Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: sdp1234 on October 25, 2010, 08:11:32 am

Title: TOS Voltages
Post by: sdp1234 on October 25, 2010, 08:11:32 am

I'm planning a TOS build and currently plan to use a salvaged PT from a Hammond Organ.  The voltages are listed as 285-0-285.  It had a 5u4 rectifier.  Based on the tube compliment I think it will be in the 350 DC range and should be able to provide over 200 ma if needed.  Heater current should be good for any tube complement.    I'm not sure what output tube I want to use but I'd like to try 6v6's, el34's 5881's and 6l6's.  Is the voltage high enough for the TOS?  Are there any of these output tubes I can't try?  For flexibility I plan to try the webber 45 watt Marshall output transformer 3400(6800) : 2(4), 4(8), 8(16), 16(32).

Title: Re: TOS Voltages
Post by: tubenit on October 25, 2010, 08:17:30 am

I am currently using a 275-0-275  150 ma PT with GZ34 rectifier and 5881 tubes.  It works fine for me. I also use 6V6's sometimes in it (but not as often). I think I have around 360v on the 5881 plates?

On top of that, I use a VVR on the power amp and LTPI which further lowers the voltages and typically have the VVR set at about "5" more or less.

You could consider using a SS rectifier which would give you around 265 v X 1.4 = 371v.

With respect, Tubenit

Title: Re: TOS Voltages
Post by: drumslinger2000 on October 25, 2010, 09:16:09 pm

Is vibrolux iron ok for a TOS build?  I have an extra set lying around.  what seems to be the ideal iron to use?

Title: Re: TOS Voltages
Post by: sdp1234 on February 09, 2011, 12:54:02 pm

I have the choice between two PT's that I have on hand. 

1. 285-0-285 - 200+ ma
2. this transformer has 2 HV taps one is 265-0-265 and the other is 320-0-320.  at 150 ma

Due to size and weight Id rather use the second PT.  Would this be enough for most tube choices or would i be better off having the extra current of the larger PT?