New amp sounds too controlled ... what to fix

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#21
Conrad Hoffman said:
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.
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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.
 
#22
Lumba Ogir said:
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.
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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.
 
#23
Lumba Ogir said:
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.
Click to expand...


I think your right....

So how do i solve it ?? !!

Can i make this SS amp more current oriented in a simple fashion ?
 
#24
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 😉
 
#26
Mooly said:



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.
Click to expand...

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.
 
#27
#28
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.
 
#29
Coolin said:


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.
Click to expand...

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
 
#31
Patrik Floding said:


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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Well its similar but after a few hours of listening its still nu up there with my cheap old beaten up freebee sony i had in storage for a few years....:bawling:

Doing chipamp mods i learned how powerfull the emotional impact of these changes was. I geuss it really is DIY as i'm not getting any pointers to do the surgery..

So no one can tell from the picture anything about the basic configuration used here? :whazzat:
 
#32
Juergen Knoop said:

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! :clown:
I would try 2-3 ohms.
regards
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Well as i said these are bass shy pro drivers so they will never sound boomy. Anyway even with 6,8 Ohm they still dont sound like the cheap old sony.

I'll open up the sony so we can see whats happening there...
 
#33
It's an STK module. And a very simple setup for the rest.
Its not a great amp but regarding the naturalness of the sound its much better.

The background of the music is also quieter. This is also using the direct through function on the Yamaha.

Perhaps that's whats the problem is i am still hearing, the not very black background.. This phenomenon also occurs with the chip amps if my memory is correct.

Does anyone know the damping factor of these modules and if the feedback is done internally?
 

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#34
The conditions of the Carver test are very near to what you want to do:

jcx said:
The Stereophile - Bob Carver Challenge (Bob wins!):

http://www.diyaudio.com/forums/showthread.php?postid=152392#post152392
Click to expand...


other useful info for “matching sound”


double blind, controls and level matching are Necessary for meaningful Subjective evaluation - not exclusive of subjective evaluation

Book:

http://www.wiley.com/WileyCDA/WileyTitle/productCd-0470869232.html

************************

Level Matching Thresholds and refs in DBT:

http://www.provide.net/~djcarlst/abx_crit.htm

http://www.provide.net/~djcarlst/abx_peri.htm
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nulling the response between the 2 amps at the speaker terminals with a combination of input signal EQ and series output Z should be the place to start - you shouldn't have to modify the feedback of the amp
although poor low frequency corner would be better fixed by increased coupling C than external EQ
 
#36
jcx said:
The conditions of the Carver test are very near to what you want to do:

other useful info for “matching sound”




nulling the response between the 2 amps at the speaker terminals with a combination of input signal EQ and series output Z should be the place to start - you shouldn't have to modify the feedback of the amp
although poor low frequency corner would be better fixed by increased coupling C than external EQ
Click to expand...



Thanks for the info JCX. I'm not surprised this can be done. You need to start out with a very capable amp though to be able to mimic others fully. The Yammy is not in that league.
Ive got quite far using the parallel resistor. Its not that I'm missing any area frequency wise now. The bass is almost the same as the sony but tighter. I don't have a problem with that as i like the real thing, natural sound that is. But the overall sound is still a bit non expressive, not making my feet tap like with the sony. I doubt a correction in the frequency response could help to get that quality back.
 
#37
Without a schematic, the endevor seems foolish, so I'd make every effort to get one, or leave well enough alone. With one of my amps I did notice a difference between a small capacitor across the overall feedback, vs using a cap further back in the circuit (miller cap?). I thought the miller cap was the better way, technically, but it ruined the sound. Tossing it and plunking about 50pF across the feedback resistor was a vast improvement. My guess is the distortion spectra changed, but I never tested the idea. You might also examine the local bypassing- use good electrolytics and film caps right at the circuit.
 
#38
Hi Coolin,

I faced the similar issue with recent AV models from Harman and Onkyo. The power amps in these receivers are well built and can compare to most of the designs available here. For bith of these receivers the culprits are the buffers/electronic switches and any Digital Processing of the signal. If the receiver has external jumper for pre-out and main-in you can hookup the external preamp to this amp to eliminate the doubts about the performance of the power amplifier. By the way what is the model number of your yamaha AV receiver, I can check if I have the service manual for this model.

Thanks,
Routhun
 
#39
!! WELL, I'M AMAZED !!

While playing with different positions of the parallel output resistor i noticed the closer to the amp the better the sound !

A had resistors on the drivers themselves for a while but it didn't sound as good as one in front of the x-over.
Then i placed the R on the outlet of the amp...BINGO !!

This is how it should be !! more natural, more dynamic, more clarity etc. etc.

I'm proud of myself 😀 😀 😀 😀

So this seems like a major unrecognized phenomenon regarding the driver/amp interaction...

It seems to me the amp needs more local feedback straight from the output instead of a delayed distorted signal first going through the drivers. Isn't the feedback loop trying to correct the distorted signal from the speaker while it should actually let it be because its already after the fact !! ????

Can someone verify this ?
 
#40
routhun said:
Hi Coolin,

I faced the similar issue with recent AV models from Harman and Onkyo. The power amps in these receivers are well built and can compare to most of the designs available here. For bith of these receivers the culprits are the buffers/electronic switches and any Digital Processing of the signal. If the receiver has external jumper for pre-out and main-in you can hookup the external preamp to this amp to eliminate the doubts about the performance of the power amplifier. By the way what is the model number of your yamaha AV receiver, I can check if I have the service manual for this model.

Thanks,
Routhun
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Hi Routhun,

I would really appreciate it if you did !
I'd really like to make these changes under the hood if possible.

I have the Yamaha RX-V861 well actually the UK version DSPAX-861SE but virtually the same exept for some minor component changes.
Perhaps you have both manuals because i'm very curious what they have changed to tune it more to the taste of the english...
 
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