#1
Hi, i own a Sunn Sceptre 1971 and i have a pretty simple question.

Is it normal that when i add reverb i get alot of gain (a pretty breakup not 'noise) from it ? Is it because of the age of the amps, my ignorance of tube amps/certain type of reverb or a problem coming from the circuits... thanks.
Fender Telecaster Texas Special MIA
Sunn Sceptre 1971 A1
Marshall JCM800 Cab 1980
#3
It is a bit of an odd circuit actually. It has two gain stages before the reverb rather than a cathode follower. It needs tweaking so at full reverb level you are getting unity gain. You could try replacing V2. It may not be a gain issue so much as a dying tube. ie distortion due to a faulty tube rather than a signal mismatch. I'd certainly try a new tube before I tried to mod it, especially if it is a recent development and not something it has always done.


Edit. Oh, it's a 12AU7. That would account for the configuration because 12AU7's have very low gain. Replace it.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
Last edited by Cathbard at Mar 17, 2013,
#4
Awww man, really ? The dude told me that he just replaced the preamp tube, i feel bummed huh. If i understand, the 12au7 is the whole 'module ? I really need to get my shit together on tube amps LOL.

What exactly is 'unity' gain ?
Fender Telecaster Texas Special MIA
Sunn Sceptre 1971 A1
Marshall JCM800 Cab 1980
#5
They're pretty cheap. http://tubedepot.com/jj-ecc82.html just pull out the old one and plug in the new one, you can do it yourself.
It isn't the whole reverb module, just the driver tube. Can't hurt to have a spare. Even if it doesn't fix it you've lost nothing really. Tubes fail, it's just a fact of life for a guitarist.

Unity gain is same out as goes in. ie gain factor of 1.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#6
Thanks for the help man, really appreciated
Fender Telecaster Texas Special MIA
Sunn Sceptre 1971 A1
Marshall JCM800 Cab 1980
#7
No probs. It could have been worse, I blew a British Brimar power tube last night at band practice. Now that's a bitch, those things cost three figures. Consider yourself fortunate.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#8
Quote by Cathbard
No probs. It could have been worse, I blew a British Brimar power tube last night at band practice. Now that's a bitch, those things cost three figures. Consider yourself fortunate.


And I thought my "used" RCA tube for 20 bucks was a lot.

Jackson RR3 Rhoads and DK2M Dinky
Peavey 6505+ w/ Avatar 212 cab
Ibanez TS9, ISP Decimator, MXR 10 Band EQ
-Digitech RP1000
#9
They're Brimar 6L6's. Those things are getting rare. If you can find them for under $100 each you are doing well. I've ordered some JJ's to replace them, $47 for the pair including delivery. I threw in a pair of JJ KT66's to get me through rehearsal. They sounded quite good actually but they are a lot more expensive than the 6L6's. The KT66's I pulled out of my JTM45. Ideally I'd like some nice NOS power tubes but they are just too damn expensive.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#10
I could've had a Sceptre for $100 at a flea market a year or two back. I didn't have the cash on me and I kick myself every damn day for not buying it
Endorsed by Dean Guitars 07-10
2003 Gibson Flying V w/ Moon Inlay
2006 Fender All-American Partscaster
SVK ELP-C500 Custom

1964 Fender Vibro Champ
1989 Peavey VTM60

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