Tore-t ReVibe grounding

[Sethyrish]

Hi,

I'm just about to start assembling a Tore-T ReVibe and would like to get the grounding correct. Does the Tore-T version still require input, output, pots and circuit grounds to be isolated from the from the chassis?
Is there grounding through connection to amplifier?
Someone on this forum mentions a ground lift switch. What is the purpose of this. Is it dangerous?
Is it worth implementing a circuit loop breaker as mentioned here:
http://sound.westhost.com/earthing.htm

Sorry for the questions but better to get it right first off if possible!

Cheers

[sluckey]

I did not use any isolated jacks or do any fancy ground lifts with my revibe. I haven't experienced and ground problems with the 4 amps I've had it connected it to.

Could you post a top view of your board?

[Sethyrish]

My board isn't standard. I've copied the excellent example (link below) and used visio to rearrange it to match my Trainwreck rocket amp. I can't be sure mine is correct as I'm a bit of a newbie.

There seems to be a bit of info on the net about ground loop problems because the original didn't have a earth ground so I assumed it was a common issue. I guess that's the net for you!

http://home.comcast.net/~seluckey/amps/revibe/revibe.htm

[sluckey]

Ah, OK. I had noticed the board seemed to be mirrored, and I was concerned that you may have put the turrets on the wrong side of the board. Now I see that you have mirrored the entire layout.

BTW, you need to remove the cap and resistor that I circled. That changed from my original. See the note about rearranged power suppy nodes .

[Willabe]

I did not use any isolated jacks or do any fancy ground lifts with my revibe. I haven't experienced and ground problems with the 4 amps I've had it connected it to.

Wouldn't the easiest, cheapest and safest way to kill a ground loop between 2 pieces of gear/chassis safety ground loop be to just use a guitar cable that connects the 2 together that has 1 end's shield not connected? 

That way both chassis would still have the chassis safety ground in place but the loop is broken in the guitar cable.

I think I'd rather rely on the chassis safety grounds and the power cord then the guitar cables shield as they would be more likely to fail?


     
                    Brad     

[Sethyrish]

Wow. How lucky am I you noticed my post. I must have overlooked that.
It's been a bit of a learning curve for me which is why I decided to piece it together and learn how to use visio first.
Yes, I mirrored it only so that my knobs, input and output match with amp. Crazy!!
Your site is very good by the way.

Brad. Yes good point. I did wonder whether that was ok.

That's good news then and will make it much easier to assemble.

Thank's

[sluckey]

Wouldn't the easiest, cheapest and safest way to kill a ground loop between 2 pieces of gear/chassis safety ground loop be to just use a guitar cable that connects the 2 together that has 1 end's shield not connected?

Have you ever done that? Sounds like an invitation for noise pickup to me.

[Sethyrish]

By the way.
I have two reverb tanks. The one recommended 9AB3c1b 3 spring and a two spring Belton  BL2AB3C1B which is 8 ohms in 2250 out. Could this amp drive the Belton?

[Willabe]

Have you ever done that? Sounds like an invitation for noise pickup to me.

Nope, just have seen it mentioned before.

Why would it invite noise? The shield is connected on 1 side and has a path to ground through that chassis. The other cable jack that has no shield connection the shield is inside the jacks metal cover sleeve that is grounded to the other chassis.

Maybe I'm missing something?



                    Brad        

[lego4040]

That is a nice build there and that head is sweet. I hope to have my reverb done soon, I made a booboo on my chassis and need to redo   it should be here by tomorrow

[PRR]

> maybe I'm missing something?

You want to use the "safety" (power 3rd pin) ground to return signal.

Ideally the Safety Ground carries *NO* current.

In any real case, it does. At least capacitive trash from lights and appliances. And usually "some" 60Hz leakage. "Some" could be very-small from a safety point of view, yet very large compared to guitar signals.

Unless you are very blessed, I think when you Try It you will be overwhelmed by hum, buzz, and hash. Next best thing to a totally broken ground.

