diytube.com

I just got done modding my sons diytube ST35 to fixed bias. I just cannot believe the difference in sound. I am lead to believe that the fixed bias in conjunction with the 565 trannys is what I am hearing.

Thinking of upgrading my Ikes with the A470S transformers. Can I just swap the Hammond 1650's out for the 470's?? Looks to my inexperienced eye that the specs are close.

mm

The A470s can be used, and most likely with better results than with the Hammonds.

If the mounting hole dimensions are the same, it will be a simple "drop-in" swap-out. Otherwise you may have to do some more chassis drilling

IIRC, the Hammonds may have a "reverse" primary to secondary phase relationship, if the amp sounds like a fog horn after the tranny change-out (Positive feedback, instead of negative FB), it is easy enough to swap the connections - the easiest way to do this, involving only two connections, is to swap the wiring from the two driver board outputs to the power tubes' control grids.

BTW, I just unboxed a 2003 vintage rev C ST-35, and will be giving it the EFB modifications, I just have to get myself an LM373, if I can't excavate one from the cellar goodies...

/ed B

Thanks Ed!

I think I will give it a try. Chassis drilling is definitely not a show stopper!! Now to find an extra couple of hundred bucks at Christmas time... sigh.

I think you will be pleased with the EFB mod. It sure opened my ears!!


mm

Marshman wrote:Now to find an extra couple of hundred bucks at Christmas time... sigh.

Convince the wife it's what your REALLY want for Christmas

Cheers!

If you have room you could use the A-431 (Mark-3) output transformers, same electrical specs just more iron!

@geek - no wife, no girlyfriend, no problem!! ;-p

@terrysmith - wow!! those things are 12lbs each!! seriously more iron! Not sure they would fit, but I will take a more serious look at them. $130 a piece too... whew...

mm