I just bough that GFA 5500 as it looked great on paper. 200wpc, 700 damping factor, Mosfets. I expected that huge brick to sound like my Hafler 500, with some extra bass control as a bonus. Am I the only one to think it sounds harsh, very harsh? I am quite disapointed... The upper mids and highs are grainy and boosted. It was obvious right off the bat.
My choices are simple. Keep it to power subs, or find an easy fix. Can anything be done that doesn't involve shipping it to Musical Concept? Perhaps some filtering/smoothing on the output caps 😉
My choices are simple. Keep it to power subs, or find an easy fix. Can anything be done that doesn't involve shipping it to Musical Concept? Perhaps some filtering/smoothing on the output caps 😉
i wonder if your 5500 uses an inductor together with a zobel in the output ... i also wonder what type and how long cables you use ....
someone has to come up with a schmatic so we can verify that ...
someone has to come up with a schmatic so we can verify that ...
Back on the subject.
Two things I immediately noted when firing up the amp was the over abundance of upper mids and low highs, and "that" grain. A few days later, I can say that the grain has disapeared. And it is not that I got used to it as I have been swapping amps. Most likely the grain was temporary and caused by the Cambridge D500 CD player which sometimes "fails" on power on. What remains is that over-generous and agressive upper mids. I guess that I can filter them out by fitting smoothing caps on the four big capacitors.
Or maybe I only used to the Hafler and Quad sound texture... ;-)
Two things I immediately noted when firing up the amp was the over abundance of upper mids and low highs, and "that" grain. A few days later, I can say that the grain has disapeared. And it is not that I got used to it as I have been swapping amps. Most likely the grain was temporary and caused by the Cambridge D500 CD player which sometimes "fails" on power on. What remains is that over-generous and agressive upper mids. I guess that I can filter them out by fitting smoothing caps on the four big capacitors.
Or maybe I only used to the Hafler and Quad sound texture... ;-)
back on the subject means exactly what ? do you belive that one of the above posts or replies is out of subject ? at least this is the way i understand it ...
No, no. no. Everyone has been helpfull and I thank you all for your help. I only meant that I was out for a few days and didn't want posters to think I quit on them ;-) I am still searching for a schematic as the amp has potential and only needs a little tweak. Who would say no to an amp with a 700 damping factor? And it is quiet, which can't be daid of my Hafler 500 which sounds great but runs on a fan.
The reviews on the net show a larger percentage of owners who find the sound smooth, while others find it agressive and somewhat harsh. So, I don't know what to think. I have been using different types of interconnects and cables. Same proeminent upper frequencies.
The reviews on the net show a larger percentage of owners who find the sound smooth, while others find it agressive and somewhat harsh. So, I don't know what to think. I have been using different types of interconnects and cables. Same proeminent upper frequencies.
I read about
Adcom GFA 5500
follow:
Many of the design features in the GFA-5500 are virtually identical to the GFA-5800 power amplifier. The primary difference between these amplifiers is power output. The circuit topology and design concepts are virtually identical.
But my english isn't enough to understand this exactly. What means the term "virtually identical" ??
only other output power devices (BjT's instead MOSFET's e. g.)?
or only lower voltage and lower value of parallel switched parts?
Perhaps the schematics of 5800 (see attachement) help a little.
Additional I read this:
Most high end amplifiers have at least 5 successive gain stages associated with their signal path. Some have even more. The GFA-5500 achieves all of its performance with only three. That's two stages less for the signal to travel through, and it makes a difference.
What means "5 successive gain stages associated with their signal path" ?? Perhaps 5 gain stages inside of the NFB loop?
Until this day I haven't see such voltage gain unit. The maximum voltage gain stages within the NFB are two pieces (three stages include the current output gain stage resp. buffer stage).
The reason for unsatisfy sound might be the cheap version of power supply caps. If you have versions like the attached picture from 5400, is this on of the reasons.
Attachments
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Hifi engine has the schematics for the 5300
EDIT - hot linking downloads doesn't work -
Download Manager
and for the 5802
EDIT - hot linking downloads doesn't work -
Download Manager
I can send them to you if you email me at mybuddylee@gmail.com
BTW I wonder if some electronic manufacturers might be designing equipment for the new MP3 generation who only wants deep bass and agressisve trebles... ;-)
EDIT - hot linking downloads doesn't work -
Download Manager
and for the 5802
EDIT - hot linking downloads doesn't work -
Download Manager
I can send them to you if you email me at mybuddylee@gmail.com
BTW I wonder if some electronic manufacturers might be designing equipment for the new MP3 generation who only wants deep bass and agressisve trebles... ;-)
Here's an inside shot of a GFA 5500. This one is not my own, just taken off the net. On this shot, I can easily see something that bugs me on the output caps. The red silicone spots portrude from the can, which I believe is a sign they are beyond their life. Shouldn't a good capacitor show the little spots slightly lower than the surface? I will open my own amp and see if it suffers from the same condition.
An externally hosted image should be here but it was not working when we last tested it.
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