# Simple audio signal generator...suggestions



## greco (Jul 15, 2007)

A friend of mine has an old SS amp that has recently stopped working. 
I want to have a look at it to see if there is anything *very obvious *to the eye that could have caused it to stop working.

This is going to be viewed as a project and I fully expect/am very aware that I will have likely have no luck determining the cause.

Obviously, I will test the speaker first as that is easy to accomplish.

I'm considering putting a simple audio signal into the amp's input and poking a few components/joints/etc *with a chopstick.*

Could I use the headphone output from my iPad and an online sine wave generator to create a constant tone into the amp's input as a way of determining any changes while I'm using the chop stick?

Any other SIMPLE approaches to supplying a constant audio signal without have to build a circuit?

I will not be spending hours on this adventure and *SAFETY will be my top priority.*

All comments welcomed. Thanks.


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## Mark Brown (Jan 4, 2022)

I use an app called frequency generator to do this for my car audio. It works well enough. I presume your plan would work well. 
It isn't like you need some ultra high fidelity signal to go poking around in there.

Happy Hunting


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## bzrkrage (Mar 20, 2011)

For your iPad. 
Audio Tech sounds


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## Paul Running (Apr 12, 2020)

At one time I used to use a 1KHz mp3 test tone output from my old mp3 player...in case you don't want to risk your iPad.
Test tones can be downloaded to your mp3 player and output from the headphone jack...the impedance will be low Z out to high Z in but it should not be a problem if you are just doing go, no-go tests...not recommended for performance testing.


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## Doug Gifford (Jun 8, 2019)

I have a cylinder with a battery compartment at one end and an xlr plug at the other. All it does is send a sine tone out the xlr end and into whatever… It's ancient and was given to me by a retiring sound guy, but they may still be available.


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## greco (Jul 15, 2007)

Many thanks for all of the responses.


Paul Running said:


> ...your mp3 player


Unfortunately, I don't have an mp3 player.



Paul Running said:


> in case you don't want to risk your iPad.


The iPad is very old but I'd hate not to have it available or have to buy a new one.
Is using it for this purpose putting it at significant risk. 

Another option I thought of was to directly input an old guitar pickup and gently drag a screwdriver across the pole pieces.
However, this will require the help of Mrs. Greco and her hourly bench fee would bankrupt me.

Any other possible SIMPLE approaches?


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## laristotle (Aug 29, 2019)

greco said:


> Unfortunately, I don't have an mp3 player.


I do. I just have to verify that it works.


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## tomee2 (Feb 27, 2017)

Sine wave from an ipad works, I've done just that to test old amps and speakers. 

You could check for DC voltage at the RCA inputs, which would be very unusual but you never know. Otherwise there should be no harm to the ipad in using it.


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## greco (Jul 15, 2007)

tomee2 said:


> You could check for DC voltage at the RCA inputs, which would be very unusual but you never know.


Sorry, I don't understand this. Could you please explain the significance/ concern further. Thanks

I'm not 100% sure (as the amp arrives this Thursday) but I don't think it has any RCA jacks.

@laristotle has seen this amp and maybe he can remember.


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## Granny Gremlin (Jun 3, 2016)

Just play music off your phone - at 50-60%% volume it's a good match for guitar signal. That's how I signal trace.

Alternatively get out your fuzz pedal and set it to self-oscillate. You can often even tune in to a specific note (run it into a tuner pedal). This will get annoying after a while though. Fuzz Factories are particularly good for this.

Also, in addition to chopstick poking, buy or build yourself a signal probe (rather easy, just need an old multimeter probe or even coathanger wire with some shrink on it for a handle, half an old guitar cable and an aligatror clip - probe to jack tip and aligator clip to sheild/sleeve). Connect the probe's jack to another working amp (or headphone amp , mixer etc), alligator clip to broken amp's chassis. Play signal into the amp (ideally disconnect the speaker and replace it with a dummy load so you can tell what's the amp and what's coming from the probe, or use headphones for the probe - careful with the volume) and touch the probe end to the input jack to make sure it's working (you'll hear the signal coming from the probe amp). Then move down the signal path until you find the point where signal cuts out or gets weird - there's your problem (the last component or solder joint before that dropout/noise/distortion).


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## tomee2 (Feb 27, 2017)

greco said:


> Sorry, I don't understand this. Could you please explain the significance/ concern further. Thanks
> 
> I'm not 100% sure (as the amp arrives this Thursday) but I don't think it has any RCA jacks.
> 
> @laristotle has seen this amp and maybe he can remember.


Sorry I was thinking of old stereo amps with RCA inputs not guitar amps. The test is the same though.
The only concern with using an ipad is the amp might have DC on the input, that maybe would damage the ipad. Maybe. It would be very weird if it did. I would just get the correct mini headphone to big headphone adapter and send the signal from the ipad to the amp using a guitar cable.








Miles Davis through a Peavey Bandit (sounds awful!)


