Active Electronics Guitar problem

[Rob Reedijk]

Howdy folks. Hope everyone had fun chasing rabbits this weekend.

I have a Musicman Stingray guitar that I like to run through a Guyatone
Tube Overdrive pedal. The Stingray has active electronics. When I
run it into the overdrive pedal and I have the bright switch on the
guitar turned on I have level problems. It seems that the last quarter
turn of the guitar's volume knob actually causes the volume to go down
instead of continuing to go up. This only happens with the bright
switch. Why is this happening? Can I do anything about it?

Other details: The tube overdrive pedal is based on a 12AX7. It is well
built with a true internal power supply as opposed to something with a
wall wart. While it has good headroom on most guitars, the Stingray
can saturate it.

So what's going on here? Is it some loading problem? Should I measure
for something on the output of the guitar?

Thanks for your help.


Rob R.

[Chris Hornbeck]

On Mon, 9 Apr 2007 04:06:02 +0000 (UTC), Rob Reedijk
> wrote:

>
>Howdy folks. Hope everyone had fun chasing rabbits this weekend.
>
>I have a Musicman Stingray guitar that I like to run through a Guyatone
>Tube Overdrive pedal. The Stingray has active electronics. When I
>run it into the overdrive pedal and I have the bright switch on the
>guitar turned on I have level problems. It seems that the last quarter
>turn of the guitar's volume knob actually causes the volume to go down
>instead of continuing to go up. This only happens with the bright
>switch. Why is this happening? Can I do anything about it?

Well, it doesn't go up to 11, does it? There's the problem.


>Other details: The tube overdrive pedal is based on a 12AX7. It is well
>built with a true internal power supply as opposed to something with a
>wall wart. While it has good headroom on most guitars, the Stingray
>can saturate it.
>
>So what's going on here? Is it some loading problem? Should I measure
>for something on the output of the guitar?

No, just turn everything else up enough to compensate. And tell the
drummer to turn down a little.

All the best fortune,
(Great Easter post; thanks!)

Chris Hornbeck
"Oh, life is a glorious cycle of song,
A medley of extemporanea;
And love is a thing that can never go wrong;
and I am Marie of Roumania."
- Dorothy Parker

[Rob Reedijk]

Chris Hornbeck > wrote:
> On Mon, 9 Apr 2007 04:06:02 +0000 (UTC), Rob Reedijk
> > wrote:

>>I have a Musicman Stingray guitar that I like to run through a Guyatone
>>Tube Overdrive pedal. The Stingray has active electronics. When I
>>run it into the overdrive pedal and I have the bright switch on the
>>guitar turned on I have level problems. It seems that the last quarter
>>turn of the guitar's volume knob actually causes the volume to go down
>>instead of continuing to go up. This only happens with the bright
>>switch. Why is this happening? Can I do anything about it?

> Well, it doesn't go up to 11, does it? There's the problem.

>>Other details: The tube overdrive pedal is based on a 12AX7. It is well
>>built with a true internal power supply as opposed to something with a
>>wall wart. While it has good headroom on most guitars, the Stingray
>>can saturate it.
>>
>>So what's going on here? Is it some loading problem? Should I measure
>>for something on the output of the guitar?

> No, just turn everything else up enough to compensate. And tell the
> drummer to turn down a little.

Thanks Chris. I don't think you understand. When the volume on the
guitar is turned 3/4 of the way up, it is at its loudest. If I continue
to turn the volume knob up on the guitar it actually causes the output
level to go down.

Maybe Scott knows. It's some sort of a problem with loading, right?
While the voltage maybe increasing is the output impedance going down?

The schematic for a sister unit to the tube pedal is
http://www.geofex.com/FX_images/westbury.gif
The input stage is likely the same.

The electronics on the guitar are a bit of a mystery---it might be potted.
But here is a wiring diagram which doesn't have the all important
potted circuit board
http://home.swbell.net/mellis99/stingrayschematic.jpg.

Scott? Anyone?

Rob R.

