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test tone generator S. O. S.
Old 12th September 2007
  #1
Gear Head
 
blue shades's Avatar
 

test tone generator S. O. S.

I'm just about to attempt calibration of a new compressor, which requires use of a test signal generator. I noticed a 'Minirator' which sells at around £200 in the U. K. - well beyond my budget for carrying out a (hopefully) one-off adjustment!
Does anyone know of a sensibly priced alternative option?? Only needs to give me a test signal of + 4 dB to get things going. Maybe some shareware download? (don't know how a software signal generator would work - but these things do seem to exist).

Can anyone help please??
Old 12th September 2007
  #2
Lives for gear
 

Digidesign signal generator?

Does all the tones I need.
Old 12th September 2007
  #3
Lives for gear
 
Jason Poulin's Avatar
 

I use the Nuendo test tone generator.



works like a charm
Old 13th September 2007
  #4
Gear Addict
 
JesseJ's Avatar
 

I'm not trying to be a smartass, but did you try searching on Google?
I typed in "test signal generator" and I got a lot of suggestions. Adding 'freeware' or 'download' pretty much filtered out hardware.

You didn't say Mac or Windows or Linux, but I did find this for windows:
"The ASIO test signal generator"

I hope this helps you!

- Jesse -
Old 13th September 2007
  #5
Gear Head
 
blue shades's Avatar
 

Thanks for the replies, folks!

I did search Google on this one - but the only (hardware) equipment I found in the UK costs around £200 - which is crazy for a (hopefully) one-off excercise!!
I'm not too sure how a software option can work (I did locate a couple of free downloads - but with very little info to distinguish 'the real thing' from related items such as (eg) guitar tuners. [by the way, I'm on P.C.]

I'll certainly follow-up the suggestions - they are hugely appreciated at this end..

All the best

Old 13th September 2007
  #6
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jupiter8's Avatar
 

http://mda.smartelectronix.com/effects.htm
The freeware MDA bundle comes with a tone generator.
Old 19th June 2010
  #7
Gear Nut
Hi Blue Shades,

Did you ever get a suitable recommendation for a simple +4dBu (0VU) analog test tone generator?
Old 19th June 2010
  #8
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miro's Avatar
 

Quote:
Originally Posted by jupiter8 View Post
http://mda.smartelectronix.com/effects.htm
The freeware MDA bundle comes with a tone generator.
that's the one i use! thumbsup

mda rocks!
Old 19th June 2010
  #9
Gear Nut
Quote:
Originally Posted by miro View Post
that's the one i use! thumbsup

mda rocks!
Thanks Miro,

I've got a plugin for test tone generation within my sequencer. The problem is that that is a digital signal in the DAW. This needs to be converted to an analog signal by my D to A convertor which may not be accurately calibrated.
Old 20th June 2010
  #10
Registered User
 

Can't you just output a low-ish tone (100Hz as recommended on here ) and measure the AC voltage on the output and adjust to get 1.23V (+4dBu).

Someone more qualified than me will probably correct me shortly!
Old 20th June 2010
  #11
Gear Addict
 
nbrecording's Avatar
For only £24 check this cable tester/tone generator out:

Behringer CT100 Microprocessor-Controlled Cable Tester | DV247

Old 20th June 2010
  #12
Gear Nut
That looks just the ticket, something simple and cheap!
Old 21st June 2010
  #13
Lives for gear
 
brianroth's Avatar
 

Gentlemen,

While the CT100 box has it's place in my "meter bag" (see sidebar, below), it is NOT a precision piece of gear.

1. It does NOT produce a sine wave, but rather a sort of "filtered" square wave.

2. According to my Fluke 87V multimeter (true RMS, bandwidth to 100 kHz, IIRC), when the switch on the CT100 is set to "+4", I measure 1.343 VAC at either of the frequency choices (1000 Hz or 440 Hz), which translates to +4.775 dBu. I also checked the CT100 output on my ancient Simpson 260 analog multimeter, and after "eyeballing" the meter scale, I also read a too-high voltage....approx 1.26 VAC, or +4.2 dBu. Regardless, the CT100 isn't a precision source if you wanna start splitting dB's! LOL I also don't have a "cheapie" meter to see how badly the non-sine wave affects the voltage, either.

3. A different CT100 may yield different numbers than mine.

Sidebar: Why do I own a CT100???

1. It was an EASY $30 (USD) choice for me....a battery operated gizmo so I can wander around in a studio project and easily "poke" test signals which were SOMEWHAT in the ballpark (level-wise) into whatever signal path I decided to test. I should get a Minerator (spelling?), but the CT100 is great for signal-poking.

2. The "sample and hold" cable testing "mode" of the CT100 caught a few BAD 1/4" and RCA cables which I had soldered together, and then wiggled. Siiigh I am not always perfect when building a cable, and the CT100 test mode found a few intermittents due to my imperfect stripping/soldering of the #&(%$*! cables going into the #()^%$(* non-professional connectors. (Did I mention that I think 1/4" phones and RCAs are junk??? lol)

Best,

Bri
Old 21st June 2010
  #14
Gear Nut
Re: test tone generator S. O. S.

