Preamp Deal of the Century

Kgturner,
The Bendix is a 5Y3GT (directly heated)and does not have the "soft start aka delayed start up time" feature that the 5AR4 has upon turn on. What it does is it wil strip your other tubes(cathode-stripping)because there is no electron cloud formed yet in the tubes before high voltage were applied(prematurely). The 5AR4 on the otherhand is a indirectly heated rectifier. They have different circuit characteristics. That is why some circuit design using the 5Y3GT has a filament heater first before applying the high voltage(delay). Here is a table of the typical "turn On" delay time (meaning full voltage appllied for maximum current)of some tubes:

5R4 5sec
5U4 6sec/6sec
5931 9s/7s/10s
GZ34 31s/33s/32s
PY88 40s
PY500A 45s/40s

Also, the 5AR4 has a lower voltage drop than a 5Y3, around 40 volts less than a 5Y3 at say 100mA current. So, replacing the 5AR4 with a 5Y3GT results in under voltage of other circuit stages that would shift all of the preamps operating parameters.

For me, it is on plain view that changing the 5AR4 with the 5Y3GT will change the characteristics of the preamp and of course its sound. That is why I stop believing that the 5Y3GT (6106) is the best rectifier for the Supratek because I think it is doing something that is not "healthy" on the preamps circuit masking as an improvement of sound. This can be proven very easily by measuring the rectified voltage (output) of the preamp PSU between two tubes.

This is the same reason why one of my previous post I commented that "the Supratek preamp parameters were voice/adjusted/calibrated to the tubes listed on the manual".

Again, all are my point of view/opinion. So take it with a grain of salt!

cheers

I thought the 6106 was indirectly heated. I remember someone telling me that I needed to wait at least a minute after turning the pre on to play music because the 6106 takes longer than most tubes to come up to full power.

Hmmm...but I thought all 5Y3xx series rectifier (6106's generic is a 5Y3)are directly heated with the exception of the 5AR4.

Again, my opinion only!

The Bendix 6106 is indirectly heated.The 6106 in my p.s.,the lower midrange on down is spectaular.I never heard Pink Floyd,The who ect.like this,accept live.The Bendix is a all around superb rectifier.I do have a matched pair of 1957 N.O.S. metal base Philips Mini GZ-34s. I am going to try,I know I will like...$20.each for early 1950s n.o.s. Bendix 6106s... $229.each for the Philips mini watts.The test values on all the tubes in my pre are outstanding. I am going to put back all the tubes that came with it some weekend just to check out to see if all time and money spent was worth it. B.t.w. the E.H. gold pin 6sn7s are [fabulous]...

The GZ34 and the Bendix 6106 are indirectly heated tubes, heater and cathode are parallel connected. Both tubes have the same base diagrams and both are bi-phase halve-wave rectifiers or full wave rectifiers.
"Slow start" means the warm-up "rise time" (time taken to change from 10% to 90%) of their output voltage when fully loaded, which reduces the inrush current of other electronic components.
I gathered this information from some books, I´m not a technician.
The question is, is it the same thing "indirectly heated" and "slow start", or in other words, all the indirectly heated tubes have slow start?.
When I asked Mick if I could use the U54, a tube with the same base diagram as GZ34 and that is also an indirectly heated rectifier, his answer was: NO!!! It is not slow start.
In some substitution book I found that the U54 can be used instead of GZ34...Could someone help and explain this technical issue?.
Slowhand here you have a very complete data for the Bendix 6106: http://www.mif.pg.gda.pl/homepages/frank/sheets/131/6/6106.pdf
(cut and paste in your browser).