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|30th June 2003, 09:32 AM||#1|
Join Date: Nov 2002
Location: Cologne, Germany
Conrad KD269: How to unrelease full potential ?
I bought from Euope's biggest Elctro-Distributor a nive, cheap power amp for my sub. I am astonished about the build quality (5mm Aluminium front, big toroid, big heat sink etc) and have no clue how they make money on this one.
It sounds not bad as well, but I think there is much more potential to unrelease, where I could need a bit help from the group.
You will find the schematic under http://www.produktinfo.conrad.com/da...ufe_kd_269.pdf
Here is what I am already working on:
- Throw out the electrolytic input cap
- Directly connect line cable on the pcb
- Throw out HF-caps c283, c229,c230 etc
- Replace Standard caps 470uF with Silmics
- Play around with the NFB-Resistor value R281 (27k)-->50k ? 100k?
The heatsink is becoming even hand warm as it is quiet big, so I guess this one works more in class b than class a. What do I need to change to get it much more in class a ?
Any other thoughts what should be modified is highly welcome as this might be a great opportunity at least for all europeans to get a really great amp as a bargain.
Thanks & Best Regards
|2nd December 2003, 08:47 PM||#2|
diyAudio Moderator Emeritus
Join Date: Sep 2002
Hello Frank, did you do the mods ? I bought the same amp out of curiousity as well and I am very surprised by the build quality. It is quite popular lately and after seeing it reviewed on a dutch forum I decided to try one.
This amp makes me almost decide to quit DIYing amps. Transformer ( 600 VA ), power transistors and heatsink cost more than this complete amp in the Netherlands
The only parts that are suspicious are the big electrolytics. In my amp the 10000 uF 63V caps are chinese LM brand. Couldn't find anything about them on the web. The other caps are Nichicon in my example. Resistors seem to be of good quality and power transistors are original Toshiba 2SA1943 and 2SC5200. The emitter resistors are nothing special. Will solder MPC resistors in.
My plans are the same except for removing the feedback resistor and the "HF" caps ( wouldn't do that ! ). I'll use Wima MKS2 series 4.7 uF 50V ( 5 mm pitch ) for the input.
Which revision of the amp do you have ? The newer ones have blue LED's and I wonder if they're electronically different from the older ones with the red LED.
It's only audio. Member of the non modular PCB design committee
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