New amp sounds too controlled ... what to fix

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Jump to Latest
P

Patrik Floding

Member
Joined 2005
Re: !! WELL, I'M AMAZED !!

Coolin said:
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 :D :D :D :D

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 ?
Click to expand...

What speaker cables are you using?
 
Coolin

Coolin

Member
Joined 2003
Conrad Hoffman said:
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.
Click to expand...


Thanks for the tip. With any luck this could have the same influence as the 15 ohm parallel. I guess it kind of fulfills the same function but only for higher freq. How low could i go in value before it gets dangerous?

I have no idea where to find any overall feedback so i'm hoping Routhun helps out.
 
P

Patrik Floding

Member
Joined 2005
Coolin said:



Thanks for the tip. With any luck this could have the same influence as the 15 ohm parallel. I guess it kind of fulfills the same function but only for higher freq. How low could i go in value before it gets dangerous?

I have no idea where to find any overall feedback so i'm hoping Routhun helps out.
Click to expand...

TBH, I think it sounds as if you will soon fry your amp, your speakers, or both!
Mucking about inside the amp is not recommended unless you know EXACTLY what you are doing!
 
Coolin

Coolin

Member
Joined 2003
Mooly said:
As long as you are happy with it :) To be sure you need it confirming under double blind listening tests with someone else doing the swapping over :)
Your understanding of feedback is well, interesting shall we say.
Click to expand...


Yes very interesting :) I know, but it still gets me where i want to go :)

Thats why i'm here, in need of some guidence :)
Yes i have alot of reading to do but like i said its a hobby and until now
the chipamp was a black box for me but i learned a great deal from influencing all of its external "feedings"
So now on to full SS !!
In the future i will try to make Carlos'es amp or perhaps yours !
But someone must build both first :)

I know all about being fooled by ones own changes and thinking they are superior each time so i try to approach it without preconceptions.
If you were here you would agree with my findings :)
With revealing speakers its a lot easier to spot the changes.

Also if your doing other things in the house it really helps to tell if the change was an improvement. Because your not too focused on the music but the emotional aspect can still grab you. Everyone who has a good amp must agree with this..
 
Coolin

Coolin

Member
Joined 2003
Patrik Floding said:


TBH, I think it sounds as if you will soon fry your amp, your speakers, or both!
Mucking about inside the amp is not recommended unless you know EXACTLY what you are doing!
Click to expand...


Do not worry i wont hold you accountable.
The way it sounds now i might not anyway. It has really improved ALOT. But i still dont like the outboard resistors dangling.

Before i make any changes i usually do some research :)
 
Coolin

Coolin

Member
Joined 2003
Eva said:
The 15 ohm parallel resistor results in a nice placebo effect for sure... This is a funny one.
Click to expand...


Eva iv'e seen some very knowledgeable post from you but I geuss your not from the subjectivist camp.

I know it shouldn't really be noticeable but with this amp it really has a big influence.. I'm going to check again tomorrow with and without as it is late already.
 
PMA

PMA

Member
Joined 2002
pmacura.cz/audiopage.html
Paid Member
I do not think much about that Yamaha, BUT parallel resistor sometimes helps. There may be more reasons. One of them was indicated here (current in case of poor low bias design), the other, usually completely overlooked reason, is when one hits resistor close to speaker cable wave impedance - it damps HF reflections, important especially for high NFB, not very stable designs.
 
Coolin

Coolin

Member
Joined 2003
PMA said:
I do not think much about that Yamaha, BUT parallel resistor sometimes helps. There may be more reasons. One of them was indicated here (current in case of poor low bias design), the other, usually completely overlooked reason, is when one hits resistor close to speaker cable wave impedance - it damps HF reflections, important especially for high NFB, not very stable designs.
Click to expand...

The bias current could be part of the story here i agree.
I notice the low level sounds cleanup most. Especially ambiance related stuff gets more loose from the speakers. I'm using 94 dB eff. speakers.


Andre Visser said:
Try using larger dia speaker cables, 2,5 mm2 to 3 mm2 twisted cable should be much better. (With the Yamaha you can even try 4 mm2)
Click to expand...

My experience says efficient speakers like thin non stranded wire. Not using this at the moment.
 
Coolin

Coolin

Member
Joined 2003
PMA said:
the other, usually completely overlooked reason, is when one hits resistor close to speaker cable wave impedance - it damps HF reflections, important especially for high NFB, not very stable designs.
Click to expand...

Could you expand on your speaker cable impedance thoughts.
its not completely clear to me. I know about impedance matching and heard about it also being part of the chain to the speaker but...
 
Mooly

Mooly

Administrator
Joined 2007
Paid Member
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.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Top Bottom