Author Topic: duelund caps issues  (Read 15427 times)

avian

  • Guest
Re: duelund caps issues
« Reply #20 on: October 12, 2010, 02:02:43 PM »
HI ,
      As mentioned we can add a timer that disconnect the dueland from the circuit and after 60 sec reconnects or the easyest way would put a switch in series with the cap but both these ideas will cause a loud pop.
       I will give this some thought and get back you .
                                                               Paul

Easy solution.  Put a timer on the heater for the tube rectifier.   Solves the popping and gives a nice slow application of b+ to the output tube once its already warm.

Well Boys,
               I have just gone and measured my voltage across the dueland in my dac and to my amazment from cold turn on the volt for about 3 second went to the same as the B+ rail.Then as the ecc88 warmed up come down to 70 volts. It appears that this would proberly be very low current as the out of the dueland goes to ground though a 100k resistors and the amp has an input cap.Never the less it could damage a cap. Some caps will tolerate a high spick better than others.I am working on a different approch for the tube output stage which would not have this problem.It takes time to develop new ideas.
                              In all the dacs with these caps in them 3 is not a lot.As a technican I see a lot more caps on regular basis changed in a LCD Monitor or TV.
                              Any way boys lets enjoy our toys
                                                                                           Paul

Im really really amazed you didnt consider it to be honest, usually people just use an output cap rated to full b+, but in the case of the duelund I understand the cost increase would be significant. 


Offline omodo

  • Sr. Member
  • ****
  • Posts: 491
  • Liked: 103
  • Green tinted glow
Re: duelund caps issues
« Reply #21 on: October 12, 2010, 02:09:37 PM »
not sure why it's to your amazement? coupling caps/output caps connected to the plate should be rated at least to the value of voltage that could be on the plate, and before the tube is conducting/heated this would be the full B+

adding a B+ timer to delay the application of HV until the output tubes are warmed is pretty trivial, or do what avian suggests and delay filament voltage to the rectifier

capacitor costs aside (the difference between a 200Vdc duelund and a 400Vdc Duelund isn't that much in the scheme of things), sending (70V!!) DC down the ICs after a cap fails could be a potentially costly issue

I'd be suprised if the Duelund warranty covers applying 1.5x the rated voltage, no matter how short...
« Last Edit: October 12, 2010, 02:13:30 PM by omodo »

Offline stevenvalve

  • Administrator
  • Hero Member
  • *****
  • Posts: 1490
  • Liked: 259
Re: duelund caps issues
« Reply #22 on: October 12, 2010, 03:26:46 PM »
not sure why it's to your amazement? coupling caps/output caps connected to the plate should be rated at least to the value of voltage that could be on the plate, and before the tube is conducting/heated this would be the full B+

adding a B+ timer to delay the application of HV until the output tubes are warmed is pretty trivial, or do what avian suggests and delay filament voltage to the rectifier

capacitor costs aside (the difference between a 200Vdc duelund and a 400Vdc Duelund isn't that much in the scheme of things), sending (70V!!) DC down the ICs after a cap fails could be a potentially costly issue

I'd be suprised if the Duelund warranty covers applying 1.5x the rated voltage, no matter how short...
Mine have about 2-3 years on them without any trouble. I do use a filament switch and disable the B+. GZ34 rectifiers have a delay standard, most do not. There has been about 30 used so far only one i have had failed. Anyway people change them, we will use them in other places in the DAC. Mike is ordering some now, so get moving.  2.2 UF or bigger  400V. He orders not that often so do it now.
« Last Edit: October 12, 2010, 03:30:21 PM by stevenvalve »

Offline stevenvalve

  • Administrator
  • Hero Member
  • *****
  • Posts: 1490
  • Liked: 259
Re: duelund caps issues
« Reply #23 on: October 12, 2010, 03:59:33 PM »
not sure why it's to your amazement? coupling caps/output caps connected to the plate should be rated at least to the value of voltage that could be on the plate, and before the tube is conducting/heated this would be the full B+

adding a B+ timer to delay the application of HV until the output tubes are warmed is pretty trivial, or do what avian suggests and delay filament voltage to the rectifier

capacitor costs aside (the difference between a 200Vdc duelund and a 400Vdc Duelund isn't that much in the scheme of things), sending (70V!!) DC down the ICs after a cap fails could be a potentially costly issue

I'd be suprised if the Duelund warranty covers applying 1.5x the rated voltage, no matter how short...
Mine have about 2-3 years on them without any trouble. I do use a filament switch and disable the B+. GZ34 rectifiers have a delay standard, most do not. There has been about 30 used so far only one i have had failed. Anyway people change them, we will use them in other places in the DAC. Mike is ordering some now, so get moving.  2.2 UF or bigger  400V. He orders not that often so do it now.
Paul has checked his dac, and with a B+ switch does not get the startup surge. Anyway change them (Caps), they are too expensive to take the risk.

tuyen

  • Guest
Re: duelund caps issues
« Reply #24 on: October 12, 2010, 04:20:46 PM »
G'day Steve,

What's your thoughts on the duelund CAST-Cu ones?

I'll ask if Mike is able to get in any of the new VSF blacks :D

crazikid

  • Guest
Re: duelund caps issues
« Reply #25 on: October 12, 2010, 05:56:09 PM »
good question tuyen...

Offline stevenvalve

  • Administrator
  • Hero Member
  • *****
  • Posts: 1490
  • Liked: 259
Re: duelund caps issues
« Reply #26 on: October 12, 2010, 06:55:54 PM »
G'day Steve,

What's your thoughts on the duelund CAST-Cu ones?

