Sunn 350B Question

[Oli]

Hi,

I got an old Sunn 350B. It runs fine and I'm very happy with the sound. I thought it was the same amp as the 2000S exept the GZ34 Tubes. When I put in all tubes after the transport i realised that the 12AX7 socked was blocked, the socket was missing instead there was a plug in there (I think they use the same board as the 2000s with the 350B). I had a look at some photos and all 350B had the same plug in there. Can anyone tell me the idea why they had choosen to drop the 6AN8A and what will be the sound difference comparing to a 2000S.
Thanks & Greetings

Oli

[EdBass]

As far as I know the 350B is just a renamed 2000S. The only socket(s) "blocked" as you put it should be where the rectifier tubes would go in an old 2000S. The later 2000S also had a solid state rectifier; it should be identical to the 350B. Neither amp would work at all without the 12AX7 in V1, 6AN8 in V2, or the appropriate substitutes.
Also there is no board in either amp; one of the coolest things about the vintage tube Sunns is the fact that they are "point to point", wired by hand.

[Oli]

Hi,

yep, sorry about the board. I just discribed the whole non wooden part as an electric block - i think the real english expression is a chassey?  The 6AN8A is quite uneasy to grap (because of the second transformator)- , so i tryed to search for a tube socked with my fingers and the part felt like a plug with two rivets in it. The amp just arrived with one preamptube, i thought thats it. I also found an old picture of the opend 350B, well it's not that good but I thought i saw the plug in there too...I'll  promise I'll use a torch this evening.

Greetings

Oliver

[Oli]

Hello,

yes, u are right with the 12AX7 in V1. It is rather impossible to see, i used a torch and could not see it or touched it. So i took a small camera and took a photo. There were two holes in the chassis: one is blocked with a plug and there a tube socked for the 12AX7 far behind it, so i could retube the amp. Thanks for your help, without it i would have never examined the amp for another tube.
I knew, that Sunn used plugs on the 350B Amps with the 2000s chassis for the GZ34 holes, but in mine case all the holes were not stamped out.
But why did they put in two holes in the preampsection? I think the 2000S has only one 12AX7 aswell?

Greetings

Oliver


 

[EdBass]

The plugged pre amp tube cutouts are because your amp uses the same chassis that is used for the 1000 series guitar amps, some of them have reverb and tremelo. If you don't have cutouts for rectifier tubes, your chassis must have been produced after Sunn fully committed to solid state rectifiers, or more likely when they ran out of the old style pre punched chassis.