looking to put el34's in my sl-x

[bennieusmaximus]

i am wanting to put el34's in my sl-x.I also have a 900 with el34's in it.comparing them side to side they look almost identical as far as the power sockets and wiring goes.I havent checked the voltage yet on sockets,but just a quick glance at it and I noticed the resistors on the pin sockets and wire colours are the same.I have goten the mod instructions of of schematic heaven and it looks pretty straight forward.Is it possible that the sl-x could have been built at the factory to accept ether tube?does any one know if these transformers are the same in these two models.both the 900 and the sl-x are from the 90's.I want to make sure I have enough heater current.thanks for any help with this.

 

[core]

They are not built from the factory to accept either or tube. It's either the amp runs EL34 or 6L6 (5881). It should say on the tube what type it is. Also is there a sticker near the tubes that is gold and says something like "Fit only 5881 Power Valves to this Marshall"? The year of your SL-X can sometimes determine what type of tube goes in it.

As far as mods, there will probably be a tech on to answer this but if you do a search you will find a lot of other members have asked this question. I think there's a lot of info here on it but it's not that straightforward I would think.

From what I gather EL34 amps can accept 6L6 valves with a proper bias adjustment but 6L6 (5881) built amps CANNOT due to the heater current being greater in an EL34 built amp.

 

[bennieusmaximus]

thanks for the info.I'll be checking out other threds to see if I can find anything.Oh yea the sticker does say 5881.

 

[bennieusmaximus]

hey I noticed that you have a flying v xlp.I have a explorer xlp,white with kayler trem.It has the gibson custom shop logo on the back of the headstock.the guitar was repainted though.I also just traded my 6100lm for a 78 jmp non master vol.Good swap?I guess.The 6100 scared me with all the things that might go wrong.Diggin' the single chanel stuff right now.

 

[MajorNut1967]

Well I looked at the schematics for that model of amp (100watt) and they use the same output transformer the C3070 so you are ok there but the Screen resistors need to be changed from 470ohm to 1Kohm and then the bias has to be set to the right range, also the pin1 on the power tube thing there it has the FAIL indicator that might need some work as well, I really dont known; So its not a simple thing, I recommend you take it to a tech if you are serious about the swap! So if it’s what you really want go to the tech is the best method.

 

[bennieusmaximus]

thanks for the info,much appreciated!I might try a fresh set of 5881's just to see if I like them.I'm used to the el34 sound though.

 

[Jonathan Wilder]

As per the official Marshall 5881 - EL34 conversion docs for the 4100/4500 -

Required component changes -

R31 - R34 (screen reistors - Omit R32 and R33 for 50 watt models) = Change from 470R to 1K 5 Watt
R28 (bias suppy range resistor) = Change from 68K to 56K
R29 (bias supply range resistor) = Change from 8.2K to 15K

Optional component changes -

R23 (phase inverter plate resistor) - Change from 100K to 91K. This will increase the symmetry of the phase inverter which you may/may not like the sound of. Vintage Marshalls use a 100K here.

R30 (sag resistor) - Change from 10K 1 watt to 22K 1 watt. Increasing this resistor's value will drop the voltage to the phase inverter as well as the rest of the preamp, which decreases headroom of everything from the PI circuit to the input circuit. May/may not be noticeable.

R17 (negative feedback resistor) - Change from 47K to 100K.

 

[MajorNut1967]

thanks for the info,much appreciated!I might try a fresh set of 5881's just to see if I like them.I'm used to the el34 sound though.

Definitely find the tone you want for your ears! And if takes EL34, so be it its not unreasonable on this amp!

 

[Sir Don]

EL34's sound great in an SLX900, I've had them in mine ever since I bought it brand new in 1993.

 

[core]

thanks for the info,much appreciated!I might try a fresh set of 5881's just to see if I like them.I'm used to the el34 sound though.

I was in the same boat man and even though I liked the 6L6 900DR that I bought first, I ended up also wanting the EL34 sound. Before coming here I never knew there were different tube types. So I bought an EL34 version just to see if there was a difference in tone. To me there was a little difference in the A channel but other than that not much to my ears. Sold the 6L6 and made $400 so in the end I made out pretty good and didn't have to mod it. Something to think about.

Yeah I love my V XLP but I need to get an old school pickup so it sounds good with the Marshall plus it's a little headstock heavy for some reason so I only play the LP till I can work on it.

I sold the 6100. It was a good amp but I like less and I wanted something that didn't scare me too when I opened it up! I would love to get a 78-79 JMP 2203 Master Volume amp those are sweet. That and the 2 channel 900 are more up my alley.

 

[MajorNut1967]

It appears both the EL34 amps & 5881 amps use the same power transformer too. I assume the heater current won't be the issue.

 

[Rockin_Lisa]

I guess hundreds of people buy 6L6 Marshall amps without giving the tube layout any thought. I've never seen so many unhappy amp owners wanting to switch from 6L6's to EL34's. I mean even I know there is a difference and that's why I bought a EL34 amp.

To me, it would be simpler to sell the 6L6 amp. That keeps it in original shape. Then I would buy an EL34 amp, again in original shape. Cutting on an amp can decrease it's value unless done by someone with the proper knowledge.

 

[RynoAZ]

To me, it would be simpler to sell the 6L6 amp. That keeps it in original shape. Then I would buy an EL34 amp, again in original shape. Cutting on an amp can decrease it's value unless done by someone with the proper knowledge.

Sometimes it's difficult to get an EL34 model, like the SL-X for example. Only certain numbers were imported with EL34's, and most were sent to the states with 5881's. That would mean the tireless and long search for a Canadian or UK model; the internet has made the world a smaller place though, so probably not as hard as it would have been 10 years ago. The EL34 swap - at least in the SL-X - is reversible.

I understand what you're saying about chopping up a perfectly good amp though. I have an older 2203 that I cringe even about changing resistors and stuff!

 

[bennieusmaximus]

I am thinking about trying a fresh set of tung sol 5881's before I mod the sl-x,but I love that el34 sound.I guess it wont hurt to try somthing different.I am probably goung to run a 2 amp system anyway.Sl-x dirty and superlead combo for my clean.Thanks wilder for your tech help.

 

[Ken]

To me, it would be simpler to sell the 6L6 amp. That keeps it in original shape. Then I would buy an EL34 amp, again in original shape. .

Somehow I don't think you'll get the grief I get when I tell someone to sell an amp they don't like, as opposed to spending $$$ trying to make it just okay.

Ken

 

[RynoAZ]

Change your name to Rockin' Ken.

 

[psphill27]

Keep the SL-X as is and buy a JCM 900 MkIII with EL-34s. Then you have both and wouldn't have to mod your SL-X.

 

[RynoAZ]

Or a 2203

 

[MajorNut1967]

Somehow I don't think you'll get the grief I get when I tell someone to sell an amp they don't like, as opposed to spending $$$ trying to make it just okay.

Ken

well who gave you grief like that?

 

[Ken]

well who gave you grief like that?

Mostly JCM 900 DR owners who want to change the voicing but not spend the money it takes to do it!

My rule of thumb is an amp sould sound great when you plug straight in, and if you want to tweak it, then do the mods to get what you're after. I would never waste time and money modding an amp that I didn't like to begin with. It's far easier to buy an amp you like straight off.

As for the SLX, I'm not sure if it's worth the hassle of modding it, but it's a unique Marshall so it's not beyond reason to try and make it even better if you have the cash and like it's voicing to begin with.

Ken