Into the rabbit hole...36 Watt EL34 Superlite TMB

Double-Bubble! Place for discussing the 36W version...

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TriodeLuvr
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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by TriodeLuvr »

ViperDoc wrote:
Thu 02/18/21 11:52 pm
Billy_Goat wrote:
Thu 02/18/21 3:32 pm
Picture of the internal wiring...
WHITE LOOP JACKS. (searching the internet...) 8)
That's a really clean build! I think AES has the white Cliff jacks.

Jack
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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by Billy_Goat »

ViperDoc wrote:
Thu 02/18/21 11:52 pm
Billy_Goat wrote:
Thu 02/18/21 3:32 pm
Picture of the internal wiring...
WHITE LOOP JACKS. (searching the internet...) 8)
1/4" Jack - Cliff, White, Solder Lug
https://www.amplifiedparts.com/products ... solder-lug
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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by JMPGuitars »

CLIFF also makes different color nuts for those jacks. I know newark.com can get them, I assume some other suppliers as well.
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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by ViperDoc »

Thanks for the link. I wonder if they make a white vintage version with the metal ferrule, but with a white bezel. I prefer those jacks to the plastic nuts. I seem to strip those too easily.

EDIT: Well what do you know?

https://www.newark.com/cliff-electronic ... Connectors
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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by Billy_Goat »

After a fair bit of playing and fussing with effects in the FX loop, it appears that the FX loop on my build is exhibiting a bit of comb filtering and / or phasing shifting that is manifesting as a slight unpleasant ‘hollow’ sound overall compared to when I play without using the FX loop. Not sure how to further confirm this and / or how I would go about trying to rectify if in fact more than just my impression? Any thoughts?
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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by JMPGuitars »

Billy_Goat wrote:
Tue 03/02/21 6:52 pm
After a fair bit of playing and fussing with effects in the FX loop, it appears that the FX loop on my build is exhibiting a bit of comb filtering and / or phasing shifting that is manifesting as a slight unpleasant ‘hollow’ sound overall compared to when I play without using the FX loop. Not sure how to further confirm this and / or how I would go about trying to rectify if in fact more than just my impression? Any thoughts?
It sounds like you have an oscillation problem. You can try chopsticking the wires to get rid of the effect, or use shielded wire and see if that helps. Post some photos of the FX loop and surrounding area.

Thanks,
Josh
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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by Billy_Goat »

JMPGuitars wrote:
Tue 03/02/21 7:18 pm
Billy_Goat wrote:
Tue 03/02/21 6:52 pm
After a fair bit of playing and fussing with effects in the FX loop, it appears that the FX loop on my build is exhibiting a bit of comb filtering and / or phasing shifting that is manifesting as a slight unpleasant ‘hollow’ sound overall compared to when I play without using the FX loop. Not sure how to further confirm this and / or how I would go about trying to rectify if in fact more than just my impression? Any thoughts?
It sounds like you have an oscillation problem. You can try chop-sticking the wires to get rid of the effect, or use shielded wire and see if that helps. Post some photos of the FX loop and surrounding area.

Thanks,
Josh

Hey Josh,

Please see attached photo. If not clear, I'll shoot another.

Not much to chopstick that I can see here based on my build. The two connections to the terminal are shielded and these two shielded connections are not more than an inch or two in length. The rest are soldered as tightly as possible to a 4 lug terminal. The terminal is lifted up from the chassis to the approximate level of the jack terminals with a 1" standoff.

I haven't had a chance to do so yet and also not sure if this would be a proper test setup, but I'm thinking that I feed a white noise signal into the amp input and connect ch. 1 of my oscilloscope to that input signal so I can monitor the input signal. Then connect a guitar cable between the two FX jacks and connect ch. 2 of my oscilloscope to the output to see if I can see any comb or phasing issues between the two traces on the oscilloscope. If ok here, then add some pedals into the FX loop to see if there's something going on there. Basically, I'm looking for a way to confirm empirically that what I'm hearing is actually happening. Would there be a better means of confirming something like this?

As mentioned previously, outside of this FX issue, the amp sounds big, strong and amazing. It is overall quiet - no background ground noise, buzzing or other operational artifacts.

Cheers,
Greg
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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by TriodeLuvr »

Is it wired like this? What's to keep the loop return signal from mixing (potentially out of phase) with the dry signal from the 68K resistor?

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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by JMPGuitars »

Your tag board appears to me that it is essentially allowing your loop circuit to run parallel to long plate wires running next to it.

Take a look how I implement the FX loop: viewtopic.php?p=247480#p247480

I keep all parts (except the 68K which I place directly on the circuit board) running in simple lines, which helps avoid issues like parallel plate wires that you currently have. It may not be the source of the problem, but from the photo, it appears to be the most likely cause.

Changing to the method I use will eliminate that issue and help you see if it's the cause. I don't use any extra wires, the leads from the components are all I you really need. I leave just enough slack to chopstick if needed.

