Need an Inexpensive Test Tone Oscillator

[soupking]

Okay, my tech has a Neutrik Mini-Rator, it's awesome. It's also $300 to provide a test tone from 100hz - 10k.

I already bought a test tone generator the produced only a 1k signal cuz I'm a fool. Additionally, it doesn't crank out a signal at +4. So, cha-ching, there's $100 down the drain.

I'm online looking at Rolls test tone gear because it's like around $100 and gives a sweeping sine signal. BUT, there's nothing in the online sales specs that says provides +4 db.

Is there anything that anybody can vary that works for tape machine cal purposes that doesn't cost $300-$400? I'd like to stay closer to $100 if that's any kind of reality.

Thanks everybody,
-soup

[JohnRoberts]

Surely there's something cheap or free that works with a computer sound card. Plenty of simple tone sound files on WWW.

JR

[Jidis]

Did you write the manual for my Loftech generator John?

[corworld]

Try this. As long as you have a VU meter to check the sig level you should be ok.

Okkibokki Tone Generator

[manning1]

heres a freebie.

freesound :: view sample :: TestTones.mp3

download cool edit 96.
you can generate test tones.

HammerHead Rhythm Station - Cool Edit 96

[soupking]

Originally Posted by corworld

Try this. As long as you have a VU meter to check the sig level you should be ok.

Okkibokki Tone Generator

I don't know if software tones would work. I have no +4 reference tone. With output ITP levels since my mixer's not very much help, I'd still need a real reference tone.

[Rick Sutton]

Hey Soup,
I've got a Navy surplus sig gen that I used to align machines with. This picture is of one on Ebay right now that is in the same case as mine and is a little fancier. It is $39.99. Built like a tank and probably cost quite a bit when new. I got mine for $35 from a local repair shop when it closed and since I don't use it anymore I'd let it go for the same ($35).
If you want to see a picture of mine let me know and I'll post a snap. The Ebay one looks like a real fair deal also.
Cheers,
Rick

Surplus Ra-Nav Labs Test Signal Generator SG-1168/U - eBay (item 270255811615 end time Jul-21-08 15:14:14 PDT)
You would need to be able to solder up a cable to work with the mil spec connectors. I've done it for mine no problem and would include it.

[DannyMac]

your DAW should be able to provide a test tone at all freq ( what are you using) your sound card should state its output level and output impedance in Ohm's.

[soupking]

Awesome Rick, that looks good to me.

I need something I can go direct in/out to the patchbay, so I don't mind soldering a connector one time to make that happen.

It's just with tape...I can't explain it, but I start to feel like the clock guy in that movie Metropolis being a one man show here with a tape machine. You'd have to be in my shoes I guess.

Adding a laptop output and converter output levels (without needle meters) to my dinky not-so flexible mixer just makes things more of a crap shoot.

Originally Posted by Rick Sutton

Hey Soup,
I've got a Navy surplus sig gen that I used to align machines with. This picture is of one on Ebay right now that is in the same case as mine and is a little fancier. It is $39.99. Built like a tank and probably cost quite a bit when new. I got mine for $35 from a local repair shop when it closed and since I don't use it anymore I'd let it go for the same ($35).
If you want to see a picture of mine let me know and I'll post a snap. The Ebay one looks like a real fair deal also.
Cheers,
Rick

Surplus Ra-Nav Labs Test Signal Generator SG-1168/U - eBay (item 270255811615 end time Jul-21-08 15:14:14 PDT)
You would need to be able to solder up a cable to work with the mil spec connectors. I've done it for mine no problem and would include it.

[soupking]

I just found in the JH24 manual that they used a Krohn Hite 8500 model for signal generation.

Their modern day equivalent is the 1200a. i don't need a top dollar model. But this led me to eBay after Rick mentioned the Navy surplus one. Good thinking Rick.

There's a whole lot of inexpensive options on eBay. Funny, I tried searching earlier and didn't find anything.

[JohnRoberts]

Originally Posted by Jidis

Did you write the manual for my Loftech generator John?

I designed the TS-1 test set and co-authored that book with Larry Blakely. IIRC there were a few errors in the discussion of dB. My excuse is that was almost 30 years ago and I never had an opportunity to revise it.