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## Latole (Aug 11, 2020)

Wich amp and model ?
1 /100000 chance to find something with a chopstic









12.03C$ |Function Signal Generator DIY Kit Sine/Triangle/Square Output 1Hz 1MHz Signal Generator Adjustable Frequency Amplitude XR2206|Home Automation Kits| - AliExpress


Smarter Shopping, Better Living! Aliexpress.com




www.aliexpress.com


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## ampaholic (Sep 19, 2006)

I'm way behind everyone else. Still wondering what "stopped working" means.


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## Latole (Aug 11, 2020)

ampaholic said:


> I'm way behind everyone else. Still wondering what "stopped working" means.


Right,
Did he hear a "hisss ' in the speaker ? Full volume ?
No hiss mean no voltage = power supply issue 
OR 
Output transistors dead.
Or issue with speaker wire or speaker


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## tonewoody (Mar 29, 2017)

Looper pedal.


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## greco (Jul 15, 2007)

Sorry, I have been away from the computer all afternoon ...jamming with a friend.

Thanks for all of the comments, suggestions, etc.




Granny Gremlin said:


> Just play music off your phone


My phone only sends and receives phone calls.


tomee2 said:


> Sorry I was thinking of old stereo amps with RCA inputs not guitar amps. The test is the same though.
> The only concern with using an ipad is the amp might have DC on the input, that maybe would damage the ipad. Maybe. It would be very weird if it did. I would just get the correct mini headphone to big headphone adapter and send the signal from the ipad to the amp using a guitar cable.


Thanks for explaining.
@laristotle is looking into putting some tones onto his mp3 player for me.


Latole said:


> Wich amp and model ?
> 1 /100000 chance to find something with a chopstic
> 
> 
> ...


The amp is a Line 6 Studio 110.

1 in 100,000 is much, much better odds than I was giving myself.

I don't want to build a device that I will likely never use again, especially if there are easier ways to accomplish it.
In addition, I am a minimalist and extra stuff drives me crazy.




ampaholic said:


> I'm way behind everyone else. Still wondering what "stopped working" means.


Apparently, it was intermittent and then stopped. That is all I know.


Latole said:


> Right,
> Did he hear a "hisss ' in the speaker ? Full volume ?
> No hiss mean no voltage = power supply issue
> OR
> ...


It could be any of those issues or a 1,000,000 +/- more.



tonewoody said:


> Looper pedal.


Thanks for the suggestion.



Granny Gremlin said:


> Then move down the signal path until you find the point where signal cuts out or gets weird


Unfortunately, I don't know how to follow a signal path.


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## Mark Brown (Jan 4, 2022)

greco said:


> Unfortunately, I don't know how to follow a signal path.


Yes you do, you just don't know it yet. All you do is literally follow the path that the signal takes from the input jack to the speaker. It is as easy as following the wire/circuit. It just sounds like a complicated thing. Don't discourage yourself and give it a go 

I didn't know how to swap car engines... but then I just did it. Turns out I did know how.


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## greco (Jul 15, 2007)

Brunz said:


> Yes you do, you just don't know it yet.


Even the signal path on a pedal schematic or simple tube amp looses me.
The signal appears to have many, many choices regarding which route it takes to get through all of this circuitry to finally get to the speaker.

This is (POSSIBLY) a pic of the amp's electronics/chassis that I found in Google images...


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## Mark Brown (Jan 4, 2022)

greco said:


> Even the signal path on a pedal schematic or simple tube amp looses me.
> The signal appears to have many, many choices regarding which route it takes to get through all of this circuitry to finally get to the speaker.
> 
> This is (POSSIBLY) a pic of the amp's electronics/chassis that I found in Google images...
> View attachment 399238


Well... I still say you can do it lol

But I shouldn't run around making assumptions. I'm just pro blind confidence, don't mind me.


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## greco (Jul 15, 2007)

Doug Gifford said:


> I have a cylinder with a battery compartment at one end and an xlr plug at the other. All it does is send a sine tone out the xlr end and into whatever… It's ancient and was given to me by a retiring sound guy, but they may still be available.


Sounds like (pun is intended) it would be a very cool little device.


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## jb welder (Sep 14, 2010)

Plugging a cord in and touching the end with your thumb is a very simple sound source. 
Any frequency test tone you want can be had on youtube (for recording mp3, etc.).
Sorry to say, but line6 is kind of starting in the wrong end of the pool, if you know what I mean.


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## Granny Gremlin (Jun 3, 2016)

greco said:


> My phone only sends and receives phone calls.
> ...
> Unfortunately, I don't know how to follow a signal path.


Sorry if I missed that earlier, but any consumer level audio device. Blue ray player; the headphone out from yer comp for example. 

Following the signal would be a little tough on that guy I suppose. Was thinking it'd be simpler and not so tight and miniaturised (older). But there are some easy things to check - all the connections for one thing. If it turns on at all (led; some sort of noise) just leave the power connectors alone for the time being. Check out the grey ribbon cables that look like they're soldered to the boards vs disconnectable and the blue one which is is +/- 15 V DC or lower and signal if I'm reading the labels right zoomed in. Poke around the pots or switches - they are the only anchor points supporting their daughter boards, which should be small and light enough - 7 9mm pots, especially if they have the structural reinforcement lugs, spaced that tightly should be fine, but if the thing got knocked around a bit stresses can happen. Also those boards hangin out horizontally from the front top and bottom - can't be sure what's going on with the bottom one, but rigid connectors doubling as the support is a likely problem spot. The top one looks to just be hanging from one end and sagging so that is sus even more.