[Mark]

On Apr 9, 10:41 am, Rob Reedijk > wrote:
> Chris Hornbeck > wrote:
> > On Mon, 9 Apr 2007 04:06:02 +0000 (UTC), Rob Reedijk
> > > wrote:
> >>I have a Musicman Stingray guitar that I like to run through a Guyatone
> >>Tube Overdrive pedal. The Stingray has active electronics. When I
> >>run it into the overdrive pedal and I have the bright switch on the
> >>guitar turned on I have level problems. It seems that the last quarter
> >>turn of the guitar's volume knob actually causes the volume to go down
> >>instead of continuing to go up. This only happens with the bright
> >>switch. Why is this happening? Can I do anything about it?
> > Well, it doesn't go up to 11, does it? There's the problem.
> >>Other details: The tube overdrive pedal is based on a 12AX7. It is well
> >>built with a true internal power supply as opposed to something with a
> >>wall wart. While it has good headroom on most guitars, the Stingray
> >>can saturate it.
>
> >>So what's going on here? Is it some loading problem? Should I measure
> >>for something on the output of the guitar?
> > No, just turn everything else up enough to compensate. And tell the
> > drummer to turn down a little.
>
> Thanks Chris. I don't think you understand. When the volume on the
> guitar is turned 3/4 of the way up, it is at its loudest. If I continue
> to turn the volume knob up on the guitar it actually causes the output
> level to go down.
>
> Maybe Scott knows. It's some sort of a problem with loading, right?
> While the voltage maybe increasing is the output impedance going down?
>
> The schematic for a sister unit to the tube pedal ishttp://www.geofex.com/FX_images/westbury.gif
> The input stage is likely the same.
>
> The electronics on the guitar are a bit of a mystery---it might be potted.
> But here is a wiring diagram which doesn't have the all important
> potted circuit boardhttp://home.swbell.net/mellis99/stingrayschematic.jpg.
>
> Scott? Anyone?
>
> Rob R.- Hide quoted text -
>
> - Show quoted text -

see the diagram where it shows the revision of adding a 1Kohm
"protection resistor"?. Does yours have that?
You may have a DC bias problem, you may try adding a DC blocking cap
in series with the output i.e. where the 1K protection resistor is
shown.... try 1 uF.

Mark

[Rob Reedijk]

Mark > wrote:

> see the diagram where it shows the revision of adding a 1Kohm
> "protection resistor"?. Does yours have that?
> You may have a DC bias problem, you may try adding a DC blocking cap
> in series with the output i.e. where the 1K protection resistor is
> shown.... try 1 uF.

No, it does not have the 1K protection resistor. What does this resistor
do?

Rob R.

[Meindert Sprang]

"Rob Reedijk" > wrote in message
...
> Mark > wrote:
>
> > see the diagram where it shows the revision of adding a 1Kohm
> > "protection resistor"?. Does yours have that?
> > You may have a DC bias problem, you may try adding a DC blocking cap
> > in series with the output i.e. where the 1K protection resistor is
> > shown.... try 1 uF.
>
> No, it does not have the 1K protection resistor. What does this resistor
> do?

It would protect the output stage against a short circuit on the jack. But
it will not influence the signal strength when looking into a 1M guitar amp
input. Chances are your active guitar outputs a much higher level than a
bare pickup and therefore overdrives the tube distortion.

Meindert

[Mark]

On Apr 9, 7:39 pm, Rob Reedijk > wrote:
> Mark > wrote:
> > see the diagram where it shows the revision of adding a 1Kohm
> > "protection resistor"?. Does yours have that?
> > You may have a DC bias problem, you may try adding a DC blocking cap
> > in series with the output i.e. where the 1K protection resistor is
> > shown.... try 1 uF.
>
> No, it does not have the 1K protection resistor. What does this resistor
> do?
>
> Rob R.

I'm thinking you also might have an oscillation problem where the
electronics break into a high frequency oscillation that you can't
hear... Try redressing the wores, in there, keep the input wres away
fomr the output wires, if it makes any change when you move these
wires around. let us know, then try a 100pF cap across the output to
ground, put is right at the output pot across the 2 outside
terminals. If you had a scope it would be much easier to
troubleshoot.

Mark

[Chris Hornbeck]

On Mon, 9 Apr 2007 14:41:43 +0000 (UTC), Rob Reedijk
> wrote:

>Thanks Chris. I don't think you understand. When the volume on the
>guitar is turned 3/4 of the way up, it is at its loudest. If I continue
>to turn the volume knob up on the guitar it actually causes the output
>level to go down.

Is this a practical or an esthetic problem? Are you really
complaining that your guitar pedal is distorting? Jimi's
spinning in his grave.

Everything compresses when overloaded; all mic's, all
electronics, all storage media, all speakers, even air,
and especially the most amazing compressor of all, our
own hearing, which compresses seven orders of magnitude
of sound pressure into something useable, all PFM.

In electronics, overload typically also causes bias
shifts and/or other bad effects. Solution: don't do it.

