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UFOs as Balanced Monoblocks? (Read 580 times)
CAJames
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UFOs as Balanced Monoblocks?
07/11/20 at 17:56:32
 
Firstly, a little about me. I've been interested in getting a SET amp since I first heard a Cary back in the 90's. But an amp based on the 300B or 2A3 just seemed like to much of a commitment, more like a lifestyle choice than a stereo. And there it sat until a couple months ago I was surfing around and came across the Decware site. And wow, a hand built in the USA SET amp that uses cheap, readily available power tubes and has tube rectification? Yes! This is exactly what I've been looking for.

Then I need to pick what model. I really like balanced connections and I like monoblocks because I really like short speaker cables and my speakers are a stretch even for 6W (eventually I'll get SET friendly speakers, but not right away). But a pair of UFO2s with XLR connections is like 4K$, and it isn't really a balanced amp. Then I see at the bottom of the UFO manual that with the right XLR to RCA splitter I can have 2 true balanced UFO monoblocks for the price of a single UFO2 with XLRs. Yahtzee! Order placed.

So the question is, is anyone else using their amps with XLR->RCA splitters? And what do you think?

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lazb
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Re: UFOs as Balanced Monoblocks?
Reply #1 - 07/11/20 at 18:27:59
 
DECWARE calls their's a ZBIT. Transformer balanced and not built in so you can use it on multiple devices if you want or need to.
https://www.decware.com/newsite/ZBIT.html
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CAJames
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Re: UFOs as Balanced Monoblocks?
Reply #2 - 07/11/20 at 19:25:54
 
ZBIT is a balanced to single ended (unbalanced) converter. What I'm talking about is different.  You take the 3 XLR pins and break them out into 2 RCA cables as a true balanced connection. One RCA is the + signal and ground, the other is - and ground. There is a picture at the bottom of the SE84UFO manual.
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ZYGI
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Re: UFOs as Balanced Monoblocks?
Reply #3 - 07/30/20 at 13:24:41
 
CAJames,

Thanks for bring this to my attention. I had a set of cables made and the results with my monos were stunning.

I had been running the Zbit which I love, but this method, is a game changer with these amps.

Zygi
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CAJames
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Re: UFOs as Balanced Monoblocks?
Reply #4 - 07/30/20 at 15:37:17
 
Excellent! Good to hear it is working for someone in real life.

This is such a cool feature IMO I'm a little surprised no one else wanted to talk about it, but perhaps everyone who is doing it is too busy listening to music to hang out on message boards  ;)
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beowulf
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Re: UFOs as Balanced Monoblocks?
Reply #5 - 07/30/20 at 18:00:13
 
So you buy 2 SE84UFO's and with this custom cable convert them into balanced mono blocks correct?  Very interesting ... who makes this cable and why isn't this talked about more?

EDIT:

You can do the same thing with 2 of the SE84UFO3's right?
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CAJames
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Re: UFOs as Balanced Monoblocks?
Reply #6 - 07/30/20 at 18:22:23
 
So you buy 2 SE84UFO's and with this custom cable convert them into balanced mono blocks correct?  

Yes. Essentially you use the left and right channel of a stereo amp as the plus and minus channel of a balanced mono amp.

who makes this cable and why isn't this talked about more?

I got mine from Signal Cable, you can google them. Dono why it isn't talked about more, it seems pretty cool to me. Instead of buying a ZBIT to convert balanced to single ended, spend a few hundred bucks more to buy another amp and use the balanced signal directly, and get double the power.

You can do the same thing with 2 of the SE84UFO3's right?

I don't think so. A true monoblock only has one channel. You need a two channel amp to make this work. You might be able to do it with two UFO3s on each side, but that seems iffy at best, and probably dangerous.
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beowulf
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Re: UFOs as Balanced Monoblocks?
Reply #7 - 07/30/20 at 19:50:04
 
CAJames wrote on 07/30/20 at 18:22:23:
So you buy 2 SE84UFO's and with this custom cable convert them into balanced mono blocks correct?  

Yes. Essentially you use the left and right channel of a stereo amp as the plus and minus channel of a balanced mono amp.

who makes this cable and why isn't this talked about more?

I got mine from Signal Cable, you can google them. Dono why it isn't talked about more, it seems pretty cool to me. Instead of buying a ZBIT to convert balanced to single ended, spend a few hundred bucks more to buy another amp and use the balanced signal directly, and get double the power.

You can do the same thing with 2 of the SE84UFO3's right?

I don't think so. A true monoblock only has one channel. You need a two channel amp to make this work. You might be able to do it with two UFO3s on each side, but that seems iffy at best, and probably dangerous.


Yeah, I didn't think that through before asking. You would need a stereo amp to sum the channels. Yes just spending the extra few bucks for a second amp makes more sense.

Another stupid question... this isn't the same as bridging wherein you would get the extra watts associated with that as well is it?
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deucekazoo
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Re: UFOs as Balanced Monoblocks?
Reply #8 - 07/30/20 at 19:58:29
 
I need to try this with my CS amps. I am not sure why I never thought about this. The old Adcom car amps are wired like this. They use RCA inputs as balanced inputs.
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ZYGI
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Re: UFOs as Balanced Monoblocks?
Reply #9 - 07/30/20 at 20:41:55
 
CAJames,

I didn't see where Signal Cable made what you need here, Can you refer me to the model you bought.

