1st tube project - newbie tranny question

[lloop9]

Hi guys!

I wanted to start a tube pre project, and have found Pete Millet's low mu pre in Audioxpress Feb issue, to be a good match for my high gain ss amp.

I have some transformer questions and hope u guys can help me.

Pete Millet's pre schematic:

An externally hosted image should be here but it was not working when we last tested it.

 

[lloop9]

Sorry guys, Pete's schematic is here:

http://lloop9.tripod.com/pre.gif


I did a graphix presentation of the trannies in question here, I hope my understanding of the transformer, with their voltage labelling is correct.

http://lloop9.tripod.com/transformer-copy.gif


My questions are:

From the schematic, filament #1 has one lead grounded with a 47uF cap in series, and filament #2 is grounded with a 5K resistor , is there a need for me to ground the center-tapped lead of both filament #1 & #2?

Or can I just insulate them and leave them floating?

And what should I do with the secondary 50V bias lead?

Thanks for any advice!

 

[dibbi]

Your links aren't working for me.

 

[w00t]

Sorry guys, Pete's schematic is here:

http://lloop9.tripod.com/pre.gif


I did a graphix presentation of the trannies in question here, I hope my understanding of the transformer, with their voltage labelling is correct.

http://lloop9.tripod.com/transformer-copy.gif


My questions are:

From the schematic, filament #1 has one lead grounded with a 47uF cap in series, and filament #2 is grounded with a 5K resistor , is there a need for me to ground the center-tapped lead of both filament #1 & #2?

Or can I just insulate them and leave them floating?

And what should I do with the secondary 50V bias lead?

Thanks for any advice!

Rename the *.gif to *.txt so you can link off site.


🙂

 

[fdegrove]

Hi,

Flamin' Tripod....

Here's the schem:

Cheers,😉

 

[lloop9]

Thks for the link Frank 🙂

My questions are, should I need to ground the centre-tapped lead of both filament 1 and 2, or can I just heat shrink the end and leave them floating?

Also, there's a 50V bias lead. What shld I do to it?

And what do you guys think of Pete's circuit? 😀

Regards,
lloop9

 

[fdegrove]

Hi,

From the schematic, filament #1 has one lead grounded with a 47uF cap in series,

Forget the heater here, that's your B+ you're looking at...I know, it can get confusing when you're not used to tube rectifiers...

and filament #2 is grounded with a 5K resistor ,

You'll also notice the 30K resistor from B+ to the heater in series with the 5K resistor to ground?
The purpose of this is to inject part of the B+ into the heater to prevent surpassing the maximum heater to cathode insulation.

is there a need for me to ground the center-tapped lead of both filament #1 & #2?

Best to ground the CT of the heater xformer.

Also, there's a 50V bias lead. What shld I do to it?

Can't see it...😕

And what do you guys think of Pete's circuit?

Guess he could have used 6C33-Cs instead of those whimpy 6AS7Gs.😀

Cheers,😉

 

[lloop9]

thks for the replies.

fdegrove, the 50v bias lead is on my Hammond's high voltage secondary. I guess I'll just insulate it and leave it floating.

by the way, I've seen ur Ultimate Preamp, I would study it and built one later. 😀

Regards,
lloop9

 

[fdegrove]

Hi,

I guess I'll just insulate it and leave it floating.

Ah...I see. O.K., that's fine.

I've seen ur Ultimate Preamp, I would study it and built one later.

Thanks,😉