All good fortune,

Chris Hornbeck
"Oh, life is a glorious cycle of song,
A medley of extemporanea;
And love is a thing that can never go wrong;
and I am Marie of Roumania."
- Dorothy Parker

[Rob Reedijk]

No no no! You're not listening. Of course it's distorting---it's a
distortion pedal. The point is that my head room peaks at about when the
knob is turned 3/4 of the way up. Then it GOES DOWN. TURNING UP THE
VOLUME LOWERS THE VOLUME WHEN IT SHOULD either do nothing (because you
have reached the limits of headroom) or continue to go up. KNOB TURNS
UP --- VOLUME/HEADROOM ACTUALLY GOES DOWN.

I think it's a loading thing.

But gee thanks for the explanation of compression---can you explain
limiting and saturation to me next time?

Jimi spins in his grave everytime engineers refuse to help a
musician with a legitimate problem choosing instead to tell them,
"There is no problem, you're just doing it wrong."

Rob R.

Chris Hornbeck > wrote:
> On Mon, 9 Apr 2007 14:41:43 +0000 (UTC), Rob Reedijk
> > wrote:

>>Thanks Chris. I don't think you understand. When the volume on the
>>guitar is turned 3/4 of the way up, it is at its loudest. If I continue
>>to turn the volume knob up on the guitar it actually causes the output
>>level to go down.

> Is this a practical or an esthetic problem? Are you really
> complaining that your guitar pedal is distorting? Jimi's
> spinning in his grave.

> Everything compresses when overloaded; all mic's, all
> electronics, all storage media, all speakers, even air,
> and especially the most amazing compressor of all, our
> own hearing, which compresses seven orders of magnitude
> of sound pressure into something useable, all PFM.

> In electronics, overload typically also causes bias
> shifts and/or other bad effects. Solution: don't do it.

> All good fortune,

[hank alrich]

Rob Reedijk wrote:

> No no no! You're not listening. Of course it's distorting---it's a
> distortion pedal. The point is that my head room peaks at about when the
> knob is turned 3/4 of the way up. Then it GOES DOWN. TURNING UP THE
> VOLUME LOWERS THE VOLUME WHEN IT SHOULD either do nothing (because you
> have reached the limits of headroom) or continue to go up. KNOB TURNS
> UP --- VOLUME/HEADROOM ACTUALLY GOES DOWN.
>
> I think it's a loading thing.

Any chance the pots wearing out at the top end of its range?

--
ha
Iraq is Arabic for Vietnam

[Meindert Sprang]

"Rob Reedijk" > wrote in message
...
> I think it's a loading thing.

Why?

> Jimi spins in his grave everytime engineers refuse to help a
> musician with a legitimate problem choosing instead to tell them,
> "There is no problem, you're just doing it wrong."

Well, the real engineers' solution would be to hook up an oscilloscope to
the output of your guitar and _observe/measure_ the signal, unloaded instead
of thinking./guessing what could be wrong. Or hook it up to a mixer with
enough headroom to be able to make a reasonable good measurement. Since your
guitar has an acive output, it might very well be connected to the line
input of a mixer.

Only by measuring properly you can really make a funded decision of what is
happening, beit clipping or a real decrease in output. It will also tell you
whether your output might be at a too high level for a quitar amp.

Meindert

[Rob Reedijk]

hank alrich > wrote:
> Rob Reedijk wrote:

>> No no no! You're not listening. Of course it's distorting---it's a
>> distortion pedal. The point is that my head room peaks at about when the
>> knob is turned 3/4 of the way up. Then it GOES DOWN. TURNING UP THE
>> VOLUME LOWERS THE VOLUME WHEN IT SHOULD either do nothing (because you
>> have reached the limits of headroom) or continue to go up. KNOB TURNS
>> UP --- VOLUME/HEADROOM ACTUALLY GOES DOWN.
>>
>> I think it's a loading thing.

> Any chance the pots wearing out at the top end of its range?

Hi Hank. Good suggestion! But as I have said, it only happens when the
bright switch is on. With the bright switch on the output of the guitar
goes down when turning the last 1/4 of the sweep. Without the bright
switch it functions normally---i.e. continues to go up or reaches
saturation depending on the headroom of whatever input stage I am
using.

Rob R.

[Rob Reedijk]

Meindert Sprang > wrote:
> "Rob Reedijk" > wrote in message
> ...
>> I think it's a loading thing.

> Why?

>> Jimi spins in his grave everytime engineers refuse to help a
>> musician with a legitimate problem choosing instead to tell them,
>> "There is no problem, you're just doing it wrong."

