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

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 26th September 2011, 09:38 PM #1 grungeman91 diyAudio Member   Join Date: Aug 2010 Please Reply I am designing an amplifier using this 6L6 datasheet. 6L6-GC pdf, 6L6-GC description, 6L6-GC datasheets, 6L6-GC view ::: ALLDATASHEET ::: The amplifier will be running AB1. The column I am using on the datasheet is for 26.5 Watts. I am trying to use the tube curves to determine the gain of this push pull stage, but none of the curves are based on the 270 V screen voltage. One set of tube curves is based on 250 V of screen voltage, but the operating point doesn't line up due to the screen voltage. Can someone help me figure out the gain of this stage please? It is the missing link for my amp. Nobody replied to my last post earlier. I'd really appreciate someone replying, or is this question too easy to be answered and I'm simply just an idiot?
 26th September 2011, 09:47 PM #2 costis_n   diyAudio Member   Join Date: Aug 2008 I ll reply! 250 to 270 = almost no difference. Just a little more G2 current and a little more power. Proceed as you planned!
grungeman91
diyAudio Member

Join Date: Aug 2010
Quote:
 Originally Posted by costis_n I ll reply! 250 to 270 = almost no difference. Just a little more G2 current and a little more power. Proceed as you planned!
Thank you man. I could not get anyone to answer my question. If wouldn't mind answering one more, for my G2 resistor, would I be using the zero signal screen current and the voltage drop across the G2 resistor to find its value?

Miles Prower
diyAudio Member

Join Date: May 2005
Location: USA
Quote:
 Originally Posted by grungeman91 I am trying to use the tube curves to determine the gain of this push pull stage...
Why make it harder than it needs to be?

P= V^2 / R

V= sqrt(P*R)

V= sqrt(26.5 * 6600)= 418.21Vrms

Vp-p= sqrt(8) * Vrms

Vp-p= sqrt(8) * 418.21= 1182.88Vp-p Across the whole primary

Vi= 45Vp-p

Av= 1182.88 / 45= 26.29 On primary side, across 6K6

If using Rl= 8.0R:

Zn= 6600 / 8= 825 : 1 (Pri : Sec)

Vn= sqrt(Zn)= sqrt(825)= 28.72 : 1 (Pri : Sec)

Av`= 26.29 / 28.72= 0.92 (Across Rl= 8R)
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 27th September 2011, 03:00 AM #6 avincenty   diyAudio Member   Join Date: Jan 2008 Location: Southern California Section 6 of the radiotron designers handbook fourth edition explains how to calculate the unpublished characteristics. You can download from pmillet technical books online. Alfredo
costis_n
diyAudio Member

Join Date: Aug 2008
Quote:
If nobody bothers to reply, sure we did.

 27th September 2011, 07:51 AM #8 aardvarkash10   diyAudio Member     Join Date: Mar 2007 Location: Auckland, NZ patience is a virtue. 24 hours is not an unreasonable amount of time to wait when people (often highly qualified and busy and incredibly knowledgeable people, far better experienced than me) are giving a reply... Impatience also looks whiney. Maybe not in this case, but in others I've noticed __________________ "It may not be easy for some to not hear differences, even if they are not there." - Vacuphile,
 27th September 2011, 08:15 AM #9 revintage diyAudio Member   Join Date: May 2007 Did this spreadsheet a few yeras ago http://www.revintage.se/PPABAMP.xls . For only outputstage gain set PI gain to 1. It is based on loadmatch3-pp-triodes You will arrive at in the ballpark of Miles figures though. To simplify his calculations you can easily make a spreadsheet for that too. Last edited by revintage; 27th September 2011 at 08:17 AM.
 27th September 2011, 02:48 PM #10 kevinkr   diyAudio Moderator     Join Date: Sep 2004 Location: Boston, Massachusetts We don't need three threads on this topic. In the future please bump the existing thread if you are not getting a response. I have merged the single response from the other threads into this one and deleted those threads.. __________________ "To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine

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