Put EL 34's in my MT-15!!

BrianC

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So I am really more of a hot rodded Marshall guy. The stock MT15 is great but still not ideal for ME. I changed some of the pre-amp tubes (still waiting to receive a 5751) and a Mullard in V2 improved things. I still felt like things could be better though.

I had a Crate Blue Voodoo many years ago that had great tone with 6L6's but when I switched to EL34's it was MUCH more to my liking, so why not try for magic again with the MT15.

I went over to my good buddy Rider's house and he did the swap and biasing for me. The result was a much more Classic Rock tone (Marshally) but with gain to spare. I will still try the 5751 in V2 to reduce the gain a bit. It is great to have a super light and portable amp that has two channels and a loop with enough volume to knock a house down - all for way under $1000!!!

I have said this before it's the best buy out there by far!!
 

X-Mann

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This is very cool info & thanks for sharing it!

So even w/ EL 34’s, it’s still a very tight amp?

I love EL 34’s in general.....but have had no desire to change this amp at all yet. :rolleyes:

Great info!

X
 

DreamTheaterRules

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yes, very cool to hear this.

Side note: While V2 seemed the place for a lower gain tube in the Archon, those who tried it said it worked much better in V3. IF the MT is identical tube layout to Archon, which I believe it is, please remember this when doing swaps. Try it both ways.
 

Rider1260

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Just an FYI re-bias on this amp is stupid easy ports and Bias adjust on the back of the amp 6 screws to get the cover off :)
IMHO the amp kept its tight bottom end response just tamed the rage abit is what I heard.
The MT15 has the response of a MUCH larger amp, does not feel like 15 watts at all, much fuller sounding and tracks notes and dynamics far better than any small amp I have tried, we had it side my side with an Orange and the MT15 was much bigger sounding to me.
 

BrianC

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This is very cool info & thanks for sharing it!

So even w/ EL 34’s, it’s still a very tight amp?

I love EL 34’s in general.....but have had no desire to change this amp at all yet. :rolleyes:

Great info!

X


Yes, super tight. It may be too tight for me actually. I also have an orange dark terror that is not as tight and wished it was more like that. If you play more modern stuff or percussive stuff tighter is better. I find that is points out my poor playing more.
 

andy474x

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The MT15 has the response of a MUCH larger amp, does not feel like 15 watts at all, much fuller sounding and tracks notes and dynamics far better than any small amp I have tried, we had it side my side with an Orange and the MT15 was much bigger sounding to me.

HUGE sounding amp. I feel like I need a big orange comb-over to describe it.

The most deceiving 15 watt rating in amps I’ve ever experienced.
 

X-Mann

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Yes, super tight. It may be too tight for me actually. I also have an orange dark terror that is not as tight and wished it was more like that. If you play more modern stuff or percussive stuff tighter is better. I find that is points out my poor playing more.
Thx again for your insights Brian & I do hear what you’re saying.

I will add that I feel that Tube amps in general point out my personal flaws as a guitar player & musician. I’m crazy good on an amp modeling device & that’s due to an endless amount of sustain & some Compression I believe.

On a tube amp, you have to fight a lot more! Then.....When it’s a fire breathing Dragon of an amp like the MT15, you need to really try hard to keep the beast of feedback & Distortion at bay...

One of my goals is to get my tube amp & live gigging chops up to the level that my practice room/digital amp chops are at....If that makes any sense...

X
 

bodia

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Open invite to my house!! I have beer....

Hey, got your message last night. Busy making room for new windows and doors getting installed today. I do already have a couple of 5751. Thanks for the offer, though!
 

DreamTheaterRules

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Yes, super tight. It may be too tight for me actually. I also have an orange dark terror that is not as tight and wished it was more like that. If you play more modern stuff or percussive stuff tighter is better. I find that is points out my poor playing more.

This is very interesting. Usually, a 6L6 would actually be more "tight" on the bottom, while an EL34 would roll a bit of that off and not have quite as much control or tightness of what bass was there. Is it possible that your perceiving less bottom end as more mid and upper mid, and thus it sounds/feels a little more analytical?

I'm only asking because usually in the really tight amps (like Mesa Marks) people say that swapping EL34s makes them not as tight and analytical (super fast, stiff) as they were with 6L6's.
 

DreamTheaterRules

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p.s. I was thinking about you MT15 guys last night when I played my Archon. I switched it over to my Mesa Mini Recto cab v30 over Mesa Thiele cab w/ Emi EM12. Those two small cabs now form a HUGE sounding stack with the EM12 in the Thiele cab. In fact, as I was warned prior to installing it, the Thiele cab really needs to be off the floor or the bass just BOOMS with the EM12 in it. But boy, you talk about a 1x12 sounding big. I played the it by itself with the Archon for about 15 minutes, and it sounds HUGE for a small 1x12 cab. Can't wait til tomorrow morning when the wife goes to work to crank that up. Even at mid level volume it was really thundering. I bet an MT15 with a Thiele/EM12 would be the biggest sounding little stack EVER!
 

BrianC

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I am NOT saying that the new tubes made it tighter, but that it’s still too tight.

I did not think the tubes made it any brighter. Swapping the V2 tubes changed the tone though especially the Tungsol and 5751.

The bias was made the same as what the 6l6s read. I did not make it any hotter as it has plenty of fire and i wanted to keep the clean as is.
 

Gustavo Posada

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I am NOT saying that the new tubes made it tighter, but that it’s still too tight.

I did not think the tubes made it any brighter. Swapping the V2 tubes changed the tone though especially the Tungsol and 5751.

The bias was made the same as what the 6l6s read. I did not make it any hotter as it has plenty of fire and i wanted to keep the clean as is.

Hi @BrianC, do you know what is the reading on both outputs of the bias? Thanks!
 

BrianC

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Rider did the work for me. I believe he read what the 6L6's were and just used that as a guide. It was a low reading and we noted that but I did not want to crank it and mess up the wonderful clean channel.
 

Gustavo Posada

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Rider did the work for me. I believe he read what the 6L6's were and just used that as a guide. It was a low reading and we noted that but I did not want to crank it and mess up the wonderful clean channel.
Hi!
Yes, usually it is between 25 and 30mV.
What I mean is, if you have a chance to read the voltage from both bias points, could you share both results?
There is only 1 adjust screw, but there are 2 read points. In my case, one reads 25.1 and the other 27mV.
I wonder if that is why it makes that weird noise... because factory tubes are not matched.
I should get myself a match pair of NOS Mullard made in USA. I only see Russian versions available in tube stores.
 

bodia

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Hi!
Yes, usually it is between 25 and 30mV.
What I mean is, if you have a chance to read the voltage from both bias points, could you share both results?
There is only 1 adjust screw, but there are 2 read points. In my case, one reads 25.1 and the other 27mV.
I wonder if that is why it makes that weird noise... because factory tubes are not matched.
I should get myself a match pair of NOS Mullard made in USA. I only see Russian versions available in tube stores.

I don't think you'll ever get "exact" readings between the two. The goal is to get them as close to each other as possible. I had a set of wonderful old Mullards that were matched, but the closest they would get was with 2mV of each other.
 
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