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Old 22nd March 2005, 06:37 AM   #1
zek is offline zek  Serbia
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Question Kd-261

Just find this schematic on the web.

http://www.produktinfo.conrad.com/da...ker_KD-261.pdf

What are yours oppinion about this amp, it looks very promissing for the price.
How it compare to NAD, Rotel or CA amps.
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Old 22nd March 2005, 03:49 PM   #2
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I have never hard this amp, however if the schematic is correct, I find one set of output devices for +/- 45VDC rails to cheap
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Old 23rd March 2005, 01:37 AM   #3
Leolabs is offline Leolabs  Malaysia
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Standard good quality product
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Old 23rd March 2005, 06:11 AM   #4
zek is offline zek  Serbia
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More details on

http://www1.int.conrad.com/scripts/w...c=X&~cookies=1

The PSU are good with two separeted rectifiers and total of 40.000 uF in caps.

The price is realy good, but what about the sound ....

Are there anybody from Germany who own or heard this amp.
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Old 26th April 2005, 03:28 PM   #5
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Default KD-261

hey dudes! i purchased that amplifier and it is great, but not for everybody! It has got power, it's really heavy :-) but there is not plug for stereo headphones... the sound is okay! never heard some anoying sounds ore something like that! but my speakers are heavy, too. don't know if it is good sound or not (maybe not for enthousyastics <- how the hell do we write that)
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Old 26th April 2005, 08:25 PM   #6
JohnW is offline JohnW  Hong Kong
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Feedbacks taken from the driver stage???

Also, whats the fuction of V208 - V210 protection circuit & / or a simple Error correction?

John
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Old 26th April 2005, 10:07 PM   #7
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Hi zek,

Thanks for the link to the schematics, I've been working from the schematics of a different model and this should make things easier for me.

I bought this amp, DSE A2760, which I believe is a rebadged version of the KD-261 for AU$146. My intention was to use the case for one of my gainclone projects, but it sounded almost as good as my gainclones I decided to mod it instead.

http://www.dse.com.au/cgi-bin/dse.st...uct/View/A2760

The first thing I noticed about this amp was the gain was way to high. So I changed R230 to 2k2 but still the gain is too high. On my amp R231 was actually 47k.

The next obvious issue was there is no adjustment for the Vbias, so I replaced R209 with a 1k pot and initially set it at 160R. I then adjusted the bias across the emitter resistors (R210 to R213) to 55mV, it was only 27.4mV.

I don't like the routing of the output wires. There are grouped with the power wires and run (touching) the toriod. All these things can be fixed.

The circuit pcb is big with lots of long tracks.This is a lot different to most DIY pcbs but I suppose is pretty typical for production amps.

The output devices on mine are 2SC5200/2SA1943 not what is indicated on the schematics.

Heatsinks are small, and run hotter than any of my other class AB amps. Nothing to worry about yet.

Sound wise I rate this as OK, especially for the money, I do have an AKSA so I have been spoilt.

Quote:
Originally posted by JohnW
Feedbacks taken from the driver stage???

Also, whats the fuction of V208 - V210 protection circuit & / or a simple Error correction?
Yeah, taking the feedback from the driver stage is weird. I haven't checked if it is what they have done, as I have found the schematics are not always 100%. This would be another area for modification.

V208 to V210 is the SOAR protection circuit and I guess it is needed because the rails are so high, mine was 42 to 44 volts. I would like to remove this circuit in the future.
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Old 26th April 2005, 11:59 PM   #8
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This one's got plenty of room for improvement.

Take the 5534 on the input stage, that could be a drop in OPA134 or similar just check the offset adjust.

can switch out the tone stage.

Look at the vol pot, 100K! - at centre it will source as 25k adding to the 1K8 and rolling off with the 100pF at 60KHz. Could soften an edgy top a bit.

12K tail resistor for the input diff'l pair and single ended output stage will cause significant 2nd HD which won't be reduced by feedback. Euphonic maybe.

The 220 ohm resistors from the drivers could be reduced to 33 ohms and replace the 75 ohm. FEEDBACH should be moved to the output to include the output stage distortions in the feedback.

The protection circuit doesn't track the 'off' half cycle ( needing pull up as well as pull down SOAR tracking) rendering a fairly fragile output stage prone on reactive loads.

For starters.
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Old 27th April 2005, 12:22 AM   #9
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i dont know the product
i cant comment
on it
subjectively
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