connect .001/50v or other value, mylar capacitor across ground, ic pin no.6 ic2b.

__________________
Publish your web page

 

The microphone needs to feed a preamp that is designed for a dynamic mic then its output level is well above the level of the hiss. Then your reverb circuit can feed a line input on the power amplifier so the hiss is not amplified.

If your mic cable doesn't pickup mains hum then its length is fine.

When you remove the battery from your reverb circuit then it should not produce sound, not even hiss.
If you unplug the output of the reverb circuit from the input (which input?) of the power amplifier then is there still hiss?

__________________
Uncle $crooge

 

http://www.securitywarehouse.co.uk/c...roducts_id=880

where did you connect your preamp output ( aux or mic input )?

__________________
Publish your web page

 

No it is not piking up any hum

In fact i tested that once, but i'm not sure, i'll set the system up again, test it and let you know.

Thanks for your replyssssssssssssssss.

__________________
Its what your friend in Your mind, what you in your friends mind

 

No, it is connected into MIC input. I tried AUX once but sounds very low.

Thanks

__________________
Its what your friend in Your mind, what you in your friends mind

 

He doesn't have a preamp. He has this reverb circuit that has a gain of only 1.
If its input is non-inverting then I would increase the gain of the first opamp so it is a preamp.

__________________
Uncle $crooge

 

It needs to plug into the AUX input (or at least a guitar input), as we keep telling you, add a mike preamp BEFORE the reverb/echo circuit to get to the correct signal level. This is what is causing ALL your problems, not using it correctly.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

look at your circuit there's no gain control, audio coming from (input) ic2b then out to ic2b going to resistor 24k then going to input(ic2a) then out ic2a output directly connected to you mic input . which means that signal are to high for mic input, all noise will be amplified generated by opamp. level (100k) controls a reverb section.



like nigel said, you need a preamp, if your going to connect your reverb to aux .

thanks
I made my mistake, I'm pointing to his reverb.

hi audioguru,nigel
correct me, if I'm wrong. with my analysis

__________________
Publish your web page

 

No.
The signal from the mic is too low for this reverb circuit which normally has line level signals at least 60 times higher. So the noise from this circuit is amplified at least 60 times by the mic preamp that it feeds.

__________________
Uncle $crooge

 

hi audioguru,

I agree with you,

forgive me, some mistake again!!,
I just want to help mr aljamri.

it should be like this,

" look at your circuit there's no gain control, audio coming from (input) ic2b (tl072)then out to ic2b(tl072) going to resistor 24k then going to input(ic2a) then out ic2a output directly connected to your mic input(pa amplifier) . which means that signal from the reverb(opamp) are to high for mic input(PA amplifier) , all noise generated by opamp(TL072) will be amplified by mic input(pa amp). level (100k) controls a reverb section. "

thanks for reply.

Attached Images

pre amp.png (56.6 KB, 5 views)

__________________
Publish your web page

 

Happy New Year for everybody,

It is me again but with good news this.

I've added a pre-amp as Nigel suggested using TL071 as audioguru suggested and the voice became quite good that made me to reduce the PA volume which resulted in low noise at output ( but not zero ). so I told myself why not to check jumids suggestion and put a piece of aluminum underneath the circuit, isolate it and connect it to ground. This made noise to ZERO. So my circuit has no hiss and no need to put your mouth on the Mic.

Thanks all of you again (Radio Ron, jumides, Nigel Goodwin, audioguru and Hero999 for you valuable participation to my circuit.

__________________
Its what your friend in Your mind, what you in your friends mind

 

Hi everybody and happy new year,

I don't know if it is OK to continue on another issue for the same circuit here in the same page or i should start a fresh one ? for now i'll ask here in the same page and If i'm wrong please anybody tell me to immegrate to a new one.

I added a switch to my reverb circuit to switch it off when not in use ( Thumbnail01). The problem is that when i switched it ON/OFF while the PA is ON, a bang nose is heard out of the speaker. Similar devices uses JFET switch instead. Is it possible for me to connect one here? In my hand a 2N5457 is O.K. for this purpose ( Proposed Circuit Thumnail 02, Datasheet Att.03 ).

Thanks

Attached Images

	Att.01.GIF (29.0 KB, 11 views)
	Att.02.gif (3.4 KB, 5 views)

Attached Files

Att.03.pdf (129.8 KB, 1 views)

__________________
Its what your friend in Your mind, what you in your friends mind

 

I am amazed that you used a lousy, noisy old 741 opamp and it doesn't cause hiss. I would use a low noise TL071 opamp for a mic preamp.

I don't think the POP comes from the opamps because their Vb slowly drops when the power is turned off.
I think the POP comes from the echo IC. The circuit must be observed on a 'scope to see if it abruptly goes high or goes low. Then a FET can be added to disconnect it when the power is removed.

__________________
Uncle $crooge

 

Sorry, I have not used 741 in my circuit, at the beginning I used LM358 and you suggested me to use TL07 Family ( The old thread follows )
http://www.electro-tech-online.com/e...processor.html

In my last working fine circuit, I used TL071 as per your recommendations.

I see, so do I have to connect at the + supply to 2399?

Thanks for all

__________________
Its what your friend in Your mind, what you in your friends mind

 

The type of FET you use and how it connects depends on the polarity of the POP.

__________________
Uncle $crooge