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Old 21st November 2009, 08:31 PM   #11
SY is offline SY  United States
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On its way to you.
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Old 22nd November 2009, 12:32 AM   #12
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If I didn't know better I would swear that Pete has been looking inside my head to see what I need but didn't get around to building myself.

About 3 years ago I got some 7 pin test boards from dsavitsk. I wired up this little test amp with a pair of 6AU6's driving a pair of 6AQ5's that was loosely based on Gary Pimms Tabor. It sounded really nice and I always wanted to build a bigger version. Along came the "red board". This was the bigger version that I wanted to make, and it was already done. I might have made it just a little bit bigger than Pete ever imagined, but other than one incident with an exploded cap, the red board has been rock solid at the 250 watt power level. It has been rocking the house for several hours a day on the past 2 weekends. You really can't turn this one to 10!

I have been using an Audiophile 2496 and WinAudio MLS for amp testing for about 5 years now. My "interface" consists of 4 pots and two load resistors mounted on a piece of perf board. I also use an 8903 so I don't really need level measuring capability. I never got around to making a better interface, so now I won't have to. I'll be ordering a set of parts to build one when they become available, and I promise to build this one according to the directions!

Pete, if you are listening, a PC based curve tracer would be nice. Once the capability for sweeping the operating point is functioning, maybe the sound card interface (or 8903) could be connected up and sweeps of distortion VS operating parameters could be done, and then....... Sorry I woke up from my dream.
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Old 22nd November 2009, 01:47 AM   #13
rknize is offline rknize  United States
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That's a nice piece of equipment Pete. It would be right at home next to my Velleman scope and signal generator...LOL.
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Old 22nd November 2009, 01:48 AM   #14
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Quote:
Originally Posted by tubelab.com View Post
...a PC based curve tracer would be nice.
Someone is working on it:
Tube Curves Tracer

I haven't tried it myself, so can't say how well it works.
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Old 22nd November 2009, 02:24 AM   #15
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Quote:
Someone is working on it: Tube Curves Tracer
This one showed up here about a year ago. It is elegant in its simplicity and the demos I have found on the web shows that it works well for generating vacuum tube curves. It uses rectified but unfiltered line voltage to generate a quasi ramp (half sine) with known characteristics for the plate voltage, and it uses the amplified and rectified sound card output for the grid voltage. The sound card input is used as the A/D converter. Obviously some software is needed to glue it all together.

I thought about building one, but I realized that the software is the most important piece of the puzzle, and modifying this (or any) instrument would require full knowledge of its operation. I would have no problem designing the hardware portion of a conventional curve tracer. I have no knowledge in the area of PC based software, so this project never got started. I haven't had the time to finish the easy projects lately, so I don't even think about the hard ones right now.

Building a project that is well designed by a person who obviously knows what they are doing, that meets my needs is a no brainer. Cranking the red board up till it explodes (literally) and backing up a bit, is just an old habit that I have.
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Old 22nd November 2009, 06:51 PM   #16
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Hi tubelab,

but the software is also available, for free and even in source code, IIRC.

BTW, this tracer was demonstrated by Yves along a lecture on it at last years European Triode Festival.

Regards, Tom Schlangen
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Old 26th November 2009, 04:08 AM   #17
TheGimp is offline TheGimp  United States
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What is a good program to do testing with?

Good - reliable, reasonably accurate, moderately easy to use.

I'd like to get away from two scope probes, a signal generator and multiple test points.
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Old 26th November 2009, 04:25 PM   #18
kevinkr is offline kevinkr  United States
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I think I'll probably be getting one of these.. I posted a somewhat similar, but less fancy design here a couple of years ago, and in the meantime I have managed to break it.. And I haven't really bothered to fix it.

I particularly like the input design which offers the option of floating differential or grounded unbalanced. Nice...

Great job Pete!
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Old 27th November 2009, 07:23 AM   #19
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this is awesome Pete!! wondering if it can be easily used for balanced input if needed simply by lowering the input gain/levels?? I would think so, the reason I ask is although my soundcard (RME9632) is capable of single ended input, I prefer using its balanced inputs. is it possible to use multiple probes at the same time to garner all manner of info from the DUT?? I can have over 10 channels of ADC

I use a MAC, the computer platform has no relevance correct?? other than the significantly lower amount of software for OSX

Last edited by qusp; 27th November 2009 at 07:29 AM.
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Old 6th December 2009, 09:45 PM   #20
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OK, I finally got some of these ready to go. The laser cut panels took a little longer than expected, and I've been gone a lot lately. So there are some available on eBay. More will be coming...

Pete
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