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

Instruments and Amps Everything that makes music, Especially including instrument amps.

Interstage transformer ratio, spacecharge tubes in PP
Interstage transformer ratio, spacecharge tubes in PP
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
Reply
 
Thread Tools Search this Thread
Old 5th August 2014, 04:09 PM   #11
jazbo8 is offline jazbo8
diyAudio Moderator
 
jazbo8's Avatar
 
Join Date: Jan 2011
Location: In Transient
Interstage transformer ratio, spacecharge tubes in PP
Ha ha, if only that was true... there are a bunch of circuits on this thread including transformer coupled ones for you to check out, and it does seem that the 600:600 transformer isn't really suitable for the job. Also by coincidence, Printer2 recently started a discussion thread on low voltage tube guitar amps that you might be interested in participating.
  Reply With Quote
Old 5th August 2014, 10:12 PM   #12
engels is offline engels  Israel
diyAudio Member
 
engels's Avatar
 
Join Date: Jan 2007
Location: Jerusalem, Israel
Thanks for the link.... studied the subject a bit more.

Though it was evident from the beginning that long tail PI will work, I'm still on a mission to find a "midget" transformer for PI. That old scheme shows 7K:15K CT so I will try to find something similar. There will probably be a need for another gain stage, but we'll see.
  Reply With Quote
Old 6th August 2014, 05:58 AM   #13
tricomp is offline tricomp  Denmark
diyAudio Member
 
Join Date: May 2004
Location: Jutland
Hi,

Looking at your schematic there seems to be something very wrong.
Grid #2 should be biased around -2V which isn't happening here.
You either need a fixed negative voltage supplied to the secondary center of the interstage transformer, AC decoupled to ground.
Or you need a suitable common cathode-resistor to raise the cathodes to around +2V, connecting the xfmr center-tap directly to ground.
In both cases DC-couple the interstage transformer to the grids, no coupling cap's.
Also the para-feed driver is maybe not such a good idea.
A 10nF coupling cap along with the 1Mohm plate resistor form a very high impedance not suitable for driving the low-z primary of the transformer.
With ideal matched circuits how much power will you get from a 12K5 push-pull stage? 50mWatt in the very best cases? That's about what came out of the first pocket-sized transistor-radios and they sounded pretty wimpy. In any case you'll need good, sensitive speakers to enjoy the tiny power from such a construction.

Rgds.
  Reply With Quote
Old 6th August 2014, 09:56 AM   #14
jazbo8 is offline jazbo8
diyAudio Moderator
 
jazbo8's Avatar
 
Join Date: Jan 2011
Location: In Transient
Interstage transformer ratio, spacecharge tubes in PP
As usual, Tubelab summarized the issue with using space-charge tubes for power amps well, you can read it here. Lots of power goes in, very little power comes out...
  Reply With Quote
Old 6th August 2014, 04:22 PM   #15
engels is offline engels  Israel
diyAudio Member
 
engels's Avatar
 
Join Date: Jan 2007
Location: Jerusalem, Israel
Default spacecharge tubes

Regarding the spacecharge tubes, why I like them:
1. Power supply can be made of some cheesy 12V transformer or simply recycle a laptop or printer power supply. Output transformers may be line 70V, again very low $$$.
2. Spacecharge tubes are still relatively chap.
3. No deadly voltages.
4. Guitar-vise, distortion and saturation may be achieved at low volumes. It is good for recording and practicing at home.
5. They sound good.
  Reply With Quote
Old 6th August 2014, 05:12 PM   #16
jazbo8 is offline jazbo8
diyAudio Moderator
 
jazbo8's Avatar
 
Join Date: Jan 2011
Location: In Transient
Interstage transformer ratio, spacecharge tubes in PP
Quote:
Originally Posted by engels View Post
5. They sound good.
Do you have soundclips that you can share? All the ones I have heard so far sounded pretty "thin"...
  Reply With Quote
Old 10th August 2014, 11:11 PM   #17
engels is offline engels  Israel
diyAudio Member
 
engels's Avatar
 
Join Date: Jan 2007
Location: Jerusalem, Israel
Default demo

I really need to make some demo to show how it sounds. I will one day.
Still,
Here's a song with a mix of two different amps, two takes through a single-ended spacecharge amp with 12AU7 output tube and two through a 30W AC-30 like amp with Marshall BluesBreaker pedal in front of it. Spacecharger is cleaner and it brings clarity to the mix. The guitar is '83 Gibson Challenger, upgraded with $10 noname Chinese pickup.

Just in case someone thinks it's thin, you know...

https://soundcloud.com/sergey-engel/...ration-comes-1

Last edited by engels; 10th August 2014 at 11:12 PM. Reason: html not working
  Reply With Quote
Old 13th February 2018, 04:31 PM   #18
efeemeka is offline efeemeka
diyAudio Member
 
Join Date: Mar 2015
Jazbo8, i have some clips of my otl's whith 12k5 for you replay.

Very good tone and solutións, and pro for audiphone solutións.

:-)

Amplificadores de Valvulas OTL sin Transformador de Salida, Muestras de Sonido.
  Reply With Quote
Old 13th February 2018, 04:39 PM   #19
jazbo8 is offline jazbo8
diyAudio Moderator
 
jazbo8's Avatar
 
Join Date: Jan 2011
Location: In Transient
Interstage transformer ratio, spacecharge tubes in PP
Bravo, they sound very good.
  Reply With Quote
Old 14th February 2018, 04:58 PM   #20
efeemeka is offline efeemeka
diyAudio Member
 
Join Date: Mar 2015
Thanks !

The speaker is one vintage 600 ohms, and it help to good and spaciate sound whit volumetric type of proyection.

Is know the limited power, but very good amp for recording and home/study.

For more power y have one tipe philips biamp whit 2 x el86 an other identical whit 2 EL34, and 5 watts aprox.
  Reply With Quote

Reply


Interstage transformer ratio, spacecharge tubes in PPHide 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
Interstage transformers, tubes, caps, toroids, transistors pabbi1 Swap Meet 4 21st February 2010 10:15 AM
interstage transformer effindi Tubes / Valves 8 10th November 2009 12:51 PM
EF86 - Interstage transformer - EL84 PP AB Joao Pedro Tubes / Valves 9 10th January 2009 05:46 PM
EL84 PP output transformer for 6L6 PP class A engels Tubes / Valves 8 30th May 2007 09:45 AM
Interstage OPT to drive 6V6 pp amplifier Maurizio Tubes / Valves 2 4th December 2006 07:40 PM


New To Site? Need Help?

All times are GMT. The time now is 02:59 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki