Signal Generator

XTRXTR

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I need one that is made for this kind of work. All I see is new unbranded from China or antiques that have worrisome descriptions about operability.

It would be nice to have an output 1/4" jack for guitar cables. Also need low mV output. My old phone is just a bit hard to work with not to mention noisy.

Anyone have some good recommends?
Is this worth it? https://www.ebay.com/itm/133840687272?hash=item1f2986d0a8:g:xCsAAOSweL1hMbpJ

Thanks
 
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myersbw

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There's a PACO 310 unit on eBay from Dragonsurplus. He'll take offers. I've dealt with him a couple years ago when I bought my Tektronix signal generator from him. Good seller and I got a super deal on what appears to be an old school lab unit that works superb for my needs.

For the money, you won't lose much if you even get just a year out of the one you linked to. Also, don't bother looking for a 1/4" jack...you can get an RCA(f) to BNC(m) adapter all day long for cheap. Then just use any RCA-RCA cable and a RCA(f) to 1/4(m) adapter to plug in. That'll work just fine for audio signal injection in the amp input.

Or, this?

https://www.ebay.com/itm/2341696411...bW7ki2HXXJJKjw%3D%3D|ampid:PL_CLK|clp:2047675
 
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Matthews Guitars

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That unit you linked to on ebay will get the job done just fine. You don't need a high precision generator for amp work, just something to get a signal into the amp with that looks like a sine wave when you want a sine wave. And with enough output to overdrive the first stage of the preamp.
 

thetragichero

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i've always just used the 500mv 1khz square wave generated by my tek 453.
not good for tracking down distortion an other such delicate things so i'm working on making a little box to turn it into a sine wave. at 1khz 4x 680r/220nf rc filters (ton of 220nf 50v caps in my spare parts bin) give me a sine wave but it's only 40mv (would be like a weak single coil) and easily loaded down by the scope's probe so i figure a 2x/2.5x op amp stage should be about perfect. have an enclosure from one of my first pedal builds that should hold it nicely
 

Pete Farrington

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An essential task for me is checking OTs, eg winding ratios, relative polarities. A sig gen that can push a volt or more of decent sine wave into an OT primary is very handy, saves having to rig up a solid state power amp to do it.
 

South Park

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The ham radio guys have this stuff to for sale to . Old rack mounted units are great
 

2L man

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An essential task for me is checking OTs, eg winding ratios, relative polarities. A sig gen that can push a volt or more of decent sine wave into an OT primary is very handy, saves having to rig up a solid state power amp to do it.
Do you get correct ratios using that low input? I use 230VAC mains voltage.
 

Pete Farrington

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Yes. I read a post by Chris Merren in which he advised that due the core magnetisation (I think), higher voltage drive was more accurate. But I get the same results with 1V from a sig gen, 50V if driving via a solid state amp, 200V if driving within a valve amp, or 240V mains.
 

KraftyBob

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I just bought this GW Instek 5MHz waveform generator for $70 on FB Marketplace. I don’t have it yet as the seller was in Indiana near my brothers house so he picked it up for me. This is plenty for amp work.

A4E479AC-3181-4F5A-A16F-57991DA54FF5.jpeg

If I didn’t get this I was looking at the Uni-T UTG932. It gets pretty good reviews from the guys over on EEVBlog and it’s on sale right now for $105 at Banggood. If you’re not a fan of that site it’s about $140 on Amazon.

https://usa.banggood.com/UNI-T-UTG9...MI1ZDQ39_58wIVwnxvBB2mIAnlEAQYASABEgIHjPD_BwE

I have a bunch of 1/4” TS connectors and a few 50 ohm BNC scope cables laying around so I’m going to make a cable to plug into the amp.
 

Gene Ballzz

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XTRXTR

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I just bought this GW Instek 5MHz waveform generator for $70 on FB Marketplace. I don’t have it yet as the seller was in Indiana near my brothers house so he picked it up for me. This is plenty for amp work.

View attachment 97193

If I didn’t get this I was looking at the Uni-T UTG932. It gets pretty good reviews from the guys over on EEVBlog and it’s on sale right now for $105 at Banggood. If you’re not a fan of that site it’s about $140 on Amazon.

https://usa.banggood.com/UNI-T-UTG9...MI1ZDQ39_58wIVwnxvBB2mIAnlEAQYASABEgIHjPD_BwE

I have a bunch of 1/4” TS connectors and a few 50 ohm BNC scope cables laying around so I’m going to make a cable to plug into the amp.
I really like that UNI-UTG932, it does some cool stuff. I haven't made a decision yet but it is on the short list. My only concern is how light weight it is and no way to mount the unit unless I modify it. That is not a real problem for me and it is much better than my phone by a long shot.
 

KraftyBob

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I really like that UNI-UTG932, it does some cool stuff. I haven't made a decision yet but it is on the short list. My only concern is how light weight it is and no way to mount the unit unless I modify it. That is not a real problem for me and it is much better than my phone by a long shot.
There's also the UTG-962 which is a 60MHz unit - which you probably already know about. I was looking at the 30MHz simply for the fact that's way more than what you need for amp work and my Oscilloscope is 20MHz.

Let us know what you end up getting.
 

XTRXTR

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I have a question about the output impedance of the generator with regard to providing a signal into OTs.
Most of the generators I have researched have either a 600 Ohm or a 50 Ohm output impedance. I may want to use this signal generator to determine turns ratio etc on some upcoming projects. Do you think the 50 Ohm output with 0-20Vpp can do a better job than a 600 Ohm 0-10V? Many of these specs are not standard between brands and models. But I think an output that can get closer impedance match to 16 Ohm OT secondary is the better choice. Can anyone help me confirm that. 600 Ohm output for line input is better for line level signal but 50 Ohm should work for that as well...right?

I just don't want to burn out the generator pushing a 1 or 10Vpp signal into an OT Secondary.
 

XTRXTR

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Have you considered driving the primary?
I had not considered that. Now that you mention it is mathematically the same I just never considered it.
What is your setup for doing this, what generator do you use and do you always approach it the same?
 

Pete Farrington

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I use an old ITT sig gen with a 50ohm output, or the sig gen output on my usb Picoscope.
I think it’s important that the winding used doesn’t load down or distort the excitation waveform, so consider checking for that.
I read a post by Chris Merren, in which he wrote it was important to use a big signal to push the primary into its normal area of operation (I paraphrase). So I tried using a beefy solid state PA amp to boost up the sig gen to 30Vrms. But I got the exact same result as just using the sig gen direct. Maybe I should’ve put a load onto the secondary, rather than measuring it open circuit.
Ive read another method, to use a LCR meter on the primary, with a resistive load on the secondary. It’s advantage is that it will include the reflected resistance of the secondary winding, which can add a surprising amount, about 0.5k on an RS DeLuxe.
 

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