... if you do a search in deja-news using the keywords jcm900, marshall mods etc ... this is some of the stuff you'll find, sorry if it's a bit messy ...

Article 17 of 855

Subject: Does anyone know the differences between the JCM900's and the old Jubilees? From: fowler@ykc.com Date: 1997/04/29 Message-Id: <5k5e7c$4mj@news.dx.net> Newsgroups: alt.guitar.amps [More Headers]

what are they? more/different tubes? circuitry? is the sound all that different - can i get the jubilee sound outta the jcm900 (add a pedal, change tubes?) someone told me my 4501 combo isnt a true all tube amp..? why would they trick us? would i be better off getting another amp-- i really like the GNR sound.. but the 900 is to edgy/spiky sounding,, i want smooth distortion,,,, is there anyway to get around this with the amp i've got--- hell of a buy $600 brand new,,, i only have 7 more days to return it,,,

Article 146 of 855

Subject: Re: Marshall JCM900 problems From: Bart Youngblood Date: 1997/01/09 Message-Id: <32D50151.18A@prism.gatech.edu> Newsgroups: rec.music.makers.guitar [More Headers]

mhaskell wrote:

I have a 2X12 JCM 900 100 watt combo that is giving me trouble. I have checked the fuses and have just replaced the tubes but when the amp comes on, there is no sound through the speakers. I don't know if the speakers >are blown. I have never played this amp loud (past 3 or 4 on the volume). Does anyone know what the problem could be. Is there an easy way to check ... what's wrong?

thanks, matt > > > ////Matt Haskell\\\ If the speakers were blown, there would still be a little noise coming from them because actually the coil is "blown" and would still move when current is applied. I would check the tubes, and make sure that one or both of them aren't bad. Reading the tube amp newsgroup, I have observed that there are certain types of Sovtek power tubes that are really crummy, and Chineese ones are even worse, especially regarding reliability. If you happened to use either kind of tube, go get them checked (I beleive that the particular Sovteks in question were 6V6's or 6L6's). Also, see if they glow bright red when the amp is on, this is a sure fire way to find a bad tube.

Bart

Article 9 of 521

Subject: Re: Marshall mods From: fulltone@aol.com (Fulltone) Date: 1996/09/24 Message-Id: <528pqr$bdo@newsbf02.news.aol.com> Newsgroups: alt.guitar.amps [More Headers]

<>

.Say what?......

Article 149 of 855

Subject: Re: JCM900 mod From: Mark Amundson Date: 1997/01/08 Message-Id: <5b04kd$r5a@lana.zippo.com> Newsgroups: alt.guitar.amps [More Headers]

> Ive modified several Marshall JCM 800 (later series) and 900s. One of >the best results was to bypass the diode clipping circuit and increase >the gain via the old style cathode bypass caps as per Plexi/ early >metal face models. You will certainly lose gain by removing the >diodes, so you may want to consider this as an alternative. > Good Luck, Jim

You mean bypassing the first stage circuit including the op amps "and" the diodes. Yeah, adding the appropriate (favorite) 12AX7 cathode bypass caps could restore some original Marshall tone. Next, you got to bypass the (effects loop and master volume) op amps and resistive voltage dividers to add gain so that a passive master volume control can dial in the all-tube clean preamp/dirty power amp sound.

Mark Amundson,

Article 152 of 855

Subject: JCM900 mod From: White Spirit Date: 1997/01/02 Message-Id: <32CBC2DE.5E0B@hotmail.com> Newsgroups: alt.guitar.amps [More Headers]

I've been thinking about putting a switch in my 900 to by-pass the diode clipping stage. While I like the tone of the amp as it is, I think it would be nice to get a more vintage sound from it at times. I'm not trying to make it sound like a plexi or anything, I just want to even up the sound a little and give it a more colourful tone. Anyway, any thoughts on how well this would work, or advice? D.

Article 173 of 855

Subject: Re: Need info on Improving JCM900 From: Brad & Dona Bolton Date: 1996/09/12 Message-Id: <32383A91.372C@earthlink.net> Newsgroups: alt.guitar.amps [More Headers]

> > In afrankow@iaw.on.ca (Adam Frankowski) writes: > > > > > >Hello, > >I have had a JCM900 for a little while now.. Don't get me wrong but > >it does sound good, but I believe it should sound a bit better. > > > >I heard JCM800's use El34's and other tubes.. I find the JCM900 is a > >little bit light. I want to get some more crunch out of it. > >This one uses 5881's. > > > > > >Can some one help me out? Should I get new tubes and get it re biased.

