5881 to EL34 tube swap in Marshall 30th
Crossfire
Methinks you have confused EL-34's with EL-84's.
SilverLull wrote:
>
> In article <199807030035...@ladder03.news.aol.com>,
> tonef...@aol.com (Tonefactor) writes:
>
> >I read somewhere in this newsgroup once that converting a Marshall 30th
> >anniversary head from 5881's to EL-34's involves more than a simple bias
> >circuit change. Does anybody know what all is involved?
>
> You actually need to mod the amp, because as you'll notice, EL-34s don't even
> fit in the slots. They're much smaller tubes, and they have less output than
> 5881s, so you'll find the amp will saturate at lower volumes. It's a simple mod
> that involves removing some resistors, but I wouldn't do it unless you're a
> skilled amp guru, because there are voltages inside those amps that will kill
> you. Of course, after the mod you'll need to rebias.
>
> Adam
Jonathan Krogh
geez, how misinformed
>You actually need to mod the amp, because as you'll notice, EL-34s don't
even
>fit in the slots.
of course they do, same octal socket
They're much smaller tubes, and they have less output than
>5881s, so you'll find the amp will saturate at lower volumes.
hhhhm, well they are thinner, different tone
It's a simple mod
>that involves removing some resistors,
or rather just changing
Alan Thompson
Are you thinking of EL84's? He's talking about EL34's. What you're saying makes
no sense.
The early 30th Anniversary amps came stock with EL34's, they changed over to 5881's
right after Tesla closed down a few years ago, and for a while there were no
consistent EL34's being manufactured. They implemented this change in all the 900
series amps at the time, and have gone back to EL34's in some of them.
The point is, the change should be relatively simple, maybe a tech here could clear
this up?
A.T.
SilverLull wrote:
> In article <199807030035...@ladder03.news.aol.com>,
> tonef...@aol.com (Tonefactor) writes:
>
> >I read somewhere in this newsgroup once that converting a Marshall 30th
> >anniversary head from 5881's to EL-34's involves more than a simple bias
> >circuit change. Does anybody know what all is involved?
>
> You actually need to mod the amp, because as you'll notice, EL-34s don't even
> fit in the slots. They're much smaller tubes, and they have less output than
> 5881s, so you'll find the amp will saturate at lower volumes. It's a simple mod
> that involves removing some resistors, but I wouldn't do it unless you're a
profrets
Jeez! Did I wake up in a parallel universe? The screen grid resistors should
be changed from the present 470 ohm to a 1K 5 watt. Make sure(they have all
been this way that I have seen) pin 1 and 8 are tied together. The amp DOES
need to be rebiased, in fact you may have to modify the circuit slightly to
get enough range. Take it to an amp tech. If you don't like the sound, the
5881/6L6's will plug back in and work (after rebiasing AGAIN).
r...@profrets.com
Tonefactor wrote in message
<199807030035...@ladder03.news.aol.com>...
Linda
SilverLull wrote:
>
> In article <199807030035...@ladder03.news.aol.com>,
> tonef...@aol.com (Tonefactor) writes:
>
> >anniversary head from 5881's to EL-34's involves more than a simple bias
> >circuit change. Does anybody know what all is involved?
>
> fit in the slots. They're much smaller tubes, and they have less output than
> 5881s, so you'll find the amp will saturate at lower volumes. It's a simple mod
> that involves removing some resistors, but I wouldn't do it unless you're a
> skilled amp guru, because there are voltages inside those amps that will kill
> you. Of course, after the mod you'll need to rebias.
>
> Adam
Hey Bud
Keep givin out advice like this!
I really appreciate it.
I mean....because of misinformation
like this, I get more amps to repair.
Thanks
Pete
Victor
Tonefactor wrote in message
<199807030035...@ladder03.news.aol.com>...
>I read somewhere in this newsgroup once that converting a Marshall 30th
>anniversary head from 5881's to EL-34's involves more than a simple bias
>circuit change. Does anybody know what all is involved?
You have to ask such a simple question as that? You are defiantly not
remotely technical yet you are the same Jack Ass that e-mailed me with your
fowl mouth and profanity saying nothing was possible to get brown sound. You
are a wana be and your ignorance is so obvious.
You also have ripped into Mill Hill.
