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Old 2nd February 2009, 10:55 PM   #1
Bartt is offline Bartt  Netherlands
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Default ROTEL amp sounds dull

For years now I have a Rotel ra980bx amp. It's sounds pretty good, but only after playing a few hours (loud). The difference is quite big. In the beginning the sound is lifeless and mechanic, not spacial at all. High frequenties sound a bit sharp. The sound isn't distorted or anything.

Do you have any idea what the problem might be and how I can solve it? I'm pretty sure it's the amp, because when I use my headphone (Sennheiser HD600) it has the same problem, also on on a different source (radio). For years I thought the speakers where the problem (Vifa Vivace '89 model) and did quite a few mods to try to fix it (Leclanche caps, tritec coils, wires ect) but not with the desired effect. I also asked around at hifi dealers but the only answer I get is "keep the power on" but that doesn't help. I already cleaned all the contacts and used contact spray cs90 for all the switches. Any suggestion?
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Old 2nd February 2009, 11:03 PM   #2
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Please don't take this the wrong way, I am only asking, but are you sure it's not listening fatigue?
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Old 2nd February 2009, 11:36 PM   #3
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Hi Bartt ,

maybe this is because of the Black Gate Caps
they need a very long time to run in .

Greetings from Germany
Jürgen
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Old 3rd February 2009, 12:51 AM   #4
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Yes, amp might be a problem (for various reasons: changes in BIAS setting and components characteristics due to elevated temperature etc. etc.) but also always have in mind that your speakers are heating accordingly after few hours of loud music!!! Measure temperature of coil and magnets if you can and you will see. Don't think that there is no any change in behaviour and sonic of your drivers during prolonged high power sesions!
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Old 3rd February 2009, 02:41 AM   #5
jaycee is offline jaycee  United Kingdom
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My guess is that "for years now" means a considerable number of years.. in which case the power supply capacitors are probably past their prime and in need of renewing.

Rotel should give you the service manual for the amp if you email them.
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Old 3rd February 2009, 03:51 AM   #6
SQLGuy is offline SQLGuy  United States
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It sounds like a bias problem to me. I think you'll need to either have the bias checked at a shop, or get the service manual and a decent multimeter so you can check it yourself.

One other question, though: how warm does the amp get when left on for an hour or so at idle? Does it get warm above the heat sinks or does it stay fairly cool?
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Old 3rd February 2009, 11:27 AM   #7
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Default Our ears plus brain adjust everything.


When you continue to listen, after the first seconds, the brain starts to proceed with "processing".... after long listening..all hell bad amplifiers will sound good.

Switch on and wait some minutes to circuit stabilization..then play the music flat...in three seconds you have the real evaluation..if bad...sound is bad.

If was different than that..... brain not doing nothing together your ears, then people talking will disturb your telephone audition turning impossible to understand...and this do not happens..in seconds your ears will adjust... depending the girl is in the other side you will listen ABSOLUTELLY NOTHING THAN THE GIRL!

Also portable radios, the ones have no bass, absolutelly no deep bass reproduction..amplifiers cutted 400 Hertz and down this frequency would be reproduced without any bass...but you switch on and go listening and brain introduces (equalizes and uses auditive memory and previous musical experiences to fill the gaps) the bass you want to listen.

Sounded bad into the first seconds...shut it!.... shoot it!...booom!

Bad amplifiers drives you tired during long listening..because hard work to "process" all that stuff into your brain... you adjust and re adjust tones and never feel satisfied... because sound is really bad to your human ears plus brain..... good amplifiers are less tiring and you can listen for long time without tweak tone controls....if you tweak, constantly... seems sound not good..and you are trying to send to brain something more clear.... we say recording not good..ahahahahahah!

Use decent recordings, and select the richest parts, where you have more harmonics, more rich instrumentos, more ballanced tones... parts you like, parts you know... alike, in my personal case:

Vangelis - New Age - Mystik - Gregorian - Medieval


regards,

Carlos
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Old 3rd February 2009, 01:40 PM   #8
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Quote:
Originally posted by Bartt
used contact spray cs90
In my humble tweak experience, contact spray doesn't really properly clean mechanical switches, a can of spray is just a bandage fix.
YooHoo
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Old 3rd February 2009, 02:14 PM   #9
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Default Helps too... and we can blame the spray because...


...made noise when the spray was out... the contact memorized the noise and when the amplifier reproduced once again that noise was free to produce interferences.

In some way this remembered me the Greek audiophile club of Athens... the one was spitting some powder into the vinyl disc to avoid statics.... he said was introducing some "spice" into the sound... salt and condiments.... i use to watch that movie into youtube and i laugh all time long.

ahahaha...just kidding.

of course contact cleaner helps Jacco.

Carlos

.................................................. .........

Athens audiophile Club from Greece:

http://www.youtube.com/watch?v=xs1aUws0Lrs

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Old 3rd February 2009, 02:25 PM   #10
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Default i will also go for the bias issues

if theamp gets warmer than its supposed to be it is possible that bias is over compensated ....

or due to years past possible thta electros drifeted and so on and on and on ....

you need to check if your amp is with in the specs ......
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