krell ksa5 klone

[GrindingThud]

Thanks! I see I have choice of board thickness. I assume .062 is adequate for this build?

 

Also see that there are two power supplies and some are using Sigma22.  Is there an opinion on what supply is best? 
 

Www.pcbnet.com
 
amp board is 10 x 7.5 inches 609 holes
10 boards from pcbnet.com would be $425
3 oz copper

[kevin gilmore]

.062 is fine, that's what the current ones are.

[trident900fi]

Www.pcbnet.com

 

amp board is 10 x 7.5 inches 609 holes

10 boards from pcbnet.com would be $425

3 oz copper

 

I order mine on www.safe-pcb.com, and there are a little cheaper...

Very good quality for the price

[GrindingThud]

Ok, so I'm building this out in Mouser and notice the Vishay resistors are 1/4 watt (except the 2ohm at 3W) vs the Xicons at 1/2 watt. Is 1/4w ok? Lol....the parts are adding up quickly.

 

Also looking at the LSK389...do we want A, B, or C version (different Idss ranges) 
 

Here is the Google doc.

[spritzer]

They are RN60D which is a military spec so what is usually a 1/2W resistor is rated at 1/4W. 

 

Any of the LSK389's will work. 

[GrindingThud]

Thanks!

They are RN60D which is a military spec so what is usually a 1/2W resistor is rated at 1/4W. 

 

Any of the LSK389's will work.

[GrindingThud]

Read the thread again....these appear to be ok.

Never mind......

The 4 extra 4.7uf Wimas are specd at 63v/5%....see any issue downsizing to 50v/10%? The main caps are 35v and these are in parallel with those. Saves $13 and they are in stock....

Has anyone settled on a nice transformer? I'm looking at this one, 50VA at 120V:

http://www.mouser.com/ds/2/410/VPT48-1040-224303.pdf

Thanks, got all of them. Not sure yet about q27 collector cap.The 4.7uf caps are at birgir's idea. (also kind of expensive)evidently no amp is complete without some wima's.will post again when i get home.

Edited March 15, 2014 by GrindingThud

[GrindingThud]

Ok, I think the last thing on my order list is the pot.... Any suggestions in this area? I was thinking an alps 50K...what was in the Original Krell?

[fordgtlover]

Read the thread again....these appear to be ok.

Never mind......

The 4 extra 4.7uf Wimas are specd at 63v/5%....see any issue downsizing to 50v/10%? The main caps are 35v and these are in parallel with those. Saves $13 and they are in stock....

Has anyone settled on a nice transformer? I'm looking at this one, 50V at 120V:

http://www.mouser.com/ds/2/410/VPT48-1040-224303.pdf

 

 

The response a page back indicates that the 50V 4.7uf caps will be OK.

[spritzer]

Ok, I think the last thing on my order list is the pot.... Any suggestions in this area? I was thinking an alps 50K...what was in the Original Krell?

 

Some of them had the Alps RK27 while others used Noble AP25.  I guess they just used what was at hand. 

[GrindingThud]

I found a picture of one online that looks like it's got an ALPS 10K....I'll try that and see how it goes.

http://www.avx.hu/forum/index.php?/topic/41329-krell-ksa-5v/?p=1313992

Looks like I'm going to try and squeeze it in here:

Some of them had the Alps RK27 while others used Noble AP25. I guess they just used what was at hand.

[wink]

Why nmot an Alpha pot?

[johnwmclean]

I found a picture of one online that looks like it's got an ALPS 10K....I'll try that and see how it goes.

http://www.avx.hu/forum/index.php?/topic/41329-krell-ksa-5v/?p=1313992

 

Nice clear photography in that link.

[kevin gilmore]

what chassis is that, and what is the internal size especially height.

[GrindingThud]

eBay link here: http://www.ebay.com/itm/400523705862

Internal height is just under 2.5"

Internal dimensions: Width 310mm Height 62mm Depth 240mm

External dimensions: width 320mm Height 70mm Depth 248mm

Front panel 8mm thickness. Back panel,Top and Base plate 3mm thickness. side panel:4mm thickness.

what chassis is that, and what is the internal size especially height.

[GrindingThud]

I plan on using Neutrik connectors. Any opinions on if it would be worth also putting 4 pin XLR output?

http://www.mouser.com/Search/ProductDetail.aspx?R=NJ3FP6C-Bvirtualkey56810000virtualkey568-NJ3FP6C-B

http://www.mouser.com/Search/ProductDetail.aspx?R=NC4FD-LX-Bvirtualkey56810000virtualkey568-NC4FD-LX-B

[kevin gilmore]

you do realize that there is no way you are going to get everything

in one chassis...  

