# Ungrounded amps



## ezcomes (Jul 28, 2008)

i have my dads old Symphonic amp...just like this one...just a little rougher...

https://reverb.com/item/1416905-symphonic-ma-13-vintage-tube-guitar-amplifier

I know some of you have amps like this...how do you play them nowadays and keep from getting shocked?

Are there any adverse affects to your pickups?

Seems like it maight be a good recording amp...although i could always use $350...


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## bzrkrage (Mar 20, 2011)

3 prong plug conversion.
No problems with the pickups.
Mine has tremolo built in.
Great recording amp, not a big gig piece.










$350? I'll be watching to see if it moves.


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## Electraglide (Jan 24, 2010)

I have a couple of Symphonic amps and a couple of Pine/Pepco made amps. Two different companies. Two different CSA# for those with CSA#s.
My MA13 is in a lot better shape than the one on reverb so according to their price I saved a hell of a lot of money when I bought it. I'd say that maybe $75 to $100 might be a very good price for one in very good shape. The one on reverb I'd ball park at $25 to $40. 
I suppose that mic'd properly they might be ok for recording. Mine hum and crackle at times and like older single coils better than newer humbuckers. So far I've been lucky and haven't been shocked. These are the amps I plug my guitars from the 60's into.


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## Cups (Jan 5, 2010)

The problem with these amps is that they have no power transformer. Dangerous current can run through the amp. Many people mod these with line transformers.


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## greco (Jul 15, 2007)

GC member Jon at NextGen could help you get an isolation transformer of the correct rating.

http://nextgenguitars.ca/categories/amp-parts/chokes-transformers.html


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## ezcomes (Jul 28, 2008)

so...how do you do the three prong cord mod?
i would assume, you would add a ground bus, and everything then goes to the ground prong on the cord?
can you still get shocked?

i have thought about an isolation transformer...but previous thinking was...the amp wasn't worth the parts that were in it, why spend a whack on that...


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## jb welder (Sep 14, 2010)

You can't put a 3 prong on an amp that does not have a power transformer (aka widow-maker). You have to install an isolation transformer *and *a 3 prong grounded plug.


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## epis (Feb 25, 2012)

Hi guys, I decided to delete my post because of a few reasons :
I don't want some kid to get hurt performing this "mod" just to have a tube amp.
Despite the fact it works, it's not in accordance with electrical standards (CSA) to tie together neutral and ground wires.
These amps aren't worth efforts, they are to noisy, with crappy speakers installed.
They are cool for amp collectors, but not for everyday playing.
The fact they are made with tubes doesn't mean they are great amps.
If you still think they are good, go with isolation transformer and 3 prong cord.
Cheers, Damir


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## epis (Feb 25, 2012)

deleted post


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## zontar (Oct 25, 2007)

I've been considering doing this on a couple of older amps or maybe selling them with advice to do it.

But I'll probably keep them & make the change


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## Electraglide (Jan 24, 2010)

zontar said:


> I've been considering doing this on a couple of older amps or maybe selling them with advice to do it.
> 
> But I'll probably keep them & make the change


Got anything from before 1965?


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## zontar (Oct 25, 2007)

Electraglide said:


> Got anything from before 1965?


No--they are probably mid 70's (Garnet Stencils).


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## Electraglide (Jan 24, 2010)

zontar said:


> No--they are probably mid 70's (Garnet Stencils).


Those I got 3 of.


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## bzrkrage (Mar 20, 2011)

ezcomes said:


> ...although i could always use $350...


Did someone say something to the seller? It's at $250 /make offer now


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## jb welder (Sep 14, 2010)

epis said:


> Hi guys, I decided to delete my post because of a few reasons :
> I don't want some kid to get hurt performing this "mod" just to have a tube amp.
> Despite the fact it works, it's not in accordance with electrical standards (CSA) to tie together neutral and ground wires.
> ...
> If you still think they are good, go with isolation transformer and 3 prong cord.


It's probably best that you deleted it, thanks. In Canada it's not so lawsuit crazy, but a mod like this is not really for public consumption, even if you or I may do it and get away with it for our own personal use.
Here is why the isolation transformer (or usual isolating power transformer) is such a big deal: we can't guarantee all the wall outlets are grounded and wired correctly.
If you tie neutral and ground together and run it to the chassis, then plug it into an outlet that is not grounded and reverse polarity, you now have 120V on the chassis (and on your guitar strings when you plug it in). This can cause electrocution.
Improperly wired and ungrounded wall outlets are not uncommon in older venues.
The use of an isolation transformer (when power transformer is absent) will avoid all these problems.


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## ezcomes (Jul 28, 2008)

Next gen doesnt have isolation trannys...any idea on where else to find one/how to install?


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## greco (Jul 15, 2007)

ezcomes said:


> Next gen doesnt have isolation trannys...any idea on where else to find one/how to install?


If Jon at Next Gen can't get one for you, I would try ordering one from a local electronics store/supplier.

You will have to determine what size you need based on the output (in watts) of the amp.
Installing the ones I have seen is basically plug and play.

Wait until the experts/amp tech respond to this thread. Especially regarding the specs of the transformer you need to get.


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## epis (Feb 25, 2012)

This one should be sufficient :
http://www.digikey.ca/product-search/en?keywords=hammond 169qs
http://www.hammondmfg.com/169.htm

It has to be installed in the amp.


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## epis (Feb 25, 2012)

This one isn't made in Canada LOL, but it's more than 50% cheaper, I would definitely go with this one :
http://www.digikey.ca/product-detail/en/N-68X/237-1624-ND/1887210


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## ezcomes (Jul 28, 2008)

Will this one work?

http://ca-en.alliedelec.com/hammond-manufacturing-transformers-6k140hf/70009022/#tab=overview


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