Noisy eTap2hw

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Re: Noisy eTap2hw

Postby GuitarPhil » Sun Nov 25, 2012 5:55 pm

David Martin wrote:How noisy is noisy? (No I'm not being silly...) my eTap produces the Brian May "snowstorm" but quietly...


Hi David,

In the short sound sample at the following link the first 10 seconds is my baseline noise level. This is recorded with the input lead to my audio interface removed from the eTap2hw and shorted. The next ten seconds is with the eTap2hw connected to the audio interface but with the eTap2hw input guitar lead shorted. The Gain on the interface and the eTap2hw settings are exactly the same. I think you will be able to hear the difference quite easily.

http://www.4shared.com/mp3/vJhk8iyI/eTap2hw_Noise_demo.html

Thanks.
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Re: Noisy eTap2hw

Postby Echotapper » Sun Nov 25, 2012 8:47 pm

Philip,

You're running too fast......audio files are not yet the instrument to find the culprit.

First use the instructions already provided without the FV-1 board installed and write-down differences.
Also, cross both channels so you'll find the channel part of your problem. Also write-down observations.
The two channel approach was intentional designed be me to help the diagnostic process.

By adhering to this structural approach you'll find it for sure and a remedy can be established.

Success!
Piet
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Re: Noisy eTap2hw

Postby GuitarPhil » Sun Nov 25, 2012 9:45 pm

Hi Piet,

I have tried the tests with the FV-1 board removed, 1-13 and 2-14, also by crossing the 1-14 and 2-13 on the 16 pin header I find the same noise on both channels so I suspect the problem may lie with the power supply or filtering - I have tried it with a 12V battery input and still hear the same level of hiss though the noise (buzz) that Roger detected http://shadowmusic.bdme.co.uk/viewtopic.php?f=73&t=8533#p60487 in the 150-200Hz range is gone when the battery is used.

I don't have a working scope so I can't trace the noise source any further however I did note no hiss when I monitored both the outputs without the links in place. Of course the gain of the output stages is probably low (maybe unity?) so we would not expect much noise there, so it looks like the noise is coming from teh higher gain input stages.

I am suspecting either a poor solder joint on a decoupling capacitor somewhere of perhaps a faulty (noisy) 7809 regulator. I don't have a digital voltmeter at the moment so my voltage checks may not be accurate with the old analogue meter I am using. It is giving 8.8V on pin 8 of IC3 and about 4.3V on pin 1. These are with an input voltage on the terminal block of 11V.

Thanks to everyone for the helpful suggestions, especially Piet who has put so much work into this 'baby' of his :)
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Re: Noisy eTap2hw

Postby Echotapper » Sun Nov 25, 2012 10:06 pm

Philip,
Try 1-13
Then 2-14
Then short 13 to ground
Then 14 to ground
Then remove the most right IC
then remove the middle IC

One way or the other it should get below -70dB on noise

Piet
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Re: Noisy eTap2hw

Postby ecca » Sun Nov 25, 2012 10:28 pm

Use a length of cable into your amplifier.
Poke it about round the board, use it instead of a scope, listening to the noise.
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Re: Noisy eTap2hw

Postby Twang46 » Sun Nov 25, 2012 11:40 pm

Hi Phil

"Hiss" & "Buzz" are two different things ...............

Using a battery as a "DC" supply removed the buzz but not the hiss, so effectively ruling out the power supply's part in the hiss problem.

All the tape echo's I have ever heard/used have had hiss as a part of the "sound"

As the Etap2HW is a hardware emulator of vintage tape machines & in particular the Meazzi range you must expect to be able to hear some hiss.

Switch your amp on & stick a mic next to the speaker with nothing plugged in ....you will hear hiss/buzz/hum & will certainly be able to record it !

What I am saying is that I think you are looking for a problem that is not there :) ....................... all vintage machines, echo's included have a degree of "noise"

Are you happy with the sound you get when you play through an amp ?.... that's the important thing

Dick
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Re: Noisy eTap2hw

Postby RogerCook » Mon Nov 26, 2012 9:33 am

Phil

It looks like you've isolated the source of the hiss to the input stage(s). It might be worth try trying different 5532s in the relvant circuits (easy to swap in and out as they are in sockets) and possibly different J201s (but more difficult if they are soldered)

Roger
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Re: Noisy eTap2hw

Postby GuitarPhil » Mon Nov 26, 2012 11:30 am

Hi Roger,

I may try your suggestions. Pity I soldered the FETs in :cry:
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Re: Noisy eTap2hw

Postby GuitarPhil » Mon Nov 26, 2012 11:35 am

Hi Dick,

Piet said the noise level should be -70dB which I think would be pretty quiet. He definitely didn't programme the noise into the FV-1 board as its there when it's been removed and the pre- and post- amp stages are linked directly.

Nice thought though to mimic the old hissy hardware :D
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Re: Noisy eTap2hw

Postby Twang46 » Mon Nov 26, 2012 12:07 pm

Hi Phil

I must be missing something here with this "hiss" business :?
The 5532's are very low noise devices but always possible one is "out of spec" the fet's can be problematical also.... who knows ?

But..............how bad is this "hiss" really ? enough to bother you obviously .... until you can get another one or two "side by side" you won't know if yours is noisier than "normal".
I've built one & a half of these (long story ;) ) so far with another one about to start this time in a "posh" enclosure with some extra's. Like all other electronic audio gear (valve or solid state) there is noise that bothers some people more than others.

-70db doesn't seem to be that quiet to me, but would fit in with what you would expect from the type of machines that Piet designed this to emulate. There are some "added tape noise" artifacts as part of the design, don't know how much they are are affecting what you are hearing though.

I'll follow this with interest to see where it goes 8-)

Cheers

Dick.
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