These things really are bad-sounding amps. They sound okay in the store, but on a gig I noticed too much compression when using distortion and lack of depth and bass in the clean channel. And my output transformer died, also! The primary was wired backwards at the factory!

Brad Bolton

Article 174 of 855

Subject: Re: Need info on Improving JCM900 From: BT2CQ4@ (Scott Blake) Date: 1996/09/12 Message-Id: Newsgroups: alt.guitar.amps [More Headers]

In <513m93$92s@lex.zippo.com>, Mark Amundson writes: >>>I have had a JCM900 for a little while now.. Don't get me wrong but >>>it does sound good, but I believe it should sound a bit better. >>>I find the JCM900 is a little bit light. I want to get some more >>>crunch out of it. This one uses 5881's. Can some one help me out? >>>Should I get new tubes and get it re biased. > >>Sell it. JCM900s are junk. I'm surprised that it hasn't eaten a >>transformer by now...most of them do. I don't care WHAT you do to it, >>it ain't never gonna kick ass. Get a JCM800 or earlier. Really.Fat Willie > Before trashing it or searching for the ultimate crunch (overdrive) bias, try patching in some different outboard preamps and auditioning the results. > Mark Amundson,

Good advice Mark. I have a JCM900 combo which I use sometimes, and basically use the clean channel with a Fulldrive II providing the distortion. I personally find the JCM900 distortion too "processed" sounding for my taste.

I don't know what I was thinking (or hearing) when I bought that amp. My taste in amps has certainly changed over the years.

Anybody want to trade me a plexi head for my JCM900? :)

Scott

Article 175 of 855

Subject: Re: Need info on Improving JCM900 From: Mark Amundson Date: 1996/09/12 Message-Id: <519npc$f63@lex.zippo.com> Newsgroups: alt.guitar.amps [More Headers]

>> >Hello, >> >I have had a JCM900 for a little while now.. Don't get me wrong but >> >it does sound good, but I believe it should sound a bit better. >> >I heard JCM800's use El34's and other tubes.. I find the JCM900 is a >> >little bit light. I want to get some more crunch out of it. >> >This one uses 5881's. Can some one help me out? Should I get new tubes >> > and get it re biased.

>These things really are bad-sounding amps. They sound okay in the store, >but on a gig I noticed too much compression when using distortion and >lack of depth and bass in the clean channel. And my output transformer >died, also! The primary was wired backwards at the factory! Brad Bolton

The compression is from the infamous full wave rectifier in the "B" channel distortion circuit. I'm there is no good way (meaning cost effective) to mod your way out of a 5881 equiped JCM900. Trading to newer or older models are the best bet. Consider staying in the "A" channel and use a pedal like a tube screamer to give a clean gain boost for power tube distortion. Those darn Op-amps and the effects loop are still mucking up signal though.

Mark Amundson, Article 176 of 855

Subject: Re: Need info on Improving JCM900 From: detritus@ix.netcom.com(William Allan Whittaker, Jr.) Date: 1996/09/10 Message-Id: <51316f$s9j@dfw-ixnews3.ix.netcom.com> Newsgroups: alt.guitar.amps [More Headers]

In afrankow@iaw.on.ca (Adam Frankowski) writes: > > >Hello, >I have had a JCM900 for a little while now.. Don't get me wrong but >it does sound good, but I believe it should sound a bit better. > >I heard JCM800's use El34's and other tubes.. I find the JCM900 is a >little bit light. I want to get some more crunch out of it. >This one uses 5881's. > > >Can some one help me out? Should I get new tubes and get it re biased.

Sell it. JCM900s are junk. I'm surprised that it hasn't eaten a transformer by now...most of them do. I don't care WHAT you do to it, it ain't never gonna kick ass. Get a JCM800 or earlier. Really.

Fat Willie detritus@ix.netcom.com QZCZ06A@prodigy.com Denver's TUBE GOD

Article 177 of 855

Subject: Re: Need info on Improving JCM900 From: Mark Amundson Date: 1996/09/10 Message-Id: <513m93$92s@lex.zippo.com> Newsgroups: alt.guitar.amps [More Headers]

>>I have had a JCM900 for a little while now.. Don't get me wrong but >>it does sound good, but I believe it should sound a bit better. >>I find the JCM900 is a little bit light. I want to get some more >>crunch out of it. This one uses 5881's. Can some one help me out? >>Should I get new tubes and get it re biased.

