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Old 27th May 2008, 04:38 AM   #211
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Hello
John65b please I'm waiting on you to finish the Naim clone ad com pared to the Krell KSA-50 amplifier .
I want to know if the Krell come close to the Naim clone or may be better ? , if it wort to give a try or not .Of course is very important what kind of parts you use on the board and on the power supp.
You know easier to sell the populated board if not fired up .
People does not think you sell it because is a bad amp .
Even I have all the parts for the KSA-50: 1000A toroid Plitron brand new and very large case all made out from all heat sink was design to the KSA 100 Clone . I want to hear from you which amp sound better .
Some people said the Symasym beat the Krell clone , I build it with good components and for me it was just a waste of money .

Regards
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Old 27th May 2008, 05:52 AM   #212
john65b is offline john65b  United States
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Quote:
NAP140 (140 = 2 X 70W)!
70 wpc @ 4 Ohm? 8 ohm?

Gaborela
As far as the Krell, mine sounded lame after I first built it. I couldn't believe what everyone was saying about the amp. It sounded dull and lifeless.

When I was trimming the DC offset, I noticed I couldn't get one of the amp channels to drop below 350mv, no matter how much I turned the pot. The other channel was able to get to 0mv, but it wandering all over the place, and needed to be reset every time I fired up the amp.

It was then I noticed that I did not have the signal grounds connected to the power ground on the board. I connected the grounds, and the DC Offset of both channels easily trimmed to 0mv. I set the bias at 650mv (1A).

I then listened, and have been smiling ever since. Best I have by quite a margin. I may be interested in your boards if you decide to sell them.

A pic attached of the Krell "guts". Just as you say - 4 heatsinks making up the chassis.
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Old 27th May 2008, 06:13 AM   #213
Kan is offline Kan
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Quote:
Originally posted by john65b


70 wpc @ 4 Ohm? 8 ohm?

Gaborela
As far as the Krell, mine sounded lame after I first built it. I couldn't believe what everyone was saying about the amp. It sounded dull and lifeless.

When I was trimming the DC offset, I noticed I couldn't get one of the amp channels to drop below 350mv, no matter how much I turned the pot. The other channel was able to get to 0mv, but it wandering all over the place, and needed to be reset every time I fired up the amp.

It was then I noticed that I did not have the signal grounds connected to the power ground on the board. I connected the grounds, and the DC Offset of both channels easily trimmed to 0mv. I set the bias at 650mv (1A).

I then listened, and have been smiling ever since. Best I have by quite a margin. I may be interested in your boards if you decide to sell them.

A pic attached of the Krell "guts". Just as you say - 4 heatsinks making up the chassis.
+/-40VDC : 70W/8 ohm
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Old 27th May 2008, 06:19 AM   #214
john65b is offline john65b  United States
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So around 140 wpc in 4 ohm?

I like.
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Old 29th May 2008, 02:35 AM   #215
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Default Re: Re: One Board Lives!

Quote:
Originally posted by Kan


Q1, Q2 and Q5 need to be installed reverse of what is marked on the PCB - depends on the model of transistor. BC546B matched the orientation of symbols of silk screen printing.

Yes, be sure to follow the schematic in any case. I was merely referring to the 2n5551 npn's that the "improved" kit comes with. I should have clarified. Sorry.
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Old 29th May 2008, 02:48 AM   #216
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Quote:
Originally posted by hoka
Blew it up again! after replacing most of the components, no luck on the second try. This time I fried R 35. at least that is where the smoke came from.

I'm about ready to give up on these boards

If R35 went up in smoke (and flame I assume, FUN!) you will have to replace R29 (big power resistor) and likely the output transistors as well.

Replace R35 and R26 first. Measure across R32 (no power on the circuit) if you get a stable reading around 31-32R then you've blown your output transistors. If the reading slowly rises to 4-6k then the output trans. are okay. If the o/p trans are blown, good luck finding the SanKens. Digikey carries the Toshiba 2sc5200 that are TubeHunter's current spec, but your should replace all four (both boards).
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Old 29th May 2008, 11:11 AM   #217
hoka is offline hoka  Netherlands
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Quote:
Originally posted by force of 1/2



If R35 went up in smoke (and flame I assume, FUN!) you will have to replace R29 (big power resistor) and likely the output transistors as well.

Replace R35 and R26 first. Measure across R32 (no power on the circuit) if you get a stable reading around 31-32R then you've blown your output transistors. If the reading slowly rises to 4-6k then the output trans. are okay. If the o/p trans are blown, good luck finding the SanKens. Digikey carries the Toshiba 2sc5200 that are TubeHunter's current spec, but your should replace all four (both boards).

I replaced r35 and r29 (was blown indeed!) The first measurement across r32 was like you said, about 32Ohm. I then replaced both Sankens.When I measure across r32 now I get and imediate reading of 4.7K not a slow rise.
What more can I check before firing up again?
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Old 29th May 2008, 09:08 PM   #218
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Quote:
Originally posted by hoka

I then replaced both Sankens.When I measure across r32 now I get and imediate reading of 4.7K not a slow rise.
What more can I check before firing up again?

It will rise slowly to around 4K7 but then holds a charge so if you check again after a few seconds it will still read over 4k.

Sounds good. Did you run jumpers from signal ground (SG) to the ground tap near the SanKens? (GND) I would check the orientation of the Q1, Q2, Q5 again. If they are the 2N5551 then they go in opposite of the marking. It seems like TubesHunter shipped kits with different transistors here so check which you have and look up the pin orientation (CBE) on the manufacturer's website. One last thing to do because it is not too much trouble is to remove the trimmer pot and check to make sure it is adjusted to the middle of its range (1K1 on either side).

Other than that, the 2N5551's are about $.08 each so you could replace them all for less than $1 USD. Might not be a bad idea if they were powered up in the wrong orientation.

BTW- where did you find replacement SanKens?
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Old 29th May 2008, 09:24 PM   #219
hoka is offline hoka  Netherlands
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Quote:
Originally posted by force of 1/2



It will rise slowly to around 4K7 but then holds a charge so if you check again after a few seconds it will still read over 4k.


That's the thing: there is no slow rise! just an instant reading of 4k7
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Old 12th June 2008, 02:06 PM   #220
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I see there are currnetly two different kits available (both with blue PCB's). Which is the preferred version?

Short, Wide Version

Click the image to open in full size.

Or the Long, Narrow Version

Click the image to open in full size.

IIRC the second version is the one with the reversed transistor markings on the PCB. Any comments or opinions are welcome.
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