hey guys,
I noticed that when I hit in my MXR Microamp, i notice a little bit of added noise.. sorta hum type noise... this is when the knob on it is set all the way to zero.

Is that somthing normal??  is it fixable??


thanks,
Duke

By the way.. i did a search and I read here:
http://diystompboxes.com/sboxforum/viewtopic.php?t=10461&highlight=microamp

that if i replace the IC from the tonepad Microamp with an NE5532 IC, it will make the Microamp quieter.  does that also apply to the Dunlop MXR Microamp version??


thanks,
Duke

that if i replace the IC from the tonepad Microamp with an NE5532 IC, it will make the Microamp quieter. does that also apply to the Dunlop MXR Microamp version??
 What IC did you use?
 High performace IC's....HP IC's...I like them. and yes they run quieter than say a 741...but it sounds to me like a problem with 'feavy hum' replacing the opamp might not do it, clip to ground and DMM beep mode check all the ground connections as on the schematic.
 Noisy OA...don't usually hum loud withthe gain down.

The MicroAmp originally came with single op amps, the reissues I've seen had the 741 in them. Tonepad's layout is a dual IC, so NE5532 is right, NE5534 if it's a single op amp.

Pete's right. You've got other issue's going on there. The Micro is a pretty quiet ckt.

hey guys,
I will check all the connections on the board it self and see. The hum is not loud or anything serious I dont think, even thought I never noticed it there before.  Right now I have the PCB of the Microamp on top of my rack.. so can that be affecting it and making it cause noise due to Magnetic feild from transformers??

I still have to replace the burnt out LED on it with a new one and put it in its case.

Hey fret wire... do I use NE5532 or NE5534.  right now it has a 741.


Duke

The tonepad version was layed out to use a dual op amp. The reissue uses a single OA. Which do you have?

741/TLO61/TLO71......5534
TLO72/4558....5532

Quote from: Fret WireWhich do you have?

I have the re-issue from Dunlop them selves. so i guess i need the NE5534. no?

If i do change the OA with that one.. is that going to affect the tone of the pedal? or just the noise level?

Thanks for the help guys.


Duke

Right, You need the NE5534. Won't change tone, just less noise..a good thing. Boost may increase slightly.

Be careful when desoldering the IC. The Dunlop boards have over-sized, through-plated holes. Desoldering wick works best here. Not that you care about the old IC, it's so you don't over heat the board and lift the traces. You'll probably have to desolder on both sides of the board. Look, and you'll see solder on both sides. Start on a pin on the trace side. Go diagonal across to an opposite pin and desolder that. Keep moving to opposite side pins. That way you won't heat one small spot on the board all at once. Then you may have to repeat the process on the other side. Put an IC socket in too.

For the LED, double check the polarity before you remove it. Use the braid again. The black tube has two small holes to guide and support the LED.

Your hum should go away when you box it back up.

Quote from: Fret WireRight, You need the NE5534. Won't change tone, just less noise..a good thing. Boost may increase slightly.

Be careful when desoldering the IC. The Dunlop boards have over-sized, through-plated holes. Desoldering wick works best here. Not that you care about the old IC, it's so you don't over heat the board and lift the traces. You'll probably have to desolder on both sides of the board. Look, and you'll see solder on both sides. Start on a pin on the trace side. Go diagonal across to an opposite pin and desolder that. Keep moving to opposite side pins. That way you won't heat one small spot on the board all at once. Then you may have to repeat the process on the other side. Put an IC socket in too.

For the LED, double check the polarity before you remove it. Use the braid again. The black tube has two small holes to guide and support the LED.

Your hum should go away when you box it back up.

Awsome stuff.. Thanks alot for the help. Will definitly be careful when unsoldering and soldering the ICs.

A slight increase in the boost isnt a problem at all. most likely I will be using the Microamp as an active buffer for those long cable runs, so I only boost it to around 9 o'clock position on the knob.

Will let you know of the results.


thanks again,
Duke

Quote from: Fret WireRight, You need the NE5534. Won't change tone, just less noise..a good thing. Boost may increase slightly.

Be careful when desoldering the IC. The Dunlop boards have over-sized, through-plated holes. Desoldering wick works best here. Not that you care about the old IC, it's so you don't over heat the board and lift the traces. You'll probably have to desolder on both sides of the board. Look, and you'll see solder on both sides. Start on a pin on the trace side. Go diagonal across to an opposite pin and desolder that. Keep moving to opposite side pins. That way you won't heat one small spot on the board all at once. Then you may have to repeat the process on the other side. Put an IC socket in too.

For the LED, double check the polarity before you remove it. Use the braid again. The black tube has two small holes to guide and support the LED.

Your hum should go away when you box it back up.

Awsome stuff.. Thanks alot for the help. Will definitly be careful when unsoldering and soldering the ICs.

A slight increase in the boost isnt a problem at all. most likely I will be using the Microamp as an active buffer for those long cable runs, so I only boost it to around 9 o'clock position on the knob.

Will let you know of the results.


thanks again,
Duke

You're welcome. I forgot another LED tip. The current limiting resistor for the LED (located by the dc jack) is valued for standard LED's. If you put a clear blue in there, chances are that you could use it for a spot light! You will have to bump the resistor up another 2k-4k for the clear super brights. Considering how they are desoldering wise, I thought you should know that.