>Sell it. JCM900s are junk. I'm surprised that it hasn't eaten a >transformer by now...most of them do. I don't care WHAT you do to it, >it ain't never gonna kick ass. Get a JCM800 or earlier. Really.Fat Willie

Before trashing it or searching for the ultimate crunch (overdrive) bias, try patching in some different outboard preamps and auditioning the results. I have a JCM900 with EL34's and greenbacks, and except for the preamp I have nothing to complain about. I scratchbuilt a '59 Bassman preamp for outboard use (a breadboard) and it returns that classic sound everyone dies for. One small capacitor/resistor change and its a plexi.

Try the 5881's with a good preamp inserted at the effects loop, you might be surprised.

One of these days I'll put the breadboard preamp on a swappable printed circuit board for substitution of the JCM900's preamp PCB. I'll make sure it gets published; like in an article for Performer's Audio Magazine.

Mark Amundson,

Article 178 of 855

Subject: Need info on Improving JCM900 From: afrankow@iaw.on.ca (Adam Frankowski) Date: 1996/09/08 Message-Id: Newsgroups: alt.guitar.amps [More Headers]

Hello, I have had a JCM900 for a little while now.. Don't get me wrong but it does sound good, but I believe it should sound a bit better.

I heard JCM800's use El34's and other tubes.. I find the JCM900 is a little bit light. I want to get some more crunch out of it. This one uses 5881's.

Can some one help me out? Should I get new tubes and get it re biased.

-- \=/, | @___oo /\ /\ / (___,,,} ) /^\) ^\/ _) ) _ / / _) -xX====================================== /\ )/\/ || | )_) Adam Frankowski <> |(,,) )__) afrankow@iaw.on.ca || distor@nether.net || / \)___)\ http://www.iaw.on.ca/~afrankow | \____( )___) )___=======================================Xx- \______(_______;;; __;;;

Article 200 of 855

Subject: Re: My gain is too HARSH!! Does anyone know how to smooth it out???? From: jrobert1@guardian.cba.ua.edu (Jeff Robertson) Date: 1997/05/01 Message-Id: <5kank1$534@guardian.cba.ua.edu> Newsgroups: alt.guitar.amps [More Headers]

In article <336504DD.6B10@bellsouth.net>, Randall Aiken wrote: >fowler@ykc.com wrote: >> >> My marshall's distortion just isnt smooth enough.. I heard that reverb muddies up gain if its placed before it... My head has dual reverb and I was wondering if it affects the sound even if its set to zero,,, (since its on the lead channel) If it does.. is anyone familiar with the JCM900 4501 combo? its fairly common.. how do i go about solving this? [....] Since so much of this amp is solid-state, there is little you can do to mod it for better tone. You could try replacing the diode bridge circuit with an asymmetrical clipping circuit, but it likely still won't sound right. You are better off getting rid of it and getting an amp that sounds the way you want it.

Maybe this would work, but you wouldn't know unless you tried it: Adjust the amp so that it isn't distorting very much on its own, and try using a tube distortion pedal. I know it seems like a run-around, but it might sound better.

Jeff Robertson , Consultant, Webmaster - System Support Services, C&BA, U of Alabama Visit My Railroad Page: http://www.cba.ua.edu/~jrobert1/rail

Article 16 of 855

Subject: Re: Is changing tubes in a jcm900 a major undertaking??? From: detritus@ix.netcom.com(Lord Valve) Date: 1997/05/01 Message-Id: <5k9hea$9v8@sjx-ixn5.ix.netcom.com> Newsgroups: alt.guitar.amps [More Headers]

In <01bc55b3$b75d8e40$a4411dc4@j-gkrogh.196.3.135.1> "Jonathan Krogh" writes: > > > > >fowler@ykc.com wrote in article <5k5fd0$5tk@news.dx.net>... >> I might wanna change the 5881's to el34's for a smoother distortion,,, >> does that require alot of technical stuff or do i just switch'em out? >> otherwise i think i'm gonna take my combo back for a refund :( >> >> >hmmmmm,i dont think that change will make it any smoother,cause EL34's are >still bright and crunchy,even more so than 5881's >the problem is with the amp itself,jcm900's are very trebly and buzzy,but >it WILL sound better with the el34's. >if you switch the tubes it will need rebiasing and thats all,

I believe it will need to have the screens changed to 1K/5W, also...

