The Feature Creep in me is fiddling with some ideas for a multi-mode power amp section (5-20W), and I need to verify a suspicion. If I wanted to switch an output stage from PP to SE modes, do I just stop driving one side, or do I need something more elaborate?
One idea is a PP transformer with a gapped stack - then I don't just stop driving the one side, I actually shut off B+ and Vscreen to the undriven phase.
I know there are a wad of things that have to happen to the bias setup - SE is of necessity Class A, for instance - but I'll leave that for a later exercise.
SE and PP modes from same OT?
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Stevem
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Re: SE and PP modes from same OT?
Another consideration is the plate voltage limit to be in class A compared to what you can run in A/B!
If you are only shooting for 5 watts of class power it might be cheaper to just use a seperate OT for that than have something custom spun up?
If you are only shooting for 5 watts of class power it might be cheaper to just use a seperate OT for that than have something custom spun up?
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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harleyboy2112
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Re: SE and PP modes from same OT?
Here's a great article on doing just what you are talking about.
http://www.ampbooks.com/home/amp-techno ... t-7173488/
http://www.ampbooks.com/home/amp-techno ... t-7173488/
Re: SE and PP modes from same OT?
I'm wanting to be able to switch between Champ and AB763 Deluxe modes, and switching entire transformers seems a little tricky.Stevem wrote:5W
Should have figured our buddy Randall would have a relevant patent. That does answer my questions, though - thanks to you both!harleyboy2112 wrote:Here's a great article on doing just what you are talking about.
http://www.ampbooks.com/home/amp-techno ... t-7173488/
Re: SE and PP modes from same OT?
(deleted)
Last edited by matt h on Fri Mar 27, 2015 4:51 am, edited 1 time in total.
Re: SE and PP modes from same OT?
DonMoose,
Check out the schematic for Mark Durham's (RIP) 18W Vajra. Schematic is on Mark Huss' site http://mhuss.com/18watt/schematics/Vajra18Scheme.jpg
Also check out the Black Star Artisan which has a switchable SE/PP mode.
Check out the schematic for Mark Durham's (RIP) 18W Vajra. Schematic is on Mark Huss' site http://mhuss.com/18watt/schematics/Vajra18Scheme.jpg
Also check out the Black Star Artisan which has a switchable SE/PP mode.
Re: SE and PP modes from same OT?
Yep.matt h wrote:There's also the simpler solution peavey goes for, which essentially rigs up a one-side-of-push-pull volume pot. I think they call it "texture" or some nonsense. Kills the AC signal to one side. Simple, elegant, and if it fails, won't endanger the expensive stuff.
Also, see the post from Renshen1957 here:
https://tubeamparchive.com/viewtopic.ph ... eavey+body
I concur, and have read about this in KOC's books since the 90's.
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Stevem
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Re: SE and PP modes from same OT?
If you ask me the plate voltage in a blackface Deluxe, like a silver face era Champ is too high for class A single ended with a 6V6!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: SE and PP modes from same OT?
It'll take a while to map this out - it's a completely bonkers project.Stevem wrote:If you ask me the plate voltage in a blackface Deluxe, like a silver face era Champ is too high for class A single ended with a 6V6!