Advice on a function/sweep generator...

[darkmoebius]

I just picked up a pristine Tek 465B 100 MHz scope that looks like it was made yesterday($150), a Fluke 8050A DMM($50), and a Global Specialties 5001 Universal frequency counter($35).

I'm looking to round out my beginner's test equip purchases with a decent function/sweep generator and soldering station.

Besides square, sine, and triangle waves what are the features to look for? What bandwidth range for amp/dac testing? Is sweep important?

I see there are quite a few older HP, Wavetek, and B+K Precision units for sale on eBay. They seem to be going in the $50-100 range for 1Hz - 2 MHz units.

 

[SY]

Sweep is a nice convenience, but normally not necessary. Understand that a function generator will have relatively high distortion, so they're useful for certain types of amp testing (e.g., power out, gain, stability, frequency response) and less so for others (THD).

For distortion testing, you can either build a notch filter (restricts you to a single frequency), use a software/soundcard source, or buy a separate sine-wave-only generator. Or do what I did and find a kind soul who will loan you a distortion analyzer. The software solution has the disadvantage of limited frequency span, but the advantage of features like sweep and tone-burst.

With the basic tools you've got now, you're ready to go into battle!

 

[darkmoebius]

Thanks Sy....

What exactly is sweep used for?

And what kind of bandwidth is best? 0 Hz thru 1 MHz? Or only up to 200 kHz?

I'll probably be getting a function generator in the next few days. And then start collecting parts for a VBIGC.

I've kind of taken the backwards approach to amp building - test equip fiirst, then build an amp. But, I've read through a lot of the archives here and AudioAsylum and whenever a newbie has a problem it always helps to have all the equip to give others a idea of what's going on. In the end, I would just be getting all this stuff anyway.

Besides, it makes me look really official

 

[SY]

Sweep can be a nice backup method to FFT or MLS testing for frequency response when paired with some sort of X-Y recording device. Or it can be a primary method if you don't like using computers, but that's taking the retro concept too far for my tastes.

 

[Mort Caldwell]

I recommend a HP 3310A function generator. It has triangle, sine, square, pulse and ramp waveform outputs, along with a great zero baseline level shift control. I've been using mine since about 1978 and it is a real performer. Freq range is 0.0001 Hz to 5 MHz and cabinet size is about 8 X 5 X 10 inches W,H,D.

Mort Caldwell
West Virginia, USA

 

[darkmoebius]

Hey I got a sweep generator!!!

After a few weeks of getting burned on eBay, I finally got a decent deal.

I picked up a supposedly mint condition Wavetek 134 for $50 - "sine, square, triangular, and sawtooth waveforms with selectable and variable outputs over a dynamic frequency range of 0.2 Hz to 2 MHz. Can be operated as a triggered or gated CW generator and as a continuous or triggered sweep generator. Sweep time of 10 µsec to 100 sec, up to 1000:1 with calibrated control."

The last few weeks they've been going for $75-120.

It hasn't arrived yet, so I'll have to wait and see if it's as nice as the picture. But, the seller does guarantees it's won't be DOA(10 days) and they say they checked it out on their bench scope for output.

I've got a universal counter and the Tek 465B, so I should be able to give it a good checkout as soon as it arrives.

I can't wait to get started on Joe Rasmussen's valve buffered GC. In fact, I was just making up a parts list when your response came in!! BTW, I also got lucky and picked up a nice Metcal PS2E-01 soldering station to replace the rinky-dink 100 watter that I have. Time to finally get off the fence and start slinging solder.