You need to match fets to each other per channel, not across them

 

lsk389 is a dual-fet package which for most cases ensures matching, so no need to buy extras unless you need them in future projects

 

you can also use 2x k170 but I'm not sure if they will fit in the krell. should be slightly cheaper

Edited March 10, 201412 yr by nopants

Thanks, just placed orders at Newark & Mouser for most of the parts.  Not sure what I will do for a case yet.

 

Did the power switch on the original switch the +/-21vdc from the psu, and psu was always on when plugged in, or did the switch run through the 9-pin cable to switch the psu on and off?

EDIT: nevermind I missed that in the pic on the first page, I just looked and the wires going to the power switch at the amp face are labeled -21 V +21 V

ksa5 was produced with both power supplies.

Got the newer power supply board started tonight.  Found out a couple things.  I forgot to order the .1uF caps, ugh.  Also, the snap in 4700uF caps I ordered do not fit fully through the holes, here are some pics.  Will these be okay like this?

 

http://imgur.com/Lb88JpV,lOdDtBe#0

 

http://imgur.com/Lb88JpV,lOdDtBe#1

I did the same for my build, I heatshrinked them but that was paranoia from building HV stuff. I think you'll be fine

Thanks, I've got some tiny heatshrink so I think I will do that as well, good idea.

What kind of cap is needed for the .1uF on the new power supply board?

Do the MJF1503x transistors need to be attached to the big heat sinks in some way?

FYI shielded & encapsulated 120v/2x27v/50VA tx from SumR was $79US + shipping.

Looking through my Mouser order.  I ordered 4x OPA227P from Mouser for the PS & amp.  Will these work okay?

 

I also mistakenly ordered 3x OPA445AU from Mouser.  Should I use 2x of these instead in the PS or amp, or just return them?  They are almost 2x the cost of the OPA227P...worth it for this use case?

Got the newer power supply board started tonight.  Found out a couple things.  I forgot to order the .1uF caps, ugh.  Also, the snap in 4700uF caps I ordered do not fit fully through the holes, here are some pics.  Will these be okay like this?

 

http://imgur.com/Lb88JpV,lOdDtBe#0

 

http://imgur.com/Lb88JpV,lOdDtBe#1

 

 

either file the pins a bit, or heat up the pins one at a time and push into the board.

really should be flush.

Thanks Kevin I am going to try to trim/file down the leads tonight.

 

For the .1uF cap next to the op amps on the new power supply can I use the .1uF film caps that are used on the amp board or does it need to be a ceramic cap?  If it needs to be ceramic would this one work?

lead spacing on those is 3.5mm.  but these are the ones I think I used  mouser # 581-SR205E104M

I made the mistake of drilling the PC board a little to make it fit.....removed the through plating. I had to take it back apart (desolder) and then put a jumper in. Don't make that sad mistake. File the cap leads a little. It must sit flush and the solder flow into the hole..

Got the newer power supply board started tonight. Found out a couple things. I forgot to order the .1uF caps, ugh. Also, the snap in 4700uF caps I ordered do not fit fully through the holes, here are some pics. Will these be okay like this?

http://imgur.com/Lb88JpV,lOdDtBe#0

http://imgur.com/Lb88JpV,lOdDtBe#1

Edited March 13, 201412 yr by GrindingThud

Got a link?

FYI shielded & encapsulated 120v/2x27v/50VA tx from SumR was $79US + shipping.

That's way too much for a transformer like that, just grab an antek unit

Got a link?

 

http://www.sumr.com/custom.htm

 

You have to call or email them since the 27v is custom.  I emailed them, Richard was great to deal with.  Email address is [email protected]

That's way too much for a transformer like that, just grab an antek unit

 

Yes it's more expensive than off the shelf units, but I could not find anywhere to get a 2x27V toroidal transformer off the shelf.  I'm only going to build this once.  I think earlier in the thread someone got a 2x27V tx from SumR that was not encapsulated for $54 + shipping if you don't need it encapsulated.

I think I got antek 28V, I'll have to ask the person to whom  I gave the amplifier to check

So because there doesn't seem to be anyone with an unneeded KSA5 board,  I have decided to order some of my own.  I know you said that you recommend 3oz copper but would 2oz work as well?  Also does one power supply sound better than the other?

the power supplies definitely have different noise spectral densities.

whether they actually sound different is very hard to tell. The one with

the TO3 transistors has better voltage regulation.

Ok thank you.  I am sorry but I am fairly knew to DIY so I have a lot of questions.  Do I need to match any of the parts?  Also how do you know what to bias the amp to and how do you know what the test points are?  Lastly, will a 160VA transformer be sufficiant?  Thanks in advance.  

I used this 50VA one from Mouser in my build: http://www.mouser.com/ds/2/410/VPT48-1040-224303.pdf

Worked just fine. I did not match anything either....

There is a post earlier in this thread about the bias.....I think it was 125mV cold across the test points on the 2 ohm resistor.

Ok thank you.  I am sorry but I am fairly knew to DIY so I have a lot of questions.  Do I need to match any of the parts?  Also how do you know what to bias the amp to and how do you know what the test points are?  Lastly, will a 160VA transformer be sufficiant?  Thanks in advance.

I used this 50VA one from Mouser in my build: http://www.mouser.com/ds/2/410/VPT48-1040-224303.pdf

Worked just fine. I did not match anything either....

There is a post earlier in this thread about the bias.....I think it was 125mV cold across the test points on the 2 ohm resistor.

 

Thanks.  It looks like this transformer is 24v when the power supply asks for 22v is that ok?

The original transformer is 27VAC. After rectification and regulation you get 22VDC. I went with that 115/24....my wall voltage is 120...so I get 25 out of it (close enough) before the diodes and about 35 peak after...which gets regulated to 22.

Thanks. It looks like this transformer is 24v when the power supply asks for 22v is that ok?

Edited March 16, 201412 yr by GrindingThud