John Mayer Signature New Build with Reverb Issue

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mhartman
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Re: John Mayer Signature New Build with Reverb Issue

Post by mhartman »

Great looking build!
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dorrisant
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Re: John Mayer Signature New Build with Reverb Issue

Post by dorrisant »

mhartman wrote:Great looking build!
Thanks again!

I got the bias set at 70% now. Need to do the design and etch for the front and back plates.
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dorrisant
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Re: John Mayer Signature New Build with Reverb Issue

Post by dorrisant »

I still get massive feedback with the return pot set too noon even with V3 pulled... I'm wondering if i need too lower the value of the 220k resistor at the input of V2b... or lower the gain of V2b.

Tony
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M Fowler
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Re: John Mayer Signature New Build with Reverb Issue

Post by M Fowler »

Is the reverb driver transformer matched for the reverb pan your using?
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dorrisant
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Re: John Mayer Signature New Build with Reverb Issue

Post by dorrisant »

M Fowler wrote:Is the reverb driver transformer matched for the reverb pan your using?
Yes... I used the reverb TX from the SoCal 50 and bought a new tank to replace the damaged one that was in the donor headcab. It could have been a mismatched replacement, not likely though. The new one is a Belton 8R - 2.25K long tank. I don't think I have another TX around here to check.

Tony
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dorrisant
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Re: John Mayer Signature New Build with Reverb Issue

Post by dorrisant »

Here is a picture of the area involved:
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amplifiednation
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Re: John Mayer Signature New Build with Reverb Issue

Post by amplifiednation »

So what exactly is the issue you are having? Is the cathode of the reverb driver grounded? I see it's tied to that lug on the perf board.
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dorrisant
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Re: John Mayer Signature New Build with Reverb Issue

Post by dorrisant »

it squeals like a pig whenever you turn the reverb return up to noon. And yes... it is grounded at that lug.

Tony
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bluesfendermanblues
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Re: John Mayer Signature New Build with Reverb Issue

Post by bluesfendermanblues »

Reverse The primary leads on The reverb driver transformer!

(Same phenomenon as with OT's)
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Re: John Mayer Signature New Build with Reverb Issue

Post by amplifiednation »

I think you need to ground the reverb jacks...they don't look like you have any continuity to ground...those plastic washers isolate them from the chassis, and I see you have them tied together and the coax shields are tied to them...but I don't see a connection to ground.

If in fact they are not grounded, they will squeal like a pig Run a wire to the main preamp grounds

edit: now i see...are you carrying the ground through the shield??
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dorrisant
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Re: John Mayer Signature New Build with Reverb Issue

Post by dorrisant »

Thanks guys...

I reversed the primary leads to the reverb transformer. That seems to have killed the feedback squeal.

Yes, the reverb jacks are grounded through the shield on the coax.

Tony
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CoffeeTones
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Re: John Mayer Signature New Build with Reverb Issue

Post by CoffeeTones »

What do you think of the Epi SoCal transformers and sound? Do you know the primary impedance of the OT?
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dorrisant
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Re: John Mayer Signature New Build with Reverb Issue

Post by dorrisant »

I can't remember off hand. I do remember thinking that Fender iron specs were the target and this one was spot on with that notion. As far as the sound... Fantastic! I remember one guy who played it not yet knowing what it was a clone of... he said that it made him feel like playing every John Mayer riff he could think of and proceeded to do so... When I told him what it was he didn't realize that such an amp existed and said that the tone was spot on. Many people have shared this same though about it. I would not hesitate to build with it.
I had planned on building it with the Epi iron and changing the OT if needed. As of right now I have no plans to touch anything about it.
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dorrisant
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Re: John Mayer Signature New Build with Reverb Issue

Post by dorrisant »

Upon further review...

I decided to go back in. I wanted to add the driver stage between the PI and the power tubes. So I did...

Wow! What a difference. Before the added driver, I was hard pressed to find a guitar that could break this amp at all. Now it can be pushed into overdrive easily, even with single coils. All of the comments of increased, tighter bass are true here as well. This amp now rattles the windows!

Gotta get an SRV-type player in here to demo it for some clips.
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Last edited by dorrisant on Sat Sep 16, 2017 4:49 pm, edited 1 time in total.
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martin manning
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Re: John Mayer Signature New Build with Reverb Issue

Post by martin manning »

How did you do the power supply for the CF?
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