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    Dynaco Center Channel

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    sKiZo

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    Dynaco Center Channel

    Post by sKiZo on Fri Aug 16, 2013 2:21 pm

    Stumbled across this the other day ...



    This method of deriving the center (third) channel of a stereo system is an exclusive Dynaco development which provides the proper in-phase (A+B) signal without loss of stereo separation and without the need for an additional amplifier. It is useful where the left and right speakers must be widely separated, and it also enables the use of the third channel speaker as a monophonic system in another location.

    Doesn't look like the circuit will work in an ST-120 as designed using my 8ohm speakers, due to the lack of 16 ohm taps for output.

    UPDATE > > See Post #13 ... apparently the ST-120 DOES have 16 ohm taps, and Bob gives a step by step on how to make it happen.

    Credit where credit's due ... here's the PDF I pulled it from ...

    http://www.the-planet.org/dynaco/Misc/Center%20Channel%20System.pdf

    .


    Last edited by sKiZo on Sun Aug 25, 2013 5:13 pm; edited 1 time in total

    Elrick

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    Re: Dynaco Center Channel

    Post by Elrick on Fri Aug 16, 2013 10:53 pm

    Buy 4 ohm speakers. Sorry I had to say that.

    skriefal

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    Re: Dynaco Center Channel

    Post by skriefal on Sat Aug 17, 2013 12:11 am

    sKiZo would probably build 4-ohm speakers... and with custom cabinets, of course. Smile

    sKiZo

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    Re: Dynaco Center Channel

    Post by sKiZo on Sat Aug 17, 2013 12:49 am

    Quite happy with my McIntosh XR16's, thankewverymuch ...

    Center channel doesn't really work for me here. I have a small listening space, and adding a center channel tends to muddy things up a bit when it comes to the sound stage in a confined area. I speak from experience there as I've experimented some with center channels using an L+R output from a Carver H9-AV holographic generator.



    That requires a separate amp, and though I really thought I liked it when I first hooked it up, turning it off proved me wrong. I liked the additional punch in the center stage vocals, but found I was missing too much instrumental positioning from the sides. Given a choice, I'll stick with two channel here ... unless ...

    I DO run a center channel off my Oppo SACD using the same amp, but for that, it works. Difference being, it's a dedicated channel scored for the program material - that maintains the unique mix for the side channels also.

    Now, on a larger room, I can see where it could really make a difference done right.

    Mostly just wondering if anyone here has had any experience with the three channel setup, or whether Dynaco ever really pushed it as an option ...

    quadaptor

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    Join date : 2009-05-04

    Re: Dynaco Center Channel

    Post by quadaptor on Tue Aug 20, 2013 3:40 pm

    Does this play back a mono signal of both channels? If so, could it be used for a passive subwoofer in the center?

    sKiZo

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    Re: Dynaco Center Channel

    Post by sKiZo on Tue Aug 20, 2013 7:09 pm

    If you look at the Carver I pictured, it has two additional outputs, L+R and L-R. L+R is recommended for the center channel as it acts as a high pass filter, and the L-R output does the opposite for a sub. That's the usual recommendation.

    Can't say for certain on this setup ... I'd think the same would hold true with the dynaco center channel hookup, with the only change being to drive the center with the bridged leads from the POSITIVE side of the speakers outputs ...

    One thing I noticed is the Dynaco hookup assUmes three identical speakers, so I imagine they're all full band, including the center. Depending on your sub, it should automatically be setup as a low pass and ignore the high band information.

    PS ... I don't do subs myself ... my big boxes are more than capable of creating all the bass I need and/or want ... I'm sure somebody out there has figured out all the do's and don'ts ...


    quadaptor

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    Re: Dynaco Center Channel

    Post by quadaptor on Tue Aug 20, 2013 10:06 pm

    My primary system includes a set of Boston Acoustics A200s in the front and A150s in the back wired through a Dynaco Quadaptor and powered by a VTA converted ST-70; plenty enough base for me. But my secondary system consists of a set of Klipsch Hereseys powered by a Fisher 800B. Its a little lacking on the bottom end and I was wondering if the diagramed setup could work for a center channel subwoofer to extend the base a little more.

    sKiZo

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    Re: Dynaco Center Channel

    Post by sKiZo on Wed Aug 21, 2013 12:41 am

    Looks like you have a few options to add a powered sub. My preference would be in the following order:

    If the Fisher has a pre out/amp in (is that what the jumpers are?), just replace the jumpers with "Y" cables and hook the sub's line level inputs up to those. Adjust the crossover and line level at the sub.

    If your tape monitor is a true loop, you could also try hooking a sub directly to that using the line level inputs ... once again, the sub gets the full signal and you adjust the line level and crossover point at the sub. Not gonna work if the tape loop kills any other signal from the preamp section when engaged.

    Looks like the Fisher only has the one set of speaker outputs? If line level isn't gonna do it for you, I'd suggest getting a sub with speaker level inputs - most do have those as well as line level. You'd have to gang connections to both your front speakers AND the speaker level input on the sub. Best you use good terminal ends on the wires as it'll get a bit crowded on the screws and you don't want to have any whiskers shorting things. Probably be easier to just make the sub connections at the speaker terminals themselves. Once the connections are made, the crossover on the sub should isolate the left and right channel signals so you won't have to worry about crosstalk, impedance matching, or feedback, and it will also do a low pass so all that's fed to the subwoofer itself is the bottom end. Only problem I see with that is if you have distortion on the bottom of your A200s ...