JR

[Rick Sutton]

Originally Posted by soupking

There's a whole lot of inexpensive options on eBay. Funny, I tried searching earlier and didn't find anything.

I've found quite a few useful items on Ebay like test gear, soldering equip., connectors, tools etc.
Soup, make sure you get an audio range sig gen and not one for radio/tv multi Mhz ranges!

[Jidis]

Originally Posted by JohnRoberts

I designed the TS-1 test set and co-authored that book with Larry Blakely.

I thought I remembered the name on that.

there were a few errors in the discussion of dB

Well, it's a good book nonetheless, and the meter is still alive and kicking. I've put it to good use. Mine's possibly an early one too, as I remember something getting added to the panel later in some pictures I saw.

And Soupking- That thing's a generator and counter/level meter. Very useful if it, or something like it, is still around.

Just grabbed a shot of mine in its own custom made stand (also as old as the Loftech)

[Jidis]

There was a 1U rack version of that TS-1??????

- just saw it on eBay

... now I've gotta go to sleep mad

[AnalogBrain]

Hey SOUP,

I know money is tight right now, but I also have the Neutrik Minirator. It is amazing! Well worth the price. I align my machine all the time with it. I also have its counter part, the Minilyzer. These two devices together make aligning my machine a snap! Really great stuff. Plus, being new, they'll last a while.

Shelling out dough is a B**ch, but I am glad I did.

-Neil

[JohnRoberts]

There was a fine frequency trim added to the TS-1 in a later version (I didn't do). One thing we learned early on is having a 1 Hz resolution frequency counter attached to a one knob sine wave generator that covers a more than 1000:1 range made customers uncomfortable when they couldn't easily dial in exactly 1000 Hz . A bit ironic as comparable signal generators were not accurate to .1%, but the customer is always right.

I had nothing to do with any rack mount version.

JR

[Jidis]

Originally Posted by JohnRoberts

There was a fine frequency trim added to the TS-1 in a later version (I didn't do)

That's what I remembered (an extra knob). That rack one looks like mine, though I can't see what that switch on the right does. Goldline appears to have another rack unit with XLRs on the face, but their TS-1 picture looks just like mine. Seems they've gone up quite a bit in price too, but it was a long-ass time ago. I thought mine was more like 3 or 4 hundred and something. They also have a 16 dollar book called "The Audio Measurement Handbook - How To Make Those Important Audio Measurements". You think that's yours?

BTW- Do you remember any specifics on the dB error in the book or was it no big deal?

One thing I remember wishing mine had for the tape stuff was a switch for some basic preset frequencies. I remember having to use the output of a Tascam 122 in "test" mode to do those 400/10k jumps, but with DAWs around now, it would be a cinch.

Soupking- Sorry for the slightly OT meter discussion, but I guess it's all related if you're shopping and rounding up info anyway.

Take Care,

George

One more PS at John- What would be the easiest way to get a reading on the exact sample rate of two DAWs? One has wordclock on BNC, but the other only provides SPDIF. They're both claiming to be at 96K, but I'm hearing a pitch difference when I bring files home. (there's an analog scope here as well)

[JohnRoberts]

Originally Posted by Jidis

That's what I remembered (an extra knob). That rack one looks like mine, though I can't see what that switch on the right does. Goldline appears to have another rack unit with XLRs on the face, but their TS-1 picture looks just like mine. Seems they've gone up quite a bit in price too, but it was a long-ass time ago. I thought mine was more like 3 or 4 hundred and something. They also have a 16 dollar book called "The Audio Measurement Handbook - How To Make Those Important Audio Measurements". You think that's yours?

BTW- Do you remember any specifics on the dB error in the book or was it no big deal?

One thing I remember wishing mine had for the tape stuff was a switch for some basic preset frequencies. I remember having to use the output of a Tascam 122 in "test" mode to do those 400/10k jumps, but with DAWs around now, it would be a cinch.

Soupking- Sorry for the slightly OT meter discussion, but I guess it's all related if you're shopping and rounding up info anyway.

