Old Heathkit IG-18 Sine - Square Audio Generator does a good job!

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rock soderstrom

Tour de France
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Oct 14, 2009
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I recently found a HAMEG HM 203-6 on a scrap yard, which surprisingly still works perfectly. After a short honeymoon, I have to say that it takes my little "workshop" to a whole new level. I'm glad to have an analog scope again.

As a signal source for the oscilloscope I have my PC, mobile phone and a horrible China 5$ function generator. None of these are really any fun, so I've been looking around for something more suitable.

HAMEG has produced some interesting devices in this area, but unfortunately they are still quite expensive, large and offer a lot of functions that I probably wouldn't need anyway.

So I looked around on ebay, at first I wanted to buy a tube audio generator because the optical design was soooo nice.:love: Unfortunately I was outbid.

Then I blindly bid on a more modern device and actually won - a Heathkit IG-18 Sine - Square Audio Generator for just around 16€ plus 5€ shipping sounded like a good deal.

1000032879.jpg

Yesterday the device arrived, quite dirty, one adhesive foot missing, some battle scars but otherwise in good condition.

The device has been used and also slightly modified - a predecessor has built in a switchable 2W amplifier to (probably) drive speakers directly. Nice.


Further tests showed that everything was in order, this generator plays perfectly, all values are correct, it's really fun!

Here is one (of the numerous) videos on youtube which explains the device in great detail.





To summarize, I have to say, a top purchase, the IG-18 fits perfectly into my cheapskate setup, that's exactly what I need at the moment.
It's a great source for test signals for checking amp circuits, microphones and quickly measuring transformers.

I like the handling very much, the thing pumps out up to 30V peak-peak as a sine wave. The signal quality is very high for my purposes. I might integrate some more mods, the WWW is full of them.

The first thing I ordered was a Banana-BNC adapter. I might add a 200R position to the internal, switchable 600R termination, we'll see if that makes sense.

I am happy 🥳
 
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I think I had one of those back in the day. IIRC there were several DIY modifications published to reduce distortion and the like.
Yep, right, there are plenty of mods on the internet for this. The device/kit has also been modified by the manufacturer over the years. Some improvements have been adopted.

Here are a few links:

http://www.heathkit.nu/heathkit_nu_IG-18.html
http://www.tronola.com/moorepage/IG-18-1.html
https://www.angelfire.com/electronic/funwithtubes/IG-18_Mod.html

But hey, I don't really need it much better than that for the things I do. 😄
Ha ha, that actually applies to me too. Most of the things I want to do with this generator, are already possible without restrictions. The thing is very practical...
 
I have one and despite doing a lot of the mods, I still can't get the distortion lower than 0.089%.
But hey, I don't really need it much better than that for the things I do. 😄
When I designed the sine wave generator inside the Loftech TS-1 I compromised on around 0.2% THD+N****. I could have made the distortion lower but that would have dramatically increased the settling time. Since I was controlling a 1000:1 frequency range with a single knob, with simultaneous level readout which did not incline customers to be patient.

JR

**** in close either/or listening tests I could hear the 0.2% distortion on LF sine waves where the distortion components were in the midrange, but 0.2% was clean enough for general troubleshooting.
 
FWIW, I have a Leader LAG-120B. 10HZ to 1Mhz, .03%thd. I've had it for 40 years and it works perfectly. I have a reverse RIAA network in it for testing phono preamps and put in RCA jacks for the output for convenience. I think you can find them used fairly cheap, certainly cheaper than a digital one.

Anyone know of a cheap audio sweep generator?
 
Decided to have another tinker with mine and add the constant current mod for Q3 collector.
The distortion is now 0.016% at 1k, 0.023% at 10k, 0.018 at 20k and 0.025 at 100Hz.
These are all unweighted mesurements using a Neutrik ML1 Minilyzer, with the Coarse o/p switch at 10,
and the Fine pot adjusted for +4dBu output level. No load on the terminals (apart from ML1 and 'scope),
but the 600 Ohm switch is in.
Much better! 😄
 
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