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 Post subject: Stereo Router Distortion
PostPosted: Fri May 29, 2015 3:45 am 
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I too have this faint "bleed" sound. Its a faint distortion. I hear it when I run stereo delay in, then out both or either output.

I've found that the distortion appears when I plug in the second input to the amp selector..... Even if it's not coming from the delay pedal or anywhere.


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PostPosted: Fri May 29, 2015 9:02 am 
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Did you build yours as a kit or buy it as a complete build?

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PostPosted: Fri May 29, 2015 4:40 pm 
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Sorry, I shoulda said that. I built mine. December 2011.

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PostPosted: Fri May 29, 2015 5:03 pm 
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simmunz wrote:
I've found that the distortion appears when I plug in the second input to the amp selector..... Even if it's not coming from the delay pedal or anywhere.

Sorry, I'm not quite understanding what you're saying here. Do you mean that once you plug something into input B, you get some distortion from the pedal even if you have no signal going through it?

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PostPosted: Fri May 29, 2015 5:23 pm 
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I get great performance in every way with it except when I plug in the left input. No buzz or hum that I can't fix with the toggles. The distortion sound only occurs when I'm putting signal through it. It comes out both outputs. It's probably always been that way. I only noticed it when I used my board at an acoustic gig and the distortion was more noticeable with the clean sound.

I just now reversed C5 as I'd read on another post.... Now input 2 passes nothing but that faint fuzzy thing under the sound.


Last edited by simmunz on Fri May 29, 2015 5:53 pm, edited 1 time in total.

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PostPosted: Fri May 29, 2015 5:53 pm 
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I would try swapping IC1 with IC2, then swap IC2 with IC3 to see if you can get it to behave any differently. Any change in behavior would indicate a noisy chip.

Or if you have extra op amps on hand, try different op amps in IC2 and IC3.

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PostPosted: Fri May 29, 2015 5:57 pm 
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Sorry, I edited my last post. I didn't test it thoroughly enough. My brain is getting jumbled. Probably need to put c5 back the way it was. Btw, I'm purely mechanical and instructions oriented on these things, so I don't know why I was supposed to swap c5 or not.
I'll try ur suggestion of the swap.
Thanks!


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PostPosted: Fri May 29, 2015 6:17 pm 
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Got c5 reversed (back to as indicated on pcb.) Swapped ic1 with ic2, then 2 with 3. Still the same.
Time to rest my mind.
Thanks for the suggestions!


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PostPosted: Mon Aug 21, 2017 2:09 pm 
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Was this ever resolved? I have the same issue. There is just a faint distortion of fizzing sound. I will test the chips tomorrow.


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PostPosted: Mon Aug 21, 2017 11:36 pm 
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When you say the problem happens when you use the left input, would that be input A or input B? And are you using only one input at a time, or both? Does it make any difference if you only use one as opposed to both?

From the schematic (assuming it is correct) it looks like the output of IC1-a gets shorted to ground when a mono plug is inserted into input B. That could cause excess current to be drawn from the power supply, and those little switched capacitor MAX1044 voltage inverters don't have much extra output current capability. You could try bending pin-7 of IC1 out a little so it doesn't go in the socket. In that case, input A won't get routed to input B, but at least with the pin lifted out of the socket, it can't get shorted to ground by a mono plug. Then see if that changes the symptom you are describing.

Also, it looks like the pins for IC2-b might be left floating. If so, that could potentially cause problems such as oscillation getting into the power supply, or other issues with IC2 operation.

What is the output of the router connected to? TL072 opamps have good and bad things about them. One issue with them is that they don't like driving low impedance loads, which primarily tends to cause increased distortion.


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PostPosted: Tue Aug 22, 2017 7:27 am 
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I did some testing on this today.

Test 1:
Fender Strat Plus, Lace Sensor Golds into the Right input of the Amp selector and Stereo FX Router.
Left out into Egnater Renegade 410
Right out into the BYOD Tweed Royal

Results: Holy s*!t I am a rock star!! This sounds unbelieveable. Clean crisp no distortion or fizz using any of the 3 possible output configs!

Test 2:
Fender Strat Plus, Lace Sensor Golds into a Rocktron Tsunami (Dual output chorus pedal)
D+E out into Egnater Renegade 410
D-E out into the BYOD Tweed Royal (just a way of labeling two outputs)

Results: Holy s*!t I am a rock star with a chorus pedal!! This sounds like a nice lush 2 amp chorus. Clean crisp no distortion or fizz using any of the 3 possible output configs!

Test 3:
Fender Strat Plus, Lace Sensor Golds into a Line 6 POD HD500X, HD500x left and right input into the Amp selector and Stereo FX Router's left and right inputs.
Stereo FX Router's Left out into Egnater Renegade 410
Stereo FX Router's Right out into the BYOD Tweed Royal
I have nothing set in the patch. Mixer set normal.

Result: There is a destinct fizzing sound as a plucked note decays. It is there on both left and right outputs and both on at the same time.

Test 4:
Fender Strat Plus, Lace Sensor Golds into a Line 6 POD HD500X
Left out into Egnater Renegade 410
Right out into the BYOD Tweed Royal

Results:
Holy s*!t I am a rock star with a really expencive multi effects pedal, If I could really play I could sound like anyone!
No fizz, pure clean tone.

