Converting a 6L6 BF Bassman to 6V6's
John Campbell
In an effort to reduce the insanely loud BF Bassman I have I want to convert it
to 6V6. How exactly is this done? I've heard references to changing the
screen resistors but to what value and what type (i.e. wirewound, cement,
carbon 1,2,5 watt?). I am planning on using a pair of 6V6-EH from LV (have
them in two other amps...excellent tubes). Other than the screen resistor is
there anything else (I know about the bias) that will need to be done?
Thanx in advance.
Andrew McWhirter
>
> Hey peepol.
> In an effort to reduce the insanely loud BF Bassman I have I want to convert it
> to 6V6. How exactly is this done? I've heard references to changing the
> screen resistors but to what value and what type (i.e. wirewound, cement,
> carbon 1,2,5 watt?).
Ceramic wirewound, 1k 5W.
> I am planning on using a pair of 6V6-EH from LV (have
> them in two other amps...excellent tubes). Other than the screen resistor is
> there anything else (I know about the bias) that will need to be done?
AFAIK, that's all you gotta do. You don't *have* to replace the screen
resistors even (DR's used the 470 ohms there as well), but it's a very good
idea.
I'd be interested to hear how they hold up. What plate voltage have you
got there?
Cheers
Andrew
--
The return address will work as is...
These opinions are hereby disowned by the company I work for.
QualityAna
If your Bassman has the 470ohm screen resistors already there, I would probably
try not to modify it, since it is a Blackface collectible amp. If yours has no
stock screen resistors present, I would still try it without modification,
especially with the EH6V6, it is supposed to be a tougher tube than most 6V6's.
However, when a 6V6 is used to replace a 6L6, the 6V6 will have approximately
twice the internal plate impedance compared to the 6L6. I even have an old
military 6L6 that internally has two 6V6 plate assemblies (parallel) inside a
shorter, fatter glass bottle than most 6L6's.
To use 6V6's and properly match the impedance with an output transformer
designed for 6L6's, you will need to double the speaker load impedance to twice
what it was designed for when the 6L6's are in.
In other words, if your amp is supposed to use a 2ohm total speaker load
originally, you would be best to use a 4ohm load instead when trying the 6V6's.
Theoretically, but I've done this with other circuits besides the Bassman and
it checks out with test equipment.
Hope this helps,
MBSetzer
*Nothing he's got he really needs . . .*
-- 21st Century Schizoid Man
Milan Plechata
On 02 Mar 2000 04:46:57 GMT, jcamp...@aol.comnospam (John Campbell)
wrote:
>Hey peepol.
>In an effort to reduce the insanely loud BF Bassman I have I want to convert it
>to 6V6. How exactly is this done? I've heard references to changing the
>screen resistors but to what value and what type (i.e. wirewound, cement,
>carbon 1,2,5 watt?). I am planning on using a pair of 6V6-EH from LV (have
>them in two other amps...excellent tubes). Other than the screen resistor is
>there anything else (I know about the bias) that will need to be done?
>
>Thanx in advance.
Miles O'Neal
>
> try the volume control instead of butchering that amp
Reworking for different tubes isn't butchering
(well, it could be, if you were boring out EL84
holes for 6L6 holes, but he isn't).
A 6V6 amp will sound different than a 6L6 amp.
A 6V6 amp run at 5 or 6 will sound *way*
different than most 6L6 amps run at 2.
-Miles
tarrotgirl
You could use a zener diode, or get a different power transformer. Then the
primary impedence in your output transformer will be different using 6v6's.
You'll have to get an o.t. suitable for 6v6's @ 4Ohms. Running ANY 6v6 at
450 volts is madness. After you've spent $2-300 on transformers you'll
realize you could have bought or built and amp for just a little more and
you wouldn't have a butchered amp. Sell your bf bassman and build a tweed
deluxe. I bought a real clean '59 lectrolab (6v6, almost identical to a
tweed deluxe) on e-bay for 250.
<enz0ATmindspringDOTcom (Milan Plechata)> wrote in message
news:38c7f876...@news.mindspring.com...
> try the volume control instead of butchering that amp
>
Milan Plechata
do it. Perhaps he should look into getting a powerbrake or hotplate
On Fri, 10 Mar 2000 04:11:30 GMT, Miles O'Neal <m...@rru.com> wrote:
>Milan Plechata wrote:
>>
>> try the volume control instead of butchering that amp
>
Lord Valve
tarrotgirl wrote:
> You would have to lower the plate voltage from 450 volts to about 400 volts.
> You could use a zener diode, or get a different power transformer. Then the
> primary impedence in your output transformer will be different using 6v6's.
> You'll have to get an o.t. suitable for 6v6's @ 4Ohms. Running ANY 6v6 at
> 450 volts is madness. After you've spent $2-300 on transformers you'll
> realize you could have bought or built and amp for just a little more and
> you wouldn't have a butchered amp. Sell your bf bassman and build a tweed
> deluxe. I bought a real clean '59 lectrolab (6v6, almost identical to a
> tweed deluxe) on e-bay for 250.
