Groove Tube Substi-Tubes

superlightweigh · November 6th, 2007, 08:30 PM

Just got the GC Pre-Holiday savings booklet and right there on page 6 is a picture of my DRRI with this little baby in front of it....

Can't find it on GC website so here goes:

"Make your Fender Amp CLass A"
Get distortion at lower volumes and run in Class A mode on your 6L6-based Fender Amp with these Groove Tubes Substi-tube converters. Simply replace your power tubes with these and get creamy class A tone without any other adjustments

The picture looks like those yellow THD tube sockets and they say "Power Reducer" on them.

I am not sure if they are selling just the reducer sockets or the complete sets...

Ummm- don't you have to re-bias your amp if you replace the power tubes??

Is this a new innovation or just new to the masses via GC? Will they harm the amp or void the warranty or anything like that?

All I know is I want them, BAD!!

superlightweigh · November 7th, 2007, 07:17 AM

bump

Anybody?

Hello..........ello............ello..........lo

FMA · November 7th, 2007, 07:26 AM

I had a set of them that I used in an Ampeg Reverberocket reissue. They did what they said they did. Not a huge difference in volume, but earlier breakup and that nice el84 tone. That amp, though, had other issues -- it wasn't a very well-built amp -- and it's gone, replaced with an AC15. Now, if you after that tone, that's the way to go.
I never had a problem with the substitubes and they worked. Just not exactly the tone I was after. I sold them to fellow TDPRI'er and he seemed very happy with them.
I can't address any technical issues that they may cause.

11 Gauge · November 7th, 2007, 08:09 AM

That class A bit is snake oil, IMO - don't get hung up on it. Other factors are more important, such as the cathode biasing.

No other adjustments are necessary, since the socket drops the parameters for the power tube (EL84 if it's a THD knockoff, which no doubt it probably is).

Biasing isn't necessary, since they convert the amp to cathode bias, instead of your amp's fixed (adjustable) bias.

Your warantee shouldn't be voided, but you may want to check your owner's manual. Since Fender gets their tubes from GT (at least they used to), they may honor these, even though they probably all come from the same source.

Make sure you get the ones with the grounding straps that attach to the chassis.

They'll drop the power, alright. You may or may not like the tones they produce.

AFAIK, Ruby and THD were the first ones to come out with them, but I wouldn't be surprised if they all come from the same or similar sources. Personally, I'd go with the THD's, but that's just me. I know that the Ruby's and THD's tend to ship with JJ's. You never know where GT gets their tubes from.

Also, the GT's adapters look on the pricey side, if you're including tubes - 120 clams for a pair (I don't know if GC has a better deal than this). The THD's tend to run around 100 or less for a pair, and you get the JJ's.

GT's socket-only adapters can't be used in class AB amps - they are designed for Champs, the THD Univalve, etc.

woodman · November 7th, 2007, 08:27 AM

gotta agree with 11 Gauge -- "Class A" hype is one of the oldest scams for getting into your wallet. the point should be what it does for your tone. if you think it's for you, go ahead and roll the dice. for the record, cathode bias has always worked best for me -- even converted my old Fender Pro, and it sounds much better for my purposes.

November 6th, 2007, 08:30 PM	#1 (permalink)
superlightweigh Tele-Meister Join Date: Apr 2007 Location: Schenectady, NY Age: 43 Posts: 383	Groove Tube Substi-Tubes Just got the GC Pre-Holiday savings booklet and right there on page 6 is a picture of my DRRI with this little baby in front of it.... Can't find it on GC website so here goes: "Make your Fender Amp CLass A" Get distortion at lower volumes and run in Class A mode on your 6L6-based Fender Amp with these Groove Tubes Substi-tube converters. Simply replace your power tubes with these and get creamy class A tone without any other adjustments The picture looks like those yellow THD tube sockets and they say "Power Reducer" on them. I am not sure if they are selling just the reducer sockets or the complete sets... Ummm- don't you have to re-bias your amp if you replace the power tubes?? Is this a new innovation or just new to the masses via GC? Will they harm the amp or void the warranty or anything like that? All I know is I want them, BAD!! __________________ Regards, Dan

November 7th, 2007, 07:17 AM	#2 (permalink)
superlightweigh Tele-Meister Join Date: Apr 2007 Location: Schenectady, NY Age: 43 Posts: 383	bump Anybody? Hello..........ello............ello..........lo __________________ Regards, Dan

November 7th, 2007, 08:09 AM	#4 (permalink)
11 Gauge Friend of Leo's Join Date: Mar 2003 Location: The East Coast Posts: 2,895 10 Photos	That class A bit is snake oil, IMO - don't get hung up on it. Other factors are more important, such as the cathode biasing. No other adjustments are necessary, since the socket drops the parameters for the power tube (EL84 if it's a THD knockoff, which no doubt it probably is). Biasing isn't necessary, since they convert the amp to cathode bias, instead of your amp's fixed (adjustable) bias. Your warantee shouldn't be voided, but you may want to check your owner's manual. Since Fender gets their tubes from GT (at least they used to), they may honor these, even though they probably all come from the same source. Make sure you get the ones with the grounding straps that attach to the chassis. They'll drop the power, alright. You may or may not like the tones they produce. AFAIK, Ruby and THD were the first ones to come out with them, but I wouldn't be surprised if they all come from the same or similar sources. Personally, I'd go with the THD's, but that's just me. I know that the Ruby's and THD's tend to ship with JJ's. You never know where GT gets their tubes from. Also, the GT's adapters look on the pricey side, if you're including tubes - 120 clams for a pair (I don't know if GC has a better deal than this). The THD's tend to run around 100 or less for a pair, and you get the JJ's. GT's socket-only adapters can't be used in class AB amps - they are designed for Champs, the THD Univalve, etc. __________________

November 7th, 2007, 08:27 AM	#5 (permalink)
woodman Poster Extraordinaire Join Date: Nov 2004 Location: Mint Hill, NC Age: 62 Posts: 5,780	gotta agree with 11 Gauge -- "Class A" hype is one of the oldest scams for getting into your wallet. the point should be what it does for your tone. if you think it's for you, go ahead and roll the dice. for the record, cathode bias has always worked best for me -- even converted my old Fender Pro, and it sounds much better for my purposes. __________________ Truth is stranger than fact ... www.myspace.com/woodymitchellmusic BAND PAGES: www.myspace.com/stragglerswing (Stragglers - Western Swing) www.myspace.com/loafersgloryband (Loafers Glory - '70s country-rock)

November 7th, 2007, 07:26 AM	#3 (permalink)
FMA Tele-Afflicted Join Date: Apr 2003 Posts: 1,077	I had a set of them that I used in an Ampeg Reverberocket reissue. They did what they said they did. Not a huge difference in volume, but earlier breakup and that nice el84 tone. That amp, though, had other issues -- it wasn't a very well-built amp -- and it's gone, replaced with an AC15. Now, if you after that tone, that's the way to go. I never had a problem with the substitubes and they worked. Just not exactly the tone I was after. I sold them to fellow TDPRI'er and he seemed very happy with them. I can't address any technical issues that they may cause.