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 HQuote 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
There's like an intuition that can Identify different type noises...SOmetTImes.
Basically you can find it, but it might take a while. Low noise floor will be there. High end parts probably do help [sometimes] , never really tried many.
I like dueling circuits sometimes these days, see if I can outperform the one I already like, especially with those dern FF's...
If everythings 'right' excessive [depends on what you call Excessive] noise shouldn't be a real issue.
SOMETIMES
you can hear a certain type of cord noise
you can wave your hand over unboxed CCT and hear noise changes.
You can definitely hear leaky caps in an amp intermittent sckrakitching
You can find the plug that got pulled out of the jack
you can turn your guitar volume down in time or hit THAT BUTTON
the atmospheric conditions are perfect
dank dampness screws with your Shhh
Cognicance of what matters is the trick to noise intuitions.
I got lucky twice recently when recording
I found an inadequate RCA cable..computer frequency was the theory that solved the problem [almost never happens this way]
The Wireless internet connection was putting ticks in...I unplugged the lighter sized widget at the end of the USB cord [what are the odds?] I remeberd it wasn't doing that before getting that puter connected [the recording computer which I still can't sign in here on...gotta call cable guy :lol: ...
So... the original one uses metal film resistors? Are u sure? I'm gonna build the tonepad one and i'd like it to be just like the original, so how carbon resistors will influence the sound? I can't find metal film resistors here!
Thank you.
You misunderstood my post. The original Script Logo Micro Amp used carbon comp resistors. When the Duke asked me how the Tonepad project would sound different or better, I said that one of the ways is that you can use quality components, like metal film resistors. The Dunlop reissues use mostly metal film, not the orignals.
I wouldn't use carbon comp resistors unless I had no choice. They will add some noise. Preserve the original values, but use better components. You can improve this pedal by using good parts and a quiet op amp. The original character of this pedal was clean, quiet, no tone coloration, but a slight sparkle or presence added to your sound. When you upgrade the components, it really sounds great. If you can't get metal film, just use carbon film. Anything but carbon comp.
OK thank you for the explaination !
A couple of things:
a) Duke my good man, did you try using it with a fresh 9v battery and not an adapter? This might be where your hum is coming from.
b) The original vintage Microamps used TL061s, most likely for it's low voltage drain characteristics on a battery (there is no DC adapter jack on them). A very sweet low noise option is definitely is a TL071. If you have a later revision stamped for a dual op-amp, go with the TL072. A NE5532 is also a very nice replacement too, but TL07x are easier to find locally.
c) You can get Metal Film resistors at Radio Shack, but for currenting limiting on LEDs, there is no need for Metal Film. Carbon comp/film will work just fine.
d) If the guts are out of the shielded chassis, yes, it will pick up hum, this is normal. The hum will be more apparent in front of a high-gain preamp such as yours.
e) Duke, since this is your first attempt at a pedal build, I assume you are going to use perfboard and point-to-point it instead of etching it. I would go for a simpler booster project to start, such as the AMZ Mosfet Boost or the LPB1 on Tonepad. Great first projects and they both are excellent transparent boosters similar to the Microamp but using FETs instead of an op-amp.
Good luck :D
-HB
Hairston, thanks for the info. I've never seen a script logo with the 61's in it, just the 741's. Which version used a dual? The Script logo didn't, and neither did the reissues. Was it during the block logo phase? I believe the block logo's I've examined had single OA's. MXR did some subbing due to availability, but that would mean a new board. I'm curious, I try to keep up on all the MXR versions and their changes.
You're right about the LED resistor, no audio path there. I use metal film resistors, it's just my preference. Although in some ckt's I'd say it's almost mandatory to keep noise down. For a booster, I like metal film. When you consider all the work you put in soldering, wiring, and box prep, I don't mind spending a little more for some extra noise reduction. But I wouldn't recommend carbon comp. Carbon film is just too plentiful and cheap to bother with the carbon comp's.
It was nice having MXR right near us. There's still plenty of former employees around too. :wink:
Fret Wire:
Are you sure there are no pinout issues between a 741 and a 5534? IIRC, Paia always had to provide an adapter for the EPFM project boards (originally for 741/7436) because of this.
Ben
Hi Ben, it depends what the ckt has going to the IC. The difference between the 741 & the 5534 are pins 1,5, & 8. On the 741 they are off/null1, off/null2, & NC. On the 5534, it's Bal, Com, & Comp/Bal, extra features if your ckt uses them. The Micro and D+ use 2,3,4,6, & 7. There is spec differences too.
I originally tried them in those ckts and they worked. Later when I saw the data sheet, I saw the differences in operating voltage and pins 1,5,8, and I got nervous. But stompbox ckts, being simple, it boils down to does it work in the ckt or not.
The TLO71 is a direct pin for pin replacement for the 741. Funny thing is the Burr Brown OPA 134A & OPA177 are also direct pin replacements for the 741, not the 5534. My guess is that they did that because the differences between the 741 and OPA's is greater than the OPA's and 5534. Maybe Paia used pins 1 or 5 differently?