    Some subs also have dual coil windings for even better channel isolation, but those tend towards wOw on pricing ...

    As always, do some of your own research first and make sure you're getting what you need.

    quadaptor

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    Re: Dynaco Center Channel

    Post by quadaptor on Wed Aug 21, 2013 1:04 am

    Thanks much. I'll have to give this a better read in the morning. The Fisher does have a preamp in/out with jumpers. I'd like to give this a try with the Heresys. Thanks again.

    sKiZo

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    Re: Dynaco Center Channel

    Post by sKiZo on Wed Aug 21, 2013 2:05 am

    Be sure to post back with your results ...

    I've been tapping my quad receivers for decades using the best available line level outputs. The old QR series Sansui's had the pre out/amp in which was the logical choice for me to feed an external amp. The QRX series got rid of that, but added so much more. For those I had to go to a tape loop, which works fine. Here's the current setup on my McIntosh MC2205 ...



    Difference being I went the extra bucks for hard "Y" connectors instead of the cables. Pricey, but pretty.

    Next up, I'm currently building an ST-120 and plan to feed that the same way. Custom case, so I added two sets of inputs at the back ...



    Those will be bridged internally, so I won't need the "Y" cables. Like your pre out/amp in jumpers, only inside, An innie instead of an outie? tongue One set of cables from the receiver tape loop, and one set out to complete the loop. If I ever decide to just feed the amp direct from a real pre, just use either set of inputs and cap the other.

    Sorry to confuse the issue ... for your setup, using the pre out/amp in connections, you'll need two "Y" cables and one dual RCA cable to feed the sub's line level inputs. And put those jumpers in a safe place ... they get lost easy and are mostly irreplaceable if you ever want to go back to the stock setup.

    quadaptor

    Posts : 59
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    Re: Dynaco Center Channel

    Post by quadaptor on Sun Aug 25, 2013 3:31 pm

    My amp has a single channel RCA output for a center channel speaker. Can this be used with a Y-connector for a sub?

    sKiZo

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    Re: Dynaco Center Channel

    Post by sKiZo on Sun Aug 25, 2013 3:40 pm

    I'd try hooking it up direct to a sub first to make sure you're getting the full range out of the jack. The sub won't have anything to work with if the amp's center channel output is set up as a high pass ...

    You'll also want to do the math and make sure the ohms rating running two separate (three really, as most sub speaker level inputs are fed to a dual coil) are within the tolerance for the amp. Bigger concern would be whether your amp has the power reserve to drive the sub also, as they tend to suck a lot of watts.

    I'd think the better and safer option would be to use the center out as intended driving just a center speaker, and do the "Y" thing on the pre-amp or receiver's line level outputs to the sub's line level inputs. The Dynaco schematic I posted is to eliminate the need for another amp - and that's not an issue with a powered sub anyway.

    Worth mentioning ... I doubt if Dynaco had big box super low bass speakers in mind when suggesting three identical speakers for the mod. Bass is non-directional, so having full range down that low in the center wouldn't accomplish anything except maybe overdriving the amp. Long as whatever speaker you use can get you down to around 120hz, you should be golden. What you MAY encounter using a smaller speaker is having that too loud - simple enough to add a load balancing volume pot for that output if it's an issue ... I'd want that anyway as the channel balance is critical between center, left, and right for a good soundstage.

    I use a Bose AV speaker here - real nice sound to it, super inert cab so it's not bouncing around in the cabinet, and additional shielding to keep any stray RF out of the speaker due to proximity with all the electronics around it.


    Bob Latino
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    Re: Dynaco Center Channel

    Post by Bob Latino on Sun Aug 25, 2013 4:10 pm

    sKiZo,

     Just to correct a minor point you made in post #1 where you said > "Doesn't look like the circuit will work in an ST-120 as designed using my 8ohm speakers, due to the lack of 16 ohm taps for output"  All the VTA amp kits DO HAVE a 16 ohm tap which is the YELLOW secondary wire on each output transformer. Since nearly all speakers made today are usually 4 or 8 ohm speakers, you are instructed in the assembly manual to connect the YELLOW (16 ohm) wire to the "NFB" (feedback) eyelet on the driver board. If you want to use 16 ohm speakers on any VTA amp, you would connect the YELLOW 16 ohm wire to the red speaker binding post and then a wire from the red binding post to the NFB eyelet. The ORANGE (8 ohm) wire and the BROWN (4 ohm) wire would then be coiled up inside the amp and not used.

    Bob

    sKiZo

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    Re: Dynaco Center Channel

    Post by sKiZo on Sun Aug 25, 2013 5:16 pm

    Thanx for the heads up on that ... I added a note to the first post ...

    So, use the 16 ohm tap and that gives 8 ohms x3 using the diagrammed circuit?

    Bob Latino
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    Re: Dynaco Center Channel

    Post by Bob Latino on Sun Aug 25, 2013 9:28 pm

    Yes - If you use the 16 ohm tap, it should work fine with 8 ohm speakers according to your wiring diagram in post #1

    Bob

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