> Well, the real engineers' solution would be to hook up an oscilloscope to
> the output of your guitar and _observe/measure_ the signal, unloaded instead
> of thinking./guessing what could be wrong. Or hook it up to a mixer with
> enough headroom to be able to make a reasonable good measurement. Since your
> guitar has an acive output, it might very well be connected to the line
> input of a mixer.

> Only by measuring properly you can really make a funded decision of what is
> happening, beit clipping or a real decrease in output. It will also tell you
> whether your output might be at a too high level for a quitar amp.

Thanks Meindert

I guess I have to say it again----this only happens with one specific
device, a 12AX7 based distortion pedal.

So it won't show up on mixer. It won't show up on a scope unless the
guitar is connected to the pedals. It just won't.

I can tell you without measuring the output is going down. It is. I
don't need to measure it. Imagine you are driving a car. You have
are accelerating and then as you continue to push down the gas, your
car goes slower--it's that obvious. I am not imagining it. I am not
being confused by perceived "loudness" due to saturation. It is very
obvious. I could hook up my scope but I know what it will show. Some
of us guitarists actually listen to what is coming out and have the
ability detect headroom changes.

Rob R.

[Rob Reedijk]

Thanks,

I did consider this but have already tried changing the battery.

Sounds like it could be a similar situation since you had an issue with
your presence control which is not unlike my bright switch.

It is a good clue...

Thanks,

Rob

spud > wrote:
> This used to happen to my active EMG's. It usually meant the battery
> was going dead. It would get more pronounced until there wasn't any
> output. That is, the loud spot on the volume control would get further
> down the sweep of the control if that makes any sense.
> After a few years of this the battery started lasting only a short
> time. I removed the presence (eq) control and now the guitar sounds
> great with more or less equal volume on all pu arrangements and the
> battery lasts forever. Just something to think about, s.

> On Mon, 9 Apr 2007 04:06:02 +0000 (UTC), Rob Reedijk
> > wrote:

>>
>>Howdy folks. Hope everyone had fun chasing rabbits this weekend.
>>
>>I have a Musicman Stingray guitar that I like to run through a Guyatone
>>Tube Overdrive pedal. The Stingray has active electronics. When I
>>run it into the overdrive pedal and I have the bright switch on the
>>guitar turned on I have level problems. It seems that the last quarter
>>turn of the guitar's volume knob actually causes the volume to go down
>>instead of continuing to go up. This only happens with the bright
>>switch. Why is this happening? Can I do anything about it?
>>
>>Other details: The tube overdrive pedal is based on a 12AX7. It is well
>>built with a true internal power supply as opposed to something with a
>>wall wart. While it has good headroom on most guitars, the Stingray
>>can saturate it.
>>
>>So what's going on here? Is it some loading problem? Should I measure
>>for something on the output of the guitar?
>>
>>Thanks for your help.
>>
>>
>>Rob R.

[Meindert Sprang]

"Rob Reedijk" > wrote in message
...
>
> I guess I have to say it again----this only happens with one specific
> device, a 12AX7 based distortion pedal.
>
> So it won't show up on mixer. It won't show up on a scope unless the
> guitar is connected to the pedals. It just won't.

But a mixer can stand a lot more signal than the pedal I suppose, since the
pedal is expecting pickup levels while the mixer expects line levels.
That again raises the question: isn't the level simply too high on that
guitar?

IMO it cannot be a loading problem because, judging from that schematic, the
input resistance of the pedal is 1Mohm.

Meindert

[Scott Dorsey]

Rob Reedijk > wrote:
>
>No no no! You're not listening. Of course it's distorting---it's a
>distortion pedal. The point is that my head room peaks at about when the
>knob is turned 3/4 of the way up. Then it GOES DOWN. TURNING UP THE
>VOLUME LOWERS THE VOLUME WHEN IT SHOULD either do nothing (because you
>have reached the limits of headroom) or continue to go up. KNOB TURNS
>UP --- VOLUME/HEADROOM ACTUALLY GOES DOWN.

It's either a loading thing, or it's breaking out into oscillation (maybe
because of loading). Stick a barrel connector with a 10K resistor between
the two boxes and see if the problem persists.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Chris Hornbeck]

On Wed, 11 Apr 2007 04:12:45 +0000 (UTC), Rob Reedijk
> wrote:

>No no no! You're not listening. Of course it's distorting---it's a
>distortion pedal. The point is that my head room peaks at about when the
>knob is turned 3/4 of the way up. Then it GOES DOWN. TURNING UP THE
>VOLUME LOWERS THE VOLUME WHEN IT SHOULD either do nothing (because you
>have reached the limits of headroom) or continue to go up. KNOB TURNS
>UP --- VOLUME/HEADROOM ACTUALLY GOES DOWN.

