From tremolu–(at)–ol.com Thu Nov 24 19:53:44 CST 1994
Article: 33136 of rec.music.makers.guitar
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From: tremolu–(at)–ol.com (Tremolux)
Newsgroups: rec.music.makers.guitar
Subject: Re: Groove Tube 6V6HD
Date: 24 Nov 1994 16:55:05 -0500
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I know what the hell is going on because I spoke to the people at GT about
the damn things.
You guessed it, the GT 6V6HD is really a Sovtek 6L6 (not the Sovtek 5881).
These particular 6L6s are really wimpy as far as 6L6s go, and are “low
yield” according to the GT representative I spoke with. These things sell
for about $5 each from Antique electronics, how much did you pay GT to put
their label on them?
I believe one guy who posted has the wrong idea about biasing, when he
said he lowered his plate voltage by 8 volts in accordance with the
instructions that came with the tubes. WRONG!!!! You need to increase
the negative grid bias by 8 volts relative to the cathode, and leave the
damn plate alone. Also, the oscilloscope method is not consistent, and
generally results in over-biased amps. If you’re going to do it, do it
right and actually measure the plate current. In this application, I
recommend an idle current of about 25 ma per tube.
Anyway, since you are re-biasing your amp for a 6L6, why the hell not just
go ahead and put in a good one instead of a wimpy “low yield” tube?????
Antique will sell the very consistent and reliable Sovtek 5881 for about
$20 for a matched pair. I bet this is less than you paid GT. BTW, the
Sovtek 5881 is what GT sells as their top of the line GT6L6B. In short, I
do not recommend using the GT6V6HD, period, it a rip-off.
Now, as far as real 6V6 tubes go, there are no decent ones being made
today, period, regardless of hype and tube designer boutique salesman’s
lies. Both the Sovtek and Chinese 6V6s suck. The’re unreliable, and in
applications where they’re subjected to overvoltage (like in Fender amps),
they have a tendency to blow. If you want to use a real 6V6, start
scouring the market and find yourself a set of old RCAs, Sylvanias or GEs.
They’ll last where the commie crap will fail.
I hope this answers your questions. Happy Thanksgiving.
Regards.
From tremolu–(at)–ol.com Sun Nov 27 17:04:28 CST 1994
Article: 33165 of rec.music.makers.guitar
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From: tremolu–(at)–ol.com (Tremolux)
Newsgroups: rec.music.makers.guitar
Subject: Re: Groove Tube 6V6HD
Date: 25 Nov 1994 15:05:04 -0500
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The additional heater current drawn by the 6L6/5881 compared to a 6V6 is
an issue in some amps, like Princetons because they have small power
transformers. It is NOT an issue in a Deluxe Reverb. FYI, I have Sovtek
5881s in my Blackface Deluxe Reverb and it sounds great. The Deluxe has a
bit beefier magnetics and they can handle it. Mine has successfully
survived several multi-hour gigs with flying colors. It will, obviously,
cause the power transformer to run a bit hotter, but it isn’t running too
hot so that it is damaged.
Since the 5881s can easily handle the higher voltage, should you decide to
put them in your Deluxe, this gives you options of making a louder Deluxe.
Most Black and early Silver Deluxes by now should have their filter caps
changed to avoid catastrophic failures, since these electrolytic caps have
finite life spans. When replacing them, I recommend using the 22 uf–(at)–500
volt caps (the originals are 16 uf–(at)–450V). The additional capacitance
will firm-up the power supply a bit without making it too stiff, and the
higher voltage rating will provide additional safety margin. These new
caps will then let you change the rectifier to one that will increase the
plate voltages, increasing gain and power output. Specifically, if your
Silver Deluxe now uses a 5U4 rectifier, you can safely plug-in a 5AR4 (the
Sovtek 5AR4 is a good one). If your Deluxe is Black and already has a
5AR4, you can go to a solid-state plug-in module. (Note: Never use a
solid state rectifier with 6V6 tubes, the increased voltage will cause
early failure.) I am using the SS module in mine, and it sounds like a
little Twin. I have had mine sitting along side another 64 Deluxe (stone
stock) at a gig, and mine was noticibly louder, cleaner, and had more low
end punch, without sounding harsh or brittle. The other guitarist
commented that mine sounds real “chunky”, and now wants me to work on his.
Mind you, all this is easily reversible should you want to sell the amp
to a collector.
Anyway, back to the original subject. I recommend avoiding the GT 6V6HD
since it is just an overpriced wimpy 6L6. If you’re going to put a
6L6/5881 in your amp anyway, put in a good one. If you want to stay with
6V6s, start looking for some American glass. Call long distance
information and get the phone number of Antique Electronics in Tempe,
Arizona. I get most of my tubes from them. I’ve scored Sylvania 6V6s
>from them before. Also. don’t discount using used tubes. I’ve found many
tubes at electronics liquidators, used, good quality tubes that test way
better than minimum, and have lots of life still in them. For this, call
Alltronics in San Jose, California. I know they have lots of good used
6V6s in stock, I saw them!!.
Regards.
