Two variacs for dummies...

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jnew
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Re: Two variacs for dummies...

Post by jnew » Mon Oct 05, 2015 10:44 am

Then you have to fabricate some old two wire electrical cord to 1/4" speaker plugs. Easy enough to do though. No ground used for this. Just + and -. 8)
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Re: Two variacs for dummies...

Post by Velva » Mon Oct 05, 2015 7:49 pm

Jnew, thanks for the help and clips! I still can't wrap my head around one thing.

When I opened up the cable there is a black and red wire. Easy enough. I can strip the wire on one end so that the black and red wire will hook up directly to terminals inside the variac. I will do this twice as I have an IN from the head and Out that goes to the cab. Done.

The part I just don't understand (maybe I'm a little slow) is:

1. Where do I connect the red and black wire coming from the Head and where do I connect the red and black wires going to the Cab in the picture I posted? Maybe I have wrong type of variac?

Thanks again... not trying to be difficult. Any thoughts are appreciated.

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Re: Two variacs for dummies...

Post by erupturchops » Tue Oct 06, 2015 9:53 am

Has anyone had any issues with this set up regarding the amps "health?"

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Re: Two variacs for dummies...

Post by jnew » Tue Oct 06, 2015 10:20 am

I'm going to make a short video on using a second variac and include how to connect and make up cables. Shoot me a PM with your e-mail address.

As far as the health and welfare of the amp, well, I've been a couple months into this and have had "0" problems. And by that, I mean cranked for hours at a time. I've been using a variac since 07 when I did my first amp. There was lots of conjecture about it being bad and a tube killer and the possibility of an OPT Trans, etc. I run at 90VAC most of the time but as low as 65VAC for some quieter moments. Between 80VAC and 90VAC is where it lives. That amp still uses the same tubes and sounds as good as the first week it was done. I call it plenty safe. Never even popped a single fuse over all those years. But this is by no means a guarantee. Just my personal experience. 8)
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Re: Two variacs for dummies...

Post by erupturchops » Tue Oct 06, 2015 12:20 pm

So you think it's safe to say that the amp is getting the correct amount of resistance so there isn't any damage?

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Re: Two variacs for dummies...

Post by jnew » Tue Oct 06, 2015 1:05 pm

I do. I think It pretty much just equates to a long bunch of copper windings that would be very similar to a speaker cable 300 or 400 feet in length as previously talked about, although it is a variable transformer. I don't know much more about the electrical specifics beyond that but thus far, it's been remarkable on harmonic tone and feel of performance with no apparent negative impacts. 8)
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Re: Two variacs for dummies...

Post by rgorke » Tue Oct 06, 2015 2:48 pm

erupturchops wrote:So you think it's safe to say that the amp is getting the correct amount of resistance so there isn't any damage?
You can also double check by putting a meter on the end and check what the amp would be seeing in terms of resistance...which we know is different that impedance but close enough.
"If you make a mistake, do it twice and smile and let people think you meant it." Jan Van Halen.

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Re: Two variacs for dummies...

Post by jnew » Tue Oct 06, 2015 3:51 pm

You have a 2nd Variac going Roger? 8)
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Re: Two variacs for dummies...

Post by erupturchops » Tue Oct 06, 2015 4:13 pm

rgorke wrote:
erupturchops wrote:So you think it's safe to say that the amp is getting the correct amount of resistance so there isn't any damage?
You can also double check by putting a meter on the end and check what the amp would be seeing in terms of resistance...which we know is different that impedance but close enough.
How would I go about checking that?

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Re: Two variacs for dummies...

Post by rgorke » Tue Oct 06, 2015 4:32 pm

jnew wrote:You have a 2nd Variac going Roger? 8)
no, just one for the wall voltage. My attenuator has a transformer in it so it may be acting the same way.
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Re: Two variacs for dummies...

Post by jnew » Tue Oct 06, 2015 4:33 pm

8)
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Re: Two variacs for dummies...

Post by mightymike » Wed Oct 07, 2015 11:27 am

When Jnew sets his variac to unity, he is basicly impedence matching, and transformer coupling the plate load to the speaker load.

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Re: Two variacs for dummies...

Post by erupturchops » Wed Oct 07, 2015 8:38 pm

mightymike wrote:When Jnew sets his variac to unity, he is basicly impedence matching, and transformer coupling the plate load to the speaker load.

Ahh thanks Mike. Appreciate the input. Can never be too careful.

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Re: Two variacs for dummies...

Post by mightymike » Thu Oct 08, 2015 9:00 am

No prob. I was ordering transformer yesterday and got that info from the horses mouth.

I'm kicking myself because next week I will be visiting Jnew with my 68's , Franky, and Destroyer, and I forgot my variac. I have 2, but 1 is the exact Vintage Ohmite one Ed used.

If different pickup matter, and different transformers matter, I'm curious how much having the exact Variac will matter. You never know till you A/B it.

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Re: Two variacs for dummies...

Post by erupturchops » Thu Oct 08, 2015 9:51 am

mightymike wrote:No prob. I was ordering transformer yesterday and got that info from the horses mouth.

I'm kicking myself because next week I will be visiting Jnew with my 68's , Franky, and Destroyer, and I forgot my variac. I have 2, but 1 is the exact Vintage Ohmite one Ed used.

If different pickup matter, and different transformers matter, I'm curious how much having the exact Variac will matter. You never know till you A/B it.

Hopefully there will be some recording during this session?????

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