I'm listening, but my attempts at small jokes are apparently
inappropriate. Sorry.

>I think it's a loading thing.

Not so much.


>But gee thanks for the explanation of compression---can you explain
>limiting and saturation to me next time?
>
>Jimi spins in his grave everytime engineers refuse to help a
>musician with a legitimate problem choosing instead to tell them,
>"There is no problem, you're just doing it wrong."

There is a problem, but you can't fix it. It's designed in.
You're clipping an amplifying stage or something that passes
for one in a guitar pedal ferchrissakes, biases are shifting,
and gain is lowering. If it bothers you so much, don't do it.
Really couldn't be simpler.

I'm really sorry to appear blunt, but you have two obvious
solutions, to adapt to this little whizbang, or to learn how
to modify it.

All good fortune either way,

Chris Hornbeck

[Laurence Payne]

On Mon, 9 Apr 2007 14:41:43 +0000 (UTC), Rob Reedijk
> wrote:

>I don't think you understand. When the volume on the
>guitar is turned 3/4 of the way up, it is at its loudest. If I continue
>to turn the volume knob up on the guitar it actually causes the output
>level to go down.

Yeah, this can happen. So don't turn past 3/4.

[Meindert Sprang]

"Laurence Payne" <lpayne1NOSPAM@dslDOTpipexDOTcom> wrote in message
...
> On Mon, 9 Apr 2007 14:41:43 +0000 (UTC), Rob Reedijk
> > wrote:
>
> >I don't think you understand. When the volume on the
> >guitar is turned 3/4 of the way up, it is at its loudest. If I continue
> >to turn the volume knob up on the guitar it actually causes the output
> >level to go down.
>
> Yeah, this can happen. So don't turn past 3/4.

Apparently the output voltage of that guitar is so high that it exceeds the
bias voltage of the tube in the pedal, and therefore shifting the bias
setting of the tubes.

Meindert

[Rob Reedijk]

I am starting to rethink this and wonder if there is a flaw in the active
circuit. As I have been using the guitar for several hours a day for the
last few weeks I have come to learn that this problem is in fact
intermittent. Furhtermore, when I use the guitar at one specific location,
I always get this white noise washing effect (sort of like making
a shushing noise with your mouth and open and close your lips).

The problem is always associated with the bright switch.

A bad cap? Problem is that Musicman sealed their circuits in some black
substance.

I guess I could just avoid the bright switch.

Thanks to all of you who helped with your suggestions.

Rob R.

[Les Cargill]

Rob Reedijk wrote:

> Thanks,
>
> I did consider this but have already tried changing the battery.
>
> Sounds like it could be a similar situation since you had an issue with
> your presence control which is not unlike my bright switch.
>
> It is a good clue...
>
> Thanks,
>
> Rob
>

Do you own a volume pedal? What happens when you insert the volume
pedal between the guitar and the fuzzbox?

All the switches and pots on the diagram end up in the circuit
board, so there's not a simple way to tell what they mean.

<snip>

--
Les Cargill

[Rob Reedijk]

Rob Reedijk > wrote:

> Howdy folks. Hope everyone had fun chasing rabbits this weekend.

> I have a Musicman Stingray guitar that I like to run through a Guyatone
> Tube Overdrive pedal. The Stingray has active electronics. When I
> run it into the overdrive pedal and I have the bright switch on the
> guitar turned on I have level problems. It seems that the last quarter
> turn of the guitar's volume knob actually causes the volume to go down
> instead of continuing to go up. This only happens with the bright
> switch. Why is this happening? Can I do anything about it?

> Other details: The tube overdrive pedal is based on a 12AX7. It is well
> built with a true internal power supply as opposed to something with a
> wall wart. While it has good headroom on most guitars, the Stingray
> can saturate it.

> So what's going on here? Is it some loading problem? Should I measure
> for something on the output of the guitar?

> Thanks for your help.


> Rob R.


Upon the suggestion of a Pre EB Musicman tech (well, one or two of you
suggested too) I installed the 1K "protection resistor" that you can see
in the referenced schematics for the guitar---this resistor goes in
line with the output of the guitar. This appears to have solved my
problems. Over the last month I had noticed the problems went beyond
how the guitar interacted with the tube pedal---overall I would say
that the output could be considered as a bit unstable and usually worse
when the bright switch was kicked in.

I have also done the same with a Sabre guitar which has also become a bit
more stable.

Thanks for all your suggestions.

Rob R.