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Old 5th August 2011, 11:15 AM   #1
UMarcus is offline UMarcus  Germany
diyAudio Member
Join Date: Mar 2011
Location: Black Forest
Default suggestions for improvement (Old Consumer Amp)

I'm attaching a scan of the circuit diagram of my power amp.

I'm looking for some improvments to more sonic / warmth sound (suggestions / tips and Comments welcome).

E.g. what would be happend if remove IC301 and IC302 ? Sound ? Risk ?

BTW I know not a lot about amp designs

Thanks a lot,
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Old 20th August 2011, 02:45 PM   #2
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Join Date: Oct 2009
Location: Hamburg
Default Don't both with your chips! Unless you have test equipment.

Dear Marcus,

I assume that you will have no risk removing the IC301, IC302 chips but I am confident the amp will not work any more until you put them back in.

Not knowing the amp in question (model and manufacturer might make more interest in your post), I cant say its worth it, as excellent amplifiers exist very cheap on the second hand market.

This said, if your amp is old (say greater than 5-10 years), replacing all the electrolytic capacitors is almost always a good move. I would start with the biggest ones, and any that are bulging. Look for low ESR ones if the amp is a quality high end item, but cheap capacitors will be fine for most amps. I have done this with Quad 303 amps, which where last serviced in the 1970's and the effect is most noticeably better.

Electrolytic capacitors age poorly, and simply replacing them with slightly larger values, in maximum voltage is a good place to start, For power supplies I often also increase the capacitance also (some times I even double it) but stick with the old values if you don't understand what the capacitor is doing to the rest of the circuit. Also please note the polarity of the electrolytic capacitor you replace, as you can expect things to break if you get this the wrong way around.

In general I would not modify any commercial amplifier design by much. I defiantly would not do big changes like removing components. Substitution is usually the most I would do as amplifiers are a system, and designed with all parts, and usually the minimum needed to make the system work.

Some people do op amp upgrades (the chips you pointed out look like op amps) but you will have to understand what your doing as their are many possible ways this can go wrong, typically high frequency instability, most often above the limit of hearing, and this should not be done without suitable test equipment and knowledge in my opinion. I am sure some op amp "upgrades" published on the internet are actually making things worse.

Stick to good amps from good brands, and typically all you need/should do is replace all the electrolytic capacitors unless your an engineer, or better still an electrical engineer.

In Germany "Wega" is a very under respected brand and hence often available at very reasonable prices on Ebay Germay, they made kit of better than typical consumer quality, and when Sony bought them the brand name was better respected than Sony was at the time, so Sony benefited from keeping their engineering independent through most of the 1980's.


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Old 20th August 2011, 03:36 PM   #3
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Join Date: Aug 2011
Originally Posted by UMarcus View Post
E.g. what would be happend if remove IC301 and IC302 ? Sound ? Risk ?
In priciple you're on the right track, in that I would expect an amp with so convoluted a signal path to lose a lot of sound clarity. What comes out of an analog stage cannot be better than what went in -but it can of course be worse- and when so many stages of amplification are involved in the power amp alone..

If you want to try some mods like removing apparently-redundant stages, follow the basic principle of doing all first-line tests on current-limited supplies, and with no speakers, or attenuated speakers. Otherwise, any mistake is inviting a blow-up.

Though if it was me I'd pick something simpler for a first attempt at modding. I suspect this will not be an easy project, not even for an experienced modder.
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Old 28th January 2012, 07:24 AM   #4
UMarcus is offline UMarcus  Germany
diyAudio Member
Join Date: Mar 2011
Location: Black Forest
sorry fo beeing late

Many thanks for suggestions and given an idea what could be done.

Up to now i replace all capacitors including big PS caps and change the OP's to OP128 and AD712, replace cables, relais and connectors, remove volume pot's ..

.. at least it sounds more sonic at all..

Off Topic:
I found the reason of cold sound by do some test's with reclockers (Behringer Ultramatch, Mutec MC6, Apogee Big Ben). The SPDIF Output of my PC is worse master clock for the dac (PCM1794) therefore it sound cold and digital. If the Reclocker is connected inbetween the SPDIF Line it become clearly more warm and "3d" sound. I'm happy to had done this tests and to gain experience..

But on other hand the reasonable reclocker are to expensive for DIYler

Therefore i'm looking forward to receive alread ordered XMOS USB Demo board which should provide better clock signals..

I'm planing to put out my feelers to Class A (F5) and Class D (SDS-254) also.. the suspense continues and DIY become more and more to passionate hobby

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