Quote from: Roly on June 29, 2012, 10:34:26 AM
Unless you happen to use cans a lot, why would you expect a mono amp to have a stereo headphone socket?  As it happens, as a soundie I do use cans a fair bit and have several pairs kicking around, so I'm well aware that they are normally stereo.

I would expect the headphone out to be a stereo jack because 99% of the headphones are stereo, and plugging stereo phones into a mono jack just give you one side working.

So, you send the same signal to L & R on the stereo jack and then you get sound to both sides.

Maybe a really old amp would have a mono phone jack (back when most home audio was still mono), but I don't recall seeing a mono jack for phones on equipment made since the mid 70s.

Quote from: QReuCk on June 29, 2012, 05:56:32 AM
Well, only stereo 1/4 cable I have currently is the amplifier side of my footswitch cable. Not ideal as it splits it into 2 distinct cables with mono jacks at each end, but that should do the trick for testing purpose.

That's actually good, as the second amp has a mono input jack, so you just want one side from the headphone jack anyway.

Quote from: J M Fahey on June 21, 2012, 12:32:39 PM
Nowadays vey little people knows what I'm talking about.
Not usual finding guys with the same kind of experiences I've had, lots of Forums filled with people with *strong* (borrowed) opinions but little to back them with.

I think you would be pleasantly surprised with the public as a whole (not to be confused with those on internet forums).

Forums, especially "music" forums can be very selective. But go to other forums and try the off-topic areas and I think you'll find a different perspective.

The real trick is for the now older generations (I'm only 40 mind you) to ensure the younger generations experience real music and gain an appreciation. And that means taking time out from other activities and going to the symphony, finding a chamber performance, a concert on a real organ, etc. Start them early. Drag them kicking if we must. It will sink in.

I was forced to listen to/ perform a lot of music I didn't like. Then years later I was able to appreciate it. Had I not be forced I don't know that I'd have ever made the leap myself.


Now, where did oleskool run off too?
What are your current plans?
Did you buy that Peavey?

Quote from: Roly on June 21, 2012, 07:23:18 AM
So yeah, when I'm talking fundamental bass I'm thinking of a bunch of orchestral basses, or the biggest Diapason on a big pipe organ - that's the sort of chest-vibrating bottom end that a bass guitarists should have at their disposal.

I think that's what any bass player really wants. Bass should be felt as much (more?) as heard.
And on the very bottom end the human ear doesn't hear the fundamental very well either. While the nominal is 20Hz, that best case in a lab. The low A on a piano is 27.5Hz (just below a 16' C pipe), compared to the 41.2Hz E on a 4 string bass. Tuba parts regularly go down to 24.5Hz G, and at least one piece has 16.3Hz C (32' pipe).

Reproducing anything below 50Hz just takes a lot of air movement, and really needs to be felt.
That's just not easy, never mind trying to do it with small drivers and low power.

Quote from: Roly on June 20, 2012, 08:07:52 AM
Interesting @STDog, didn't know that.

A lot of horn players don't understand it either. They just know those false partials sound bad.

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Do people still go to orchestral performances any more?  I was sorta thinking of massed German basses when I wrote that, but I thought that most readers wouldn't know what I was talking about.  In my misspent youth I used to go around playing pipe organs and 32 foot Diapasons spoil you for real bass.

Some do. Not nearly enough.
Speaking of the land down under, I'd really like to go to the Sidney Opera House and hear that organ.

In the States you can always find a good college marching band on Saturday during football season. That's the best place to find lots of sousaphones.
Catch them practicing, inside, for the best effect

And drum corps is still pretty good, though the switch to Bb horns has hurt the bass. The old horns in G have/had a lot more punch.

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Because the replaced fundamental is all in the mind you could actually call it wishful thinking.    I was talking to a techno mate about this topic who pointed out that MP3 encoding makes heavy use of this subjective effect.

And OGG Vorbis relies on it even more than MP3.

Gotta love how easily the human mind can be tricked.

Motion pictures rely on that effect (multiple stills looking like motion).
Even our displays (monitor, TV, etc) as you have 3 distinct color points (RGB) that the mind blends into a color.

Quote from: mexicanyella on June 20, 2012, 02:01:42 AM
STDog, I think I've experienced something like that "false partial" effect when trying to play lap steel in a tuning that didn't lend itself to minor chords without fancy hand moves that were out of my reach at the time. You could play part of the minor triad without abusing your inexperienced hand, and even if the other instruments were'nt covering the note you left out, sometimes it would still seem to be there. So it wasn't just wishful thinking, huh?

The false partial is a bit different. It's cheating the natural harmonic series on the horn and using the overtones to mimic the note.

Say you have a Bb horn. open partials are Bb, Bb, F, Bb, D, F, etc..
That octave jump between the bottom 2 is the issue. With 3 valves (or a 7position slide) you can play down to the E between them, but no lower. You need 4 valves to get all of that octave. But, you can fake an Eb between them that has zero fundamental and is all overtones. And, many can fake all the way down to the B.

