#19 biased class A - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

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

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 19th December 2002, 06:52 PM   #1
Joel is offline Joel  United States
diyAudio Member
 
Joel's Avatar
 
Join Date: Oct 2002
Location: Brooklyn, NY
Default #19 biased class A

I can't find any data sheets describing a #19 in class A operation. Only in class B.
I want to use one as a phase inverter. Anyone know what the bias point should be? Or, can I operate it in "zero bias" mode? Now that would make things easier.... is that asking for trouble?
I've seen a 6N7, another class B amp, used in a similar way.
  Reply With Quote
Old 19th December 2002, 07:22 PM   #2
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Default NO SURPRISE THERE.

Joel,

RCA has designed that tube for class B operation.

You have a RCA tube manual on that one?

In class B servive you can bias the grid negative or at 0 V.

I suggest you choose another 2 digit tube.

Ciao,
__________________
Frank
  Reply With Quote
Old 19th December 2002, 07:38 PM   #3
dhaen is offline dhaen  Europe
diyAudio Moderator Emeritus
 
dhaen's Avatar
 
Join Date: Jun 2002
Location: U.K.
So what makes one valve best at class A, and another at class B?
And I don't want the antwoord "because they're designed that way
  Reply With Quote
Old 19th December 2002, 07:43 PM   #4
stigla is offline stigla  Norway
diyAudio Member
 
Join Date: Nov 2001
Location: Trondheim
After taking a quick look at the curves, in the RCA manual, it will be possible to bias it in a normal class A point, say at -3V grid, 140V anode and ~2,5mA of plate current... giving a very approximate mu=25, gm=1mA/V and rp=25k... (just rough calculations)

But, if you then take a look at the -6 grid line, you can see that this tube will be very non-linear in this region of its curves.

As fdegrove say; Its made for class B operation.

Though the grid current at Zero-bias will be minimal, as soon as any signal starts to swing the grid, the grid-current will be a problem.

But with that said, I've got a plan to play with the #19 some day. I'm thinking of trying to make a PP class A2 headphone amplifier of it! Some day...

Bad news if you already have the tubes; Don't use them as phasesplitters.

Stigla
  Reply With Quote
Old 19th December 2002, 07:45 PM   #5
dhaen is offline dhaen  Europe
diyAudio Moderator Emeritus
 
dhaen's Avatar
 
Join Date: Jun 2002
Location: U.K.
The perfect reply.
Thanks stigla.
  Reply With Quote
Old 19th December 2002, 07:47 PM   #6
Joel is offline Joel  United States
diyAudio Member
 
Joel's Avatar
 
Join Date: Oct 2002
Location: Brooklyn, NY
Thanks Stigla. Unfortunately my RCA manuals are later editions, and did not have that transfer curve.
  Reply With Quote
Old 19th December 2002, 07:49 PM   #7
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Default WAAROM ZIJN DE BANANEN KROM?

John,

Tubes are designed for a certain class of operation.

This one has absolutely ugly looking curves.
They wanted the higher mu and messed up the linearity in the process.

They do that by changing the spacing between elements and a dozen other parameters.

Surely you don't use those big Class D devices for audio either?
At least most of them have not been designed for that kind of service.

Full moon maybe?

Ciao,
__________________
Frank
  Reply With Quote
Old 19th December 2002, 08:02 PM   #8
dhaen is offline dhaen  Europe
diyAudio Moderator Emeritus
 
dhaen's Avatar
 
Join Date: Jun 2002
Location: U.K.
Yes the full moon occurs here tonight too. But probably a few 10's of minutes different in time to you.

Yes, I'm aware of the inter-electrode spacing effects, and grid pitch. But I have always been open minded about class and application. After all, some of the best respected devices we use for audio, were not intended for audio at all!

Class D:
Never heard of it being done with valves / tubes.
Done a fair bit of class C in my time. Capacitance and dissapation were the only issues I can think of.
  Reply With Quote
Old 19th December 2002, 08:07 PM   #9
Joel is offline Joel  United States
diyAudio Member
 
Joel's Avatar
 
Join Date: Oct 2002
Location: Brooklyn, NY
Also a "class B" tube would have a tougher grid wire, I do believe.
  Reply With Quote
Old 19th December 2002, 08:09 PM   #10
dhaen is offline dhaen  Europe
diyAudio Moderator Emeritus
 
dhaen's Avatar
 
Join Date: Jun 2002
Location: U.K.
Quote:
Also a "class B" tube would have a tougher grid wire, I do believe
Why Joel?
  Reply With Quote

Reply


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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
<WTA>Tube biased by LED arwan_zoel Tubes / Valves 1 24th October 2008 02:33 PM
Symasym biased for class A Dr_EM Solid State 29 28th July 2008 06:19 PM
The Importance of Being Biased Nelson Pass Pass Labs 74 26th July 2007 01:58 PM
CCS Biased Class A davidallancole Solid State 8 11th February 2006 04:51 PM
ccs biased output device davidallancole Solid State 2 26th November 2005 07:33 PM


New To Site? Need Help?

All times are GMT. The time now is 09:23 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2