Switching to 2 EL34's in 2466

[daddydick]

I've decided I am switching to 2 EL34's in my 2466.. instead of 4 KT66's

I know maybe this isn't good for the amp. But i've decided this is how im going to go.

I will be using 2 NOS RFT EL34's. To further help my hunger for JMP sound mixed w/ Vintage modern.

All I want to know, is how to keep this from hurting my amp too badly,
and what actions are to be taken, to prevent them from happening.

Also, what should they be biased to ?

Steve, please help.

Thanks,

BigFatDaddyDick

[slowpokerhino]

Have you considered switching to 2 KT-88s instead. Sounds similar but you retain the responsiveness of the amp which you lose with EL34s?

Here's a clip with a VM with EL34s:

[Tnjpekar]

for 100 watts you need 4 el34's
http://www.thegearpage.net/board/archiv ... 50776.html
there is some info in there as to how to get 75 watts or so out of a pair of el34's, but even they admit you are looking at some extreme plate voltages. far easier to get 100 watts from 6550's or kt88s
marshall used 6550's in its american amps from around 71 or 72 into the 80's. much of the hair band and 70s marshall sounds you hear from american bands was a result of those tubes in our favorite amps
if using 6550s the customary bias is around 48, but I run mine in the low 50s and they can handle it.

[daddydick]

Yes, I considered 6550's (KT88) But I only found VERY expensive NOS 6550's.. (and I will only do NOS..)

I know the JCM800's used 6550's (I like that tone) But I'm even more in love with the JMP master volume's EL34 tone.
Plus I got a great deal on the pair of RFT NOS EL34's.

I just need help to not screw up the amp too bad if possible.

PS - I'm doing only 2 EL34's (for 50 watts) take this into consideration.

Thanks !


- BigFatDaddyDick

[slowpokerhino]

Please read this thread before you do anything:

http://vintagemodern.informe.com/viewto ... th+busters

[Dave W]

It seems like that may be like trying to cram a square peg in a round hole. If you have not already check out the recent post titled "Pulling 2 tubes from a 2466" on the forum. To paraphrase Steve D's comments the KT88 made the amp have more EL34 charachter but droppping in EL34 made the amp sound like crap. That was after he actually did the tests in response to forum inquiry about the EL34 topic. If your concerned about the quality of KT88 new manufacturing check out the JJ brand. There are all kinds of positive things on the internet about the build quality of the JJ KT88. If you are concerned about the metal bases causing problems with the design of the Vintage Modern then all you have to do is remove the metal bear claw tube holders. (I have read that there may be some problems with using the JJKT66 causing problems with the JJKT66 because it uses metal bases similar to the JJ KT88, I called Bob at Eurotubes and he said all you have to do is remove the bear claws and it will be fine, his advice has always been sound, call them.) The Marshall Kerry King model JCM800 uses JJ KT88 tubes. Kerry King said in an interview something to the effect that the amp Marshall designed for him was based of his favorite Marshall thta had certain charachter different than his other 800's and they were able to get the sound similar after designing it with KT88. That amp is a monster. One of the popular guitar magazines reviewed it and said they were surprised at the excellent blues to rock tones that were in side of it though thanks to the KT88's in part. You can get a couple of new JJKT88 shipped for $80 shipped if the price has not changed in the last week. Maybe worth a try to at least even compare. If you do not like them you could always dump them on Ebay and get a good $50 back even after fees. I know that there is not a EL34 breakup pedal but maybe even usinfg a quality overdrive could give you sort of an A/B option that could get you closer to the sound you want with using the amp at hand. Another odd but possible option may be to use an attenuator like the Weber Mass Lite 100 watt with post amp tone controls. I do not know where you put your master volume at now. If it is extremely very high you can use the attenuator to get more tube breakup and possibly a different tone? With that model you are rolling of the treble/mid and bass mid volumes off so you might be able to shape the final tone to be a little more loose or with a little more bite or whatever you are going after. Best wishes with whatever you decide.

[Dave W]

In my above post there is a type error. In the parenthesis about the JJKT66 tubes it should read ( JJKT66 possibly causing problems with the Vintage Modern) not JJKT66 causing problems with JJKT66. Just wanted to clarify as I wrote a long response with multiple numbers and ideas.

