Go Back   Home > Forums > >

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

Valve DAC from Linear Audio volume 13
Valve DAC from Linear Audio volume 13
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
Old 26th November 2020, 10:29 AM   #1071
diyAchim is offline diyAchim
diyAudio Member
 
Join Date: Dec 2012
Default -300V HT

How critical is the voltage on the HT supply?

I have a 260VAC transformer instead of the specified 230V trafo.

I will drop voltage by using higher R values in the RC nodes of the supply line.

May I drop a little less or more voltage than the 41 volts that calculation suggests? Would like to use resistors from the box.
  Reply With Quote
Old 26th November 2020, 10:44 AM   #1072
diyAchim is offline diyAchim
diyAudio Member
 
Join Date: Dec 2012
Default Error in TH BOM

There is a quantity error in the BOM list for the through-hole components:

pos.61
R14, R25, R26, R27, R103, R104, R105, R106
Resistor_Vertical_RM5mm
Quantity 4
value 2K0, 1 %

Quantity needs to be 8.
  Reply With Quote
Old 26th November 2020, 06:13 PM   #1073
rowli is offline rowli  Sweden
diyAudio Member
 
Join Date: May 2010
Hi,
changed plans for me. I will not build my DAC. Added my circuit board + suitable R-core transformer in the Swap Meet forum if anyone is interested.

Thanks Ray and Marcel!

And for the others in the group purchase, good luck with your builds, will be interesting to see the results!

/ Micke
  Reply With Quote
Old 26th November 2020, 11:35 PM   #1074
MarcelvdG is online now MarcelvdG  Netherlands
diyAudio Member
 
Join Date: Mar 2003
Location: Haarlem, the Netherlands
Quote:
Originally Posted by diyAchim View Post
How critical is the voltage on the HT supply?

I have a 260VAC transformer instead of the specified 230V trafo.

I will drop voltage by using higher R values in the RC nodes of the supply line.

May I drop a little less or more voltage than the 41 volts that calculation suggests? Would like to use resistors from the box.
My main worry would be start up at 10 % too high mains voltage. I've dimensioned many things for a maximum voltage at start-up of -400 V. -400 V at 10 % above nominal mains is -363 V at nominal mains.

During start-up, only the voltage divider R47, R43, R139, D16, R140, R141 loads the -300 V supply, so the voltage drop across R132 and R136 will be less than normal and the transformer will deliver a bit more voltage than normal. If needed you could consider replacing R136 with a series connection of a Zener and a resistor, to reduce the difference in voltage drop between start up and full operation.

Once everything is heated up, if you manage to get the negative supply somewhere between -290 V and -330 V at nominal mains voltage, that should be OK.

Do you happen to know the unloaded voltage of your transformer (or equivalently the regulation) and the VA rating?
  Reply With Quote
Old 27th November 2020, 08:55 AM   #1075
diyAchim is offline diyAchim
diyAudio Member
 
Join Date: Dec 2012
Quote:
Originally Posted by MarcelvdG View Post
Do you happen to know the unloaded voltage of your transformer (or equivalently the regulation) and the VA rating?
Thank you, as far as I remember, it's 290V unloaded, and 40VA. Can't check at the moment because I have to pull it from another build.

I did a sim in PSU Designer, assuming 10% regulation. This does look ok, given that C1-47uF is a 500V cap.

Valve DAC from Linear Audio volume 13-valvedacpsu-jpg

I will see how it turns out, the Zener is a good idea and another option.
Attached Images
File Type: jpg valvedacpsu.jpg (199.2 KB, 202 views)
  Reply With Quote
Old 3rd December 2020, 05:59 AM   #1076
NickKUK is offline NickKUK
diyAudio Member
 
Join Date: Dec 2019
Hello again. Just was thinking of a variant of the RAW DSD512..

I'm been thinking of a version of this with 6SN7s. With two triodes per envelope and medium mu, it got me thinking as the 10mA differential output should be used to drive a push pull configuration of two 6AS7s in OTL for headphones (I'm designing a PP 6SN7/6AS7 OTL headphone amp at the moment in LTSpice). Three 6SN7s could provide the 6 triodes needed in small neat headphone sized amp package.

* 6SN7 coping with MHz in real life vs simulation. Gut feeling is that it probably won't have a problem.

