isoloated or not on input\output jacks?

[rutledj]

I was reading about the grounding scheme recommended by Merlin (Valve Wizard?) and he seems to indicate isolated input\output jacks should be used. So I'm wondering, on you Fender style builds, has anyone done this (and was it noticeably quieter) or do you just stick with the way Leo did it?

Thanks,
Rut

[ViperDoc]

I did it both ways on the two Princeton Reverbs I built and I couldn’t attribute any noise reduction to the jacks; more for overall lead dress and good soldering, as well as good separation of AC and DC on the chassis.

[Roe]

always isolated for least noise. the output jacks matter alot

[Stevem]

If the rest of the build was done following a good grounding layout scheme and with no Daisy chaining of any grounds then I have never found any benefit to isolated jacks .

I also do not like how they are made of plastic and one good hit cracks them .

I have lost count as to how many of these types of jacks I have replaced in customer Fender amps that use them, both tube and SS!

[jabguit]

I also do not like how they are made of plastic and one good hit cracks them .

Isolating washers with standard Switchcraft jacks are how I fly.


cheers,

[dorrisant]

I like to use #14 solid copper wire for a preamp ground buss terminating at the input jack(s), sometimes at the chassis conveniently close to the input. When using an active effects loop, I ground all things associated with that part of the circuit at that set of jacks. Passive loop grounds are at the jacks too. The OT secondary gets grounded at the output jacks and any footswitch grounding is usually at the power supply dedicated for it, and the jack for that is the only one I would isolate with fiber washers, and absolutely when the supply is bipolar. All of this is done with Switchcraft. I have repaired/replaced too many broken Cliff jacks to ever want to use them in my own builds, so only when the customer wants that "look". Think about how many vintage Fender amps are still being used with the original (40+ years) jacks compared to anything else. Most all PT center taps are grounded close to the PT but never the PT mounting bolts. Mains ground is always as close to it's entrance as possible and always by itself. If this doesn't yield satisfactory results, I will lift the loop ground and probe for a better spot. Sometimes lifting the PI ground and probing will reveal wether it should be grounded with the preamp or not.

[martin manning]

My view is that either type can be equally quiet, if you insure that the ground connection is low-resistance and reliable. Advantages of an isolated jack are that a soldered connection to a ground lug is required (the ground connection is not subject to loosening due to plug insertion and removal forces), and the ground connection can be located as desired. Non-isolated jacks should have toothed washers on the bushings to insure a durable low-resistance ground connection.

[bepone]

here important question is always.. how the amp will work if the chassis is from plastic?
where do you connect input jack?

so for everybody if want to learn about best grounding need to forget chassis at all, like it doesn't exist at all and think little bit.. how, why, where ..

[romberg]

here important question is always.. how the amp will work if the chassis is from plastic?

I think this is good advise. A good grounding scheme will have all the ground current flowing in wires and zero on the chassis. Then a single connection is made from the circuit to the chassis for reference purposes only.

It is of course possible to get away with not doing this all the time. For example using the chassis as a reference connection between star ground points. But then wires are more secure connections and I find it easier to just think about everything as if the chassis is not even there (or a plastic insulator as you mention .

Mike

[bepone]

here important question is always.. how the amp will work if the chassis is from plastic?

I think this is good advise. A good grounding scheme will have all the ground current flowing in wires and zero on the chassis. Then a single connection is made from the circuit to the chassis for reference purposes only.

It is of course possible to get away with not doing this all the time. For example using the chassis as a reference connection between star ground points. But then wires are more secure connections and I find it easier to just think about everything as if the chassis is not even there (or a plastic insulator as you mention .

Mike

yes..
if you are using chassis, then this job level is very advanced .. you cannot route how you want chassis currents , need to be installed by experienced user for no humm and hiss.

also it is not good to learn how to do good grounding! first amplifiers need to be in plastic chassis! then when you achieve to be without humm , hiss and oscillations, you can pass to chassis grounding, then is very easy.. you know where need to be insulated and where is better to use non-isolated jack, where to connect which capacitor etc. which current belongs to which capacitor (current always start form + terminal on dedicated electrolytic cap and finish to the same negative - terminal). you cant mix currents in the ground plane (like chassis) how you are traveling upstream , it is a river of currents,and this need to be respected.

also chassis gnd method gives you problem with the connections with time , 5-10 years, specialy mounting output tubes groundign to output tube socket screw, this is major fail IMO, seen this many times
theoretical "floating amp wiring" in the air, or without chassis , or in wodden plane, or in plastic chassis cannot give this kind of connection problems, you did all handwired and fixed, no humm if the input jack is rusty . so amp wiring topology in total need to be "floating", not in the air but "floating" from the chassis and grounded for safety in one point , usualy on input jack, but in multichannel amp better is where are the channel mixing (or fx loop)