2 rect tubes on the same HV coil

[pjd3]

Hello,

I was hoping to hear thoughts on having 2 rect tubes on one HV coil as opposed to just one - what the problematic considerations may be if there is any.

Example - you are building a stereo tube amp who's PT originally had a single GZ34 rect but, since it is 2-channel and you don't care about saving pennies on the dollar, you consider if say, a 5V4 for each channel is perhaps more electrically efficient and forthcoming than one GZ34 serving the 2 channels.

This is assuming that max current draw is within ratings for either scenario.
I see that rect tube data sheets call out plate impedances in the opening specification so, it call the question if two rect tubes are trying to share the same HT coil, they will see half the impedance maybe, and perform differently.
Just speculation here.

Some other reasons I consider doing this is that its much more cost saving to buy the best 5V4 NOS rect tubes than to dish out the $250 or greater for the best NOS GZ34 it seems. Also, if I were to go with 2 5V4's, I could purchase a separate 5 volt transformer for there heaters and take some of the "heat" off the 60 year old power transformer that I will be using. That right there seems like a reason almost by itself.

But, I've only built 2 tube amps each with one rectifier tube so, I need to educate myself a bit more before assuming I can "just do it".

Thanks!
Best,
Phil Donovan

 

[coresta]

yes you can i did it with 2 GZ32 on 2 coils . Result is lowering instantaneous impedance of the PSU ...

 

[pjd3]

2 rect tubes on one coil

Hi coresta,

You had two separate HT coils from the same PT? What would you suspect could be the implications of paralleling 2 rectifier tubes from one HT coil?

Do you suspect that there are problems associated with that? Unmatched rect tubes?

I have a feeling that there are issues inherent with that idea but, the jury isn't out on that totally yet,

Thanks for sharing that. Damn. I wish I had 2 coils in my PT.

Best,
Phil

 

[pjd3]

One rect tube on each end of the HT

I'm starting to see schematics of 2 rectifier tubes on the same HT coil but each rect tube tends to have both their plates tied together, one on each end of the coil. So, I guess someone somewhere thinks its quite fine to do,

But, I'm probably just being over zealous about it. I probably should just shut up and use a single GZ34 like normal people. It would probably serve the 2 channel amp fine. Since I'm not going for any "sag" and trying to keep things fairly stiff, it just seemed like a worthy consideration. (2 pairs of EL34, probably) And the price and availability of good old reliable NOS 5V4's.

Thanks
Best,
Phil Donovan

 

[coresta]

Hi Phil , everything is possible : 5V4, 6AU4 as did Marantz on 2 and 5 amps ... or Thomas Mayer in full wave single coil power transformer. EY88 are good too !Play with what you have on hand . I used 2 coils // from mono amps in order to increase max current capability .