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Old 30th August 2008, 08:10 AM   #21
Coolin is offline Coolin  Netherlands
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Quote:
Originally posted by Conrad Hoffman
Coolin, you said it improved when you put 15 ohms in parallel. That actually increases the damping seen by the speakers, though not by much. My guess is the amp is now supplying more current (you have to drive both the resistor and the speakers) and maybe the amp isn't very good at low power levels- it just likes working a bit harder, or it doesn't like the cables, the speakers or something. As long as the combined value isn't too low, I'd just leave the resistor in parallel.

Yes the parallel configuration is the way to go and could be used long term but it is burning some energy which i would rather solve in the amp if possible. It sounds much more "organic" free flowing. The difference in volume is too small to say the amp likes working a bit harder. Besides in series it has too work even harder but sounded worse.
Its an old trick and makes the load more resistive and less reactive.
In series it sounded much harder in the midrange and with less depth. This tells me the drivers have stored energy and the amp cannot damp this as well with the resistor in between.
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Old 30th August 2008, 08:13 AM   #22
Mooly is offline Mooly  United Kingdom
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Quote:
Originally posted by Lumba Ogir
Hi,
I strongly suspect the notorious Japanese commercial amplifier philosophy of huge open-loop gain an GNF resulting in an extremely clean, lifeless sound without any kind of warmth, spirit and dimension. The musical qualities can thereby be rated as negligible.

I agree -- sadly Just guessing but it probably uses the most horrendous topology with nested feedback loops etc all over the place to achieve very good "on paper" specifications. If you start altering the feedback factor you will almost certainly run into stability issues.
Sorry, I agree with PMA's comment on this one.
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Old 30th August 2008, 08:15 AM   #23
Coolin is offline Coolin  Netherlands
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Quote:
Originally posted by Lumba Ogir
Hi,
I strongly suspect the notorious Japanese commercial amplifier philosophy of huge open-loop gain an GNF resulting in an extremely clean, lifeless sound without any kind of warmth, spirit and dimension. The musical qualities can thereby be rated as negligible.

I think your right....

So how do i solve it ?? !!

Can i make this SS amp more current oriented in a simple fashion ?
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Old 30th August 2008, 08:28 AM   #24
Mooly is offline Mooly  United Kingdom
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Hello Coolin,
I have been in the same situation. Many years ago I bought a Pioneer A80 amp. Unbelieveably well specified and I bought it on this alone. It was as you describe. As an electronics engineer I felt the "wire with gain" philosophy was the way to go. Sadly it wasn't. I tried to convice myself it was good, that it was the recordings that were being shown up etc. I was wrong there as well.
In the end I went back to designing my own amps again and have never looked back. A simple design can blow all these technological wonders out of the water sonically.
Sorry there is no easy answer -- well there is - but it's not what you want to hear
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Old 30th August 2008, 08:37 AM   #25
Mooly is offline Mooly  United Kingdom
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Have a read at post 107 here
My MOSFET amplifier designed for music.
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Old 30th August 2008, 08:43 AM   #26
Coolin is offline Coolin  Netherlands
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Quote:
Originally posted by Mooly



I agree -- sadly Just guessing but it probably uses the most horrendous topology with nested feedback loops etc all over the place to achieve very good "on paper" specifications. If you start altering the feedback factor you will almost certainly run into stability issues.
Sorry, I agree with PMA's comment on this one.
Ok, we agree on the problem...

If i change the resistor thats only effecting the local feedback then its relatively safe right? I'm only thinking of doing it to the last stage as this is where the emf from the speaker is coming in. I would only need to be carefull not going to far and causing occilations.
Even just moving the feedback resistor closer could help here..

Anybody have any Yamaha schematics of recent AV models
They must be using this topology elsewhere.
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Old 30th August 2008, 10:36 AM   #27
Coolin is offline Coolin  Netherlands
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Quote:
Originally posted by Mooly
Have a read at post 107 here
My MOSFET amplifier designed for music.

Yes i know better amps is the answer but since this Yamaha will only power my rears i'm still hoping i can improve it somewhat so that its usable... the rears in a 7.1 HT are not doing much work anyhow but should sound more open.

How does your amp sound compared to the great Carlos'es ?
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Old 30th August 2008, 11:50 AM   #28
Mooly is offline Mooly  United Kingdom
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I have never built one of Carlos's designs so can't comment on that. And I guess Carlos hasn't built mine either
As for modding the Yamaha, without a full circuit no one can say what the effect of altering components will do.
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Old 30th August 2008, 01:08 PM   #29
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Quote:
Originally posted by Coolin


Ok, we agree on the problem...

If i change the resistor thats only effecting the local feedback then its relatively safe right? I'm only thinking of doing it to the last stage as this is where the emf from the speaker is coming in. I would only need to be carefull not going to far and causing occilations.
Even just moving the feedback resistor closer could help here..

Anybody have any Yamaha schematics of recent AV models
They must be using this topology elsewhere.
Hi Coolin!
Isn't it a bit drastic to modify the amplifier's internals, if it is a new amp? Especially if you can acheive a similar result buy using some power resistors externally.
Regards
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Old 30th August 2008, 01:25 PM   #30
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Quote:
Originally posted by h_a


May I ask why reducing the damping factor could help?

Don't forget to use a high-power resistor.
putting a large enough resistor in series to the output would seriously misalign most speakers, resulting in a more boomy, warmth response.
Tube sound for free!
I would try 2-3 ohms.
regards
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