Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Where are the 307A / VT225 amps?
Where are the 307A / VT225 amps?
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 31st January 2012, 05:53 PM   #61
rcavictim is offline rcavictim  Canada
diyAudio Member
rcavictim's Avatar
Join Date: Jun 2004
Location: Next to an open wormhole NW of Toronto
Originally Posted by Zen Mod View Post
which OPT you're using ?
I don't own any SE iron and am not presently funded for this sort of research, so I have to get creative.

The plate is powered through a plate choke and the output xfmer is a hammond 1610, P-P gapless xfmer using one half of the 10k P-P primary only. 8'ish ohm loudspeaker is on the 4 ohm output winding placing the load north of 5k ohms and south of 10k. The plate choke represents a parallel load as well that I don't know the Z of, so perhaps the real tube load is just under 5k.

You asked and I could have stopped at Hammond 1610...

A vintage 4 uF @ 600 VDC Sangamo (like Sprague Vit-Q) foil, oil and kraft paper metal can cap is used as a DC block in parafeed connection back the the o/p tube cathode.

BTW, my initial tube wiring was G1+G2 tied together and used as control grid. G3 was grounded to cathode neg term. The tube refused to draw plate current even at zero bias and only made grunts with peak positive audio modulation. Since G3 is an actual grid, not beam forming plates, this makes sense. As mentioned before, the fix was go in g1 as normal, tie g2 ang g3 to the plate. Marvelous!

I have not brought a sinewave generator or o-scope near this thing yet. All my perception so far is by ear and I'm pleased/encouraged by what I'm hearing.
"There are more worlds than the one you can hold in your hand." Albert Hosteen, Navajo spiritual elder and code-breaker, X-Files TV Series.
  Reply With Quote
Old 31st January 2012, 06:19 PM   #62
Zen Mod is online now Zen Mod  Serbia
Official Court Jester
diyAudio Member
Zen Mod's Avatar
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Where are the 307A / VT225 amps?
considering that my question was more in sense "which plate load you are using " , I'm more than pleased with an answer
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa... by Mighty ZM
  Reply With Quote
Old 31st January 2012, 08:47 PM   #63
Tubelab_com is offline Tubelab_com  United States
diyAudio Member
Tubelab_com's Avatar
Join Date: Jul 2005
Location: West Virginia panhandle
My SE experiments used a 5K Edcor OPT. Power output was 8 WPC in triode. See post #7.

My P-P experiments used a 6600 ohm OPT and generated about 25 to 30 WPC.
Tubelab, it's 5 year mission. To explore strange new tubes, to seek out new circuits and topologies, to boldly go where no tube has gone before......
  Reply With Quote
Old 22nd February 2012, 10:11 AM   #64
radiostar is offline radiostar  Yugoslavia
diyAudio Member
Join Date: Apr 2009
I'm building my new SE 307A with 4.5K trannies ...
  Reply With Quote


Where are the 307A / VT225 amps?Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
SMPS for diy audio amps and multi-channel diy amps (and their power supplies) tlparker Solid State 20 12th May 2015 12:23 PM
For Sale: Tube Amps, Class-A Amps, BG Ribbons, Chassis and Other Goodies! opc Swap Meet 23 2nd November 2009 05:04 PM
Big sale thread: PHL, Raven, Amps, In-wall/ceiling speakers, Amps, VideoRequest mbcouple Swap Meet 2 27th October 2008 10:27 PM
Why do some Bogan amps sound so good as guitar amps? amperex Instruments and Amps 7 22nd June 2006 11:46 AM
Has anyone compared GC amps(LM3875/3886/4780) with other DIY SS amps(Leach,ESP) ? percy Chip Amps 31 13th January 2006 01:33 AM

New To Site? Need Help?

All times are GMT. The time now is 03:05 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio