Two variacs for dummies...

For all things to build the brown sound

Moderators: VelvetGeorge, RACKSYSTEMS

Robocop101985
New Member
Posts: 30
Joined: Mon May 28, 2012 2:09 am
Just the numbers in order: 7

Two variacs for dummies...

Post by Robocop101985 » Sun Aug 23, 2015 10:12 pm

Hey guys...

Pretty intrigued by this two variac system here... Have one I'm using at 90v for my metro which is slaved into another amp right now but was wondering how the second variac system works. Basically can someone tell me how this works and what I need to do to make it happen. Where do I get that variac as well?? Any help would be greatly appreciated.

User avatar
plexified
Senior Member
Posts: 856
Joined: Sun Dec 25, 2005 12:49 pm
Just the numbers in order: 13492
Location: amidst the wreckage of a hot Plexi

Re: Two variacs for dummies...

Post by plexified » Tue Aug 25, 2015 10:52 pm

Hey whats up ,
to clarify a bit , one variable autotransformer is used to adjust the line voltage or stabilize it . New amps run 118 line voltage, vintage amps were designed for 110 for full voltage. Sometimes if you measure the wall voltage its got variances , so this is used to set the voltage. Some like to turn down this voltage to get a tone and when doing so the bias needs to be of concern. The second variac you refer to is used in between the amp and cabinet . A setting of 90 is considered unity . Turning down just lowers output . But you need to wire a jack from the amp into the variac input . Plus and minus , ground is not used . Out is to the cabinet , again wired in the same polarity . So fat blade could be plus or minus on the input or output , but they must be the same in and out.So its a conversion from a wall plug to a 1/4 inch jack .
To again use the main line voltage correctly do this . Power the amp on and with standby off into the mains variac . Bring the voltage up slowly to power the amp . Let it warm for say five minutes to warm the heaters . Then dial it down to zero Now flip the stand by switch ON and slowly bring the amp to power slowly . This is called a soft start . Now your ready for action. The second variac can be lowered to attenuate volume . That's about it .

jnew
Senior Member
Posts: 1577
Joined: Mon Jan 07, 2013 9:34 am
Just the numbers in order: 13492
Location: Front Row Seat From the Outer Continental Shelf

Re: Two variacs for dummies...

Post by jnew » Wed Aug 26, 2015 10:40 am

I found the 2nd variac that I'm using, on e-bay. There are lots of them. An old one that has no ground connections and old school binding post's, is the way to go for this. Mine was like $40 or $45. With this old type, you can just leave your normal speaker cable plugged into the head and cab, simply cut the cable a couple feet from the head, strip down to bare wires and bind them. Easy as pie. Just do like David said and keep the phases the same or your amp will be trying to push the speakers inward instead of outward. Hmm, :scratch: did I just throw out an idea to try.
________________________________
I SEE THINGS BETTER, WHEN I LISTEN


http://www.soundclick.com/bands/default ... ID=1214336" onclick="window.open(this.href);return false;

User avatar
plexified
Senior Member
Posts: 856
Joined: Sun Dec 25, 2005 12:49 pm
Just the numbers in order: 13492
Location: amidst the wreckage of a hot Plexi

Re: Two variacs for dummies...

Post by plexified » Thu Aug 27, 2015 11:36 pm

J , in fact you did. The traditional Marshall plays 'backwards' compared to a 'Bassman' in which it was a brother in design. The Bassman pushes the cone forward , the Marshall actually plays backwards when you hit a note. The cone pulses into the cab. You would simply reverse the polarity on the speakers to try the two . I had interesting results with a pair of cabs I did this with. I had to develop at least a mental note , because with my Kendrick/Trainwreck Climax I have to insure the speaker polarity is the same or it cancels frequencies when played together and sounds weird. But when set up correctly , it sizzles and peels paint of the wall and makes the girls smile like the vibrations do to them when riding a Harley . So in that sense the binding posts are killer to just flip it around. Personally I have a jack I made that switches the polarity and its sweet. Might see the light of day in your mailbox. Whats your pickup in those clips J ? Again wrap your arms around the fact that your tone slays the iso tracks for Mean Streets. Just wanted to make that sink in player. Its so nice also cause its not drenched in Eventide. Drenched in some mad scientist special J sauce . Me likey .

dirtycooter
Senior Member
Posts: 2923
Joined: Fri Oct 03, 2008 3:02 pm

Re: Two variacs for dummies...

Post by dirtycooter » Fri Aug 28, 2015 3:11 am

Phase really isn't THAT noticeable until you have two cabs running and one is reversed. Bass response says SEEYA! Thins right out. Phase cancelation occurs. Inward or outward excursion matters not-they just have to match. True the Marshall was a bassman copy-with a reverse phase output from the bassman-but which is really correct??? :lol: . But kinda irrelevant I think to tone. Maybe there are some differences playing around with inward or outward excursion. But not like having two out of phase cabs in the same rig. When wiring up your cabs? Make sure they are all done the same and correctly -positive and negative swap just at the input jack can reverse the entire cab. Out of phase speakers in the same cab raise hell too. Thin wimpy and shitty tone. Flip over to "in phase" and feel the phatness :wink: In phase is simply "matching phases" as neither is wrong really.
I dunno how much it matters with one cab being one way or the other though if that's all you are using is one cab. :what: A bassman sounds fat and so does a Marshall. In fact the right bassman sounds like a Marshall ALOT sometimes. Sounds fine if you have both in a band running same time with two guitar players using one each. Phase cancelation only can occur in a single source or player rig. Mics put a spin in there too but that's another story and subjective really-as out of phase blends can make things swing. There is in and out of phase here and many other points in between this even. 45 and 90 degrees + or- . Even PCM's have offsets like this in the stereo field image. None is right or wrong-just different.
I have a switch for phase of my slaved wet cabs-instant A/B and noticeable.
Then.... There is latency. Another subject but raises even more hell than phase I think or at least just as much. Nonlatency and then latency running together generally sound more than horrid-its gritchy harsh.

jnew
Senior Member
Posts: 1577
Joined: Mon Jan 07, 2013 9:34 am
Just the numbers in order: 13492
Location: Front Row Seat From the Outer Continental Shelf

Re: Two variacs for dummies...

Post by jnew » Fri Aug 28, 2015 11:42 am

:shock: :shock: :shock:
NO SHIT? Well damn. I will definitely have to try this. So for anyone who's doing a wet/dry with the dry being straight head to cab, then it's likely to be out of phase with any power amp powering the wet cab. Or at least something one needs to be cognizant of. Wow. I have to make a swap and give it a good listen. There has to be a noticeable difference even with just one 4X12. For one, the cone punching outward first should theoretically be more present and punchy as it is not coming outward on the rebound part of the cycle. However, it also seems that the influence of the cab resonance may be lessened. How much? Who knows but very intriguing stuff in my mind. Recording some close mic A/B clips would probably be most revealing. I'm on it.

David, awesome compliments bro. Really glad you dig it. The PU is just a plain old Duncan Custom. I know most are all about an AlNiCo II, PAF type. I don't know if it has ever actually been confirmed what was really used but I just hear ceramic. At least with my amp. There's a lot of photo's with DSD's and old MM knock off's which say a lot to me about those times. And to me, the AlNiCo 8 tone in the Destroyer would closer resemble a ceramic mag than an AlNiCo II. :what:
________________________________
I SEE THINGS BETTER, WHEN I LISTEN


http://www.soundclick.com/bands/default ... ID=1214336" onclick="window.open(this.href);return false;

jnew
Senior Member
Posts: 1577
Joined: Mon Jan 07, 2013 9:34 am
Just the numbers in order: 13492
Location: Front Row Seat From the Outer Continental Shelf

Re: Two variacs for dummies...

Post by jnew » Fri Aug 28, 2015 5:10 pm

Quickie A/B clip with the Phase reversal. 1st half is standard Marshall, head to cab phase. 2nd half is reversed at the 2nd variac, a la Fender. Not a huge difference at all but there is something noticeable. :lol:

http://www.soundclick.com/bands/page_so ... D=13198323
________________________________
I SEE THINGS BETTER, WHEN I LISTEN


http://www.soundclick.com/bands/default ... ID=1214336" onclick="window.open(this.href);return false;

User avatar
plexified
Senior Member
Posts: 856
Joined: Sun Dec 25, 2005 12:49 pm
Just the numbers in order: 13492
Location: amidst the wreckage of a hot Plexi

Re: Two variacs for dummies...

Post by plexified » Sun Aug 30, 2015 1:41 am

Of course phase needs to be in 'concert' , but remember , Marshall was using 20 watt paper cones . Tell me what you think about a reverse throw to the back panel with a wicker can grille or bluesbreaker grille cloth? It was done to make the cones live. It also was pushing against the inside air mass of the cabinet . Much more forgiving than throwing out. It made those speakers live . Like I had said many times , I could play my 12 series with 6ca7's proper on 110 with a 20 watt ceramic G12 cab and the tone is amazing. Its a tug of war. Feedback and cone control here. If you cannot control the cone you bounce the coil off the backplate , heat it up and these days burn up a 5K$ cabinet. Be it angle or straight. Now factor in open back bluesbreaker cabs and combos and phase and really think , because its not something to ignore. Where are you throwing the tone , how and in what circumstance. And Greg was right , I am not an EE , but I learned from the best and try to pass it along to you guys. Kudos to Greg for pointing that out. In a cab the cone has to push and suck off the backside of itself if sealed when pushing or 'backup and suck off itself" when reversed and the cloth is their to filter and limit. Limit mike stands crashing into it , as well as restricting high end and air movement. Two different sounds and done for a reason . Now back to combos and pushing off the back wall or pushing away from it . Hmmm.

Robocop101985
New Member
Posts: 30
Joined: Mon May 28, 2012 2:09 am
Just the numbers in order: 7

Re: Two variacs for dummies...

Post by Robocop101985 » Tue Sep 01, 2015 1:48 am

Ok guys... I appreciate all the advice but I'm still a little confused. Not sure if it's just cause I'm confusing myself with overkill on detail or it's just late on when I'm reading this. Essentially, I have a couple more questions that should be easy to answer.

Number one: are these the same variac
image.jpg
image.jpg (55.08 KiB) Viewed 4821 times
image.jpg
(1.35 MiB) Not downloaded yet
Number two: If they are the same variac, do you guys need a power supply for the variac between the cab and amp? The red variac pictured does not have a power supply. I'm used to seeing some attenuators with a power supply so I just assumed the modded variacs would have it's power supply in use.

Jnew said at this point all I would have to do is strip the speakers cable wires and apply them accordingly to the posts. Is that right so far?

Is there a specific way I can tell which wire goes to which post? Also having the wires exposed on the varic is there any danger if I were to touch a bare wire? (Better safe than sorry)

Now with the second variac basically this can be thought of a master volume? So if the variac would be on zero, there would be no sound coming from the cab right?



Sorry about the "airheadiness" with this. Just wanna make sure im not screwing something up and end up blowing up something. I'm sure I'll have more questions as more of you post so I'll apologize in advance. Thanks again for all the help.

User avatar
JimiJames
Senior Member
Posts: 3550
Joined: Fri Dec 23, 2005 6:32 pm
Just the numbers in order: 13492
Location: Chicago
Contact:

Re: Two variacs for dummies...

Post by JimiJames » Tue Sep 01, 2015 9:12 am

plexified wrote:"...Now back to combos and pushing off the back wall or pushing away from it . Hmmm.
IDK Does something like this happen ? :what:
Image
:scratch:
Last edited by JimiJames on Tue Sep 01, 2015 11:04 am, edited 1 time in total.
RIP Mark Abrahamian-rockstah -classmate/roommate
RIP Ben Wise -StuntDouble- comrade-in-arms

__________________________________________
Build'sClip'sVid's

jnew
Senior Member
Posts: 1577
Joined: Mon Jan 07, 2013 9:34 am
Just the numbers in order: 13492
Location: Front Row Seat From the Outer Continental Shelf

Re: Two variacs for dummies...

Post by jnew » Tue Sep 01, 2015 10:20 am

Robocop, that red variac is perfect for placing between the head and cab. Very similar to the old POS I use. That red one has an on/off switch that you would just leave "ON" all the time. Remember, this 2nd variac is not plugged into the wall power but still has to be "ON" for the signal to pass from the head to the cab. So to answer your question, no power supply. Think of this 2nd variac as a signal transport terminal. Just a place where the speaker cables +'s and -'s connect, ONLY. No AC voltage and no ground connections. It looks like there is a fuse too. Make sure a fuse is in there. (new ones might be shipped without)

So all you have to do is cut the speaker cable, strip the +'s and -'s to the bare wire and bind them to those red and black binding post's. Keep the positives of the head and cab on the red post's and the negatives on the black post's and your phase will be proper. Although, you can switch this around and experiment as I did.

As far as touching any bare wires, I can't imagine you would even feel anything. I hot swapped mine with my amp on standby with no issues. Put it this way, working inside the amp chassis is waaayyyy more dangerous in comparison. So if you use all the same precautions, you're completely in the green, safe zone.

Setting the 2nd variac at about 90 (again, even though there is no AC voltage) is where the unity is realized. Meaning the cab will be as loud as if the head was plugged straight to it. I've not gone above the 90 mark so I can't speak of any results. I have dialed it down to 70 just to see if it gets quieter, and it does but really not by much at all. As far as dialing it down to "0". I don't know. I haven't done it and I really don't recommend it. Remember, your OPT tubes and transformer are looking for a particular range of impedance/resistance. So pinching down too much (dialing down too far) may not be desirable. Just my suggestion.

Keep us updated on your progress with this. :wink:
________________________________
I SEE THINGS BETTER, WHEN I LISTEN


http://www.soundclick.com/bands/default ... ID=1214336" onclick="window.open(this.href);return false;

Robocop101985
New Member
Posts: 30
Joined: Mon May 28, 2012 2:09 am
Just the numbers in order: 7

Re: Two variacs for dummies...

Post by Robocop101985 » Tue Sep 01, 2015 12:31 pm

Thanks again Jnew for the input.

So what does the 2nd variac actually do? I've been thinking this was acting like an attenuator, where i would be able to cut the volume at a reasonable level and still have a cranked marshall tone while the amp is still happy with the load.

My current set up has a variac from the wall set at 90 from my metro which is cranked into a dummy load then signal goes into a landry amp. Basically what I'm trying to achieve here is the clearest signal from my Metro head to my cab that is still cranked. I'm putting the signal through another amp which is gonna color the tone in an unique way as other things such an attenuators and power amps.

jnew
Senior Member
Posts: 1577
Joined: Mon Jan 07, 2013 9:34 am
Just the numbers in order: 13492
Location: Front Row Seat From the Outer Continental Shelf

Re: Two variacs for dummies...

Post by jnew » Tue Sep 01, 2015 2:09 pm

A couple things I could suggest. I don't know where you're amp is biased but as an example, I've recently biased mine to 70% dissipation using 110VAC on the the first variac. Then dropping the voltage to 90VAC. I used to bias it at 70% dissipation at 90VAC, and it was still pretty friggin loud. (Note: there is A LOT of experimentation that can be done here. Plate voltages vs. bias dissipation vs. desired volume, etc. Mucho variances here for tone and volume options)

Are you running your head on 16 ohms, into a 16 ohm cab? If so, drop the amp to 8 ohms. This is a one step mismatch which many, including myself, use. It doesn't make a tremendous difference volume wise but it helps. More importantly, it shifts the frequency slope a bit which helps some amps with flubby low end issues. Also changes the compression dynamics a bit (for the better IMO)

Is your amp a 100 watter? Pull the two outer power tubes and drop the impedance selector on the head one position. This will also help with volume issues. I do this with my 100 water and set the head to 4 ohms, into the 16 ohm cab.

