Hoffman 30 watt amps on the bench

[LooseChange]

Hi Guys!


I know I've been absent for quite some time but I got to share what's on my bench...


Building and Repairing... Life is good.

[uki]

Beautiful amp!! What are the PA tubes?

[LooseChange]

EL84's.
Here's the circuit....
https://el34world.com/Hoffman/images/2El84skem.gif

[ginger]

And the complaint ?

[LooseChange]

Came in for general maintenance and a small mod reversal.

[jjasilli]

 

[EL34]

A blast from my past
They look good

[DummyLoad]

how are those even making 30W with a pair of EL84?


--pete

[sluckey]

Looks like some of the early ones actually used EL34s...


And on the layout the text says EL84s but the octal sockets are wired for EL34s...

[EL34]

how are those even making 30W with a pair of EL84?
--pete

Fake name, just to draw in the crowds 

[EL34]

Looks like some of the early ones actually used EL34s...

And on the layout the text says EL84s but the octal sockets are wired for EL34s...

The top picture is inside one of the 50 watters
Not sure what the layout is all about
Looks like it was copied over from a 50 watter and then labelled wrong
I'll have a look through some of the old documents to see if I can find the EL84 layout

[EL34]

Looks like I made some with 6v6's
I found these drawings on the library page
I do not even remember the 6V6 versions
One with DC heaters and one with AC heaters
And the el84 version also

[EL34]

Looks like some of the early ones actually used EL34s...
And on the layout the text says EL84s but the octal sockets are wired for EL34s...

Hey Steve, where did you find that image?
I don't see it linked on the library page

[sluckey]

It's way down a rabbit hole! 

Look way down near the end of the library page. There's a section called "Hoffman Amplifiers stuff" and a sub section called "Photo pages". Click on the first link called "The original Hoffman 30 watt head" which leads to this page...

     https://el34world.com/Hoffman/Original30.htm

Finally click on the last thumbnail (bottom/right) to get that pic. I thought 30 watts was a realistic power for a push/pull cathode biased EL34s. So, are those really 6V6s?

[EL34]

Ok, I found it
I'll add the 6v6 and el84 layouts to that page

I have a bunch of customers images that were sent to my over the years
I'll upload all that stuff just for history

[shooter]

are those really 6V6s?

my money is on 6L6's running hot, although my '34 pp self biased does run ~~30W

[EL34]

Over the years, I have been collecting customer images when they send them to me
I uploaded a bunch of customer images of the H30 heads

There was even one that was a special order and was built into one of the metal 50 watt chassis
Powder coated in gray speckle
It looks pretty cool

Here's the images page
https://el34world.com/Hoffman/Original30.htm

Here's all the layouts I could find for those amps
https://el34world.com/Hoffman/Original30layout.htm

[shooter]

Steve's image through me for a minute, couldn't understand why you used all dual-ganged pots 

[EL34]

Steve's image through me for a minute, couldn't understand why you used all dual-ganged pots 

Haa, I see it now
reflections in the plexi