New amp sounds too controlled ... what to fix

[Coolin]

Try the D Self X.D. trick with a resistor ( choose carefully ) from one of the rails to the output

Give me some credit Mooly, ive actually done this before on chipamps and it does work well. That should improve/eliminate the x-over distortion right? instead of burning a lot of power in the parallel resistor. The problem is where to place it as this is new territory for ne.

I believe a lot is to do with the way the amp responds to "voltage" that finds it's way back into the feedback node. Each speaker works as a pretty good microphone as well, forcing current back into the amp. This causes some disturbance to the feedback signal, something resistive testing will never show. Just flick the cone of a speaker connected to an amp and see what happens to the feedback signal. As Pavel hints at, the high feedback factor designs suffer the worst.
I honestly find it hard to believe a 15 ohm across the outputs "transforms" the sound. I don't doubt you feel it does, but a double blind test is needed.

Yes that's what i said in layman language
Exactly, the speaker is a highly dynamic device.
I have not removed the resistor yet to check again. don't have a lot of time today either..

I meant influence of HF EMI induced into speaker/cable, that appear on speaker terminals of the amplifier.

OK. Wouldn't a very small cap function better in this regard?

Do you know if there are any monolithic opamps in the signal path? If so, there's a world of possibilities.

I'll have to read up on what that is exactly first
No the amp looks built up " pretty discrete " is that the right wording ?

 

[Coolin]

My experience is that Yamaha's tend to sound harsch in the mid / high frequencies, thin non-stranded wire will only make it worse.

Yes it a kind of tradeoff but with matching speakers its not a problem.
I build my own speakers, that's how i rolled into the high end amp building/modding venture
Also this is the UK version of the amp which has been tuned to the English taste. Not sure in which way though. They seem to be more stereo oriented folk so they had to "improve" it some ways to stay competitive there i guess..

 

[lineup]

As I said earlier here
even if nobody remembers this, by now,
keep your amplifier inctact .. so to sell in original condition,
if you like, later.


Then you go buildsome output amplifier which does not care firstly
about damping factor.

Nelson Pass diy has got several such high quality amplifiers.
And more precisely Nelson Pass www.firstwatt.com amplifiers
address this issue.
And so he has made those great creations be
outputting current in accordance to loudspeaker impedance variations.

Which makes the sound reproucer and not the amplifier
be the component that determining what sound will be re-produced.

Links:
http://www.passdiy.com/default.html
http://www.firstwatt.com/default.html

 

[lineup]

The more precise links
to Nelson Pass audio articles and DIY Builders Projects:

http://www.firstwatt.com/downloads.htm
... some unique smaller audio amplifiers for good sounds

http://www.passdiy.com/articles.htm
... some classical audio amplifiers for DIY

 

[Mooly]

Adding caps across the output could be interesting
Adding a resistor X.D. style which has been done for years with OpAmps shifts the crossover region away from 0 volts, and there is evidence that it can be audibly beneficial. The actual distortion is still present essentially just as before, but it's less subjectively audible being moved from the sensitive ( hearing wise ) zero crossing.
I think you have to accept that musically/subjectively this amp hasn't got that magical "X" factor, which once you have experienced it, there's no going back. Sorry but that's the bottom line I feel here -- and I have been there on more than one occasion

 

[Coolin]

Adding caps across the output could be interesting
Adding a resistor X.D. style which has been done for years with OpAmps shifts the crossover region away from 0 volts, and there is evidence that it can be audibly beneficial. The actual distortion is still present essentially just as before, but it's less subjectively audible being moved from the sensitive ( hearing wise ) zero crossing.
I think you have to accept that musically/subjectively this amp hasn't got that magical "X" factor, which once you have experienced it, there's no going back. Sorry but that's the bottom line I feel here -- and I have been there on more than one occasion

Very small caps for RF frequencies... like being used in power line filtering.. I think these are relatively high ESR types

No it doesn't have the X-factor but good enough for my surround channels now. The Main amps are are to be put into use in the future and these must have the full X...
I'm afraid i wont have it all operational before Q2 2009 as i have many things to do before its all operational. Moving/building new HT/Building new speakers etc.

 

[Mooly]

Not exactly. Take a TV coax downlead. Stick a pin through it shorting center to outer. The signal at the receiver increases - Discuss.
Add a cap across the lead in the same way. That has to short out the signal. It doesn't touch it Discuss.

I do wish you luck tweaking your set up, just be careful it doesn't bite back in cloud of smoke

 

[Coolin]

I won't humor you any longer

Not much to discuss for me. Did you pull that out of the electronics fairy tale handbook ?

We will meet again someday, somewhere. Perhaps to explore how i can improve on the mooly amp

BTW, any PCB's and part kits available ?

Collin

 

[Mooly]

Hi Coolin,
Now why would I do that Have you actually tried it. Why do you think it's a fairytale ? Please tell me
As to the "Mooly" amp, I'm afraid there aren't any PCB's, but it's a very easy design to build.
I have just been watching a video on Youtube, from one of Carlos's links. The "Mooly" amp with my speakers achieves all this. Do watch it all -- it's really good.
Will edit this with a link to it

Post #1282
http://www.diyaudio.com/forums/showthread.php?s=&postid=1599368#post1599368

 

[Coolin]

Yes a fun, very recognizable documentary.

When i just started out in audio i thought if i ever had the money i just might be crazy enough to spend 50000 on one of those audiofile amps to have the highest achievable in reproduction..
I actualy quit the hobby for a few years as i knew i was going to spend too much on it...

Now i know better, it CAN be achieved with very simple amps !
I saved myself alot of money. I was very happy when i discovered this.

I also know what it is to be "transported"into the music. Thats my drive in audio it is indeed an addiction...

Regarding the shorted cable, sure some signal will still get through but i read somewhere else the signal improved on some frequencies.Cant explain but audio and RF is still a black art to all but a few individuals who know a bit more.

 

[Mooly]

Hi Collin,
If I ever post another design it will have to be given a proper name. "Mooly" amp doesn't quite cut it does it
Let us know how you get on with it all, and how your system ends up -- whether bought or D.I.Y. or what changes you make to your Yamaha.
And enjoy the music
Regards Karl

 

[Coolin]

Originally posted by routhun
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



Hi Routhun,

Do you have this service manual? Perhaps someone else can hint where i can find them ?

Its not placebo....

Regards,

Collin

 

[routhun]

Hi Collin,

Unfortunately I don't have the service manual for this model, you can try at www.sharefx.com someone will post the service manual.

Thanks,
Routhun