'll be tweaking the circuit a little more, and hopefully I can get some SE measurements this weekend.

qusp:

I ran the headphone option through the simulator, and it doesn't look like it's going to work. I'm not sure what the headphones need for voltage to get decent listening levels, but the output voltage has dropped quite a bit by the time you get a 300 ohm load across the output. You'd be down to under 2V p-p which may or may not be enough. I don't know how much voltage a pair of headphones would need.

What I can do is add a connector at the output to allow a separate headphone amp to piggy-back on the outputs. If it were me, I'd probably build a scaled-down SOZ designed to drive headphones, but an op-amp could work well too. You could also use a multitude of other headphone amps designed specifically for the purpose and get very good performance. I often listen to music on my headphones at work, so I could be easily persuaded to do a headphone amp option.

Cheers,
Owen
  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 09:55 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