Anode loaded 6080 giving less than unity gain, Why?? - Page 3 - 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 23rd May 2006, 11:45 AM   #21
jeapel is offline jeapel  Canada
diyAudio Member
 
Join Date: Sep 2003
Location: quebec
hi shoog

90ma for bias

don t forget pa max=13 watt (26 watt for one 6080)

and 70% of pa max is better for tube life

what is your idle watt / triode

bye
  Reply With Quote
Old 23rd May 2006, 12:55 PM   #22
Yvesm is offline Yvesm  France
diyAudio Member
 
Yvesm's Avatar
 
Join Date: Jul 2004
Location: Ardeche
Quote:
Originally posted by jlsem
"Please see RDH, pages 199-203."

I swiped this from another thread.

John
Or even;
http://www.audioxpress.com/resource/...ss/ga300ac.pdf
and
http://www.audioxpress.com/resource/...ss/ga400ac.pdf

Yves.
  Reply With Quote
Old 23rd May 2006, 02:37 PM   #23
diyAudio Member
 
Shoog's Avatar
 
Join Date: Aug 2002
Location: Eire
I am running 102mA against 100V plate voltage (taking the 30V bias). This gives me 100x0.1=10W or 20W per valve. It is a little less than one of the suggested operating points on the datasheet.

Shoog
  Reply With Quote
Old 23rd May 2006, 10:07 PM   #24
diyAudio Member
 
Dave Cigna's Avatar
 
Join Date: Oct 2003
Location: Finger Lakes, NY
Quote:
Originally posted by poobah
You are talking about a method for PP analysis though, and I would like to learn more. I'm having trouble following why the impedance changes. You are talking about the effects of primaries driven simultaneously and a non superposition way of looking at the circuit?

If you look at class A PP as a balanced source then it might make sense. jlsem is right; it's not really that simple because rp varies with signal, so they don't make a truly balanced source. But it's a good simplification because it makes the analysis A LOT simpler.

Anyway, consider a 1:1 PP transformer. Put 1000 ohm resistors across each half of the secondary. Since it's a 1:1 transformer the plate to plate load seen at the primary is 2000 ohms.

Now ask yourself the question: what load is seen across each half of the primary? Seems obvious by inspection that it must be 1000 ohms. It's a 1:1 transformer; the same load that's across each half of the secondary must appear across each half of the primary. That's 1/2 the plate to plate load.

If you drive only one side of the primary then you have a 1:2 voltage ratio which is a 1:4 impedance ratio. In that case the load seen would be 1/4 * 2000 ohms = 500 ohms. 1/4 plate to plate.

Incidentally, it's not hard to prove using conservation of energy. Since it's a 1:1 transformer the same currents and voltages must exist at both the primary and secondary. If the tubes each saw 1/4 the plate to plate load in class A then there would be a different amount of power going into the transformer than coming out. In fact, IIRC (it's been a while since I proved it to myself) you'll get different calculated powers depending on whether you use i*v, v^2/R, or i^2*R.

OTOH, when driving only one side (pure class B, if such a thing existed) then the power calculations work out ok at 1/4 plate to plate load.

-- Dave
Attached Images
File Type: gif balancedpp.gif (3.8 KB, 101 views)
  Reply With Quote
Old 24th May 2006, 09:24 AM   #25
diyAudio Member
 
Shoog's Avatar
 
Join Date: Aug 2002
Location: Eire
Thanks for all the information. Another jump on the learning curve.
Heres a related question. Assuming we stay in pure class A PP, what can we expect as max efficiency. Would it be 50%.

Shoog
  Reply With Quote
Old 24th May 2006, 12:19 PM   #26
diyAudio Member
 
Shoog's Avatar
 
Join Date: Aug 2002
Location: Eire
I just wanted to correct some statements I have made.
The drive to the 6080's is 60Vpp which gives aplate output of 55Vpp.
The measurements I stated before were down to problems with I have with interpreting my scope. I apologies for any misunderstanding.

Shoog
  Reply With Quote
Old 24th May 2006, 02:48 PM   #27
poobah is offline poobah  United States
diyAudio Member
 
poobah's Avatar
 
Join Date: Nov 2005
Thanks Dave,

We were really talking apples and oranges... I didn't realize at first they we were talking about an "effective impedance" as a result of a compound analysis rather than a superposition type.

I'm itching to build a PP tube rig... if I can design or purchase OPT's that truely thrill me.

Funny you mention energy calcs... I am always using energy calcs to solve stuff. Crunch tricky stuff in a hurry and avoid all that Simulation and Laplace ****. One of these days I'll fork out for Mathematica and let it crunch instead... in the meantime, spreadsheets...



  Reply With Quote
Old 25th May 2006, 01:02 AM   #28
jlsem is offline jlsem  United States
diyAudio Member
 
jlsem's Avatar
 
Join Date: Jun 2003
Location: Dallas,TX
Quote:
We were really talking apples and oranges... I didn't realize at first they we were talking about an "effective impedance" as a result of a compound analysis rather than a superposition type.
Effective impedance is the same as the impedance seen by each tube in a push-pull scheme, which is the term I used in my post, for which I got hammered. Not apples and oranges.

Nice try,
John
  Reply With Quote
Old 25th May 2006, 03:54 AM   #29
poobah is offline poobah  United States
diyAudio Member
 
poobah's Avatar
 
Join Date: Nov 2005
jlsem,

Thanks...
  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
Heretical Unity Gain line stage PLUS a little gain ? yagas Tubes / Valves 7 24th January 2006 01:30 PM
Unity Gain (AV=1) Zen Amp LS Pass Labs 2 16th September 2004 04:40 AM
Unity Gain Operation (or low gain) Tomo Chip Amps 12 22nd January 2004 01:47 AM
Gain for common anode.... Gunders Tubes / Valves 9 14th February 2003 10:05 PM


New To Site? Need Help?

All times are GMT. The time now is 04:07 AM.


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