So I believe the Amp selector and Stereo FX Router is having a hard time with the output of the HD500X. I adjusted the Master out on the HD500X but that did not change the fizz sound heard during note decay.

Any ideas, and thanks for the input. No pun intended!


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PostPosted: Tue Aug 22, 2017 8:36 am 
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What if you try only one channel of the POD at a time?

Also, on the schematic the inputs are labeled A and B, not left and right. Therefore, its not clear from your description which one is which.


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PostPosted: Tue Aug 22, 2017 9:15 am 
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A is the Right input. Which is also the one I plugged just the guitar into.

If I take a mono output out of the HD500X and run itinto the A of the Amp selector I can still hear a faint fizz, but not as much as running 2 outputs from the HD500X to A and B.


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PostPosted: Tue Aug 22, 2017 9:33 am 
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If coming from the router, the fizz is likely to be from the -9 volt power supply. You could remove the 1044 charge pump voltage inverter and connect two 9 volt batteries up as a test, one for the +9 volt power, and other other battery for the -9 volt power. Or maybe use a battery just for the -9 volts and still use the wall wart supply for the +9 volts. Or use a bench power supply instead of the 1044 for everything.

In other words, just see if the 1044 is causing the problem. Not that it is likely to be defective although it could be. They just don't supply very clean power, or very much current. They are popular for use in some guitar pedals, but guitar pedals are typically built to a price point and dual external power supplies are expensive. And, most guitar players don't notice the difference anyway.

You could also try dropping in a LT1054 charge pump instead of the 1044. http://www.ti.com/lit/ds/symlink/lt1054.pdf They are a little better than 1044 versions.

Also, it helps to use low ESR (Equivalent Series Resistance) capacitors with charge pump power supplies. Aluminum Organic Polymer Electrolytics with ESR or 40 milliohms are available and not too expensive. Normal electrolytics, either aluminum or tantalum, typically have ESR values up around 25 ohms or maybe even higher. Maybe 500 times worse than Organic Polymer caps. That would be C3, C4 and C5 on the schematic.

Also, shorting one of the opamp outputs when one of the input jacks (applies to input B only) is plugged in could worsen any power supply problem. Perhaps a good idea to put a resistor in series with that output or with the ring connection on the input jack. 10k would probably be plenty, and 1k might even be enough. Probably somewhere around there, a few k-ohms. It would probably be better than relying on current limiting on the opamp output which might waste a few 10's of mA's of power supply current.


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PostPosted: Tue Aug 22, 2017 10:40 am 
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I'd try what Markw1 suggested. I'd start with the ESR caps first. I'm most curious about that. There seems to be a growing problem with digital modeling pedals interacting with analog pedals that use charge pumps. Of course, I think the onus lies with the manufactures of the digital pedals to make sure they don't have this problem, but if it's a simple matter of just using ESR caps in the power section of the pedal with the charge pump, that would be very easy to fix.

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PostPosted: Tue Aug 22, 2017 2:10 pm 
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byoc wrote:
I'd try what Markw1 suggested. I'd start with the ESR caps first. I'm most curious about that. There seems to be a growing problem with digital modeling pedals interacting with analog pedals that use charge pumps. Of course, I think the onus lies with the manufactures of the digital pedals to make sure they don't have this problem, but if it's a simple matter of just using ESR caps in the power section of the pedal with the charge pump, that would be very easy to fix.

Changing to an LT1054 charge pump at the same time couldn't hurt. We've seen that chip solve a couple of other noise problems in the past....

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PostPosted: Wed Aug 23, 2017 11:17 am 
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I would like to try changing the charge pump as recommended. I looked at a local suppliers web site for the LT1054 and got 10 different results. Would someone be kind enough to tell me which is the correct one? I would be very grateful. Here is the web site.

http://se.rs-online.com/web/c/semiconductors/power-management-ics/charge-pumps/?searchTerm=lt1054


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PostPosted: Wed Aug 23, 2017 12:57 pm 
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Any of the 8-pin PDIP/through-hole type should work. I think the main difference is the cost per IC depending upon how many you buy. I only see one that is listed as letting you buy a single chip, and that one is 65 kr. FYI, that's about twice what we pay for them here in the US (~$4 is typical). You can do better if you buy a package of 5, though you'll obviously pay more overall (~111 kr). Incidentally, the difference between the LT1054CP and IP versions is just a wider operating temperature range for the latter, but both are well suited to a pedal application.

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PostPosted: Thu Aug 24, 2017 1:52 am 
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duhvoodooman wrote:
Any of the 8-pin PDIP/through-hole type should work. I think the main difference is the cost per IC depending upon how many you buy. I only see one that is listed as letting you buy a single chip, and that one is 65 kr. FYI, that's about twice what we pay for them here in the US (~$4 is typical). You can do better if you buy a package of 5, though you'll obviously pay more overall (~111 kr). Incidentally, the difference between the LT1054CP and IP versions is just a wider operating temperature range for the latter, but both are well suited to a pedal application.


Thank you for the reply, and taking the time to help. You guys rock!


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