You are not even remotely in his shadow. Tell you what "TONEFACTOR" define a
simple differential input for us? What's that?.... to hard ?...Hmmmm how
about something less complicated. Less technical. More on the lines of
Layman talk for guys like yourself???? Ok I'll give you a dollar if you can
tell me which side is up on the doohickey thingamabob? You only get a half
an hour...??? which way???? up??? ..... Dollar.........??????
I'm sure you will respond with your typical @#$%&%*$#%#@@#$% answer. That's
what makes you the mental giant that you think you are.
Tonefactor
SilverLull
You actually need to mod the amp, because as you'll notice, EL-34s don't even
TUBEL34
I'm a little confused. What do you mean that the EL34 will not fit into a 5881
slot? An EL34 will fit into a 5881 tube socket. They have the same base.
The amp does need not be modded and rebiased.
Mitch
Mitchell Colby
Andrew McWhirter
BOGUS INFO! See below...
SilverLull wrote:
>
> In article <199807030035...@ladder03.news.aol.com>,
> tonef...@aol.com (Tonefactor) writes:
>
> >I read somewhere in this newsgroup once that converting a Marshall 30th
> >anniversary head from 5881's to EL-34's involves more than a simple bias
> >circuit change. Does anybody know what all is involved?
>
> You actually need to mod the amp, because as you'll notice, EL-34s don't even
> fit in the slots.
Bulldust. They both use a regular octal socket. (Are you thinking of EL84?)
> They're much smaller tubes, and they have less output than
> 5881s, so you'll find the amp will saturate at lower volumes.
EL34 has 33 watts total dissipation, 5881 has 26. I can't see how the EL34's
would put out less power.
> It's a simple mod
> that involves removing some resistors,
The sockets may have pin 6 used as a tie point for a resistor (since the 5881
doesn't use pin 6), and this will have to be removed for a EL34. For EL34,
this pin should be tied to ground (or the cathode, pin 8).
> but I wouldn't do it unless you're a
> skilled amp guru, because there are voltages inside those amps that will kill
> you.
That's good info...maybe not 'guru', but you certainly need to know what you're
doing.
> Of course, after the mod you'll need to rebias.
The bias supply may need modifying, depending on it's range of adjustment at
the moment. You probably need something like -30 -40V (ballpark figures
only!).
ALSO:
The filament current for EL34 is 1.5A, for 5881 it's 0.9A. Your power
transformer needs to be able to supply that extra juice, or else you'll need
another transformer to supply it.
Hope it helps.
Andrew
--
Andrew-dot-McWhirter-at-Bigfoot-dot-com
These opinions are hereby disowned by the company I work for.
SilverLull
>Methinks you have confused EL-34's with EL-84's.
woops, me too.
sorry about that.
Adam
TimTube
>
>I read somewhere in this newsgroup once that converting a Marshall 30th
>anniversary head from 5881's to EL-34's involves more than a simple bias
>circuit change. Does anybody know what all is involved?
>
>
In addition to the bias adjustment you need to change the 470ohm screen
resistors to 1K5W.
Tim
A great amp can make a lousy guitar sound great.
A lousy amp will make a great guitar sound lousy.
Tonefactor
>In addition to the bias adjustment you need to change the 470ohm screen
>resistors to 1K5W.
I was aware of this, but I heard somewhere that other parts of the circuit were
changed as well, to make the 5881's sound good in this amp.
DB>)
Wrong again weedhopper - they are both octal sockets, and will physically
swap out, but there is a difference in bias voltages between the two types
of tubes about 10v IIRC. Fail to change the bias and things could get ugly
tone and reliability wise.
Simple to mod, just check out the other replies here and/or the schematics
for the differences.
Dave Blackhurst
Blackhurst Custom Guitars
TUBEL34 wrote in message
<199807030125...@ladder03.news.aol.com>...
RSmith
Andrew McWhirter wrote:
>
> BOGUS INFO! See below...
> ........snip
> ALSO:
> The filament current for EL34 is 1.5A, for 5881 it's 0.9A. Your power
> transformer needs to be able to supply that extra juice, or else you'll need
> another transformer to supply it.