Quote from: Fret WireYou're welcome. I forgot another LED tip. The current limiting resistor for the LED (located by the dc jack) is valued for standard LED's. If you put a clear blue in there, chances are that you could use it for a spot light! You will have to bump the resistor up another 2k-4k for the clear super brights. Considering how they are desoldering wise, I thought you should know that.

Thanks for the tip.

Well.. is there a certain way to identify what kind of LED i have/need? or they go by size?

The resistor on there has 5 stripes:
Red
Red
Red
White
Orange

What kind of resistor is that?? metal filment?


thanks,
Duke

Yes that's a metal film, but not the right one. Just use a standard 5mm T1 3/4 led. The neg side (flat) faces the switch. One of the plain red ones will drop right in and have the same birghtness as original. Use the box as a jig when you solder the led in. Stick the led in the plastic holder, put it in the board and bend the leads over to hold it. Then put the board back into the box and tighten down the switch and pot nuts. Check the LED for protrusion on top, adjust if necessary and re-bend the leads. Then solder. The box acts like an alignment jig.

Quote from: Fret WireYes that's a metal film, but not the right one. Just use a standard 5mm T1 3/4 led. The neg side (flat) faces the switch. One of the plain red ones will drop right in and have the same birghtness as original. Use the box as a jig when you solder the led in. Stick the led in the plastic holder, put it in the board and bend the leads over to hold it. Then put the board back into the box and tighten down the switch and pot nuts. Check the LED for protrusion on top, adjust if necessary and re-bend the leads. Then solder. The box acts like an alignment jig.

Awsome stuff!! I might get a different color LED. like Blue. I'll leave the resistor as it is.  I am hopfully gonna build the Tonepad.com Microamp (single) and see how that goes.

Any idea whats the difference between the 2??

EDIT - also, is there a website i can use to find out the values of Metal Film Resistors??  I have one for "regular" resistors:
http://www.dannyg.com/examples/res2/resistor.htm


thanks,
Duke

Here's a calculator for metal film. Scroll down and you'll see it.
http://www.eatel.net/~amptech/elecdisc/resistrs.htm

The tonepad Micro is layed out for a dual op amp, 4558. Here you can use that NE5532. The difference IC wise, they're just using half of a dual op amp. Gives you more choices for replacements than single IC's do.

Difference sound wise? It's true bypass for one, so no tonesucking problems when off. It will still buffer you long cables when on. Because you can use quality components, and a better IC, it will sound a little better than the reissue. Which in a booster means more quiet and transparent. The jacks and switch will last longer than the reissue too.

Quote from: Fret WireHere's a calculator for metal film. Scroll down and you'll see it.
http://www.eatel.net/~amptech/elecdisc/resistrs.htm

The tonepad Micro is layed out for a dual op amp, 4558. Here you can use that NE5532. The difference IC wise, they're just using half of a dual op amp. Gives you more choices for replacements than single IC's do.

Difference sound wise? It's true bypass for one, so no tonesucking problems when off. It will still buffer you long cables when on. Because you can use quality components, and a better IC, it will sound a little better than the reissue. Which in a booster means more quiet and transparent. The jacks and switch will last longer than the reissue too.

Ahhh alrigth.. will definitly do that later.  smallbearelectronics.com is a good place to get the quility components for it??


Duke

Small Bear has everything but metal film resistors. You can get those locally or from Mouser:  1/4 watt metal film. The two main things a booster should do is boost and be quiet. Even Dunlop used mostly metal film on the reissue, and they're all about cutting cost.

That's a good project from Tonepad. They're back from vacation and fully stocked on boards. With that one board, you can make a Micro Amp, Distortion Plus, or DOD250.

Quote from: Fret WireSmall Bear has everything but metal film resistors. You can get those locally or from Mouser:  1/4 watt metal film. The two main things a booster should do is boost and be quiet. Even Dunlop used mostly metal film on the reissue, and they're all about cutting cost.

That's a good project from Tonepad. They're back from vacation and fully stocked on boards. With that one board, you can make a Micro Amp, Distortion Plus, or DOD250.

thanks for the help fret.. I will hopfully replace the OA in this microamp and do the tonepad one in the future.

For parts, I guess I can order from Small bear electronics and get the Metal film resistors locally. Ofcourse I am gonna check first because somtimes it doesnt seem to be easy to find stuff like that here.


Thanks again,
Duke

Quote from: Duke of MetalRight now I have the PCB of the Microamp on top of my rack.. so can that be affecting it and making it cause noise due to Magnetic feild from transformers??Duke

Out of the box? I think that's a very likely cause of your hum.

-Eric

Quote from: Eric H

Quote from: Duke of MetalRight now I have the PCB of the Microamp on top of my rack.. so can that be affecting it and making it cause noise due to Magnetic feild from transformers??Duke

Out of the box? I think that's a very likely cause of your hum.

-Eric

Thanks for the reply Eric.. Yes, its out of the box and thats most likely whats causing the noise on it. But I'll replace the OA anyways and see how much improvment there will be.  I dont want to put it back in the box until I've replaced the OA and the LED, that way, i can put it in its box, close it up and put it on my pedal board.


Thanks,
Duke