Scope Question.

SamBooka · November 26th, 2009, 12:04 PM

I am troubleshooting an issue with one of my amps and I noticed something that I "think" is normal but am not sure.

When I put a sine wave on the input of the amp and look at the scope I see a nice sine wave. As I increase the volume I see the amplitude increase. Seems normal to me.

When I get to the point of clipping it is only the top half of the sine wave that is clipping. This is before the power tube. Is this because the tube that is clipping is single ended? It would make sense to me but would like to confirm this.

Happy Turkey day down there.

Drew

sjhusting · November 26th, 2009, 12:25 PM

This is all pretty well described in the Valve Wizard book, chapter 1, which is also available free online here -

http://www.freewebs.com/valvewizard1...Gain_Stage.pdf

steven

SamBooka · November 26th, 2009, 12:48 PM

Wow.. thanks Steven.
I heard about the book before. Looks like a worthwhile addition.
And yes.. the article seems to answer my question.
Thanks

SamBooka · November 26th, 2009, 08:06 PM

I am such a twit.. bought the book when it came out a couple of months ago.. went on the shelf and was forgotten :)

Scott S · November 26th, 2009, 11:54 PM

Heh, at least you found it before accidentally buying another copy -- like I'm prone to do with books and records.

- Scott

sjhusting · November 27th, 2009, 03:27 AM

It is a great book; it's been very useful to me already.

steven

SamBooka · November 27th, 2009, 11:30 AM

Quote:

Originally Posted by Scott S

Heh, at least you found it before accidentally buying another copy -- like I'm prone to do with books and records.

- Scott

I went to see if it was on on amazon and it say in big letters YOU BOUGHT THIS BOOK ON SEPT 23 2009.

It looks like a good book. I am reading the Morantz book now. Will dig into the other one when I am done.

Thin69 · November 27th, 2009, 11:35 AM

Thanks for posting that link, lots of great information on tube preamp design. I noticed that there is additional information on the Valve Wizard site also.

http://www.valvewizard.co.uk/

Super descriptions of the various stages of the tube amplifier including power amp, power supply and lots more.

Very cool indeed!!

sjhusting · November 27th, 2009, 02:35 PM

What I like about Merlin's book, is that it presents just enough math to be useful, but understandable. He presents the 'textbook' cases and then gets into how it is done in guitar amps. Lots of useful circuits. His chapter on the cathodyne inverter alone was worth it to me. The book is packed full of good, useful stuff, easy to understand.

steven

November 26th, 2009, 12:04 PM	#1 (permalink)
SamBooka Tele-Holic Join Date: Apr 2007 Location: Montreal Age: 39 Posts: 630	Scope Question. I am troubleshooting an issue with one of my amps and I noticed something that I "think" is normal but am not sure. When I put a sine wave on the input of the amp and look at the scope I see a nice sine wave. As I increase the volume I see the amplitude increase. Seems normal to me. When I get to the point of clipping it is only the top half of the sine wave that is clipping. This is before the power tube. Is this because the tube that is clipping is single ended? It would make sense to me but would like to confirm this. Happy Turkey day down there. Drew __________________ I used to be DH82c but I changed so the 'copters wont spot me

November 26th, 2009, 12:25 PM	#2 (permalink)
sjhusting Tele-Afflicted Join Date: Jul 2003 Location: Germany Posts: 1,000 16 Photos	This is all pretty well described in the Valve Wizard book, chapter 1, which is also available free online here - http://www.freewebs.com/valvewizard1...Gain_Stage.pdf steven __________________ "When you have to kill a man it costs nothing to be polite" - WSC

November 26th, 2009, 12:48 PM	#3 (permalink)
SamBooka Tele-Holic Join Date: Apr 2007 Location: Montreal Age: 39 Posts: 630	Wow.. thanks Steven. I heard about the book before. Looks like a worthwhile addition. And yes.. the article seems to answer my question. Thanks __________________ I used to be DH82c but I changed so the 'copters wont spot me

November 26th, 2009, 08:06 PM	#4 (permalink)
SamBooka Tele-Holic Join Date: Apr 2007 Location: Montreal Age: 39 Posts: 630	I am such a twit.. bought the book when it came out a couple of months ago.. went on the shelf and was forgotten :) __________________ I used to be DH82c but I changed so the 'copters wont spot me

November 26th, 2009, 11:54 PM	#5 (permalink)
Scott S Friend of Leo's Join Date: Dec 2005 Location: SW CR IA US NA PE Age: 29 Posts: 3,453	Heh, at least you found it before accidentally buying another copy -- like I'm prone to do with books and records. - Scott __________________ "The chorus pedal is God's gift to the untuneable guitar." - Peter Holsapple

November 27th, 2009, 03:27 AM	#6 (permalink)
sjhusting Tele-Afflicted Join Date: Jul 2003 Location: Germany Posts: 1,000 16 Photos	It is a great book; it's been very useful to me already. steven __________________ "When you have to kill a man it costs nothing to be polite" - WSC

November 27th, 2009, 11:35 AM	#8 (permalink)
Thin69 Tele-Meister Join Date: Oct 2009 Location: Teleland USA Posts: 300	Thanks for posting that link, lots of great information on tube preamp design. I noticed that there is additional information on the Valve Wizard site also. http://www.valvewizard.co.uk/ Super descriptions of the various stages of the tube amplifier including power amp, power supply and lots more. Very cool indeed!!

November 27th, 2009, 02:35 PM	#9 (permalink)
sjhusting Tele-Afflicted Join Date: Jul 2003 Location: Germany Posts: 1,000 16 Photos	What I like about Merlin's book, is that it presents just enough math to be useful, but understandable. He presents the 'textbook' cases and then gets into how it is done in guitar amps. Lots of useful circuits. His chapter on the cathodyne inverter alone was worth it to me. The book is packed full of good, useful stuff, easy to understand. steven __________________ "When you have to kill a man it costs nothing to be polite" - WSC

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