[daddydick]

thanks for the suggestion.

However, I don't like JJ Tesla tubes. I was debating getting a pair of NOS Tesla tubes though... but as I said, decided on the RFT's

I'm really stuck to the idea of EL34's. Dose anyone know how I can keep the amp from problem's when using EL34's ?

I read the topic by slowpokerihno, but still believe in 2 EL34's in the 2466. I previously had another amp, and used 2 EL84's instead of 4 KT77 ( I used yellow jacket converters). It never had a problem after 1 and a half years playing on it.. still plays great !

Anyway, thanks for suggestions.

Any help on keeping the amp healthy with EL34's in it is appriciated !

Thanks !

[SteveD]

I've never tried two EL34s in a 2466, only four so I don't know what it will sound and feel like.

OK, if you are adamant that you want to check out this route you first have to short pins 1 and 8 of the output valves on the PCB with tinned copper wire, otherwise they will be working in tetrode mode. Most output valves have these grids internally shorted but not the EL34!

Next replace the KT66s with the two EL34s (use the inner pair of bases) and switch on. Immediately set the bias to around 35mV per valve (if you have enough range on the bias trimmer) and let the amp come up to temperature. After 10 to 15 minutes check the bias again and adjust if necessary.

That's it, try it and see if you like it.

The HT voltage will be high on the plates of the 34s (maybe around 530 to 545V) but EL34s are actually more robust than you think, especially if you have good ones. The old 'Series 12' as used by EVH had very high HT voltage on the plates also.

The screen grid currents should be within acceptable limits.

The output transformer primary impedance is 4K and 2 EL34s are rated at 3.5K so that is not too far away.

Be aware that by doing this mod you are voiding your warranty.

NOTE: Do not do this with two KT66s as they are less forgiving of higher plate voltages, i.e. do not pull two KT66s out of a 2466 in order to achieve 50 Watts.

[ville]

The output transformer primary impedance is 4K and 2 EL34s are rated at 3.5K so that is not too far away.

Just to make sure, 2 x EL34 equals the impedance of 4 x KT66, so the impedance selector should be kept at the same position with 2xel34 and 4xKT66. Right?

I tried my VM with svetlana 2x6550. It had a different feel, but I felt that you had to crank the master volume a lot more to get that creamy distortion. In the end I liked KT66's more and went back... As I predict you will do to ;)

Anyway, it's a lot of fun experimenting with pre and power tubes to see what different tubes sound like!

[daddydick]

THANKS STEVE !

Glad yo know it can handle 2 EL34's

[surfnorthwest]

Question I would ask is why even own the VM if you are going to put EL34s in it. I mean that is why I bought this amp because of the unique vintage sound that only comes from a KT66 amp. I also like the tone of EL34s but I went and got a DSL to cover that.

[zappatista]

Question I would ask is why even own the VM if you are going to put EL34s in it. I mean that is why I bought this amp because of the unique vintage sound that only comes from a KT66 amp. I also like the tone of EL34s but I went and got a DSL to cover that.

Exactly!

But I would love to see Marshall put out an amp that would be an EL34 version of the Vintage Modern. SIngle channel, plexi amp with the added gain stage. I'd buy that up in a nanosecond! Then run both amps together, man that'd be some amazing tone.

[Mats A]

How come the VM sounds like crap, as you say, with EL34´s? I mean the amp is very much like a regular plexi style Marshall but with KT66 valves. Why didn´t the Marshall amps of the 60´s sound like crap all of a sudden when Marshall changed from KT66 to EL34´s back then?

[zappatista]

How come the VM sounds like crap, as you say, with EL34´s? I mean the amp is very much like a regular plexi style Marshall but with KT66 valves. Why didn´t the Marshall amps of the 60´s sound like crap all of a sudden when Marshall changed from KT66 to EL34´s back then?

Well, I'm sure at the Marshall Utility Muffin kitchen, they just didn't unexpectadly run out of KT-66's and in a panic jammed some EL-34's in the sockets to plug the dikes!

I have a pretty postive feeling that they did some reconfiguring of circuits to change over to the EL-34's.