I was reading one of the tube faqs and thought that it was a recommended
mod to reduce the heater current (to extend tube life) by lowering the
heater supply voltage. No apparent sonic differences were noted. does
this only apply to preamp tubes?
rick
tcl...@frank.polymer.uakron.edu
In article <359C2DEB...@bigfoot.com>,
> >
> > In article <199807030035...@ladder03.news.aol.com>,
> > tonef...@aol.com (Tonefactor) writes:
> >
> > >I read somewhere in this newsgroup once that converting a Marshall 30th
> > >anniversary head from 5881's to EL-34's involves more than a simple bias
> > >circuit change. Does anybody know what all is involved?
> >
even
> > fit in the slots.
>
> Bulldust. They both use a regular octal socket. (Are you thinking of EL84?)
>
> > They're much smaller tubes, and they have less output than
> > 5881s, so you'll find the amp will saturate at lower volumes.
>
> EL34 has 33 watts total dissipation, 5881 has 26. I can't see how the EL34's
> would put out less power.
26? I don't remember if I've seen that # quoted before.
'course these ca. mid '90's marshalls would have used that
slobtek 5881 tube which. hmm, don't know exactly what they dissipate.
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Jonathan Krogh
RSmith wrote in message <359CF5...@ns.sympatico.ca>...
>Andrew McWhirter wrote:
>>
>> BOGUS INFO! See below...
>> ........snip
>
>> ALSO:
>> The filament current for EL34 is 1.5A, for 5881 it's 0.9A. Your power
>> transformer needs to be able to supply that extra juice, or else you'll
need
>> another transformer to supply it.
>
>I was reading one of the tube faqs and thought that it was a recommended
>mod to reduce the heater current (to extend tube life) by lowering the
>heater supply voltage. No apparent sonic differences were noted. does
>this only apply to preamp tubes?
>rick
WHAT???that doesnt apply to any tubes,
low heater voltage=cathode stripping-------->premature tube death
Tonefactor
I'd like to thank everybody for all your advice.
However I already know how to convert a Marshall from 5881's to EL-34's. What I
need to know is, what other components in the amp were changed. I went to
Dejanews and found the article to which I was referring. Here it is:
>>>I thought the 6100 model conversion from 5881 to EL34 would be as simple
as rebiasing, too, until I saw the Marshall tech bulletin describing the
conversion. Apparently they changed all kinds of parts in the phase
inverter and the bias supply to get 5881's to sound decent. There are
minimum 11 resistors and 4 capacitors that changed, possibly an
additional 3 resistors and 2 caps (the service bulletin copy I have is
not too clear). Being a PCB amp, this would involve a fair amount of
work, although "$300 and no one else is qualified to do it" is a crock
of bollocks. Admittedly, you could just throw in a set of EL34's and
rebias, but you'd forever wonder what effect these other component
changes would have....
Randall Aiken
rai...@bellsouth.net
MC WHIRTER Andrew David
tcl...@frank.polymer.uakron.edu wrote:
>
> In article <359C2DEB...@bigfoot.com>,
> Andrew McWhirter <SPAM....@bigfoot.com> wrote:
> > EL34 has 33 watts total dissipation, 5881 has 26. I can't see how the EL34's
> > would put out less power.
>
> 26? I don't remember if I've seen that # quoted before.
> 'course these ca. mid '90's marshalls would have used that
> slobtek 5881 tube which. hmm, don't know exactly what they dissipate.
Dunno what version of the 5881 that number refers to, I got it from
Duncan Monroe's website, via the tube data search (adding the plate and
screen dissipations together). Sorry I don't have the URL to hand...
Cheers
Andrew
Jonathan Krogh
MC WHIRTER Andrew David wrote in message <35A04C...@bigfoot.com>...
>tcl...@frank.polymer.uakron.edu wrote:
>>
>> In article <359C2DEB...@bigfoot.com>,
>> Andrew McWhirter <SPAM....@bigfoot.com> wrote:
>> > EL34 has 33 watts total dissipation, 5881 has 26. I can't see how the
EL34's
>> > would put out less power.
>>
hey guys, dont forget some crappy current chinese tubes (GT EL34R)
that i measured doing 18 watts each before glowing.
profrets
The EL34R is Russian. You know, they don't even like Chinese or Russian
EL34's at GT. They only sell them because, for some idiotic reason, people
WANT them and ASK for them. Probably because they are misinformed, like you.
