dac tube output stage..pls help. - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 13th March 2003, 08:48 AM   #1
diyAudio Member
 
tone's Avatar
 
Join Date: Aug 2002
Location: Malaysia
Send a message via ICQ to tone
Default dac tube output stage..pls help.

hi all,
need advice.
what would be the optimum Rload resistor for my dac tube output stage, im getting cracking sound from high level volume music, this is without the resistor,
i did try with 1M resistor, but distortions..

i have posted in digital section but not getting any advice..

>hope might get a reply from this forum..thanks.

>best regards,
>tone.
Attached Images
File Type: jpg tda1541atubeoutput.jpg (23.4 KB, 1511 views)
  Reply With Quote
Old 13th March 2003, 10:18 AM   #2
diyAudio Member
 
Join Date: Feb 2003
Location: Birmingham, UK
I am not familiar with this particular circuit, but I would suggest that if the output is fed into a SS amp then the resistor should be 50-100k and if into headphones then probably 10k or less. If the problem is overloading you could replace the resistor with a pot of the same value and take the output from the wiper.

However, if you are getting distortion and crackling I would also check the 1uf coupling capacitor, as it might be leaky and passing DC.
  Reply With Quote
Old 13th March 2003, 10:47 AM   #3
dhaen is offline dhaen  Europe
diyAudio Moderator Emeritus
 
dhaen's Avatar
 
Join Date: Jun 2002
Location: U.K.
Tone,

The purpose of the resistor is only to stop high voltage from appearing on the output. 1M will do. A bit lower is probably OK too, but if you go much lower you will start to "load" the previous stage.
I think that this design will not work well into a low impedance.

Cheers,
  Reply With Quote
Old 13th March 2003, 11:11 AM   #4
diyAudio Member
 
Join Date: Nov 2002
Location: North Herts, UK
Default ...Welcome back John!!!

Fully agree with John's advice 1M to 500K should do the trick nicely...

ciao

James
  Reply With Quote
Old 13th March 2003, 11:27 AM   #5
diyAudio Member
 
Join Date: Feb 2003
Location: Birmingham, UK
If this amp is feeding into a main amp the chances are that the resistor is unnecessary, as in the main map the input will feed across a load resistor anyway, possibly a volume pot - only if there is an isolating cap will a load resistor here be useful.

As far as any distortion/cracking is concerned, I think that this will caused elsewhere in the circuit, possibly the coupling cap, dry soldering joints, even noisy anode resistors (seems to be two in parallel) possibly...
  Reply With Quote
Old 13th March 2003, 12:00 PM   #6
diyAudio Member
 
tone's Avatar
 
Join Date: Aug 2002
Location: Malaysia
Send a message via ICQ to tone
Default dac

hi all,thanks for the advice..

will do what u guys have advice, will get back to u all soon..

btw:feeding directly a Inverted Gainclone "Thorsten Circuit".

thanks again.

tone.
  Reply With Quote
Old 13th March 2003, 11:26 PM   #7
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Default DAC.

Hi,

Not a digital expert but I find this setup rather errr... odd.

At the input of the xformer you have I/V conversion, the xformer steps up 1:15, than you have the tube stage where you take the output from the anode?? This ends up again in a highish Zo...

Looks odd to me.

Cheers,
__________________
Frank
  Reply With Quote
Old 13th March 2003, 11:29 PM   #8
diyAudio Moderator Emeritus
 
jean-paul's Avatar
 
Join Date: Sep 2002
Location: Germany
Quote:
If this amp is feeding into a main amp the chances are that the resistor is unnecessary, as in the main map the input will feed across a load resistor anyway, possibly a volume pot - only if there is an isolating cap will a load resistor here be useful.
Real bad advice if one want to disconnect DAC/cdplayer and amp now and then....

Or if one touches the center of the RCA cable...


It will give a plop from here to Tokyo and possibly the ( if SS ) amp will be dead too afterwards.

Old design techniques weren't invented for fun.

Jean-Paul
__________________
It's only audio. Official member of the Norske Brillegeit Gang.
  Reply With Quote
Old 14th March 2003, 07:20 AM   #9
diyAudio Member
 
tone's Avatar
 
Join Date: Aug 2002
Location: Malaysia
Send a message via ICQ to tone
Default dac

hi all,

1M resistor works.or should i use 500K?

hi bournville : u were right, the 1uf solen caps was leaking or something is wrong, replace the caps with new one..works fine..thanks.no more cracking sound.

Hi frank: what u would recommanded? i couldnt find any one tube for both channel circuit for the dac..so i use my preamp circuit for the dac.pls advice..thanks.

btw:it seem the dac is lack of bass, would a higher cathode caps helps>?

best,
tone.
  Reply With Quote
Old 14th March 2003, 07:33 AM   #10
diyAudio Moderator Emeritus
 
jean-paul's Avatar
 
Join Date: Sep 2002
Location: Germany
1 M is OK. Maybe you could check some tube output stages on these sites. Don't forget that the TDA1541A puts out more current than other DAC chips !

http://users.podolsk.ru/boga/Images/DAC_Buffer.gif

http://www.ndh.net/home/kboehm/T-DAC-P2.htm

http://www.ahfartaudio.com/6021W2doc.htm

http://www.megabaud.fi/~jtolonen/ga/tubedac/part1.html

http://home.netcom.com/~wa2ise/radios/tubedac.htm
__________________
It's only audio. Official member of the Norske Brillegeit Gang.
  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
Help with PSU for tube DAC output stage luvdunhill Tubes / Valves 1 6th May 2008 09:10 AM
Tube Output Stage Mighty Mouse Tubes / Valves 3 24th August 2004 08:08 PM
Tube output stage for DAC ackcheng Tubes / Valves 10 14th January 2004 12:13 PM
Tube output stage for DAC ackcheng Digital Source 0 9th January 2004 05:03 PM
need help on tube output stage.. tone Digital Source 2 19th March 2003 04:52 PM


New To Site? Need Help?

All times are GMT. The time now is 10:25 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