Second Gen Model T Modifications...

[JoeArthur]

Hi...

I've been playing around with my second generation Model T (the one with the mid select switch under the midrange control) and I have put up a website discussing the modifications I have made to it to improve it's sound.

If you have one of these amps, then it might be worth your time to take a look...

http://members.cox.net/joeaarthur/modelt.html

Thanks... and any feedback or comments will be welcomed!

[Geoff]

Outstanding!!!  Nice work.  Gonna really take a good look at these pages again when I have some free time.  I may have some questions for you

Geoff

[JoeArthur]

Thanks!  At least one person looked!!

I've changed my email address in my profile so I get any questions quicker.  I'm working a contract in the Chicago area now, and I can only access with my laptop using AOL.

[Don T.]

Hello Joe:
 Wow, Looks like you really know your stuff about tube amps. That is a subject I wish I knew more about but have not had the time to research. I have one of those amps and do not like it on stage for the very reasons you state. It is also pretty darn loud for small clubs where I use my stereo Supro amp setup. Me thinks I will try your mods.
Don T.

[Greg Z]

Excellent work JA.
 As I'm in the process of cloning a "T", your
explaination of the stages and tone network is ex. and saves me a lot of brainwork and your mods are cool. Having salvaged the
iron out of a V4 and already owning a 1200s
I was contemplating many amp designs finally
arriving at somewhat classic bassman/jtm design but incorperating some of the features of the model "T". As I enjoy keeping
an eye on the firebottles, all my homebrews
have a semi-open front industrial design.
 Toying with the name "M.T. Super B".
Probably run either GE 6550's or try some kt-90's.

[MarkG]

Joe,,Very interesting !! I just picked up a 1st Generation,and felt maybe I should have held out to find the newer one,but since catching your writeup I am pleased I got this one. Are we pretty sure that all the Non Midselect switch versions were infact wired as "1st Gen" per the original schematic? You have any idea if they may have gradually started employing changes?  I have not opened mine yet but I did check for the more volume at 8 than 10 syndrome. It for sure does NOT suffer from that. I want to use for bass. Any recommendations on a specific brand of 6550 that would be optimum for bass?  Again..Nice job ,thanks for taking the time to write it all up.

[JoeArthur]

I wouldn't have much concern that a factory original wired first generation Model T wasn't wired as per the schematic.  Minor production changes aside... like the use of 50 ohm vs 47 ohm resistors between the plates and output transformer of the 6550's which would really make no audible difference.

I wouldn't see any "creaping" in of the second preamp stage changes between the two generations.  These were solely for the introduction of the mid-select switch.  

However, it might be possible that that master volume reduction white wire with blue stripe thingie could have been added in the last months or so of first generation production, but I have no real reason to believe that... I would just watch out for it and it is simple enough to remove.

As for tube recommendations... I generally stick with tung-sols - I just happen to like them because they seem to last forever for me.  If I couldn't find those, then I would go for the Svetlanas.

[Tom Loizeaux]

Joe, You've done a great job of defining the Sunn Model Ts!  My first Model T was a 2nd generation and I sinply didn't like the tone for electric bass. I wanted to scoop the mids and this amp wouldn't let me do that. I found a 1st generation without the MID SELECT and loved it! I sold the 2nd generation head and bought several more 1st generation heads. They've got a great, rich, warm bass sound that I haven't found anywhere else. They also look great on top of my 1-15 Sunn stacks! I made a Layout drawing for the 1st genderation Model T...if someone would like a copy.
Thanks again for your work and willingness to share it.

Tom

[Sunnburst]

Hey Joe, where ya' going with that soldering gun in your hand? Great article on the 2nd gen Model-T!!! I have a mint condition 1975 version, with the mid select, has the regular silver insert knobs though (not red like yours). Bought it in 1980 for around 2 bills. Had plans of becoming famous and using it on stage, got married instead!

I have it sitting on a Sunn 6x10 cabinet that I modified. I may try some of your mods, at least the one regarding the white/blue stripe wire on the master. If you don't hear from me again, it means I'm dead!