John Curl's Blowtorch preamplifier

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#16,001
lumanauw said:
Hi, Xpro,

How about EMU0404USB (completely different from EMU0404)?
Click to expand...

If it uses the same control panel I would not recommend it. My main aggravation with 0404 is its horrible control panel and problems with different programs I've tried. IMHO - loop measurements on 0404 are OK, however to use it for real work requires too much effort and attention. Comparing to that my RME card feels like a proper tool, easy to use, precise, very flexible and dependable.

Alex
 
#16,005
dimitri said:
For my limited knowledge, the first distortion magnifier was used here: Jan Lohstroh and Matti Otala, "An audio power amplifier for ultimate quality requirements." IEEE Transactions on Audio and Electroacoustics, Vol.AU-21, No.6, December 1973, pp. 545 - 551.

Does anybody aware about earlier implementation of this idea?
Click to expand...


Yes, this is a pretty old idea. I first used it in 1983 to make possible the distortion testing of my MOSFET power amp with error correction, and mentioned it in my JAES paper.

Cheers,
Bob
 
#16,006
Joshua_G said:



Thank you, Bob.
Any chance for a detailed schematic?
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Hi Joshua,

Let me see if I can dig something out of my files. The DM was implemented on perf board and the schematics were hand-drawn.

Send me an email.

The pic below shows the front panel layout.

Cheers,
Bob
 

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#16,007
anatech said:

Hi Bob,
Thank you very much for responding. I've got a copy now and I'll be able to try these things out with my equipment. You may have helped me quite a bit here!

-Chris

Edit: I've been looking at the residual output from the THD meter for years. That alone is a huge advantage over simply noting the number.

Edit #2: Bob, I have been watching your site for the pages to be completed. You didn't think anyone actually visited your site, did you? :angel: Anyway, I just checked again to see if I could give Joshua a link and download that information for myself also. No such luck, still under construction in those areas.
Click to expand...


Hi Chris,

Good point about the web site. I'm embarrassed that I have not kept adding material to the web site. Twenty four hours sometimes is just not enough in the day. I should probably spend less time posting on DIYaudio and spend more time putting material up on the site 🙂.

Cheers,
Bob
 
#16,008
andy_c said:


Fortunately, the 0404 USB does not use the dreaded PatchMix (which I hate also).
Click to expand...

I gave up understanding PatchMix a long time ago. Just using the pre-defined templates. The RMAA templates are all you need for measurements.

But then grounding for a single ended connection between the sound card (PC internal) input and the analyzer notched output was something I was never really able to figure out 🙁
 
#16,009
Hi Bob,
Twenty four hours sometimes is just not enough in the day. I should probably spend less time posting on DIYaudio and spend more time putting material up on the site 🙂.
Click to expand...
That might actually be a good idea. We don't want to have you burn out here and become tired of the place. Getting more involved with your interests will also tend to bring more material here. A win-win for everyone, but especially you.

About that 24 hours in a day comment. Yeah. I could easily burn 48 hours every day.

If you don't mind, can you also send a copy of the information to me as well? My email address for large attachments is: bomester at gmail dot com.

Thanks again Bob, Chris
 
#16,010
Joshua_G said:
Concerning scopes.

I just ordered locally the following scope:
http://www.m-r-c.co.il/media/uploads/PDS5022SPEC.PDF
For equivalent to US$434 and with local taxes US$502 plus US$14 shipping.
It has 8 bits vertical resolution and DC accuracy of +/- 5%.

I'm looking for additional PC scope and consider 1 of the following 2:

1. http://www.tiepie.com/downloads/documents/HS4_spec.pdf
With 12 – 16 bit resolution and DC accuracy of 0.2% +/- 10 counts. It costs EURO 648 for the 5 MHz version, which is equivalent to US$840.

2. PicoScope 4224 http://www.picotech.com/picoscope4000-specifications.html
With 12 – 16 bit resolution and accuracy of +/- 1%. It costs abut $823.35.

Any opinions about which may be better choice?
Click to expand...


I did the survey in detail some years ago. It became obvious the big issue is the software. That is where the Picoscope was far better. I have been using the new Picoscope 12 GHz box and its software is good, in some ways more useable than the big Tek sampler scopes.

I have not used the software for any of the current crop but I would look to who wrote it. You should be able to download the software and try it before you commit to any of them.
 
#16,012
Bob Cordell said:



Yes, this is a pretty old idea. I first used it in 1983 to make possible the distortion testing of my MOSFET power amp with error correction, and mentioned it in my JAES paper.

Cheers,
Bob
Click to expand...

I saw once (and should have bought for my collection) an RCA distortion bridge using the cancellation technique. Judging from its construction I would say it was built in the late 1940's or early 1950's.
 
#16,014
syn08 said:


I gave up understanding PatchMix a long time ago. Just using the pre-defined templates. The RMAA templates are all you need for measurements.

But then grounding for a single ended connection between the sound card (PC internal) input and the analyzer notched output was something I was never really able to figure out 🙁
Click to expand...


what about using a battery powered laptop?

JPV



JPV
 
#16,015
anatech said:
Hi Bob,

That might actually be a good idea. We don't want to have you burn out here and become tired of the place. Getting more involved with your interests will also tend to bring more material here. A win-win for everyone, but especially you.

About that 24 hours in a day comment. Yeah. I could easily burn 48 hours every day.

If you don't mind, can you also send a copy of the information to me as well? My email address for large attachments is: bomester at gmail dot com.

Thanks again Bob, Chris
Click to expand...

Hi Chris,

Will do. Thanks for your interest.

48 hours would be great. I've been extremely busy at work. I was in California on business twice in February. In this economy, no less. Sure beats the alternative.

BTW, will anybody here be at the FSI audio show in Montreal the first weekend in April? I'll be there.

Cheers,
Bob
 
#16,016
dimitri said:
For my limited knowledge, the first distortion magnifier was used here: Jan Lohstroh and Matti Otala, "An audio power amplifier for ultimate quality requirements." IEEE Transactions on Audio and Electroacoustics, Vol.AU-21, No.6, December 1973, pp. 545 - 551.

Does anybody aware about earlier implementation of this idea?
Click to expand...


Hi Dimitri,

I remember reading that paper a long time ago, but seem no longer to have it. If you have a copy could you email it to me at audiohead7 at yahoo dot com? I'd like to review what they did.

Thanks,
Bob
 
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