 

amp board is 254 x 191  mm

 

original power supply board 150 x 98 mm

[GrindingThud]

Yes, PS will be in a remote chassis. .

I may also use a sigma22 PS in one of these: http://www.ebay.com/itm/120945750823

Like this: http://cdn.head-fi.org/9/90/9037f0cb_b22_2ch_insides.jpeg

you do realize that there is no way you are going to get everything

in one chassis...

amp board is 254 x 191 mm

original power supply board 150 x 98 mm

[fishski13]

fired up the PS: http://i23.photobucket.com/albums/b353/fishski13/002_zps0d93dd0f.jpg

 

SumR 27V x 27V/50VA = 21.1V output unloaded

Secondaries = 32.3V

Collector Q1,Q2 = 42.5V

Collector Q3,Q4 = 27.5V

 

can i assume that when loaded, the V across the BJTs will drop a bit?  with the above numbers, assuming a total current draw of 400mA and power dissipation of 200mA on each rail, i'm looking at 3W on Q1,Q2 and 1.3W on Q3,Q4.  should be fine with 2" heatsinks and a little thermal grease with adequate ventilation. 

Edited November 11, 2013 by fishski13

[GrindingThud]

Very nice! What transformer is that?

fired up the PS: http://i23.photobucket.com/albums/b353/fishski13/002_zps0d93dd0f.jpg

 

SumR 27V x 27V/50VA = 21.1V output unloaded

Secondaries = 32.3V

Collector Q1,Q2 = 42.5V

Collector Q3,Q4 = 27.5V

 

can i assume that when loaded, the V across the BJTs will drop a bit?  with the above numbers, assuming a total current draw of 400mA and power dissipation of 200mA on each MJF pairs/heatsink, i'm looking at 3W on Q1,Q2 and 1.3W on Q3,Q4.  should be fine with 2" heatsinks and a little thermal grease with adequate ventilation.

[fishski13]

the TX is from SumR.

 

above maths is just the quiescent current draw.  anybody have an approx total current draw per channel?

Edited November 11, 2013 by fishski13

[GrindingThud]

Thanks. I'm assuming if it stays in class A, the amp won't draw much more from where it is biased at.

the TX is from SumR.

 

above maths is just the quiescent current draw.  anybody have an approx total current draw per channel?

[kevin gilmore]

WARNING to any one that would even think of buying a Revelation Audio Labs power supply

to amplifier cable for a real krell ksa5. These fucking morons can't even wire a simple cable

and get the pins in the right order.

Tom found this out when his ksa5 blew up. So its sitting on my lab bench, and about 3 hours

of repair time to repair the damage. And tom was very lucky, it could have been worse.

Ended up with -21 on the +21 line and vice versa. Without the protection diodes, very

bad things would have happened.

Waiting for tom to give me permission to rip the cable apart and see how bad the assembly

job is. Shades of coconut audio with blobs of modeling clay.

Edited November 15, 2013 by kevin gilmore

[fishski13]

planked the amp out with a Blue Velvet.  sounds excellent even with a cheap pot.  some noise beyond sane listening levels with the 102dB AD2000 and 103dB D2000, and basically dead silent until the last hour or so on the pot with the 93dB K701, but a rats nest of wiring right now.  can't wait to get it in a chassis with a TKD or GP. 

 

if my maths are correct, the gain is 5x?

Edited November 15, 2013 by fishski13

[Kerry]

WARNING to any one that would even think of buying a Revelation Audio Labs power supply

to amplifier cable for a real krell ksa5. These fucking morons can't even wire a simple cable

and get the pins in the right order.

Tom found this out when his ksa5 blew up. So its sitting on my lab bench, and about 3 hours

of repair time to repair the damage. And tom was very lucky, it could have been worse.

Ended up with -21 on the +21 line and vice versa. Without the protection diodes, very

bad things would have happened.

Waiting for tom to give me permission to rip the cable apart and see how bad the assembly

job is. Shades of coconut audio with blobs of modeling clay.

yeah, I saw Tom at the NY meet after this happened. He wasn't happy.

Glad you could fix it for him. He's a good guy.

Edited November 15, 2013 by Kerry