Bri,

Thanks for the warning!
Old 21st June 2010
  #15
I recommend the mda testone too
Old 21st June 2010
  #16
Gear Nut
Quote:
Originally Posted by 4damind View Post
I recommend the mda testone too
4damind,

The mda testone is presumably the plugin. What I'm looking for is an analog test tone with real volts.
Old 21st June 2010
  #17
Lives for gear
 
brianroth's Avatar
 

Shrug no one will spend the money.

Bri
Old 25th June 2010
  #18
Gear Nut
Actually Bri, for simple level calibration of AD convertors, does it really matter whether the Behringer CT100 gives a pure sine wave or not?
Old 26th June 2010
  #19
_gl
Gear Maniac
 
_gl's Avatar
 

re. the CT100 not producing accurate voltage ref tones, the leaflet that comes with it actually mentions that it doesn't (I just bought one).

It explains the output voltage depends on the battery voltage - so Nimh rechargeables (the newer ones that hold their charges longer like Hybrio & Eneloops) should at least give consistent results, as they hold their voltage until they run out. I'm using Duracell rechargeables (same tech) and they work fine.

Good gadget otherwise (surprisingly heavy).
Old 27th June 2010
  #20
Lives for gear
 
brianroth's Avatar
 

Quote:
Originally Posted by amathie View Post
Actually Bri, for simple level calibration of AD convertors, does it really matter whether the Behringer CT100 gives a pure sine wave or not?
Dear Amathie,

You raise an interesting point. In the back of my mind was the fact that inexpensive meters (particularly digital multimeters) are calibrated to display correct AC voltages when they are clean sine waves. All bets are off when attempting to measure waveforms which are far away from a sine. Also, see my footnote, below.

I don't own a cheapie meter to see what voltage it reports from the CT-100, so I can't make any comments. I also cannot say how the metering circuitry of any given A/D converter will behave with something besides a sine wave.

In a studio setup (particularly with multiple devices in a patchbay), it is important that levels be reasonably matched. Hence, having a "gold standard" sine signal reference along with accurate metering is necessary.


Footnote: In addition, inexpensive digital meters are only accurate up to perhaps 400 Hz, the "mains" frequency used in aircraft. Any AC voltage measurements above 400 Hz are typically bogus.

Best,

Bri
Old 27th June 2010
  #21
Lives for gear
 
brianroth's Avatar
 

Quote:
Originally Posted by _gl View Post
re. the CT100 not producing accurate voltage ref tones, the leaflet that comes with it actually mentions that it doesn't (I just bought one).

It explains the output voltage depends on the battery voltage - so Nimh rechargeables (the newer ones that hold their charges longer like Hybrio & Eneloops) should at least give consistent results, as they hold their voltage until they run out. I'm using Duracell rechargeables (same tech) and they work fine.

Good gadget otherwise (surprisingly heavy).
I just re-read the CT100 flyer which is stashed in the carrying box, and indeed it says the levels are not totally accurate. Hehehe..I find it strange that mine reads HIGH with random alkaline batteries of unknown strength!

As I mentioned in an earlier post, I am glad to have the CT100 as part of my kit, since it offers a number of good functions in a small box....and yes, I like the "heft" of the small package.

Best,

Bri
Old 27th June 2010
  #22
_gl
Gear Maniac
 
_gl's Avatar
 

Quote:
Originally Posted by brianroth View Post
I just re-read the CT100 flyer which is stashed in the carrying box, and indeed it says the levels are not totally accurate. Hehehe..I find it strange that mine reads HIGH with random alkaline batteries of unknown strength!
I guess they have accounted for non-rechargables dropping their voltage as they run out, so it would make sense to have the output higher than rated when the batteries are good, else it would drop too low as they gradually run out.

If it helps I have a cheapo multimeter I can try to get a ref later.
Old 27th June 2010
  #23
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brianroth's Avatar
 

Dear gl,

Indeed it would be interesting to "see" your measurements from your CT100.

In "my world", I have always used 1.23 VAC as the voltage for +4dBu (and +4 dBm into 600 Ohms).

123 was easy for me to remember (lol), and it also translates into +4.01 dBu, which is WAY beyond any "hair splitting" that I care to "play with". hehe

Best,

Bri
Old 27th June 2010
  #24
_gl
Gear Maniac
 
_gl's Avatar
 

Well, turns out my meter's lowest AC voltage range is 200V, so the reading has no useful precision. With my rechargables full at 1.375V each, it reads as 0.9V (but interestingly it takes a second or so to climb up to that when first touched).

(EDIT: corrected battery reading)
Old 27th June 2010
  #25
Lives for gear
 
brianroth's Avatar
 

Dear gl,

Indeed, without a readout for lower voltages, your measurements are "suspect"!!!

Best,

Bri
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