On a stringed instrument, you can play two strings and sympathetic vibrations will sound the third if you have the chord fretted properly. That's similar to the effect I mentioned, in that the missing note has to fit in the tube as played. Say you play Bb, sing F, and the D magically sound in the head. That because if the interactions of the overtones of the 2 real notes, the horn characteristics, and the human ear.

Not sure about other effects on strings. Whatever you are playing would need to emphasize enough of the right harmonics to trick the ear.

Quote from: Roly on June 16, 2012, 06:14:32 AM
There is a thing that all small speakers such as "bookshelf" and computer speakers depend on, and it's called the "replaced fundamental".

If you present the human ear with a group of third harmonics it is possible to fool the brain into thinking that it is hearing not harmonics but the fundamental note, even though there may be no fundamental there at all.

As a brass player (tuba and trombone) I'm well acquainted with that effect.

Firstly it's used for what we call a "false partial", that allows playing notes that don't exist on the horn. Handy in a pinch, but they never sound quite right.

Also I've seen similar effects where you play one note of a triad, sing the another (not the easiest thing to do), and the horn natural harmonics cause the ear to fill in the missing note and hear the full triad. (only works when all 3 notes play with the same "fingering")

Really freaky the first time you hear it.

Quote from: Roly on June 17, 2012, 12:46:30 AM
About the only time you actually hear real fundamental bass these days is at big arena rock shows

Live performances of unamplified music. Nothing like the bass (i don't mean guitar either), tuba, tympani on a proper stage in a hall with good acoustics.

Or stand in front of 20+ sousaphones playing a grove at fff.

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{I sometimes wish I had taken up the flute}

You and me both.

Quote from: monkeycabbage on August 31, 2009, 07:49:57 PM
When you say:

Quote from: STDog on August 31, 2009, 01:06:05 PM
Then check TP30 and TP31 for the levels given on the schematic.
Since the LED is not working, I suspect them to be bad.

But maybe TP30 is good, and the problem is U8 or related components like CR39 & CR40, or R122 & R123.

Do you mean a continuity test to see that the circuit does continue through them or do you mean a voltage test to see what is going through them? Any extra tips on testing would be very helpfull and seriously appreciated.

Measure the voltage checking for the values called out in the schematic (you did download the schematic right?).


You may well be in over your head with this.
It's all basic stuff, but if you don't know how transistors (BJTs and FETs) are biased, or how an opamp works you're in deep.

I highly recommended finding a tech, or taking an electronics course.

The schematic and component diagram are helpful.

I also see several test points to help debug.

Form a quick glance, one does reverb work?
Then check TP30 and TP31 for the levels given on the schematic.
Since the LED is not working, I suspect them to be bad.

But maybe TP30 is good, and the problem is U8 or related components like CR39 & CR40, or R122 & R123.


Q7 (controls the LED) and appears to be conduction, but Q1 & Q3 appear off given the clean channel works.

Those diodes, and the nearby capacitors and the resistors, look like part of a power supply circuit.
If the previous problem was in the PS, the diodes my have overheated and caused the traces to laminate for the board.

If so, he was trying to fix that, though not in the best manner.

Be careful when you remove the solder, and see if you can run wires from the good parts of the traces to the component leads.

That said, I think the connection your worried bout is correct, based on what I see from the top side.
A schematic or unmolested board would be the best way to tell.


I think your problem lies elsewhere, but without a schematic it's hard to say.

Time to find a new tech that's nearby.

If you absolutely have to work on it, first, remove all the excess solder using a vacuum tool or solder wick.
Then you can see what's going on.

Maybe post pictures of the carnage so we can offer more advice.

Maybe I misunderstood. I thought the first 2 samples were the "old" speaker(SMC). Then he turns up the volume and/or moves the mic near the speaker so you can hear the sound.

The recording stops and he changes to the "new" speaker(generic HiFi type), with a clean and distorted examples.

The noise with the SCM speaker sounds like some sort of oscillation.
Does changing the different volume controls affect it?

Are you moving the mic closer to the speaker to pickup the noise of something else?
Can you leave the mic in the position where the noise is picked up while changing the volume setting and switching channels.
Also, try the same with the HiFi speaker.
I suspect the HiFi speaker just isn't sensitive enough to pick it up.

Don't pick/strum the strings, or just use a single string, so the out of tune strings don't add beats to the audio.


If the distortion channel really doesn't have the noise, I suspect it's coming from an early stage, and a high/band pass filter in the distortion channel is blocking it. I don't know for sure how that Crate distortion circuit is done though.
(I have a GFX amp which I think is basically the same. The main tone controls are after the clean/distorted channels reconverge)

You might should read teemuk's book.
http://www.ssguitar.com/index.php?topic=711
He discusses some of the issues with "Hi-Fi" speakers for instrument amplifies.


In short, you need to find a good instrument speaker.

The cheap speaker you had my have damaged the circuit too.

I have a Optimus (Radio Shack) A/V receiver that has to be raised to ~20% before the right channel output starts, but then I can lower it until it's powered off again.

Since it's in the bedroom, I haven't bothered to look ito it.

I've had several audio components that had pots develop dead spot, over 50% if the range was lost.