* Cross talk vs higher B+ to Va/Ia - I suspect this may cause more RF issues in close proximity. one option is to allow low Hz (DC) and high Hz (rise/fall of the digital signal) only using a blocking filter.

* Reconstruction filter - the temptation to put this between the 6AS7 and headphones but would have to play with a simulation.

I may quickly knock up a simple DSD512 clocked LTSpice simulation - perhaps use a input file with DSD512 and then output a WAV file and see (although this may take some time to simulate).
  Reply With Quote
Old 3rd December 2020, 07:23 AM   #1077
nautibuoy is offline nautibuoy  United Kingdom
diyAudio Member
 
nautibuoy's Avatar
 
Join Date: Jan 2010
Location: Somerset, England
Looking in a different direction, I have wondered previously about a version of Valve DAC using a Russian subminiature valve equivalent to the E88CC to make the board smaller/cheaper - 6S28B or 6S29B seem to be suitable but are only single triodes so the opportunity for a smaller board largely evaporates with the need for twice as many valves.

IIRC 6N16B is a well regarded dual triode sub-min equivalent to the 6SN7?
  Reply With Quote
Old 3rd December 2020, 08:04 AM   #1078
NickKUK is offline NickKUK
diyAudio Member
 
Join Date: Dec 2019
6N16B double triode miniature tube → OTHER tubes → Tubes-Store.com

Hmm interesting.. less power handling but that's to be expected. I think it depends a little on what it's driving on the next stage - 6AS7 needs a fair whack of current.

I can't read Russian but ... hang on full stats here: 6N16B-VI Double Triode Miniature Tube MELZ Soviet Russian NEW all photos and images | photorp.com
curves: https://photorp.com/media/photorp/vi...ure-tube-1.jpg
Click the image to open in full size.

Last edited by NickKUK; 3rd December 2020 at 08:07 AM.
  Reply With Quote
Old 3rd December 2020, 08:45 AM   #1079
NickKUK is offline NickKUK
diyAudio Member
 
Join Date: Dec 2019
Do - edit timed out as I was playing with the load line calculator (Triode / Pentode Loadline Simulator v.1.0 (20161216 www.trioda.com)). Looking at the load line, in the architecture we have for the valveDAC the valve will see the 16Kohm resistance (Ra) as it's got two 32R in parallel. A 0-5V grid (not using ±2.5), 153Ua, 16K Ra, will see ~ 2.59mA Iq (10mA at 0Vg, 3mA at about -5Vg) mu of 22.5V/V. There's still a little more you could give the tube by increasing the anode voltage.

Maybe I'm wrong and need of another coffee after a 5am start..

Last edited by NickKUK; 3rd December 2020 at 08:48 AM.
  Reply With Quote
Old 3rd December 2020, 02:06 PM   #1080
NickKUK is offline NickKUK
diyAudio Member
 
Join Date: Dec 2019
Well got the 6SN7 model running on LTSpice lol - DSD512 simulation

Screenshot 2020-12-03 at 14.04.19.png

This is literally the same voltages so probably not the best for the 6SN7's performance but it's 'working' (there needs to be a load of testing for distortion etc) plus I've not put in part of the filter (Lundhl transformer not in) so there's likely to be a load of digital signals output. I also had to use the 74HC74 which is 0.5V instead of the 74HCT74 which is 1.3V due to LtSpice model availability.

Last edited by NickKUK; 3rd December 2020 at 02:22 PM.
  Reply With Quote

Reply


Valve DAC from Linear Audio volume 13Hide this!Advertise here!
Thread Tools

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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
13.8V 80A Linear PS circuit design analysis for Ham Radio Use FJHookah Power Supplies 71 27th October 2019 03:52 PM
Is it tradition that we use linear PSUs for valve amps? Paul Uszak Power Supplies 9 2nd September 2016 11:58 PM
Audio Valve Eklipse volume pot value? Ki Choi Tubes / Valves 0 27th March 2015 06:22 PM
Londog Audio VDt1 Valve Output 24/192 DSD DAC mainscablesrus Mains Cables R Us 1 1st October 2013 07:52 PM
Audio Note DAC 2.1x valve DAC juancho Swap Meet 0 6th July 2005 10:16 PM


New To Site? Need Help?

All times are GMT. The time now is 11:32 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Copyright ©1999-2021 diyAudio
Wiki