free audio tools...... are they worth it?

[Andy Le Blanc]

Ive found a free download called a "Rightmark Audio Analyzer"
its neat little download that uses your computers sound card to do among
other things....... THD...IMD.....freq, responce....and spectrum analysis...

Now I know its not spectraplus....HpW....... or cliowin or tomacsoftware
but it looks ok and its free...... the best part looks to be its reporting feature
so that results can be shared......

it does require a good sound card...... THD % of .003/.001 to be accurate
but if its a usable tool, a hundred or so for a good sound card is a heck of a
lot better than what could be spend for bench tools...

anybody have any experience or comments with software based audio diagnostics?

[VacuumVoodoo]

It depends on how you intend to use it. Rightmark is about the best there is on par with professional $$$ SW.

[Andy Le Blanc]

thank you for the responce. Im hopeing that it will be useful to obtain
distortion figures. Its the one piece of information that I dont have the tool
to measure. Its nice to have a spectrum analyser to "see" distortion products
but I would very much like to have a solid THD figure to fully describe the
"typical operation" of an amplifier. With guitar amps, it is a bit of overkill,
but knowing how the amp colors as gain levels rise would be valuable.

I also think that it would be very nice to post and share real information obtained
from a project in a more valid manner than a sound clip or a subjective or
qualitative observation.

[skyboltone]

I agree Andy. There is one area that I would like to know a lot more about and that is stage distortion at various gain levels. How does the first stage look compared to stage two.....etc. And this is across the board. Trainwrecks, Fender amps, Marshall, Vox. Soup to nuts.

[Andy Le Blanc]

Thats exactly the point. As I continue to research and develop my understanding
of valve circuits, Im continually finding aspects of an amp that need to be more
fully described. Just how is it that that choice of design or bias choice sounds like that and why.

[Merlinb]

Ive found a free download called a "Rightmark Audio Analyzer"
its neat little download that uses your computers sound card to do among
other things....... THD...IMD.....freq, responce....and spectrum analysis...

Wow! I wish I'd know about this sooner! I used to have access to some serieously hot gear at work, but no longer. This looks good enough for home enthusiasts though, cheers!
http://audio.rightmark.org/products/rmaa.shtml

[Andy Le Blanc]

heres a report. just to see if itll be a go. hopefully it will be accessable when posted.

[Andy Le Blanc]

the report is of a common gain stage pre. both sides of a 12ax7 operating
with a shared 100k plate resistor, and a shared 820 ohm cathode resistor
a .1 mf coupling cap.. see the second order harmonic distortion.

[Chappy]

the report is of a common gain stage pre. both sides of a 12ax7 operating
with a shared 100k plate resistor, and a shared 820 ohm cathode resistor
a .1 mf coupling cap.. see the second order harmonic distortion.

Was this report derived from a circuit simulated within the program itself?

As well, how does one go about sampling the high voltage signals within an amplifier and then converting it to a safe useable signal for injecting into the soundcard? Would a simple voltage divider network suffice, or should some sort of isolation device be used?

Steve

[Andy Le Blanc]

the circuit is actually in an old champ carcass, test bed now with a power supply.
bone yard hero. Anyway, the coupling cap at the plate is the "isolation device".
And the 1M volume pot. is the "simple voltage divider", if its needed.
The rest of the control is the computers "audio controls" and the program has
a test signal to judge the levels and whether or not something is clipping.
I have looked around for quite some time, being a cheap skate, for the tools
needed to gather more information from a dynamic tube circuit. bench tools can be really expensive.
Ive had the same worries about smoking the computer too.
But the good thing about modern consumer electronics is that theyre total crap
especially computers.......so...... the $20 yard sale or dumpster trophy yields
damn near free and endless audio diagnostic tools. Ye haaa.

getting beyond that, the results are only as good as the sound card.
the cheap and easy can ony get you to maybe to distortion of .01% at best, when you
really need .001% , the old HI-FI requires distortion levels less than 1%, but
testing with any sort of valid result demands a much better sound card, so
Im hunting for the most economical card with a testable THD of around .001%.

[Chappy]

Andy

Thanks for the quick reply. I'll try your technique with just the coupling cap and the pot, but I will use my old desktop computer first! I'm just looking to use this on guitar amps, so I dont think that the 0.01% distortion resolution will be an issue. I'm not trying to nail precise figures, I just want to see where the distortion is coming from, and how it is affected by adjusting various components.

I've been playing around with this a bit in the digital realm with the trial version of Peavey Revalver III, but I really would like to step up to the real thing and find out exactly what makes them tick.

I've got an 1972 vintage JMP 50W head which sounds quite nice. I'd like to pick it apart with a scope and a distortion analyzer to see exactly when, where, and how it distorts. Hopefully I'll be able to learn enough from it in order to design my own sweet sounding amps.

Steve

[Andy Le Blanc]

I dont blame you at all for mistrusting the hook up, try it first maybe from the wiper of the volume pot.,
after the first gain stage. in your amp.
Im using the rightmark 6.2.1 free download from their web site.
use the mono mode, and the line out (spk) and line in. they have a stereo split.
The program was designed with an intent, sound card etc. but its used by
audio reveiw'ers to test gear.

the mic input on most cheap sound cards is mono, I think, and has a lot more
distortion

the software O-scope that seems to be pretty good is a thing I found on the web
some years back called "visual analyiser 5.5" it works for me so far with out any
change of hook up between the two programs. its a dual trace scope with
a fairly low distortion wave generator, spectrum analyser, itll show phase and
freq. patterns and has a more limited "reporting function".

but thats whats the rightmark program really nice . It generates a report
that has presentations of the THD, frequency responce, etc.

the "VA" does have the capability of makeing an ocillograph which can be moved around as a file
which the rightmark program doesnt do.

Ive been suprised that more in these forums dont post results and think
that any drive towards that end would be very good, itll help many from
getting lost with the subjectivities and generalization that come along for the ride.

[Chappy]

Andy

Thanks again for the pointers. I just realized that I can probably use my relatively inexpensive Line 6 Toneport A/D box as the interface. It will probably give me less added distortion, and if I do screw something up I'll just fry the Toneport, and not the soundcard inside my computer.

Steve