I'll ask if Mike is able to get in any of the new VSF blacks :D
You will have to find the voltage rating. As for sound wise, are you going to be the ginea pig. may be crap

crazikid

  • Guest
Re: duelund caps issues
« Reply #27 on: October 12, 2010, 07:11:17 PM »
does that mean i've gotta replace my duelunds?

tuyen

  • Guest
Re: duelund caps issues
« Reply #28 on: October 12, 2010, 07:20:01 PM »
What price can Mike get the 400v 2.2uf vsf cu for?

Offline stevenvalve

  • Administrator
  • Hero Member
  • *****
  • Posts: 1490
  • Liked: 259
Re: duelund caps issues
« Reply #29 on: October 12, 2010, 08:14:32 PM »
does that mean i've gotta replace my duelunds?
You can use them but take the risk that one day they may stop. Or buy the 400V version maybe never have a problem. Ring mike for a price he is aussie distributer. They may sound even better. usually higher voltage caps do.

crazikid

  • Guest
Re: duelund caps issues
« Reply #30 on: October 12, 2010, 09:25:37 PM »
awesome.. thanks.. :D

Offline stevenvalve

  • Administrator
  • Hero Member
  • *****
  • Posts: 1490
  • Liked: 259
Re: duelund caps issues
« Reply #31 on: October 12, 2010, 09:29:58 PM »
does that mean i've gotta replace my duelunds?
We use 65V dc.  They are rated at 100V ac. Even at switch on. peak is still well with specification. They are hand made and vulnerable to variances.  

Offline kajak12

  • Hero Member
  • *****
  • Posts: 2445
  • Liked: 67
    • http://killerdac.com/forum/index.php
Re: duelund caps issues
« Reply #32 on: October 12, 2010, 09:48:13 PM »
just measured my dac for dc on the cap.b+ switched off and a waiting time of 10min then i turned the b+ on the dc voltage reading was 136v dc for about 30 sec.well below the 200v dc raiting
« Last Edit: October 12, 2010, 09:50:17 PM by kajak12 »
still discovering the link between electronics and audio reproduction.so much to learn and so little time

Offline zenelectro

  • Hero Member
  • *****
  • Posts: 781
  • Liked: 146
Re: duelund caps issues
« Reply #33 on: October 12, 2010, 10:04:27 PM »
Guys,

The simple solution to this is to protect the Duelund with a 100V clamp circuit on it's input.

This will prevent the input (tube) side of the Duelund from ever going above 100V.

Refer to my schematic below. Basically there are 3 connection points, ground, Duelund IP and HT (300V).

cheers

Terry

Offline zenelectro

  • Hero Member
  • *****
  • Posts: 781
  • Liked: 146
Duelund voltage clamp
« Reply #34 on: October 12, 2010, 10:12:48 PM »
I ran Ltspice simulator to design the clamp and optimise it so as not to degrade any 'killer sound'

With 3V pk OP and at 20kHz which is worst possible condition, the clamp adds 0.00033%
distortion - mainly 2nd harmonic.

I will knock one up and try it on Stevenvalves system.  

Terry
« Last Edit: October 12, 2010, 10:15:11 PM by zenelectro »

crazikid

  • Guest
Re: duelund caps issues
« Reply #35 on: October 12, 2010, 10:21:38 PM »
terry... your a genius...  thanks steve and mario for your input

tuyen

  • Guest
Re: duelund caps issues
« Reply #36 on: October 12, 2010, 10:26:24 PM »
Appreicate it greatly zen!




Offline kajak12

  • Hero Member
  • *****
  • Posts: 2445
  • Liked: 67
    • http://killerdac.com/forum/index.php
Re: duelund caps issues
« Reply #37 on: October 12, 2010, 10:35:15 PM »
thanks terry for sharing cant wait for steves feed back(i like harmonic distortion) ;D
still discovering the link between electronics and audio reproduction.so much to learn and so little time

avian

  • Guest
Re: duelund caps issues
« Reply #38 on: October 13, 2010, 02:27:48 PM »
Hasnt this place been a flurry of activity since yesterday.  I was the one who emailed duelund.  I was concerned you people were tarnishing his reputation with your acts of stupidity.  Amazing how everyone here was so quick to blame the capacitors before even looking at your half arsed circuit.  If it wasnt for me and omodo you guys would still be blowing caps and blaming duelund. I also wanted to make sure if he got any returns from misused caps he knew why.  Dont see why Frederick or Lenehan should bare any cost from your mistakes.  Im not hiding. and Im not posting here anymore, there is honestly no point.  Ive had my vent over on diyaudio, now my life will exist as though there is no such thing as a killerdac, and it will be a state of wonderful oblivious ignorance (just how the dac is built).

i know of 3 caps failing in killer dacs caps will be replaced seems their is a quality control issue with the caps or a manufacturing fault.


You might want to look at editing your original post now that you've learned something new.

3bm

  • Guest
Re: duelund caps issues
« Reply #39 on: October 13, 2010, 04:00:21 PM »
Ok time to get things on track. Please try and keep things constructive.

Avian, you obviously know quite a lot about electronics and your feedback is certainly welcome. Please do be constructive rather than outright condemning though. Please remember that most of the people here are new (some more than others ie me) to electronics and enjoy the learning curve. The points you raise are certainly helpful and I'm sure will be taken on board by the guys putting these things together. Proof that more people contributing means a better end result for everyone.

There is unfortunately a lot of reactive type posts going on here which I am going to delete out of the thread. Some by regulars and some by external people. In this case both are a out of order and inflammatory leading to people getting hot under the collar. Again, please keep things constructive, this type of posting is not what we want to achieve here.

Most of you guys here have TDA dacs and love them dearly. It is time to start using that as a bit of common ground and getting back to that :)



« Last Edit: October 13, 2010, 04:55:02 PM by 3bm »