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## Hammerhands (Dec 19, 2016)

I have a free app called Beeping.









‎BEEPing App - Tone Generator


‎BEEPing App is simple tone generator app that generates tones from 20Hz - 20,000Hz in 4 different wave shapes(sine, triangle, square, and sawtooth). Possible uses for this app: - Annoying your friends, family, coworkers, or anyone really - Learning about sound waves - Testing your device the...



apps.apple.com





I noticed this week that Apex sells a Test Tone Oscillator. Not really cheap, but available locally.









Apex Electronics - Compact Test Tone Oscillator


Apex Electronics - Compact Test Tone Oscillator




www.long-mcquade.com


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## Lincoln (Jun 2, 2008)

how about this?


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## Latole (Aug 11, 2020)

" Apparently, it was intermittent and then stopped. That is all I know."
-greco
*___*
First ; Check input jack ; solder and contacts

No need a signal generator for now.
Signal generator with no schematic and no skill in solid state amp amp repair it's useless


IMO amp have issue in power supply and or power supply rail anywhere.
You have to check and reheat all solders in those circuit.

For a $200 amp ; put it in a garbage or sell it for parts


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## Paul Running (Apr 12, 2020)

Can you provide the model of the amp? Ensure that all the power supply voltages are present at the power supply and remain constant throughout your testing. If a supply is intermittent, the voltage may fluctuate but not necessarily at the supply output...it may happen further down the line. By the look of the image that you provided, the amp is SMT and if it is semi-digital it will have several supplies: may be: +5VDC, +3.3VDC, ±15VDC, ±35+VDC. I always verify the power supply first...if it's intermittent, virtually all the other circuits will present that symptom.


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## Latole (Aug 11, 2020)

Paul Running said:


> Can you provide the model of the amp? Ensure that all the power supply voltages are present at the power supply and remain constant throughout your testing. If a supply is intermittent, the voltage may fluctuate but not necessarily at the supply output...it may happen further down the line. By the look of the image that you provided, the amp is SMT and if it is semi-digital it will have several supplies: may be: +5VDC, +3.3VDC, ±15VDC, ±35+VDC. I always verify the power supply first...if it's intermittent, virtually all the other circuits will present that symptom.



Answer #16 The amp is a Line 6 Studio 110.


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## greco (Jul 15, 2007)

jb welder said:


> Sorry to say, but line6 is kind of starting in the wrong end of the pool, if you know what I mean.


I will be hanging onto the edge of the pool in the deep end for dear life and slowly pulling myself along with my hands. After a few feet I'll likely climb out when I realize this to just too scary to be fun and I will have to gain confidence and learn to swim a bit before attempting something so silly again.


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## Paul Running (Apr 12, 2020)

In the image, check the connectors with pink dot. Sometimes just unplugging and re-seating will clear a fault.


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## greco (Jul 15, 2007)

Thanks again for all of the interest, responses and suggestions.


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## Paul Running (Apr 12, 2020)




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## tonewoody (Mar 29, 2017)

AC voltage safety knowledge is your first priority.

After you decide on your Signal Generator, you might want to look up "Audio Probe". A simple and useful device to follow the audio signal path.

edit: Already suggested by Lincoln... derp. +1 on the Audio Probe...


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## greco (Jul 15, 2007)

Please see post #1 re: Safety



tonewoody said:


> ...follow the audio signal path.


Please see post #16, 17, 18


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## jb welder (Sep 14, 2010)

Here, this should make things way easier.


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## tonewoody (Mar 29, 2017)

greco said:


> Please see post #1 re: Safety
> 
> 
> 
> Please see post #16, 17, 18


I will see myself out...


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## greco (Jul 15, 2007)

jb welder said:


> Here, this should make things way easier.


Thanks! I'm pleased that there are so many colour pics and such detail. 
80 pages!!


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## greco (Jul 15, 2007)

jb welder said:


> Plugging a cord in and touching the end with your thumb is a very simple sound source.


I used this method...Thanks


Paul Running said:


> ....In the image, check the connectors with pink dot. Sometimes just unplugging and re-seating will clear a fault.


I did this...Thanks


jb welder said:


> Here, this should make things way easier.


I read much of this ...Thanks (again)

I also cleaned the input jack.
It appears to be working fine now. 
I have gently bumped it around and tried all of the knobs and various amp settings.
I will try it again a few times.

It seems as though I was VERY lucky. It certainly was a learning experience!

Again, thanks to all for your help, suggestions, comments, support, etc.


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## Rski (Dec 28, 2013)

The simplist signal injector, your finger, solid state amplifiers power amp rails, +/- 60 volts at best, knowing where the coupling paths along the signal chain is essential


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## Marshtech (May 8, 2021)

I use a free App on my Android phone. Simple, perfect.


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