Lord Valve

[Article 29 of 521

Subject: Re: Torres amp mods? From: cmiy565@hpcf.cc.utexas.edu (Thomas C. Clancy) Date: 1997/04/24 Message-Id: <5jnl8g$kua@spica.cc.utexas.edu> Newsgroups: alt.guitar.amps [More Headers]

In article <5jmgsn$q1j@news1.mnsinc.com>, higain wrote: I had a Marshall JMP 50 that I sent to Dan for a full 'Brown sound' ultimate Marshall mod. It took him two full months (kept saying that it developed a noise problem) and when I got it I was dissappointed. I hesitated calling because I was afraid he'd get offended but I wanted to know if there was anything I might do to help the terrible flabbly low end & general 'farting' out at higher gain settings. Well he immediately got pissed off and just said "it sounded fine at the shop" and hung up. If he had just been decent about it I wouldn't have minded since I wasn't asking for a refund and certainly didn't want to ship it back. > Well I eventually sold the amp. I still think he might do some good work -- he sure makes it sound cool in his newsletters and book, but I'm just hesitant to send another amp to CA and spend all the $ to 'try again'.

haha. one of the posters here stated once that he gets a certain amount of business just undoing the dreaded Torres mods.

Scott Davey wrote in article ... Just encountered the Dan Torres shop (San Mateo, CA) and his catalog of amp & guitar mod kits. Any opinions on them? His amp book seems excellent. >>

Article 35 of 521

Subject: Re: Marshall JCM900 Suggestions From: O'Connor Date: 1997/02/08 Message-Id: <32FC5890.CB8@wwdc.com> Newsgroups: alt.guitar.amps [More Headers]

One option for you is to replace the output tubes with 5881s or 6L6GCs. They have more low end and a rolled off high end compared to the stock EL34s.

There are many mods that can be performed on the 900-series, but due to the PCB construction, some of these can be difficult to implement (and thus expensive). The most extensive-- and expensive-- mod replaces all of the solid-state distortion circuit elements with all tube elements, plus, replaces the PCB with an eyelet card. Have fun! Kevin O'Connor

Article 51 of 855

Subject: Re: Marshall JCM900 Suggestions From: jjhodges@aol.com (JJHodges) Date: 1997/02/18 Message-Id: <19970218063501.BAA05917@ladder01.news.aol.com> Newsgroups: alt.guitar.amps [More Headers]

For mods and tube suggestions, try "The Tube Amp BooK" by Aspen Pittman. Going to an output tube that distorts earlier will give him a grittier output tube distortion; going to a tube with "softer" distortion characteristics will also tone down the briteness a little.

He might also be able to go to a hotter preamp tube, maybe something from Sovtek.

Jim

Article 52 of 855

Subject: Re: JCM900 From: lenkguy@aol.com (Lenkguy) Date: 1997/02/17 Message-Id: <19970217144201.JAA14496@ladder01.news.aol.com> Newsgroups: alt.guitar.amps [More Headers]

As owner of a JCM900 50W Dual Reverb (paired with a 4X12 1960AV cab, with the Celestion 30 Vintage speakers) I suggest you play a few 100W amps, with relatively efficient 12" speakers, at LOWER settings to see if you like what you get. The problem with higher powered amps unless driving a real power-soaking speaker cab, is that at volume levels appropriate to clubs, VFW halls, and the garage, you can't get the tones you like when blasting away at 10 or 20 on the dial. The 50W can get painful at its high end, but driving the power tubes at lower volumes produces nicer tone than the 100W versions, in my personal opinion. Even though the 100W JCM900 has a 1/2 power switch on the rear, it alters the tone as well by changing the portions of te tubes that are in use. Also remember, in a club you may well be getting your volume from a house PA, rather than from blasting your own amp. That suggests you should concentrate on tone.

Article 57 of 855

Subject: Marshall JCM900 valves question From: Kurt De Prins Date: 1997/01/27 Message-Id: <5chsib$cmu@hpcc48.corp.hp.com> Newsgroups: rec.music.makers.guitar,alt.guitar [More Headers]

I have a Marshall JCM900 Dual Reverb (half stack). How do I replace the valves ? Do I just have to pull them out and stick new ones in it or is there more to do ?

