Anyone try different tubes?

[BrokeDownSouth]

I was thinking about trying a lower gain tube like a 12AU7 in lieu of the 12AX7's.  I'm thinking it might be a little cleaner.   Anyone tried this?

[rnolan]

I haven't. With the MP1 and I spose some extent MP2 the general trend is more gain (e.g MP1 3TM) and high gain tubes. But for bass it's a slightly different story as your primary purpose is not necessarily to drive a tube into clipping/distortion.  My take on the MB1 however, is it's designed to keep all that in control so reducing the available gain in the MB1 may not be the best direction to take (no harm in trying though, I'm pretty sure (MJMP, pls correct me if I'm wrong) 12AU7s will swap in electrically without issue).  But back to the idea of cranking your power amp and tuning the MB1 down to suit means less gain needed in the MB1 at the same volume.
There are also lower gain variants of some 12AX7 tubes (another way to go....)  Also a different tube inV1 and V2 gives more variations....

[Peter H. Boer]

I was thinking about trying a lower gain tube like a 12AU7 in lieu of the 12AX7's.  I'm thinking it might be a little cleaner.   Anyone tried this?

It works :) (although I am always on the search for less clean  )

[BrokeDownSouth]

Thanks, rnolan.  That might be a better way - swapping a 12AX7 and 12AUT between V1 and V2 to see what I get.  I was looking at audiotubes.com last night to see what I could get, most NOS tubes are pretty pricey.    The guy that runs the site is knowledgeable and answers questions quickly.

[rnolan]

Hey BDS, Doug's tubes have a good reputation and seem to have a decent variety of models (http://www.dougstubes.com/preamp-tubes/12ax7-ecc83-7025.html).  While NOS tubes are nice they tend to be very expensive.  One of the main differences between NOS tubes are recent manufacture is they used to pump the tubes longer (1.5 to 2 hours kind of thing) these days apparently they only pump for half an hour or so, basically equates to NOS tubes lasting longer as better vacuum (they also got into some pretty interesting metalurgy back then).  Hopefully the attached zip will open for you (it's a htm page and needs the sub directory for the pictures), it an interesting read.
Have fun, let us know how you get on

[BrokeDownSouth]

Thanks that was fascinating.  I've read a couple articles like that before.  I've built a couple of Fenders and a Dumble clone for my guitar so I've put more than a little thought into tubes.  In my experience, I've bought a few reasonably priced NOS tubes and can't really distinguish between them and a good new production Russian or Eastern European tube.  OTOH, the first amp I built was a kit for a blackface Fender and it came with a set of chinese 5881's that were harsh.  I swapped them for a set of Winged "C" 6L6GC's and the difference was pretty drastic.

[MarshallJMP]

Don't use 12AU7,the bias won't be correct and the gain drops with a factor 5.Go for some NOS 5751 tubes,these will be cleaner and good sounding in a MB-1.Also these are NOS tubes that are affordable.Another option is a 12AT7 or an ECC81.

[MarshallJMP]

The MB-1 uses a different bias system then the mp-1 so you need to be a bit carrefull what you use (soundwise,you won't blow up something).

[Dante]

  My previous post about trying different tubes has been removed (actually, it's in the MP-1 section now)

I was thinking I was in the MP-1 section for a minute there

My apologies

[Peter H. Boer]

Don't use 12AU7,the bias won't be correct and the gain drops with a factor 5.Go for some NOS 5751 tubes,Another option is a 12AT7 or an ECC81.

That's what I tried 12AT7 & NOS5751, the latter being preferred.

[rnolan]

Thanks MJMP, good to know  .

Thanks that was fascinating.  I've read a couple articles like that before.  I've built a couple of Fenders and a Dumble clone for my guitar so I've put more than a little thought into tubes.  In my experience, I've bought a few reasonably priced NOS tubes and can't really distinguish between them and a good new production Russian or Eastern European tube.  OTOH, the first amp I built was a kit for a blackface Fender and it came with a set of chinese 5881's that were harsh.  I swapped them for a set of Winged "C" 6L6GC's and the difference was pretty drastic.

No worries, I found it a good read and helped when I was tube deliberating, glad it opened for you.  I like the new Russian Mullards, great tubes.  Must try a pair of the new short plates at some point. I saw these NOS 5751 (https://tubedepot.com/products/us-made-jan-philips-5751?gclid=CIWertXYgr0CFUsIvAod6BUAgA), $45, so a bit more than double a current prod tube (depending) but certainly affordable and probably well pumped so it should last well and the description indicates it's pretty much what you're after. Or some NOS 12AT7s (ECC81) (http://www.dougstubes.com/preamp-tubes/12at7-ecc81/nos-12at7.html) at a good price.
How's the rig coming along ? Enjoyment plus ? Cheers R

[MarshallJMP]

Actually 5751 are mil spec 12ax7 dropins but with  lower gain,less noise and far less microphonic.Since these are mil spec they have been tested alot.

[BrokeDownSouth]

Ok thanks everyone.  I didn't realize that the 12AU7 requred a different bias - I just thoght that from X / U / T was a stepdown in gain.  I've got a little box full of tubes whenever I feel like pulling the mb1 out of my rack.  I know I promised a video demo of my rig but I got real lazy this weekend, no rehearsals etc. :-[

[rnolan]

Hey BDS, happy MB1 ing