1776 Cardinal Tremolo Build Help

[amazingalf]

I'm currently building a 1776 cardinal trem and have run into a problem. When the effect is connected I am hearing a buzzing/hum which sounds like it is a grounding issue. Here is what I've been able to determine so far:

• The Rate and Depth knobs appear to be working and cause the hum to happen faster and more deeply. The LEDs connected to the vactrols (d1 and D2) are blinking and changing as I would expect them to
• The volume knob does not appear to be working. The humming noise does not increase or decrease when the knob is turned
• I have been grounding the L pad on the PCB to the sleeve of the output jack

I've double checked the vactrols and they look to be connected correctly. The capacitors, Diode and LEDs also appear to be properly oriented.

I omitted C5, C8 and C2. I filled these pads with solder.

I was able to bias Q2 and Q3 as well as the LEDs. These readings appeared to be within the acceptable ranges.

I originally had this hooked up to the 1776 optical bypass, but removed it during my troubleshooting process. The issues I'm having are unrelated to the optical bypass.

Any assistance or tips on where to start in diagnosing this problem would be greatly appreciated! I have attached photos which may be useful.

The build doc for the tremolo is located here: https://cdn.shopify.com/s/files/1/0022/3952/9069/files/Cardinal-Trem-V2.pdf?16138734983046189115

[PRR]

> a buzzing/hum

Is it in a metal box yet?

[amazingalf]

PRR, I've been testing it inside of a metal box. There is no lid on the box (I don't believe the lid should matter, but please correct me if I am wrong).

From what I can tell, there is no signal from the guitar making it to the output of the effect.

[PRR]

The lid matters. How much? It depends.

No signal from guitar is a significant fault and we should track that first. Usually not an "obscure fault" but simple like mixing IN and OUT or not using the right lugs on the jacks.

[ElectricDruid]

+1 agree with PRR. I'd be looking for one of those apparently-obvious-but-impossible-to-spot errors like not connecting a ground, or getting the signal/ground connections on a jack back to front. I would start by assuming the fault is *not* on the board and work from there.

[amazingalf]

So here it is back in the box. Fingers crossed on something obvious. I haven't wired a stompbox without a switch in the past, so please let me know if there is something glaringly wrong...

Does the sleeve on the input and output need to be wired, or is it sufficient that it is grounded to the chassis?

[amazingalf]

A bit more clarity for where the wires are going.

[PRR]

> is it sufficient that it is grounded to the chassis?

Jack ground, circuit board ground, power ground ALL need to be commoned together.

Looks like you may have both jacks together, and board and power together, but those two not connected to each other.

Clip-leads ARE friends.

[amazingalf]

PRR, thanks for the feedback. I grounded both jacks to the power jack and the effect and then there was no noise coming out of the amp. No hum. But then as I turned up the amp I realized there was a very faint signal coming thru.

I played around with the Bias on Q1 and Q3 and this thing is working!!!! It sounds amazing.

Appreciate the help. Now to install the optical bypass again...

[soggybag]

I built the first version of this and couldn't get it to work. I have a PCB for this version built but not wired up. I'll try and finish this up and see if it works maybe we can compare.

[jimitrader]

PRR, thanks for the feedback. I grounded both jacks to the power jack and the effect and then there was no noise coming out of the amp. No hum. But then as I turned up the amp I realized there was a very faint signal coming thru.

I played around with the Bias on Q1 and Q3 and this thing is working!!!! It sounds amazing.

Appreciate the help. Now to install the optical bypass again...

sweet!

[amazingalf]

I wanted to stop back in to say that I was able to get the optical bypass working and everything is functioning perfectly.

This pedal is awesome. It truly sings. It is a wonderfully clear and customizable tremolo. Highly recommend this to anyone who is thinking of building one. I've built 7 or so pedals the past few months and this is hands down my favorite!

[rankot]

I've built Cardinal Tremolo too, but I notice it has a lot's of distortion (which cleans up when I roll down guitar volume pot). It seems that my input stage is overdriven, although I removed 22uF capacitor. And I tried to bias it as much as possible, until it has minimum amplification, but it still gets overdriven when I turn guitar volume more.

So my question is - if I understood schematics well, it's just another Fetzer valve - is it normal behavior, or I should recalculate Rs and Rd using my JFET's I_dss and V_gs(off)?

Maybe I should add Gain pot instead of 1M gate resistor?

BTW, I have measured my 2N5457, and those are the values: I_dss=1.5mA, V_gs(off)=0.406V.

[duck_arse]

you could try remove C6 22uF as well, or reduce it some. I remember I got distortion when I tried this on the bb years back, too.

[rankot]

I'm already having distortion on the first stage, so 2nd stage is not a problem, but I will try to remove it's source cap as well.

[duck_arse]

perhaps you could add an input cap and a gate-bias to supply resistor, might give you some headroom. maybe?

[rankot]

perhaps you could add an input cap and a gate-bias to supply resistor, might give you some headroom. maybe?

I'll try that, although this input stage is designed as a Fetzer valve.