[Sethyrish]

I stumbled on JBGretsch post (see link half way down) before I started the project as well as a few other posts regarding ground loop problems and just became a bit fearful it was going to be noisy.
As sluckey said he had no problems, I'm happy not to go isolating pots etc.
The amp I built has a subtle hum at low volume which my friend said is standard for valve amps. Basically, I'm not that confident  or experienced with grounding vs star grounding or the idea of using the chassis in the circuit.

I bought some 1mm brass plate today to etch the face-plate using the toner transfer method used for etching PCB's. It looks nice on my guitar amp.

http://gretschpages.com/forum/other-equipment/weber-5g15-reverb/21999/page1/

[Sethyrish]

I finally finished this project and are very happy with the results. It makes my amp sound so much better!
Many thanks to Doug and sluckey for their excellent information allowing inexperienced DIY’s to get a finished project.
As sluckey mentioned, I had no issues with noise using his ground plan.
I did end up using pot isolation just in case I had to back track but they’re still grounded to chassis in the same locations apart from pot shells.
I etched the brass face plate using the toner transfer method which was a bit of a hassle as I had to align two A4 sheets. The coppery patina was achieved by pouring a copper sulphate solution to the etched plate and heating up with a blow torch. A bit hit n miss with regards to final colour as the back plate shows. The aged pine look was achieved with 0000 steel wool left in a bucket of vinegar for a week, then paint on to raw wood and wax with the same grade steel wool. The more Tannin in the wood the darker the colour.

It didn’t work at start-up and made some horrible noises but checking the circuit from input I discovered one of the jumper wires under the board went to wrong location! Note to self ‘triple check before assembly’.

The foot pedals are a side project and one reason why it’s taken so long to finish.

[Willabe]

Very Nice!!!!!!!

I love the cab and face plates!!!!!!

I'd bet the guys would love it if you would start a thread in Effects on your pedal builds! (There's a number of guys here that build great pedals from scratch, a good number of them are posted in the effects section with schemos and pics.)

Do you have a link on how to etch the face plates that you could post? Can you use different colors with the etching other then what you have? Like blue or red........



                               Brad         

[Willabe]

What's the little geared motor for in the upper right hand corner of the pedals pic?


                       Brad     

[Willabe]

I was looking at your T-verb and it looks like you didn't use either a rubber or plastic grommet where the verb PT wires go through the chassis? (I can't see the PT wires going through the chassis.)

There's high B+DCV on the PT's primary and if the wires insulation wears because of vibration and shorts to the chassis.......  Blammo


                Brad   
   

[Sethyrish]

Thanks for the comments Willabe. Yes your right about the grommets. I better get some.
I watched all the youtube's on toner transfer and modifying laminators. I think there's some Indestructables as well. Same technique as PCB etching.
I swapped the temp switch and safety fuse to handle 175 deg C instead of 145 and swapped the motor from 5RPM to 1RPM. all parts from ebay. $20 US in total maybe. Lots of hours spent stuffing about so probably only worth it if you plan to do a lot.
I used the cheap yellow toner transfer paper from ebay and a HP Laserjet 1102w.
https://www.youtube.com/watch?v=B9LmE-H-SHU

Ferric chloride with some citric acid powder to etch.
http://www.nontoxicprint.com/etchcopperandbrass.htm
http://www.instructables.com/id/Toner-transfer-no-soak-high-quality-double-sided/

OK, I'll put the pedals up when there finished and working.
The motor is out of a old printer. I was tossing up whether to use the toothed belt and rod to make the  wah pedal PCB on the right.
To make the picture stand out, I applied artists oil paint (any colour) with a credit card, then gently wipe of the surface with phone book paper. The paint is left in any crevice so you have to be conscious of this when designing artwork. This was done after the blow torch chemical patina. I used illustrator and photoshop.
http://www.sciencecompany.com/Patina-Formulas-for-Brass-Bronze-and-Copper.aspx

All of this took longer than making the actual amp but useful for future projects. Next, maybe Bassman 5E6A!

Cheers and good luck!