What kind of valves do you suggest ? Would it be allright if I tried Fender valves or Sovtek valves ?

Thanks in advance !

Greetings,

Kurt De Prins

---------------------------------------------- "I used to fly like peter pan..." (radiohead) ----------------------------------------------

Article 90 of 855

Subject: Re: Need info on Improving JCM900 From: icolossus@aol.com (ICOLOSSUS) Date: 1996/09/23 Message-Id: <5261sr$9pq@newsbf02.news.aol.com> Newsgroups: alt.guitar.amps [More Headers]

even though they are billed as a tube amp there is solid state circuits inside that Marshall used to get the distortion...noo gooddd...............

Article 92 of 855

Subject: Re: Need info on Improving JCM900 From: tashlava@aol.com (Tashlava) Date: 1996/09/10 Message-Id: <515csp$7ed@newsbf02.news.aol.com> Newsgroups: alt.guitar.amps [More Headers]

sell it!!!!!!!!!!!

Article 140 of 855

Subject: 5881 - EL34 From: Ton Date: 1997/01/16 Message-Id: <32DE1562.235D@best.ms.philips.com> Newsgroups: alt.guitar.amps [More Headers]

Hi,

can I change the 5881 (sory if the digits are in the wrong order) powertubes for EL34's in my JCM900??? What is the nominal bias current for the 5881 powertube??

regards,

Ton Schuwer RF Coil Development, Magnetic Resonance Hardware | Philips Medical Systems Netherlands | tel: +31-40-2763248 fax: +31-40-2763771 |

Article 142 of 855

Subject: Re: Marshall Mods - JCM900 From: Mark Amundson Date: 1997/01/23 Message-Id: <5c7p3u$gaq@lana.zippo.com> Newsgroups: alt.guitar.amps [More Headers]

>The LEDs are for the A channel, look instead for a diode rectifier >bridge, it should say BR2 on the board. Remove the bridge and the diode >named D10, they are used together to simulate 2 pairs of 3 diodes in >series. You should probably put a resistor in there instead to let >some signal to ground, to not get too high level. The resistor should >in that case go from end of the cap C36 that pointed to the bridge to >ground.

>Hope it helped! Good luck, and remember that there are high voltages >inside the amp, even though the clipping is done with diodes and ICs :) >/Richard

Another item to consider for removal or bypass is the tone stack like "Pre EQ" network. Since you'll be removing the diodes, the network does not have to be there to reshape the bandpass characteristic.

Mark Amundson,

Article 20 of 855

Subject: JCM900 Mod ? From: "Jay Bateson" Date: 1997/02/14 Message-Id: <01bc1a77$841db0e0$4dbc5ac6@rsa.rsa.cirrus.com> Newsgroups: alt.guitar,alt.guitar.amps,rec.music.makers.guitar [More Headers]

Does anyone know about a JCM900 mod that replaces the preamp silicon with 2 preamp tubes? Is this even possible? It would certainly be useful.

Jay Bateson

Article 23 of 855

Subject: JCM900 - is it all tube? From: mark@mgilbert.demon.co.uk (M. P. Gilbert) Date: 1997/01/24 Message-Id: Newsgroups: alt.guitar.amps [More Headers]

Is the JCM900 Hi-Gain Master Volume Mk III model 2502 50-watt combo all-valve distortion or is there, as I've heard suggested, a transistor element in there? Thanks.

Mark Gilbert

Article 24 of 855

Subject: Re: JCM900 - is it all tube? From: armitage@globalserve.on.ca (Armitage) Date: 1997/01/24 Message-Id: <32e910f1.2715711@news.globalserve.on.ca> Newsgroups: alt.guitar.amps [More Headers]

On Fri, 24 Jan 1997 01:51:35 GMT, mark@mgilbert.demon.co.uk (M. P. Gilbert) wrote:

>Is the JCM900 Hi-Gain Master Volume Mk III model 2502 50-watt combo >all-valve distortion or is there, as I've heard suggested, a transistor >element in there? >Thanks. > >-- >Mark Gilbert

The Marshall JCM900 uses a couple clipping diodes to give it more edge.

Article 30 of 855

Subject: Re: Does anyone know the differences between the JCM900's and the old Jubilees? From: mark@mgilbert.demon.co.uk (M. P. Gilbert) Date: 1997/05/11 Message-Id: Newsgroups: alt.guitar.amps [More Headers]

Absolutely right - I got a Blues deluxe (non-Hot Rod but still great) the other day after wrestling with a dumb, buzzsaw Boogie DC-5 for two months and this cheap little amp burns - there is not a bad sound in there.