OMG!!!.. its Hairston :D.. hows it going bud??
Thanks for the info. to be honest, I dont like using batteries. Adapters are the way to go for me. I am gonna try to replace the LED somtime soon and get a repalcement OA too. If the pedal is quiet after I put the pedal back in its box and on the floor, then i might not bother with replacing the OA. if its still noisey, then I'll replace the OA and see what the results are.
Thanks guys.
Duke
hey guys,
well.. i got a replacement LED and Opamp.. I repalced the LED with a Blue one and it worked fine.
Now.. after I got the Opamp.. i realized that we did nothing. I got the TLO71 like you guys said and thats what the pedal has originally :?..
but anyways. i replaced it and the problem was the same.. I even put the Circut board inside the MXR case and tried it and same problem. I notice a little bit of hiss and a bit of hum added to the sound even when the control on the Microamp is all the way down.
I am thinking of ordering a tonepad Microamp PCB and transfer the parts from the MXR Microamp to the tonepad.. question is, can I do that?? do i need extra parts or I can use the exact parts from the MXR to the tonepad??
will the tonepad Microamp PCB fit in an MXR pedal case??
also, where the does DPDT switch get soldered to the tonepad PCB?? and can the Tonepad version be powered with an adapter? or just battery?
(http://img.photobucket.com/albums/v146/adadepot/duke/tonepadpmicroamp.jpg)
Any info would help.
Thanks again guys,
Duke
Quotebut anyways. i replaced it and the problem was the same.. I even put the Circut board inside the MXR case and tried it and same problem. I notice a little bit of hiss and a bit of hum added to the sound even when the control on the Microamp is all the way down.
I am thinking of ordering a tonepad Microamp PCB and transfer the parts from the MXR Microamp to the tonepad.. question is, can I do that?? do i need extra parts or I can use the exact parts from the MXR to the tonepad??
will the tonepad Microamp PCB fit in an MXR pedal case??
also, where the does DPDT switch get soldered to the tonepad PCB?? and can the Tonepad version be powered with an adapter? or just battery?
...Something in the circuit is causing the noise, this may be hard to find, did you use a new electrolytic?
You can probably use the same parts, but I'd compare schematics.
The DPDT info for true bypass wiring is at GEO.
I don't know if the PCB'll fit in the MXR case.
Thanks for the reply Pete..
what kind of switch does the tonepad version use anyways?? cause it doesnt say on the pdf file i downloaded from there.. and where can I get the schematic for the MXR version of the Microamp??
Thanks,
Duke
what kind of switch does the tonepad version use anyways?? cause it doesnt say on the pdf file i downloaded from there.. and where can I get the schematic for the MXR version of the Microamp??
Well the only switch I know of for a standard MA is the bypass switch.
GEO has the bypass article...much better source than my typing.
circuit input circuit output
input jack output jack
bypass jumper
these rep the six lugs of a DPDT, use the DMM to find where the switch show continuity to either side...input jack to BP [in one sw posistion] input jack to circuit side [other sw position].
If you're not getting that, turn the switch 1/4 turn and test again.
Edit...my switch representation got kind of skewed when entered...it makes no sense...check the GEO Bypass article.
hey Pete,
Thanks for the info.. would you be able to give me a link to the page that that has the True Bypass or dpdt wiring link on the geo site?? i looked on there and couldnt find it.
EDIT - I found this page, is it the one?
http://www.geofex.com/Article_Folders/bypass/bypass.htm
thanks,
Duke
refering to pic in article showing double pole double throw...
Assign p1 and p2 to in out jacks
in this case were making P1 for input
P1 to input jack
P2 to output jack
T1A to circuit input
T2A to circuit output
T1B and T2B connect with wire for bypass
These labeled circle dots represent the 6 lugs on the switch...the dotted line means both 'sides' of the switch [each side being an SPDT] are thrown at the same time...hit the switch and both sides switch
The dotted line shows where the solid lines connect inside the switch.
The way I figured it out was with a pen/paper, draw six lugs for DPDT, then use the DMM beep mode to map where the connections I can't see inside the switch are made...
Look for schematics that show dpdt wiring, Bobtavia EZ Build shows the switch body in the schematic...
Basically you want bypass to connect the signal straight through from input to output jacks...
Then on the other 'side' you want it fed through the circuit, injack to input, output to outjack.
Test one side of the switch [spdt]. find where two lugs have continuity. one will be a middle of the SPST [DPDT is two simultaneous SPDT"S] the outside lug will switch 'off' but 'on' to the other outside lug of the SPDT.
The other side is a mirror...one side for input one side for output.
All the typing got me to put a 5534 in the MA. I'm not getting any noise, I used Vellman Resistors from a 480pc. pack, they're 5% Cfilm resistors.
Put it in a box with T.bypass, amazing sounding..
anybody with an idea of what might be causing the noise??
I tried it with a battery too and its the same thing noise wise. Ofcourse i put the circut back in its case and its still noisey.
Thanks,
Duke