Fixing Adcom's GFA 5500's harshness

Lee in Montreal · 18th July 2010, 12:11 PM

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

djk · 18th July 2010, 04:16 PM

Do you have the schematic?

I thought the GFA5500 was a BJT design, and that the GFA5800 was FET.

Lee in Montreal · 18th July 2010, 04:24 PM

I have only been able to find the owner manual by now. Still searching for some schematic ;-)

Lee in Montreal · 19th July 2010, 01:27 AM

Little info here, and still searching for a schematic

Adcom GFA 5500

sakis · 20th July 2010, 10:25 AM

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 ...

Lee in Montreal · 21st July 2010, 02:49 PM

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... ;-)

sakis · 21st July 2010, 04:53 PM

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 ...

Lee in Montreal · 21st July 2010, 05:02 PM

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.

sakis · 21st July 2010, 05:03 PM

that is ok then .... lift the cover and let me know if there is an inductor ..please

Lee in Montreal · 21st July 2010, 05:08 PM

Quote:

Originally Posted by sakis

that is ok then .... lift the cover and let me know if there is an inductor ..please

I will. Sorry for the confusion

18th July 2010, 12:11 PM	#1
Lee in Montreal diyAudio Member Join Date: Oct 2009	Fixing Adcom's GFA 5500's harshness 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

18th July 2010, 04:16 PM	#2
djk diyAudio Member Join Date: Feb 2001 Location: USA	Do you have the schematic? I thought the GFA5500 was a BJT design, and that the GFA5800 was FET. __________________ Candidates for the Darwin Award should not read this author.

20th July 2010, 10:25 AM	#5
sakis diyAudio Member Join Date: Jan 2006 Location: nea makri athens greece	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 ... __________________ SERVICE ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr

21st July 2010, 04:53 PM	#7
sakis diyAudio Member Join Date: Jan 2006 Location: nea makri athens greece	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 ... __________________ SERVICE ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr

21st July 2010, 05:03 PM	#9
sakis diyAudio Member Join Date: Jan 2006 Location: nea makri athens greece	that is ok then .... lift the cover and let me know if there is an inductor ..please __________________ SERVICE ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr


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18th July 2010, 04:24 PM	#3
Lee in Montreal diyAudio Member Join Date: Oct 2009	I have only been able to find the owner manual by now. Still searching for some schematic ;-)

19th July 2010, 01:27 AM	#4
Lee in Montreal diyAudio Member Join Date: Oct 2009	Little info here, and still searching for a schematic Adcom GFA 5500

21st July 2010, 02:49 PM	#6
Lee in Montreal diyAudio Member Join Date: Oct 2009	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... ;-)

21st July 2010, 05:02 PM	#8
Lee in Montreal diyAudio Member Join Date: Oct 2009	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.

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