Jonathan Krogh wrote in message <6ns9sn$e6b$1...@news.carib-link.net>...
Jonathan Krogh
beside the single yugo factory.
now i doubt anyone WANTS and ASKS for an 18 watt EL34,so why do GT pass them
on to the buyers? you'd think they would refuse these from the factory, in
favour of the GOOD european EL34's being made that are well up to the spec.
im not misinformed about anything GT does, i guess you have misinterpreted
the tone of my previous message.
profrets wrote in message <6nsb67$lcq$1...@supernews.com>...
>The EL34R is Russian. You know, they don't even like Chinese or Russian
>EL34's at GT. They only sell them because, for some idiotic reason, people
>WANT them and ASK for them. Probably because they are misinformed, like
you.
>
>Jonathan Krogh wrote in message <6ns9sn$e6b$1...@news.carib-link.net>...
>>hey guys, dont forget some crappy current chinese tubes (GT EL34R)
LarrySB
first rate tube in my experience. Sounds great, lives long, reasonable price,
what more could you want?
I don't have as much experience with the Tesla E34L, but reliable sources like
those too.
I haven't been as pleased with Sovtek EL34's, but have not tried their later
flavors.
Chinese EL 34 are crap.
--
Dr. Nuketopia
Read the Blue Glow in Tubes FAQ at http://www.persci.com/~larrysb
This address gets lots-o-spam. Please note that your letter is *not* spam in
the subject line.
profrets
a flame with an incorrect designation, so I responded. A lot of people on
the planet have prejudices toward companies based on innuendo and
misinformation, I am just tired of hearing it. Every tech seems to know the
Sovtek EL34G ain't great, blaming Groove Tubes for something Mike Matthews
and New Sensor brings in to the country seems a little misdirected.
r...@profrets.com
Jonathan Krogh wrote in message <6nta4c$1er$1...@news.carib-link.net>...
peatea
silve...@aol.com (SilverLull) wrote:
> In article <199807030035...@ladder03.news.aol.com>,
> tonef...@aol.com (Tonefactor) writes:
>
> >I read somewhere in this newsgroup once that converting a Marshall 30th
> >anniversary head from 5881's to EL-34's involves more than a simple bias
> >circuit change. Does anybody know what all is involved?
>
> You actually need to mod the amp, because as you'll notice, EL-34s don't even
> fit in the slots. They're much smaller tubes, and they have less output than
> 5881s, so you'll find the amp will saturate at lower volumes. It's a
simple mod
> that involves removing some resistors, but I wouldn't do it unless you're a
> skilled amp guru, because there are voltages inside those amps that will kill
> you. Of course, after the mod you'll need to rebias.
>
> Adam
A typical mod can be done for about $100 less the price of the tubes.
Advantage....EL34's will distort at lower volumes.
PT
Tonefactor
>Advantage....EL34's will distort at lower volumes.
>PT
I've yet to come across an EL-34 that will distort at lower volumes than the
Sovtek 5881's.
Also, anybody who charges $100 + the price of tubes for this simple mod is
ripping you off.
ste...@my-dejanews.com
>Andrew McWhirter <SPAM....@bigfoot.com> wrote:
> EL34 has 33 watts total dissipation, 5881 has 26. I can't see how the EL34's
> would put out less power.
> Hope it helps.
> Andrew
Hey Andrew: You either have a very good memory or you have a chart that you
have filled out as you check tubes. As you know, RMS power must be directly
related to % distortion to have any meaning at all. If you have a chart with
these figures on it, would you publish it here to settle all of these
discussions! My tube has more power than your tube.. I have a small chart
like this too, but it is not up to date....It would be intersting for all the
techs here to note this information for the next few weeks and publish the
results...How would we structure this chart? Cordials Dr. Stereo
Randall Aiken
<snip>
>As you know, RMS power must be directly
> related to % distortion to have any meaning at all.
<snip>
Not true, Doc. RMS power is simply that; a measure of RMS power. You
don't have to tack on a distortion figure to give it meaning. I am sure
what you meant to say was that two amps should be spec'd at a certain
distortion level at a certain power output to be able to accurately
compare them.