In article <862587751.20991@dejanews.com>, PCollen@Harris.com wrote:

> In article <5k5e7c$4mj@news.dx.net>, > fowler@ykc.com wrote: > > > > what are they? more/different tubes? circuitry? is the sound all that different - can i get the jubilee sound outta the jcm900 (add a pedal, change tubes?) someone told me my 4501 combo isnt a true all tube amp..? why would they trick us? would i be better off getting another amp-- i really like the GNR sound.. but the 900 is to edgy/spiky sounding,, i wantsmooth distortion,,,, is there anyway to get around this with the amp i've got--- hell of a buy $600 brand new,,, i only have 7 more days to return it,,, > Go to a Fender dealer who has a HOT ROD Deluxe (40 watts, 1-12 speaker, all tube signal path) or HOT ROD Deville (60 watts, 2-12's or 4-10's, all tube signal path) in stock and play it RIGHT NOW. See if this is the tone you like on both the clean and overdrive channels. You should be able to buy the Deluxe locally for $450 to $475. If not, I'll tell you where you might be able to get one mail-order for that price range. > For at home and small gigs, check out the Fender Blues Junior (15 watts, 1-12 speaker, tube signal path) for around $300. > > You can read reviews on these amps, and others, by owners (not > sales-hype) at the Harmony-Central wev-site : > http://www.harmony-central.com. > > -------------------==== Posted via Deja News ====----------------------- > http://www.dejanews.com/ Search, Read, Post to Usenet -- Mark Gilbert

Article 33 of 855

Subject: Re: If the JCM900 4501 is a hybrid amp -- is the 2500 SLX (master volume model) a hybrid as well?? From: "John Crooks" Date: 1997/05/05 Message-Id: Newsgroups: alt.guitar.amps [More Headers]

john.crooks@worldnet.att.com

Article 36 of 855

Subject: Re: If the JCM900 4501 is a hybrid amp -- is the 2500 SLX (master volume model) a hybrid as well?? From: Ken Gilbert Date: 1997/05/03 Message-Id: <5kfhot$t4t@bubbla.uri.edu> Newsgroups: alt.guitar.amps [More Headers]

It depends on what you call hybrid and solid state. I have a Silver Jubilee, and it has a diode clipping circuit. I wouldn't call this a hybrid design, or even part solid state. If you want to argue that diodes don't belong in an all tube amp, then you'll have a big uphill battle. Diodes have been in Fenders since the Tweed era, as a rectifier in the bias supply. I think that diode clipping circuits sound pretty good if done right. Drive pedals are good examples. The tube screamer has a diode clipping circuit.

interestingly enough, if you look at a jcm 900 dual reverbs schematic youll notice theres no diodes in the signal path of the "clean" channel, "a." and when you play one, youll notice that as you crank the amp more and more, the distortion you hear out of channel "a" with preamp at 10 and post at 10 is very sweet indeed, with less "buzzing" and "fuzzing" than out of channel "b." all of this simply tells me that the diodes just arent necessary, and are squishing my signal needlessly.

i dont use the head much nowadays. -ken

Path: news.lynx.bc.ca!news.van.rns.net!news.rns.net!torn!newsfeed.direct.ca!newsfeed.dacom.co.kr!xfer.kren.nm.kr!hammer.uoregon.edu!news.carib-link.net!not-for-mail From: "Jonathan Krogh" Newsgroups: alt.guitar.amps Subject: Re: EL34 Correct load impedance for push-pull? Date: 9 Jul 1997 17:51:11 GMT Organization: Carib-Link Ltd. Lines: 12 Message-ID: <01bc8c8f$e9d084a0$59411dc4@j-gkrogh.196.3.135.1> References: <33C33A87.69F5@roke.co.uk> NNTP-Posting-Host: pm3-89.carib-link.net X-Newsreader: Microsoft Internet News 4.70.1155 Xref: news.lynx.bc.ca alt.guitar.amps:40606

according to specs at ampage,its 6500 ohms

Colin Davis wrote in article <33C33A87.69F5@roke.co.uk>... > Can some one tell me what is the load impedance which a push pull pair > of EL34s need to see. > > > Regards > > Colin >

