Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: macula56 on July 08, 2011, 10:30:03 am

Title: SS rectifier in tube base
Post by: macula56 on July 08, 2011, 10:30:03 am

I was thinking about putting one of Doug's 1000 volt - 3 amp bridge rectifiers in a tube base. anybody used these?

Title: Re: SS rectifier in tube base
Post by: phsyconoodler on July 08, 2011, 10:50:34 am

Yeah,but why? Two diodes across the rectifier tube and you have a solid state rectifier.
 Be aware of the large voltage increase.

Title: Re: SS rectifier in tube base
Post by: xm52 on July 08, 2011, 12:43:37 pm

I've used similar products, they work just fine in many amps.

There are modules available that not only have the diodes, but also have a resistor to simulate the voltage drop, and a thermistor to limit inrush and add a slow turn-on.

The advantage is that you can plug in either the SS module or the tube adding some flexibility to the way that the amp performs. Also you can save on filament current that the tube rectifier normally draws, making the amp run a little cooler.

Title: Re: SS rectifier in tube base
Post by: macula56 on July 10, 2011, 06:31:25 am

thanks for the replies gentlemen.

Title: Re: SS rectifier in tube base
Post by: Rev D on July 11, 2011, 04:37:59 am

 I use a weber copper cap in one of my el84 amps because way back when the Rec tube went south and the price of the copper cap was nearly the same so I went for it. well once when removing said copper cap the copper lid popped off. What do I see? Two of the diodes your talking about and a large ceramic resistor (which I assume dumps (resists?) a little voltage so its not quite as high as using just the diodes. I didn't write down the size of the resistor, I have a rather bad picture of the contraption somewhere. I will say I have gigged that little 18 watt amp in several different styles of build (lite 18IIb, 18watt TMB finally) and of course the copper cap has lasted for all these years (over 5). All in all it was a good investment. I know some of the Vox guys use them on the newer ac15 and ac30's I'm told because they're known to go out in those amps (as I say so I'm told). Anyway just thought I'd mention the makeup of the copper cap, if you do have voltage problems, a large resistor might just be your friend.  :icon_biggrin:

Regards,

Don

Title: Re: SS rectifier in tube base
Post by: kagliostro on July 11, 2011, 06:10:51 am

Google "sag resistor" you'll find lot of documentation about that mod

http://www.tone-lizard.com/Mods_and_Odds.htm (http://www.tone-lizard.com/Mods_and_Odds.htm)

Kagliostro

Title: Re: SS rectifier in tube base
Post by: macula56 on July 11, 2011, 06:40:19 am

thanks for the replies everyone. i am not looking for any sag. i just want the ease of plugging in a ss rectifier without having to build a little board in the amp. i had a ss recto in a tube base many years ago in my Super but it got broken.

Title: Re: SS rectifier in tube base
Post by: kagliostro on July 11, 2011, 06:48:56 am

Quote

i am not looking for any sag. i just want the ease of plugging in a ss rectifier without having to build a little board in the amp.

I've understand it but it will be better if you put also the resistor instead of only the diodes, in order to reduce the B+ that will surely rise only with SS rectify instead of tube rectify

Kagliostro

Title: Re: SS rectifier in tube base
Post by: macula56 on July 11, 2011, 06:54:37 am

thanks Kagliostro. i have taken the voltage increase into account.