Thanks,
Josh
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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by Billy_Goat »

TriodeLuvr wrote:
Thu 03/04/21 10:11 pm
Is it wired like this? What's to keep the loop return signal from mixing (potentially out of phase) with the dry signal from the 68K resistor?

Hi TriodeLuvr,

Yes, 68K resistor was in place as required. Thanks!
JMPGuitars wrote:
Fri 03/05/21 10:05 am
Your tag board appears to me that it is essentially allowing your loop circuit to run parallel to long plate wires running next to it.

Take a look how I implement the FX loop: viewtopic.php?p=247480#p247480

I keep all parts (except the 68K which I place directly on the circuit board) running in simple lines, which helps avoid issues like parallel plate wires that you currently have. It may not be the source of the problem, but from the photo, it appears to be the most likely cause.

Changing to the method I use will eliminate that issue and help you see if it's the cause. I don't use any extra wires, the leads from the components are all I you really need. I leave just enough slack to chopstick if needed.

Thanks,
Josh
Hey Josh,

Ok, I rebuilt my FX connections.

With all due respect, I'm not a fan of wiring components without providing solid mechanical attachment for the same which your photo appears to indicate, so I built a little turret board where the two caps connect directly to the jacks and the two 'in series' resistors from the caps are attached to turrets. Then shielded wire from there to the main turret board and the last 68K resistor placed on the main turret board. I also added some foil shielding underneath the FX turret board and grounded that. The new turret is also now 1.5 inches above the plate wires lying on the chassis. All components and wiring is now more or less 90 degrees away from the plate wiring lying against the chassis. Nothing parallel.

It seems better upon first check, but admittedly I only had a few mins to play and analyze. So, the jury is still out atm.

If it's determine that this rebuild is still not working properly, I'll reluctantly try wiring as your photos suggests.

Cheers
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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by JMPGuitars »

Billy_Goat wrote:
Mon 03/08/21 2:54 pm
With all due respect, I'm not a fan of wiring components without providing solid mechanical attachment for the same which your photo appears to indicate, so I built a little turret board where the two caps connect directly to the jacks and the two 'in series' resistors from the caps are attached to turrets. Then shielded wire from there to the main turret board and the last 68K resistor placed on the main turret board. I also added some foil shielding underneath the FX turret board and grounded that. The new turret is also now 1.5 inches above the plate wires lying on the chassis. All components and wiring is now more or less 90 degrees away from the plate wiring lying against the chassis. Nothing parallel.

It seems better upon first check, but admittedly I only had a few mins to play and analyze. So, the jury is still out atm.

If it's determine that this rebuild is still not working properly, I'll reluctantly try wiring as your photos suggests.

Cheers
No worries, I understand that not everybody likes to do things PTP, and I too prefer mechanical support for things. BUT, consider this: if you make good mechanical connections on the solder joints, and twist the leads of the components before soldering, you still have mechanical connections and support. The FX loop is physically light, and shouldn't generate any heat, so risk is low. Another option is to use your tag board to hold a zip tie locking the loop physically in place. There's plenty of ways to deal with it, find what works best for you. That's assuming you haven't already sorted the problem.
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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by TriodeLuvr »

Billy_Goat wrote:
Mon 03/08/21 2:54 pm
TriodeLuvr wrote:
Thu 03/04/21 10:11 pm
Is it wired like this? What's to keep the loop return signal from mixing (potentially out of phase) with the dry signal from the 68K resistor?
Hi TriodeLuvr,

Yes, 68K resistor was in place as required. Thanks!
My point was that the 68K might allow a return signal to mix out-of-phase with the dry signal and create the comb effect you're describing.

Jack
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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by Billy_Goat »

TriodeLuvr wrote:
Mon 03/08/21 3:33 pm
Billy_Goat wrote:
Mon 03/08/21 2:54 pm
TriodeLuvr wrote:
Thu 03/04/21 10:11 pm
Is it wired like this? What's to keep the loop return signal from mixing (potentially out of phase) with the dry signal from the 68K resistor?
Hi TriodeLuvr,

Yes, 68K resistor was in place as required. Thanks!
My point was that the 68K might allow a return signal to mix out-of-phase with the dry signal and create the comb effect you're describing.

Jack
Hi Jack,

Sorry, I thought you were asking if I had installed the 68K resistor rather than asking if the 68K resistor might be causing a mixing issue.

With the above in mind, I don't know, but I'm guessing that could be in play based on how I believe the circuit is likely working. Either way, I followed the build as documented. Are you suggesting removing or altering something here?

Cheers
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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by TriodeLuvr »

Billy_Goat wrote:
Mon 03/15/21 8:45 am
TriodeLuvr wrote:
Mon 03/08/21 3:33 pm
Billy_Goat wrote:
Mon 03/08/21 2:54 pm

Hi TriodeLuvr,

Yes, 68K resistor was in place as required. Thanks!
My point was that the 68K might allow a return signal to mix out-of-phase with the dry signal and create the comb effect you're describing.