Article 15 of 521

Subject: Re: Torres amp mods? From: watusi1100@aol.com (Watusi1100) Date: 1997/04/27 Message-Id: <19970427111600.HAA24060@ladder01.news.aol.com> Newsgroups: alt.guitar.amps [More Headers]

One more...... Having several customers purchase Torres kits and bring them to the shop left me partner and I singularly unimpressed. When installed, the kits seemed mediocre at best. We also reversed or removed several "ultimate" Marshall mods he had done to customers amps. Never encountered a customer service problem but his technical information (installation intsructions for kits, schematics, etc.) seems substandard. Our overall opinion is that a good local amp guy could duplicate any of the Torres kits, mods, Sper Texan, etc etc for significantly less money. Although most good techs would inform customers of the delterious effects on the amp in advance.

Article 1 of 4

Subject: Re: Post driver master vol mod on Marshall?? From: jc@lynx.bc.ca (jc maillet) Date: 1997/02/12 Message-Id: Newsgroups: alt.guitar.amps [More Headers]

In article <5dqasr$s9a@lana.zippo.com>, Mark Amundson wrote:

> I for one would be interested if more individuals took to > modding JCM900's into super Marshalls. > > Mark Amundson,

the best I can do for now is scan the pages from my work book which would cause the files to be huge, lemme think of a better way.

jc

Article 2 of 4

Subject: Re: Post driver master vol mod on Marshall?? From: Bluestrat Date: 1997/02/12 Message-Id: <3301DCB7.116@erols.com> Newsgroups: alt.guitar.amps [More Headers]

jc maillet wrote: > > In article <5dnu2g$8rc@lana.zippo.com>, Mark Amundson wrote: > In article <32FF41D0.7404@scunthorpe.ericsson.se>, Jeff says... Hi- has anyone out there had a Post driver master volume on a Marshall JCM900 head? I can't get that good cranked sound at a lower volume and I am getting ready to ship the amp to a amp guy that can add the Post driver master to the head so I can crank the original master volume and gain then bring the overall volume down. Any info would be appreciated!!!! Any neg info on this modification??? > > > > >WinLaw29 wrote:

I did this mod to my head and liked it a lot. You can do this mod and books by O' Conner, Weber, Torres, etc. may show the implementation, but IMO you are not getting what you probably want for a Marshall cranked tone. The output tubes, transformer, and speakers are so much of the sound that you are not buying much tonality from the JCM900's solid-state/tube preamp and driver circuitry. You got to play the high volume game if want to extract all the tone. > > > > Mark Amundson, >

I stuck a 1959 circuit with switchable gain stage, plus post driver master volume (Ken Fischer's) in the JCM900 and it's probably the best Marshall I've ever modded, considering the shitty sound it came from. The new "organic" version got an early Joe Perry sound to it that's blasting (you can't really go on ten with this thing believe me) ... it's pure and natural Marshall sounding all the way, ... it blew me away, it's amazingly responsive and dynamic. I think the trannys are perfect for it also. The switching circuit feeds off a dual post driver master volume circuit which allows two master volumes along with two gains. No chassis drilling. Also, the tone control circuit works equaly well in both normal and high gain settings. In my opinion a marshall with sillicon ain't a marshall > ... >

> if anybody's inerested I could pass on Ken Fischer's ideas on making a > pre-73 JMP super lead 100 sound a bit more like a plexi (this is from a > phone conversation going back a few years). > > jc maillet

JC: Please share! Mike

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Subject: Re: Which has higher gain, Marshall JCM 900 or JTM series? From: jc@lynx.bc.ca (jc maillet) Date: 1996/08/23 Message-Id: Newsgroups: alt.guitar.amps [More Headers]

In article <4v7dsb$7ut@ftpsvr.cyberway.com.sg>, Chang Yoong Pin wrote:

> I like to play solo and Marshall JCM 800 just not good enough in terms of > overdrive gain. I need a stomp box to up the gain. > > Now I;m looking to buy one of the above amps. > > > Greeting from Singapore > Pin

you can save big bucks by buying a 2x12 celestion JCM900 (JCM800 easier) and mod it for a 70's high gain style Marshall sound. Take the sillicon out and insert a plexi circuit along with switcheable gain stage for AMAZING marshall performance. I've done a few of these and they've turned out to be real jawdroppers as far as a 55watt amps go. Stores are selling them at discount prices because few people like 'em (no kidding!)

jc

@ Viva Analog jc@lynx.bc.ca