Andrew was commenting that you should be able to get more power out of a
tube that has a 33 watt plate dissipation rating than one that has a 26
watt plate disssipation rating. Of course, the circuit would have to be
designed to take advantage of this.
For instance, class A amplification has a theoretical maximum efficiency
of 50% (although in practice, it usually never exceeds about 33% or so).
This means that you should theoretically be able to get 16.5W of audio
output out of the 33 watt tube, and 13W out of the 26 watt tube, before
the plates start to glow cherry red. Of course, in real life, there are
many other factors that come into play, but that is the general idea.
Randall Aiken
rea...@innova.net
Andrew McWhirter
>
> In article <359C2DEB...@bigfoot.com>,
> >Andrew McWhirter <SPAM....@bigfoot.com> wrote:
> > EL34 has 33 watts total dissipation, 5881 has 26. I can't see how the
> > EL34's would put out less power.
> <snip>
> > Hope it helps.
> > Andrew
>
> Hey Andrew: You either have a very good memory or you have a chart that you
> have filled out as you check tubes.
Neither, Doc. I looked it up on Duncan Munro's site.
> As you know, RMS power must be directly
> related to % distortion to have any meaning at all. If you have a chart with
> these figures on it, would you publish it here to settle all of these
> discussions!
Well, I was really only pointing out that the EL34's have a higher plate+screen
dissipation rating, so at the limit you should be able to get more out of them
than 5881's. I'm not at all sure that the resulting %distortion is too
important for some guitar players...I certainly couldn't give a hoot how high
it is...but, yeah, I guess a 'clean headroom' freak wouldn't feel the same way.
Regards
ste...@my-dejanews.com
> rea...@innova.net wrote:
<snip>
> Not true, Doc. RMS power is simply that; a measure of RMS power. You
> don't have to tack on a distortion figure to give it meaning. I am sure
> what you meant to say was that two amps should be spec'd at a certain
> distortion level at a certain power output to be able to accurately
> compare them.
> Randall Aiken
> rea...@innova.net
Yes Randall, I always use some type of bench mark for comparison...I just
like to choose distortion since that can be related to some calabration
standard. I would like to see all of these guys think in terms for a
calabrated strandard when they want to say "mine's bigger than yours". BTW.
Thanks for good discussion in the chat room. -- Cordials Dr. Stereo Meet us
at http://www.firebottle.com/ampage/chat/ for good discussion at HIGH NO
Ned Carlson
>Hey Andrew: You either have a very good memory or you have a chart that you
>have filled out as you check tubes. As you know, RMS power must be directly
>related to % distortion to have any meaning at all.
Of course he's talking about total tube dissipation, Doc.
However, plate dissipation has little relation to power output,
anyway. Plate dissipation ratings tell you how hot the tube is
allowed to get during operation: that's it. How much power comes out
depends on the operating conditions....there are tubes like
2E26 and EL36, which have 10 to 12W rated dissipation, which
can put out up to 40-45W per pair.
BTW, 6L6-GC have 35W total (plate + screen) dissipation..
>If you have a chart with
>these figures on it, would you publish it here to settle all of these
>discussions!
There is such a thing, Doc..it's called a TUBE MANUAL.
Ever heard of one of those, or have you been working on amps
all these years & guessing at the tube pinouts?
Not that it would surprise me if you did..
Oh, yeah, you could check out:
http://www.triodeel.com/tubedata.htm or
http://www.duncanamps.simplenet.com
if buying a tube manual is beyond your means..
Ned Carlson Triode Electronics,2225 W Roscoe Chicago, IL, 60618 USA
ph 773-871-7459 fax 773-871-7938
12:30 to 8 PM CT, (1830-0200 UTC) 12:30-5 Sat, Closed Wed & Sun
http://www.triodeel.com
Text file catalogs:Catalog 'Bot at cat...@triodeel.com
Ned Carlson
>Yes Randall, I always use some type of bench mark for comparison...I just
>like to choose distortion since that can be related to some calabration
>standard.
Probably your benchmark is assorted seafood, so you can compare
the amp to a calamari standard.
>I would like to see all of these guys think in terms for a
>calabrated strandard when they want to say "mine's bigger than yours".
My "calabrated" standard is a ruler, and, yes, I'm sure mine's bigger
than yours.
If ignorance were oil, Doc, you'd be Spindletop II.