Take Care,

George

One more PS at John- What would be the easiest way to get a reading on the exact sample rate of two DAWs? One has wordclock on BNC, but the other only provides SPDIF. They're both claiming to be at 96K, but I'm hearing a pitch difference when I bring files home. (there's an analog scope here as well)

I just went back and reread the section on the decibel and it wasn't horrible. I should have pointed out it was specifically intended for power ratios while it is more commonly used for voltage ratios today... There may be some small error in terminology but I didn't see it in a quick read.
-------

Sorry I can't help you with your wordclock questions.

------

The extra switch may have been for an impedance measuring capability. I had that built into the the original TS-1 in combination with a look-up table in the booklet, where you had to look up the dB drop and convert that to ohms. They may have made it a direct readout.

JR

[Jidis]

Thanks for the clarification on the book John.

Yeah, mine has that impedance chart in it. Looks like Goldline sells a "TS2" impedance meter as well now.

I'll look around on the clock thing. I'm guessing if anything, I can just import or generate something at a known rate and see how close it matches on the TS-1.

George

[ulysses]

Soupking,

You can't do any kind of tape deck calibration without something to MEASURE the signal level with. So yo have to have some kind of AC voltmeter, preferably one that reads on a decibel scale. Once you have this, you can use it to measure the output level of a tone generated by your DAW. Adjust the level in the DAW for the reference level you want.

I have an HP 400E analog meter that I rarely use because it's kind of flakey, but it's perfectly suited to this kind of work because it has a big needle that's easy to see from a distance. I also have a Fluke 8050A digital multimeter which will read AC volts on several dB scales. It works great and is accurate across a wide range of frequencies (unlike some lesser meters). The only downside is it takes a little longer to read a digital scale since you have to wait for it to settle down. Both of these meters originally cost more than you want to spend but can be had used for almost nothing.

[Rick Sutton]

Don,
here's a picture of the old Navy signal generator that I have.

[corona blue]

Originally Posted by JohnRoberts

I designed the TS-1 test set and co-authored that book with Larry Blakely. JR

Hello John-

I realize this is an old thread, but I have one of these TS-1's that's in need of calibration. I recently pulled it out of storage have been running it on the bench for a couple of days now, trying to wake up the caps. Unfortunately, the counter will not accurately track the generator's frequencies. Nice unit, well made inside, would like to bring it back to spec. I figure that I will re-cap it first, but just wondering if there was a procedure for calibration? Thought I would ask before diving in. PM me if you wish.

Thanks in advance,

Allen

[JohnRoberts]

Originally Posted by corona blue

Hello John-

I realize this is an old thread, but I have one of these TS-1's that's in need of calibration. I recently pulled it out of storage have been running it on the bench for a couple of days now, trying to wake up the caps. Unfortunately, the counter will not accurately track the generator's frequencies. Nice unit, well made inside, would like to bring it back to spec. I figure that I will re-cap it first, but just wondering if there was a procedure for calibration? Thought I would ask before diving in. PM me if you wish.

Thanks in advance,

Allen

Not a lot of trims IIRC. There was one internal trimpot to adjust the oscillator LF start frequency since the >1000:1 adjustment range with a simple current controlled sine wave generator meant that the LF end might not start at too low of a current thus the trim.

The dB level calibration is actually a user rear panel trim, and there should be a factory calibration notation written on the back near the trim access hole. To restore the TS-1 to factory calibration, turn the internal sine wave generator to max volume at around 1kHz, and adjust the rear trim so dB meter reads the same as the number written on the back. While you can calibrate to other nominal 0VU references using that trim, that will return you to factory settings and be accurate as long as you don't change internal voltage regulators.

That is a pretty old design, but fairly tricky so tired old electrolytic caps could interfere with several circuits.

How is the frequency counter off? It is designed to stop reading at low levels where it could get false readings due to noise. So best case is with oscillator set full volume.

Normally is is counting zero crossings per half second, so it updates twice as fast as counting cycles per second. It also takes it's input from inside the precision rectifier circuit so it is logged already to get a stronger reading at low levels.

After several decades it wouldn't be that easy for me to debug, so have fun. Look for bad solder joints, maybe dried up caps. Some parts are obsolete now so be careful.

JR

[corona blue]

Originally Posted by JohnRoberts

Not a lot of trims IIRC. There was one internal trimpot to adjust the oscillator LF start frequency since the >1000:1 adjustment range with a simple current controlled sine wave generator meant that the LF end might not start at too low of a current thus the trim.

