Shshshshshs on Out put - Electronic Circuits Projects Diagrams Free

aljamri · 24th December 2007, 06:48 PM

Merry Christmas to everybody,

I've built the attached circuit and it works fine. The only problem is at the output, a low Shshshs sound is there, if you talk into the input or not.

What can be the problem. Please help me.

Sorry for not using the proper AUDIO terms.

Thanks and happy new year.

RadioRon · 24th December 2007, 09:58 PM

Your schematic diagram is incomplete, missing useful information. For example, what is the part number for the delay line IC and what is the part number for the unidentified op amp?

Also, I don't quite understand the point of the 9V battery. It appears to subtract 9V from the 9V supply rail to insure that the ring connection of your jack is at zero volts. That can't be right, is it?

audioguru · 25th December 2007, 02:20 AM

It seems to use a microphone that is not the normal electret type. A dynamic microphone? They normally feed a low impedance amplifier, not the 1M in parallel with 510k like this preamp.

The Shshsh hiss might be caused by the unknown input opamp.

The circuit has the input opamp feeding directly into the output opamp without any lowpass filter.

jumides · 25th December 2007, 09:58 AM

it looks like guitar preamp to me.

**Nigel Goodwin** · 25th December 2007, 12:26 PM

Yes, it's a guitar preamp with reverb - no idea what the delay chip is, but I would expect the noise is from the BBD delay device, as it shifts data through itself.

aljamri · 25th December 2007, 12:59 PM

sorry guise ! i forgot to put the IC number it is TL072. And i used a dynamic Mic as what Audioguru expected. Jumids circuit it is simmilar to mine but i am not using it for guitar, it is for speaking/singing only.

thanks for all.

jumides · 25th December 2007, 02:05 PM

Quote:

Originally Posted by aljamri

sorry guise ! i forgot to put the IC number it is TL072. And i used a dynamic Mic as what Audioguru expected. Jumids circuit it is simmilar to mine but i am not using it for guitar, it is for speaking/singing only.

thanks for all.

hi aljamri,
It was not similar, but it was your diagram/circuit and add some wiring for the completeness of the circuit, sorry for editing your diagram. Those circle "mark" are base only on my experience during repair works.

Quote:

Originally Posted by Nigel Goodwin

Yes, it's a guitar preamp with reverb - no idea what the delay chip is, but I would expect the noise is from the BBD delay device, as it shifts data through itself.

I agreed to Nigel Goodwin's idea.

Another source of "hiss" are PCBoard, lack of grounding/earth and metal shield, be sure to used good shielded wire from mic to preamp to amplifier.

**Nigel Goodwin** · 25th December 2007, 02:10 PM

Quote:

Originally Posted by aljamri

sorry guise ! i forgot to put the IC number it is TL072. And i used a dynamic Mic as what Audioguru expected. Jumids circuit it is simmilar to mine but i am not using it for guitar, it is for speaking/singing only.

If you're using it with a microphone then add a mike preamp to the front end, it's not suitable for mike level signals, and that would be a major reason you're hearing the switching noise from the BBD - because you're operating at MUCH too low a signal level.

As we've suggested, it looks more like a guitar circuit, with actually zero gain, and about 400Kohm input impedance.

Actually, after a few seconds thought, it's actually a guitar reverb foot pedal - switched by plugging the quitar in, and with a bypass switch operated by your foot, and a gain of zero so it doesn't alter volume when you switch.

audioguru · 25th December 2007, 02:33 PM

I didn't notice that the circuit has no gain.
It certainly needs a microphone preamp that is designed for a low impedance dynamic mic.

aljamri · 25th December 2007, 03:00 PM

Quote:

Originally Posted by RadioRon

Your schematic diagram is incomplete, missing useful information. For example, what is the part number for the delay line IC

its 2399 ( Echo processor )

Quote:

Originally Posted by RadioRon

Also, I don't quite understand the point of the 9V battery. It appears to subtract 9V from the 9V supply rail to insure that the ring connection of your jack is at zero volts. That can't be right, is it?

no it is the whole circuit supply, and wherever 5V required it comes from the 7805 regulator.

Thanks

aljamri · 25th December 2007, 03:15 PM

Quote:

Originally Posted by Nigel Goodwin

If you're using it with a microphone then add a mike preamp to the front end, it's not suitable for mike level signals, and that would be a major reason you're hearing the switching noise from the BBD - because you're operating at MUCH too low a signal level.

You are right again, I used it as a pre amplifier for TOA PA Ampliger Model A-1061 where i control the output to the loud speakrs and adjust Bass and Tereble.

By the way what is BBD ?

Hero999 · 25th December 2007, 03:35 PM

I didn't know they still used BBDs for delays, I thought digital signal processing units are more common nowadays.

audioguru · 25th December 2007, 04:05 PM

The PT2399 echo IC is not a BBD. It has an ADC, digital processor and DAC.
It has fairly low distortion and low noise.

**Nigel Goodwin** · 25th December 2007, 04:12 PM

Quote:

Originally Posted by aljamri

You are right again, I used it as a pre amplifier for TOA PA Ampliger Model A-1061 where i control the output to the loud speakrs and adjust Bass and Tereble.

By the way what is BBD ?

It's a Bucket Brigade Device, but now you've given us it's number we know it's not one of those.

aljamri · 25th December 2007, 04:23 PM

Quote:

Originally Posted by audioguru

The PT2399 echo IC is not a BBD. It has an ADC, digital processor and DAC.
It has fairly low distortion and low noise.

yes all that information as per its datasheet but unfortunately i cannot attach it here.

but as i said guise, it is working fine, just the little hiss which prevent it to be perfect, what can be adjusted even as trial step

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24th December 2007, 09:58 PM	(permalink)
RadioRon	Your schematic diagram is incomplete, missing useful information. For example, what is the part number for the delay line IC and what is the part number for the unidentified op amp? Also, I don't quite understand the point of the 9V battery. It appears to subtract 9V from the 9V supply rail to insure that the ring connection of your jack is at zero volts. That can't be right, is it? __________________ RadioRon

25th December 2007, 02:20 AM	(permalink)
audioguru	It seems to use a microphone that is not the normal electret type. A dynamic microphone? They normally feed a low impedance amplifier, not the 1M in parallel with 510k like this preamp. The Shshsh hiss might be caused by the unknown input opamp. The circuit has the input opamp feeding directly into the output opamp without any lowpass filter. __________________ Uncle $crooge

25th December 2007, 12:26 PM	(permalink)
Nigel Goodwin	Yes, it's a guitar preamp with reverb - no idea what the delay chip is, but I would expect the noise is from the BBD delay device, as it shifts data through itself. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

25th December 2007, 12:59 PM	(permalink)
aljamri	sorry guise ! i forgot to put the IC number it is TL072. And i used a dynamic Mic as what Audioguru expected. Jumids circuit it is simmilar to mine but i am not using it for guitar, it is for speaking/singing only. thanks for all. __________________ Its what your friend in Your mind, what you in your friends mind

25th December 2007, 02:33 PM	(permalink)
audioguru	I didn't notice that the circuit has no gain. It certainly needs a microphone preamp that is designed for a low impedance dynamic mic. __________________ Uncle $crooge Last edited by audioguru; 25th December 2007 at 02:50 PM.

25th December 2007, 03:35 PM	(permalink)
Hero999	I didn't know they still used BBDs for delays, I thought digital signal processing units are more common nowadays. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez

25th December 2007, 04:05 PM	(permalink)
audioguru	The PT2399 echo IC is not a BBD. It has an ADC, digital processor and DAC. It has fairly low distortion and low noise. __________________ Uncle $crooge