Most of these XLR to RCA just tie the #1 and #3 to the ground and #2 is the tip.  Also a single XLR and a single RCA.  I think that is why in the manual it states "custom" adaptor.

One way to tell quick enough....on one mono block reverse the two inputs or swap two the opposite of the other. The speakers will be out of phase with each outer, much like swaping + and - speaker terminals.

Zygi
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CAJames
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Re: UFOs as Balanced Monoblocks?
Reply #10 - 07/30/20 at 20:46:11
 
Another stupid question... this isn't the same as bridging wherein you would get the extra watts associated with that as well is it?

Yes, you get extra watts. But it is bridging in parallel so I don't think you get as many extra as if you were to bridge in series the "regular" way.

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CAJames
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Re: UFOs as Balanced Monoblocks?
Reply #11 - 07/30/20 at 20:49:30
 
I didn't see where Signal Cable made what you need here, Can you refer me to the model you bought.

I sent them an email explaining what I wanted, and had them custom made. Mine were $99 for 5' FWIW. I won't have the amps for months yet, so I can't tell for sure, but the cables look good to the multimeter  :)
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Donnie
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Re: UFOs as Balanced Monoblocks?
Reply #12 - 07/30/20 at 22:27:56
 
Are you guys talking about these kind of cables?

https://www.amazon.com/gp/product/B005KBM160/ref=ppx_yo_dt_b_asin_title_o05_s00?...

I bought a pair of these a while back to run out of my Denafrips's XLR's into Dan the Amp's RCA's.
They are cheap as heck and seem to do the trick.
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CAJames
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Re: UFOs as Balanced Monoblocks?
Reply #13 - 07/30/20 at 22:37:02
 
No. The cables you need for this are special XLR to 2xRCA. They split XLR pin 2 to one RCA and XLR pin 3 to the other to preserve the balanced signal. If you look at the bottom of the SE84UFO manual there is a picture. The cable in your link just passes the positive signal to the RCA to make the balanced signal single ended. Sort of a poor mans ZBIT.

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Lon
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Re: UFOs as Balanced Monoblocks?
Reply #14 - 07/30/20 at 22:56:02
 
CAJames wrote on 07/30/20 at 22:37:02:
Sort of a poor mans ZBIT.


And I would believe without the full voltage of the balanced signal.
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CAJames
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Re: UFOs as Balanced Monoblocks?
Reply #15 - 07/30/20 at 23:22:20
 
And I would believe without the full voltage of the balanced signal.

Yes. You also lose the common mode noise rejection when you don't difference the two phases. You don't get a ZBIT for ten and a half bucks, but it does allow you to plug a balanced source into a single ended device.
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deucekazoo
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Re: UFOs as Balanced Monoblocks?
Reply #16 - 07/31/20 at 14:11:06
 
From the manual
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XLR.png
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CAJames
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Re: UFOs as Balanced Monoblocks?
Reply #17 - 07/31/20 at 16:14:22
 
Quote:
Posted by: ZYGI      Posted on: Yesterday at 20:41:55

...Most of these XLR to RCA just tie the #1 and #3 to the ground and #2 is the tip.  Also a single XLR and a single RCA.  I think that is why in the manual it states "custom" adaptor.

One way to tell quick enough....on one mono block reverse the two inputs or swap two the opposite of the other. The speakers will be out of phase with each outer, much like swaping + and - speaker terminals.


Actually, the way it is wired if you do this with just the single ended signal instead of the plus and minus phases of a balanced signal I think you'll get nothing from the speakers. You'll be driving the + and - speaker terminal with the same signal so there will be no potential across the speaker and no sound, or only a little noise.

There is a difference between bridging these amps for balanced mono and single ended mono. For balanced you are amplifying different signals in the two channels, so you short the two - speaker outputs and connect the two + outputs to the speakers. I'd call that connecting in parallel. For single ended you are amplifying the same signal twice, so you short one set of +/- speaker outputs and connect the remaining -/+ to the speakers. So connected in series if you will.


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ZYGI
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Re: UFOs as Balanced Monoblocks?
Reply #18 - 07/31/20 at 19:04:38
 
Actually, the way it is wired if you do this with just the single ended signal instead of the plus and minus phases of a balanced signal I think you'll get nothing from the speakers. You'll be driving the + and - speaker terminal with the same signal so there will be no potential across the speaker and no sound, or only a little noise.


 James,   No the volume remains the same, just out of phase. I did it again, and as you install the first RCA you get "X" volume and it doubles when you add the second.

As far as the wiring, years ago on the early "C's" you could use one set of speaker binding posts on one side, with a jumper to both terminals on the opposite side. If my memory serves me correctly, that was the parallel configuration. Or you could do like the manual states above the balanced configuration, and that method, series configuration.

I run the mono's in the shop during the day while I'm working. I went to switch back to the Zbit RCA in's (shorted or tied together inputs on one channel) with the same output (speaker) wiring as balanced, that  was when I had just a little noise, no music.

Either way, you are in for a treat. Sorry you have to wait!!!
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