Maybe Roger will chime in here but I think using one speaker out to a dummy load with the other speaker out to the cab also makes a pretty considerable difference. I have not done this myself but it makes sense to me.

I have also had a custom 2X12 cab made that is nearly the same size as a 4X12. The idea here is moving less air. And it too makes a difference. David offered up the brilliance of wiring only two speakers in a 4X12. The two speakers not being used, become bass resonance devices, so to speak, which further offers tightening and control of any unwanted flubby stuff. Thinking about this concept alone, if you only had the bottom two speakers going, your can get away with a lot because you don't have it beaming at your face. Especially if you have an angled cab. Just keep in mind, all of your impedance stuff if doing this.

Lots to play with here bro and yes, the 2nd variac can also be dialed down and it too will make a difference. I don't use the 2nd variac to lessen volume though. Just for the magic that it does to the tone and feel.

Overall, I think my volume is about spot on for rehearsing with a band and/or gigging average sized clubs. I could be way off base as I haven't jammed with anyone in a long, long time. And I don't ever have anyone come over and play or talk gear because none of my friends locally are into guitar or music. Only one actually but he's yet to hear my stuff fired up. He was actually the owner of TTM Guitars and Kerri King of Slayer tried to sue him. :lol: Long story but funny.
________________________________
I SEE THINGS BETTER, WHEN I LISTEN


http://www.soundclick.com/bands/default ... ID=1214336" onclick="window.open(this.href);return false;

Robocop101985
New Member
Posts: 30
Joined: Mon May 28, 2012 2:09 am
Just the numbers in order: 7

Re: Two variacs for dummies...

Post by Robocop101985 » Tue Sep 01, 2015 6:34 pm

I'm running a 100 watt 12xxx series metro at 90v. My plate voltage is running around 350v and I biased at 60%. I tried running them hot at one point but wasn't too impressed on how it sounded so I went back a bit. So essentially I'm turning the variac to 90v and staying there with the tubes biased at that voltage. I might have to try the variacs voltage turned up with it biased and then turn down the variac to 90v. My Metro runs into the dummy load at 16 ohms, but the Landry is running 8 ohms into the 16 ohm cab.

Wiring only two speakers in the 4x12? Anyone have a diagram that will tell me how to go about that?

So for the 2nd variac, what is it actually doing. You guys said that 90 is the sweet spot for the for this one. Is this something that I would have to try in order to understand it?

If I keep my current set up where I'm slaving my metro, where do think I would put the 2nd Variac? Between the Landry amp that is actually going into the cab or would I put it in between the amp and the dummy load? Again, thanks for all the help guys.

jnew
Senior Member
Posts: 1577
Joined: Mon Jan 07, 2013 9:34 am
Just the numbers in order: 13492
Location: Front Row Seat From the Outer Continental Shelf

Re: Two variacs for dummies...

Post by jnew » Tue Sep 01, 2015 7:59 pm

Ok. Let's get the Landry out of the equation here. The 2nd variac goes between head and cab. All the other things I talked about, are things to help with your volume management. I assume you are re-amping for volume management. When you bias your amp at X Voltage, and then drop the voltage, the bias goes colder as you turn down the voltage so it's ok for the tubes. If you drop the voltage and re-bias, you'll get louder again. Lots of options here but you get the idea. Head to cab is where you want to be.
What 4X12 are you running and what impedance a are the speakers?
________________________________
I SEE THINGS BETTER, WHEN I LISTEN


http://www.soundclick.com/bands/default ... ID=1214336" onclick="window.open(this.href);return false;

Post Reply