Jack
Hi Jack,

Sorry, I thought you were asking if I had installed the 68K resistor rather than asking if the 68K resistor might be causing a mixing issue.

With the above in mind, I don't know, but I'm guessing that could be in play based on how I believe the circuit is likely working. Either way, I followed the build as documented. Are you suggesting removing or altering something here?

Cheers
You might want to disconnect one end of the 68K and try it again, just as a test. That would eliminate the possibility of an out-of-phase mix from your effects device.

EDIT: If the problem goes away when you do this, it might indicate the need to revise the effects loop. Again, this is just a test. The root cause might be something completely different.

Jack
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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by JMPGuitars »

TriodeLuvr wrote:
Mon 03/08/21 3:33 pm
My point was that the 68K might allow a return signal to mix out-of-phase with the dry signal and create the comb effect you're describing.

Jack
Assuming it's wired correctly, this method has been around for a long time, and is well tested. The only issues I've seen are PO if it's placed poorly, or the fact that it's passive doesn't work for all effects.
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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by Billy_Goat »

JMPGuitars wrote:
Mon 03/15/21 1:52 pm
TriodeLuvr wrote:
Mon 03/08/21 3:33 pm
My point was that the 68K might allow a return signal to mix out-of-phase with the dry signal and create the comb effect you're describing.

Jack
Assuming it's wired correctly, this method has been around for a long time, and is well tested. The only issues I've seen are PO if it's placed poorly, or the fact that it's passive doesn't work for all effects.
Josh,

I'm wondering if I still have incorrect wiring on the jacks?

The image you pointed to for your build example isn't high enough res for me to zoom in closely to clearly analyze, but are you using CLIFF jacks for your FX jacks? If so, it would appear the BLUE the wire I have connecting my two FX jacks are NOT connected as you have your jacks connected together? Assuming your jacks are CLIFF and all CLIFF jacks are mechanically the same, am I mis-reading this?

Cheers
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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by JMPGuitars »

Billy_Goat wrote:
Mon 03/15/21 3:36 pm
Josh,

I'm wondering if I still have incorrect wiring on the jacks?

The image you pointed to for your build example isn't high enough res for me to zoom in closely to clearly analyze, but are you using CLIFF jacks for your FX jacks? If so, it would appear the BLUE the wire I have connecting my two FX jacks are NOT connected as you have your jacks connected together? Assuming your jacks are CLIFF and all CLIFF jacks are mechanically the same, am I mis-reading this?

Cheers
They are cliff jacks, and they're wired the same as my diagram. I don't know that all Cliff jacks are exactly the same (but most probably are). Though I suspect yours are wired the same as mine anyway, but you switched the jumper wire to the outside instead of inside. It shouldn't matter since one side of the jumper should be lifted when both jacks are inserted.

Take a close look at the diagram here: files/JMPGuitars_18_Watt_Tremolo_TMB_Reverb_Layout.pdf

Both of our FX loops have the capacitors on the right side of the jack. Confirm that the right side of your jack is the latching side (which I'm guessing it is, or you wouldn't get a signal).

Thanks,
Josh
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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by TriodeLuvr »

Does the loop exhibit this issue if you plug in a patch cable?

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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by Billy_Goat »

TriodeLuvr wrote:
Tue 03/16/21 11:22 am
Does the loop exhibit this issue if you plug in a patch cable?

Jack
Jack,

I finally had some time to spend troubleshooting a little deeper. It appears that the amp is not really exhibiting any issues with or without the FX loop in play - at least that I can determine measurement-wise.

I hooked the amp up to my Two-Notes Torpedo Reload box in my studio and ran both pink and white noise into the amp input using a spectrum analyzer feeding into the amp input and then monitoring the output with a second instantiation of the spectrum analyzer .

I then patched a short 6" instrument cable into the FX loop ( no pedals ) and compared the no FX output against the patched FX output. While the noise fluctuates a bit which makes a direct comparison a little dicey, but I was unable to see ( large differences ) or hear any obvious differences between the signals with or without the FX loop patched in. I understand this test may not be 100% scientific, but it's all I can think of to try and eliminate any human bias.

Anyway, I'm guessing that the combination of my pedals is not playing nice with the FX loop unfortunately for whatever reasons. With my pedal board in front of the amp, all is well. I wasn't able to bring along my pedal board to the studio this trip, so I was unable to test that to make any deeper confirmations.

Top screen grab below is the signal without the FX patched in. The bottom with the FX loop patched. The frequency graph on the left of both screen grabs is the input signal being fed into the guitar amp input as a common. The right hand frequency graph on both screen grabs is the output signal.

Cheers!
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Re: Into the rabbit hole...36 Watt EL34 Superlite TMB

Post by TriodeLuvr »

That probably rules out oscillation, which is why I asked the question. This result still doesn't eliminate the possibility of shifted-phase signals mixing in that resistor, though. The only way to know is to plug in the effects that are creating the problem and temporarily lift the resistor out of the circuit.

Jack
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