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Parafeed Circuit

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#2
I just built this, and I like the performance so far.
The choke labled "1.8k ohms" is actually the primary of a Fender spring reverb driver tranny from a Deluxe Reverb reissue. It's probably around 30 Henrys.
 

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#3
PARACHUTE...

Hi,

Like to try SE parafeed circuit, anybody knows where I can find a good parafeed circuit I could try?
Click to expand...

Any half decent SE amp is a parafeed candidate depending on what OPT type you to use.

Read: can't afford the right OPT for the job? Try parachute technology using a regular PP OPT and prevent DC on it by using a coupling cap, never measure anything anymore and according to some this presents the nec plus ultra...

Ok...just stopped laughing, almost fricking choked.

Fair enough some good SE exist but I can get better results with half the working budget though.

O.K. I'm back to the bunker...😉 :goodbad:
 
#4
Head over to Bottlehead.com. You should be able to glean some information over there. I was under the impression they pioneered parallel feed although they are more into the parallel feed kit business. But you can opt to buy just the construction manual and schematic for their 2A3 and 300B kits.

Also you can check out their Valve magazine which has designs that I would imagine involve parallel feed from time to time.

If nothing else, you might find some links to other sites with PF info.
 
#8
I did not mean to imply they invented it. But Doc does have some gray hair. Maybe he's older than he looks.

You can buy the schematics/construction manual from them for $15. And you can get good support at the Bottlehead forum which is completely free of :dodgy: and :scratch:.
 
#10
HAVE A LOOK INTO MY WALLET...

Hi,

Well, actually i just happen to have them on hand, not really looking forward to buying one.
Click to expand...

And I suppose it's your right to spend your money as you feel fit.

MC Hammer at work:


Ahh. Yes... I can see how the decreased transconductance, increased plate resistance, oddball filament voltage, and enormous pricetag would be appealing...
Click to expand...

Look at your own circuit for a change, silly.
And FWIW, any circuit is meaningless without it's PSU...guess it's going to take you an other fifty years to grasp that?
Not that you'd hear a difference...

Joel, Joel...how much longer? Is it so hard to put your cheapskate ego aside?

Be a sport for a change and we might just reach out and help you too.

Blimey,🙁
 
#11
Originally posted by ultrachrome
Head over to Bottlehead.com... I was under the impression they pioneered parallel feed...

Joel replied:

Not unless they were around in the early 1930's.

Gibson used parafeed in their guitar amps in the thirties (resistor plate load)

The Royal Navy Wireless Handbook shows describes several parafeed applications (choke plate load) 1934 edition

The Australian Edition of STC transmitter valve manual shows several parafeed stages (choke plate load) 1935 edition

Parafeed seems to have occured world wide in the early thirties. I have no idea where it was first used...

ciao

James
Click to expand...
Click to expand...
 
#12
Hi James,

Both yours, and Joel's comments are correct; parafeed is an old technique. However in recent times, say the last 50 years it's been used rarely and the classic texts did not go into it's use in the level of detail as series feed, nor were parafeed circuits implemented anywhere near as often. Mike LeFevre of Magnequest was the most obvious "re-introducer" of this into more mainstream thinking, certainly being the first person <i>I</i> can think of in a long while to specifically develop optimised OPTs for parafeed use. Dan Schmalle (Doc Bottlehead) tried it and liked it, and I think it would be fair to say that much of the current interest in it has grown from there. That's where the comment by ultrachrome came from I feel.
 
#14
...full disclosure...

Hi Brett,

I fully agree with your comments.

And in support of Mike LeFevre's work on output stages it should be noted that the references I quoted all use parafeed for interstage coupling...

I haven't checked the WE references yet but I seem to recall that they did indeed use it in output stages.

ciao

James
 
#17
ultrachrome said:
You can buy the schematics/construction manual from them for $15. And you can get good support at the Bottlehead forum which is completely free of :dodgy: and :scratch:.
Click to expand...

Awww, ultrachrome feels I have gone too far with the 🙁 icons... :bawling: :bawling: :bawling: :bawling:

Well, schematics of great amplifiers are everywhere on the net, and they are free. And yes, I would go to AA to get advice if I wanted to build a battery powered 300B amp that weighs 412lbs, operates for 10 minutes before needing a recharge, runs with a distortion level of 14%, and cost $12,000....

:dodgy: :scratch: :dodgy: :scratch: :dodgy: :scratch: :dodgy: :scratch: :devily:
 
#20
Re: LOVE YOU TOO...

fdegrove said:
Too bad you can't find any used 300Bs, right?
Click to expand...

Boy, it really irks you that I like to use low cost parts, doesn't it? Why is that exactly?

Many others, including Tim, Sy, and John have made similar comments about designer tubes - no witty comments for them? Just for me?
Ahhh, well, it's nice to be noticed I suppose...

(now you see the reason for my signature)
 
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