Thanks for the reply, John...

the TS-1's freq counter seems to be off above 3-5kHz. I slowly sweep and with a freqency that I know by ear is around 10kHz, it displays something around 5kHz. When the tone becomes inaudible it displays something around 10kHz... if it's right, my hearing really has fallen off!

Don't suppose you have a schematic tucked away somewhere... (?)

Thanks in advance,

Allen

[JohnRoberts]

I don't recall the exact circuit but if it is under reporting by a factor of two, that could be in the zero crossing detector. If the detector is only reading in one direction you would get 1/2 F.

I published a scanned schemtic to the WWW, a few years ago. I spent about a half hour looking for it yesterday..

OK.. here is a copy somebody else saved. TS1.jpg - 4shared.com - photo sharing - download image

Ok, the section in question is roughly in the middle of the page... three transistor total to double the zero crossing pulse and shape the output for clean counts. If one of the two front end transistors is open circuit or bad, you will only get half the zero crossings so 1/2 Hz count.

good luck.

JR

edit- here's a better copy that I couldn't find before
http://www.proaudiodesignforum.com/f...4&p=4531#p4531

OK, the section is a little more complicated. The opamp in front of it boosts the Vp-p of the log output to drive +/- 1 Vbe harder. That opamp also has a DC input from the log output of the dB meter to cut the freq counter off below -X something dB.

So reading 1/2 freq error could be related to DC operating point of this opamp, or one of two polarity ZC detectors not functional, or..something else.. Like I said, lots going on inside.

JR

[corona blue]

Thanks John-

I will probe around with a meter and see what I find. I think it's more than likely a leaky e'lytic. The unit looks like new inside, no heat scorches anywhere. I think the prognosis is good.

The schematics will make everything a lot easier, thanks so much!

Best,

Allen

[Jim Williams]

Low cost units with a sweep function are available from MCM electronics for around $25.

MCM Electronics: Home and Pro Audio/Video, Security and Test Equipment

[brianroth]

I think Jim was a bit optimistic about the pricing of the MCM generators:

Tenma Compact Audio Generator | 72-490 (72490) | Tenma

Tenma Hand Held Audio Generator | 72-505 (72505) | Tenma

The first one has the entire 20 Hz to 20 kHz range on a single pot, which seems a bit crazy to me, and the frequency range is a bit limited, especially if being used to align an analog tape recorder. Both units also have limited output voltage capabilities.

For the DIY'er, there is this kit:

JE2206: JAMECO BENCHPRO: Education & Hobby

It has a wide frequency range, but again a limited output voltage capability, especially if powered from +/- 6 VDC rails. The Exar chip CAN handle up to +/- 13 VDC which should increase the maximum available output voltage. Of course, you can always add an output buffer operating from higher rails (say, +/- 22) for high output levels. Or, use a THAT Corp "OutSmarts" buffer chip for a balanced output!

Best,

Bri

[JohnRoberts]

wow, that exar 2206 is an old soldier. I didn't know they were still selling those.

IIRC those are not very low distortion. While it may work I would be apprehensive that a couple percent THD, may interfere with tweaking bias for low distortion at HF on a decent tape machine.

I repeat my initial comment, these days it seems you should be able to find digital audio files of high purity sine waves for any number of consumer audio platforms.

One reason I am reluctant to do a modern redesign of the TS-1 is that some cheap software and an IPHONE might cover the same applications.

JR

PS: wrt to 20kHz on one knob, the TS-1 did 30kHz on one knob and it worked reasonably well (IMO) but the fact that there was a frequency counter attached, with one Hz resolution, made the customers crazy trying to tweak it to exact frequencies. You don't want to connect a frequency counter to any of the other inexpensive switched frequency sine wave sources, but the customer is always right so the TS-1 got a fine freq knob (after my involvement in it).

[brianroth]

Dear John,

That ancient Exar can be trimmed down to around 0.5% THD, at least according to the spec sheet.

FWIW, any of the "newer" MRL tapes are recorded with a function generator that Jay McKnight concocted for his application. Hence, the THD isn't stunningly low, but "good enough" for the application.

I like function generators for general purpose applications due to the super-flat frequency response and super-fast settling time. That being said, a function generator isn't useful when attempting to measure THD.

Best,

Bri