Jump to content

krell ksa5 klone


kevin gilmore

Recommended Posts

On 3/2/2017 at 5:24 PM, Pars said:

Linear Systems makes one now. Trendsetter has them, and they also have the LSK389.


Sent from my iPhone using Tapatalk

Trendsetter want to charge me like hell for shipping. Found some on ebay. hope they are not fake ;-)

I am looking for a transformer, I read in this forum, that 2x27V 50VA should be used. my question is 27 V with or without load.

Is my understanding correct that the board will draw less than 400mA (0.4 A x 21 V= 8.4 VA)so should not make a difference for a 50VA transformer?

Link to comment
Share on other sites

http://www.antekinc.com/as-0528-50va-28v-transformer/

Earlier in the thread (had you read it) KG said you need ~35V raw dc, so 27 * 1.414 will get you ~38V minus the diode drops for the rectifier(s). I haven't looked at the schematic, but assume a bridge, so -1.4V, so you are at about 32.6V raw DC. Might work. 27-28V transformer will get you closer. 28V Antek above would put you at (28 * 1.414) - 1.4 = 38.2V. It appears some have built this with a 25V transformer.

Edited by Pars
  • Like 1
Link to comment
Share on other sites

http://www.antekinc.com/as-0528-50va-28v-transformer/ Earlier in the thread (had you read it) KG said you need ~35V raw dc, so 27 * 1.414 will get you ~38V minus the diode drops for the rectifier(s). I haven't looked at the schematic, but assume a bridge, so -1.4V, so you are at about 32.6V raw DC. Might work. 27-28V transformer will get you closer. 28V Antek above would put you at (28 * 1.414) - 1.4 = 38.2V. It appears some have built this with a 25V transformer.

 

Thank you for explaining. I have read this thread several times, nevertheless it happens to me to ask silly questions as I know less than a little about electronics ;-)

Am I correct ?The best would be to have a transformer maid with a voltage between 27 and 28 V so that DC right after the rectifier (bridge) is 35 V. I think this can be done since my toroids are custom made.

I have also read in this thread that some pushed PSU voltage higher and changed opamps. Could someone tell me if this is worth it? What are the benefits? I can still return my ops. So why not benefit from a good advise.

 

 

Sent from my iPad using Tapatalk

 

Link to comment
Share on other sites

Hi Kelvin! After some time, i have discovered that my amp have some serious problem: when i turn the volume up, after half volume the noise is increased to very audible level, so i measure the output with nothing connected, maximum volume and got this:

sNddnS8.png

Some serious 50hz harmonic at -55dbv lvl !

At min volume, it's fine:

YbBgWnU.png

I thought it could be the power supply problem but i measure the PS and it's fine:

EHFINl9.png

So the problem must come from amp board, do you think what can cause this? Thanks!

Link to comment
Share on other sites

  • 4 weeks later...

Dear Dr. Gilmore,

  Thank you !!  I am a total nOOb with electronics, trying to teach myself.  Have purchased the ebay amp and power supply.

Just wanted to thank you for sharing your knowledge !

All the best,

-Mark 

Hi All so far I can only find one of the two power supplies (ZeroZone): 

TB1B2enLXXXXXXCXXXXXXXXXXXX_!!0-item_pic.jpg_600x600.jpg

Is the other power supply also available? Can someone help me with specifying an Antek transformer ? Thank you !  

27815181946_16c2a4f1b7_h.jpg

Link to comment
Share on other sites

I haven't built one of these and am not familiar with that particular PSU, but don't you just need a single PSU (dual, which that one appears to be)? Not sure what the other one you refer to is?
As for transformer, see the rest of the thread. A dual secondary in the range of 25-27Vac seems to be what is recommended. I posted an Antec AS-0528 above, but an AS-0525 50VA 2x25V might work as well.
I'm not sure, but I might be inclined to use a GRLV PSU set for +/-22Vdc for this, with a 2x18Vac transformer. Of course that moves away from a strict clone however.
Someone who has built one of these might comment...


Sent from my iPhone using Tapatalk

Link to comment
Share on other sites

  • 1 month later...

I am having a bit of problem with the PSU (re-testing and substituting components after an accidental short between +22 and gnd).  Does the components in it get warmish after 15 min without load.  On PSU, I noticed that PNP and NPN and lm4040 diodes can get warm or slightly hot (how high?).  Second, the short happened  when amp was connected.  Do you think I damaged any component on amp.  Thanks.

Link to comment
Share on other sites

I got the ones at Ebay.  They are OK.  3-4 weeks to arrive thru USPO.

On 4/24/2017 at 5:20 PM, kevin gilmore said:

I did both ksa5 power supplies. The original is triple pass transistor/zener regulated

 

I am having a bit of problem with the MJ15025/15024 version of PSU (re-testing and substituting components after an accidental short between +22 and gnd).  Does the components without heatsink get warmish after 15 min without load.  On PSU, I noticed that PNP and NPN and lm4040 diodes can get warm/slightly hot (how high?).  Second, the short happened  when amp was connected.  Do you think I damaged any component on amp.  Thanks.

Link to comment
Share on other sites

  • 3 weeks later...

Just finished building up the Krell power supply at 300V rails. Took me a really long time to figure out what was wrong, I was swapping parts and messing with traces like crazy, and of course it was the one thing I didn't expect. The pre-reg caps aren't connected to ground. I did already drill out a cap hole that wasn't supposed to be connected to ground. Probably should have read this thread first...

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.