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PP amp build

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Posted on May 11, 2015 at 09:02:22
rage
Audiophile

Posts: 793
Joined: December 17, 2010



I decided I was tired of messing with the usual chassis materials and bought a 12U rack to build something like what I've seen in some old tube transmitters.

Hammond 1650R outputs, KT120 tubes, EL84 drivers, using the E-linear topology by Douglas.

Lots of work left to do... filament wiring, CCS for the drivers/phase splitter tubes...

Power supply is dual mono choke input, 1H 12 ohms dcr, followed by 240uf of capacitance that are GE oilers.. if I can fit more C in there I will yet.

I am a bit concerned about the lack of filtering given the front end runs off of the UL taps. I've considered adding a bunch of capacitance or another LC stage. I've got another pair of 1H chokes on hand I might put in.

The power transformers are TWO Antek 4T360 toroids in paralell into a Cree Schottky bridge.


Always welcome suggestions from this group! This has been a fun albeit slow build.

When done the DC2a3 amp goes back on the bench for more fun.

 

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RE: PP amp build, posted on May 11, 2015 at 09:19:56
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 I would be a little more concerned about regulation rather than filtering with a project like this.

 

RE: PP amp build, posted on May 11, 2015 at 10:04:48
Tre'
Industry Professional

Posts: 17297
Location: So. Cal.
Joined: February 9, 2002
 With it being push pull, as long as he keeps it operating in Class A he should be alright. No?

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: PP amp build, posted on May 11, 2015 at 10:11:27
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 Yes indeed, I suppose we don't know what his intentions are in that arena.

 

RE: PP amp build, posted on May 11, 2015 at 10:31:34
rage
Audiophile

Posts: 793
Joined: December 17, 2010
 Class A. Roughly 300V and 300ma per channel. Running UL on the finals.

 

RE: PP amp build, posted on May 11, 2015 at 10:47:44
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 Are there UL curves floating around for the KT120?

 

RE: PP amp build, posted on May 11, 2015 at 10:58:41
rage
Audiophile

Posts: 793
Joined: December 17, 2010
 Might be triode and pentode curves, I don't remember. Don't read them well anyhow. I'll just get the distortion analyzer out when I'm done and see what happens. :)


 

RE: PP amp build, posted on May 11, 2015 at 15:18:58
PakProtector
Audiophile

Posts: 12363
Joined: May 14, 2002
 Looks like a stout build. As you noted, more capacitance is a good thing.

For the 6CB5A amp I built, with B+ bit lower..I ran 8k plate loads to the EL84. Something near there should be brilliant.
cheers,
Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

 

RE: PP amp build, posted on May 12, 2015 at 16:24:01
deathtube 667
 Looks like something that would provide deadly volts to an electric chair.

What speakers will get subjected to all that tube power?

 

RE: PP amp build, posted on May 13, 2015 at 03:54:56
rage
Audiophile

Posts: 793
Joined: December 17, 2010
 AE speakers Lamba TD-15m and BMS 4552 compression drivers on QSC waveguides... 98db @ 1 watt. Econowaves.

I'm also on the hunt for a set of JBL 4412s for my basement system, which would be the long term pair for this amp.

 

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