Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: DummyLoad on July 22, 2019, 12:21:27 am

Title: hollow-state voltage doubler.
Post by: DummyLoad on July 22, 2019, 12:21:27 am

never have seen one implemented with a guitar amp. until now. odds are, others do exist.

100uF stack seems kind of hefty for a hollow-state - alas, it is lower voltage / higher current - love the 1/2 tap for the screens.

guestimating should be around 250V plates and 125V screens and satisfies supply tension tp the delicate screens of the 25L6.   

--pete

(http://djlservice.com/Project%20Photo%20Gallery_files/image003.jpg)

Title: Re: hollow-state voltage doubler.
Post by: PRR on July 22, 2019, 12:37:48 am

My guess is nearer 75mA 200V DC, 360mA peak in the rectifier (OK)
http://www.mif.pg.gda.pl/homepages/frank/sheets/093/2/25Z6GT.pdf

Even though the B+ floats, they use the 68k in the groundy-side of the input stage to limit the lethal currents to user. (This may be hang-on from a totally transformerless plan banned by UL.)

It is not at all clear why the extra 22Ks or the way-low 39Ks. 400Hz bass-cut seems awful high for a "deluxe" amp at the bottom of the scale. I wonder transcription error or just real darn cheap speakers?

Title: Re: hollow-state voltage doubler.
Post by: DummyLoad on July 22, 2019, 12:59:03 am

It is not at all clear why the extra 22Ks or the way-low 39Ks.

maybe they are actually 220K and 390K - perhaps they wanted to load 6SJ7 cathodyne and and 390K are well, the grid-leaks? 

--pete

Title: Re: hollow-state voltage doubler.
Post by: DummyLoad on July 23, 2019, 02:13:01 am

here's another cool implementation with hollow state volt dobler: WE 140A amp with a quad of 25L6 and a pair of 25Z6 duo diodes doubled up in ||. not a guitar amp, but it's neat in that it can take a battery stack or AC supply for power source, however, it makes less power on battery. the PI and 1st pre-amp are a damn brain tease. yet another UNSAFE to use amp with AC or DC power


--pete

Title: Re: hollow-state voltage doubler.
Post by: PRR on July 23, 2019, 11:47:18 am

> yet another UNSAFE to use amp with AC or DC power

If you don't open the box, this is "safe" at the input and output connections, both transformer isolated.

As soon as you start messing with the insides, beware.

Title: Re: hollow-state voltage doubler.
Post by: shooter on July 23, 2019, 11:59:43 am

ok, I couldn't help myself surfed "hollow-state" since I'm ignorant on that term, webin didn't help so far, got the Vdoubler down fine.  Did find a somewhat fun article though, like the section on degraded Q from broken strands in multi-strand wire  :icon_biggrin:

http://navy-radio.com/manuals/hsn/hsn-issue%2044.pdf

Title: Re: hollow-state voltage doubler.
Post by: DummyLoad on July 23, 2019, 07:12:42 pm

vacuum rectifier. 😝  but you fingered that one out, right? 🤓


--pete

Title: Re: hollow-state voltage doubler.
Post by: shooter on July 23, 2019, 07:37:37 pm

I was just web'n! did you hack my computer  :violent1:

so far "hollow state design" seems to be a company selling a book on tubes, BUT the Author posted this;
https://hollowstatedesign.tumblr.com/post/54272117178/why-thermatrons

now I'm gonna hit myself  :icon_biggrin:

and NO, I haven't made it to rectifiers except inferred from the schematics, maybe I'll hit twice   :m17

Title: Re: hollow-state voltage doubler.
Post by: silverfox on July 26, 2019, 05:11:09 pm

Quote from: DummyLoad on July 23, 2019, 07:12:42 pm

vacuum rectifier. 😝  but you fingered that one out, right? 🤓


--pete

Yes I did- A leak.


fox.