Gibson GA5 Question

tele1 · November 25th, 2006, 03:03 PM

I have a new GA5 that is a little noisey. Would a re-tube probably help? Since there is only 1 power tube is there anything to bias? What kind of tubes are the best? Are Groove tubes any good? Tanks in advance for your input........

JohnnyCrash · November 25th, 2006, 03:29 PM

Single ended amps are generally a little noisier than Class AB type amps.

A retube will not help a whole lot with the noise. I am assuming it's a low end "hum" and not a high end "fuzz"?

You can DC rectify the heater filaments if you're handy with a soldering iron... otherwise, get used to the hum.

These amps are cathode biased, which means you can simply pop in any EL84 and not have to bias them. Some folks call cathode bias "self bias".

JJ EL84s are nice. I really like ElectroHarmonix 12AX7 preamp tubes too. But it really depends on your tastes.

Maybe you should taste-test several 12AX7's and EL84's. Especially since the amp doesn't require any rebiasing.

Gee · November 25th, 2006, 03:32 PM

Quote:

Originally Posted by tele1

I have a new GA5 that is a little noisey. Would a re-tube probably help?

It may do. I have 2 self built GA-5's and they are both noisier than I would like. I have spent lots of time trying to tame them and not really succeeded. I know that a small 5W EL84 amp can be quiet because my Epi VJ was very quiet.

Quote:

Originally Posted by tele1

Since there is only 1 power tube is there anything to bias?

No.

Quote:

Originally Posted by tele1

What kind of tubes are the best? Are Groove tubes any good? Tanks in advance for your input........

I believe the Grove Tubes EL84 is a re-badged JJ tube. The JJ tubes (both EL84 and 12AX7) are well thought of. I am currently using Tungsol 12AX7 reissues in my GA-5's which I find are much brighter that the JJ 12AX7's.

RomanS · November 25th, 2006, 05:10 PM

Another vote for JJ EL84 tubes - since I replaced the Sovtek in my Epi Valve Jr. with one of those, it sounds like a 500 $ amp.
I never believed that a different brand of tube would make such a difference until I tried this!

tele1 · November 25th, 2006, 06:04 PM

It came with JJ tubes in it. The hum is not bad, just a low pitch that is noticable at low levels. I think it is probably normal so I will probably just let it ride......BTW I love this little amp...........

November 25th, 2006, 03:03 PM	#1 (permalink)
tele1 Tele-Meister Join Date: Feb 2004 Location: Central Ohio Age: 54 Posts: 318	Gibson GA5 Question I have a new GA5 that is a little noisey. Would a re-tube probably help? Since there is only 1 power tube is there anything to bias? What kind of tubes are the best? Are Groove tubes any good? Tanks in advance for your input........

November 25th, 2006, 03:29 PM	#2 (permalink)
JohnnyCrash Poster Extraordinaire Join Date: Mar 2005 Location: Lost Angeles and Orange County Posts: 7,128	Single ended amps are generally a little noisier than Class AB type amps. A retube will not help a whole lot with the noise. I am assuming it's a low end "hum" and not a high end "fuzz"? You can DC rectify the heater filaments if you're handy with a soldering iron... otherwise, get used to the hum. These amps are cathode biased, which means you can simply pop in any EL84 and not have to bias them. Some folks call cathode bias "self bias". JJ EL84s are nice. I really like ElectroHarmonix 12AX7 preamp tubes too. But it really depends on your tastes. Maybe you should taste-test several 12AX7's and EL84's. Especially since the amp doesn't require any rebiasing. Last edited by JohnnyCrash; November 25th, 2006 at 03:30 PM. Reason: I can't spell

November 25th, 2006, 06:04 PM	#5 (permalink)
tele1 Tele-Meister Join Date: Feb 2004 Location: Central Ohio Age: 54 Posts: 318	HMMMMMM It came with JJ tubes in it. The hum is not bad, just a low pitch that is noticable at low levels. I think it is probably normal so I will probably just let it ride......BTW I love this little amp...........

November 25th, 2006, 05:10 PM	#4 (permalink)
RomanS Friend of Leo's Join Date: Jun 2006 Location: Vienna, Austria Age: 37 Posts: 2,886 14 Photos	Another vote for JJ EL84 tubes - since I replaced the Sovtek in my Epi Valve Jr. with one of those, it sounds like a 500 $ amp. I never believed that a different brand of tube would make such a difference until I tried this!