Lord Valve Speaketh:
Nonsense. The Z mismatch is inconsequential. The new Sovtek 6V6EH can
easily run at 450 volts and over. (I burned four of 'em in at 515 volts, 15
watts
static to see if they'd die and they just laughed at it.) Just change the
screen
resistors to 1K 2 (or 5) watt and tweak the bias component values to get the
supply into the right range. All of these changes are easily reversible, and
the whole conversion is going to cost less than $25 INCLUDING the tubes.
Give it a shot and let us know how it sounds.
Lord Valve
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Jonathan Krogh
Lord Valve wrote in message <38C94A12...@ix.netcom.com>...
Oh my Gawd, a 450v drop in 6V6??
*Really*? Its not a rebottled 5881?
Hats off to Reflektor on that one.
Lord Valve
> >Oh my Gawd, a 450v drop in 6V6??
> >*Really*? Its not a rebottled 5881?
> >Hats off to Reflektor on that one.
>
> I've installed the 6V6EH in two DRs now, and CRANKED them for an extended time.
> No failures. Do change the series screen resistor to 1k@2W though. LV's
> matching is the tightest I've seen. Less than 0.5 ma difference. The only
> thing yet to be seen is how long these tubes will last. Given the low price,
> if they go a year of steady gigging, I'd say you got your money's worth.
>
> Yep, hats off to Mike Matthews and his Russkie buddies.
>
> Say, does GT sell these things yet?
Lord Valve Speaketh:
Hmmm, I don't know if you can get these with the Boob Toobs label
on 'em; I saw a thread a little while ago where someone was mentioning
that he ran into some "GT-6V6NOS" tubes, and he was speculating
that they were Mazdas. A dude sent me a 5E3 Tweed Deluxe from
San Mateo, and I finally got around to opening up the box today; it
had a set of those GTs in it. They didn't look like any of the Mazdas
I have on hand, nor like any of my Visseaux, but all three (my Mazda
and Visseaux stock, and the Boob Toobs in the Deluxe) shared a
little glyph that was screened onto the tubes...a thing that looks
sort of like a Leslie horn on a stick with a bowtie underneath it.
I finally looked at a whole bunch of my Visseaux with a magnifying
glass and figured out that the glyph consists of a radio tower with
"waves" coming off the top, and a pair of crossed semaphore flags.
(Could be a lighthouse, too, but the printing was old and blurry.)
Bingo: must be the French Signal Corps insignia. I don't know if
those Boob Toobs were Mazdas, but I *do* know that one of 'em was
pulling 33 mA and the other was pulling 56 mA. I'm sure they were
matched more closely than that when they left the Boob Toobs
factory, but they sure as hell didn't stay that way very long...and they
appear to be brand new. Whatever they are, the head Boob better hope
most of 'em last longer than that one did, or he's gonna be lookin' at
a shitload of warranty returns.
Lord Valve
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in the header.) I specialize in top quality HAND-SELECTED NOS and
current-production vacuum tubes for guitar and bass amps. Good
prices, fast service. TONS of gear and parts in stock...let's DEAL!
NBS Electronics, 230 South Broadway, Denver, CO 80209-1510
Phone orders/tech support after 1:00 PM Denver time at 303-778-1156
NOW ACCEPTING VISA AND MASTERCARD
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Philo T. Farnsworth sez, "Vacuum tubes kick major ass.
Be a MAN...and buy some TODAY!"
Hack butchers suck
>*Really*? Its not a rebottled 5881?
>Hats off to Reflektor on that one.
I've installed the 6V6EH in two DRs now, and CRANKED them for an extended time.
No failures. Do change the series screen resistor to 1k@2W though. LV's
matching is the tightest I've seen. Less than 0.5 ma difference. The only
thing yet to be seen is how long these tubes will last. Given the low price,
if they go a year of steady gigging, I'd say you got your money's worth.
Yep, hats off to Mike Matthews and his Russkie buddies.
Say, does GT sell these things yet?
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RonSonic
Hack butchers suck <trem...@aol.com.no.uce> wrote
> I've installed the 6V6EH in two DRs now, and CRANKED them for an extended
time.
> No failures. Do change the series screen resistor to 1k@2W though. LV's
> matching is the tightest I've seen. Less than 0.5 ma difference. The
only
> thing yet to be seen is how long these tubes will last. Given the low
price,
> if they go a year of steady gigging, I'd say you got your money's worth.
>
> Yep, hats off to Mike Matthews and his Russkie buddies.
I gotta say, these are interesting times in the tube world. The competition
between the Svet and Sovtek has been great for us. Over in the audio world
they've been doing some interesting stuff and the quality of all of it is
actually getting downright good.
Not like the days of "you can have any power tube you like as long as it
uses '5881' guts."
> Say, does GT sell these things yet?
Sure, they're made special for GT in their own factory to their own specs.
Ron
Miles O'Neal
> Whatever they are, the head Boob better hope
> most of 'em last longer than that one did, or he's gonna be lookin' at
> a shitload of warranty returns.
He's fairly safe, for two reasons.
1) Everyone knows how great the stuff is, so the GT tubes
can't *possibly* be the problem.
2) Most of the people out there are sheep, despite their
declarations of individuality and independence.
-Miles