Four speakers to ST70

I'm upgrading my ST70 and when it's done, I'd like to use four speakers playing the same time. The speakers are Dynaco A35 and KLH FIVE. First of all, is it fine to do so and if yes, what's the best way to connect them to the ST70? Use the 16ohm taps? If someone can post a wiring diagram or drawing that would be great.

Thanks

It is safe to do so. I would connect them in PARALLEL to Ground and the 4Ω taps. If you
were to connect them to the 16Ω taps, there would be a mismatch unless you were to connect
the speakers in series, in which case any impedance fluctuations in one would affect the
frequency response of the other.

Thanks!

Keep an eye out for one of these ...



Not only do you get two pairs of load balanced outputs, you also get the famous Hafler circuit for ambiance. I use one on the rear channels of my quad for sexophonic sound ...

It DOES alter the phase of the sound to the back speakers. If you're looking for pure stereo out of both sets, it's easy enough to modify the box internally. Pretty sure the mod was even listed in the original manual, but mine disappeared somewhere, somewhen ...

Impedance matching and load balancing is done internally, so just match your output to your speakers.

You can probably score one off that auction site for around $25-30 ...

sKiZo wrote:Keep an eye out for one of these ...

What?

What what?

sKiZo wrote:What what?

Is there supposed to be an image/pic?

Yup ...

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Oh. Guess you can't see it ...

Try this one.

sKiZo wrote:Yup ...

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Oh. Guess you can't see it ...

Try this one.

Thanks for that, but I'll be stacking them.

Yup!

Yup yup?

I take it from your forum name that you've got a Quadraptor?

I love mine ... using it right now on the rear channels of my system. It's set up with two pairs of Bose speakers, 161's high and just behind the listening chair, and 201's mounted on the wall about 10 foot back of that. The Quadraptor's phased channels are the ones overhead as that way I can use the gain pot to adjust the balance. We all know how Bose likes to play with reflected sound too. Makes for a real nice blend, and one helluva depth of field. Got a set of McIntosh XR16's up front, so I don't miss the reduced bass capabilities of the smaller speakers. And I don' need no steekin' sub neither.

Oh. Did I mention I'm driving it all with a Sansui QRX-9001 vario-matrix quad receiver?

Yeah, I discovered the clever little device a few years back. To me, the Dynaco Quadaptor opens up the stereo sound stage in a very pleasing way. I use a VTA ST-70 amp and PAS3X preamp to drive a set of Boston Acoustics A200s in the front and A150s in the rear. The A150s are probably overkill in the rear position, but they do sound good. I'm sold!

does the QD-1 series II L essentially do the same thing or is it a different device altogether?

Yes ... and no. It's still a passive hafler, but adds a center channel tap and allows some additional control as well. I've heard rumors that the build quality slipped some compared to the original series.

Never tried one myself, as the original suits me just fine. I've done the center tap thing by just bridging the positive leads on the rear channel outputs with good results, but there you also should probably add a balancing pot so the amp sees the correct load and you can independently control the volume on the center. Maybe not necessary depending on your equipment and speaker distances.

Maybe someone else can answer whether the ST70 can handle a center channel tap directly off the main outputs? If so, no reason either the QD-1 (any series) couldn't work for that.

Never saw the need for a center channel here ... I've got a Carver H9-AV Holographic taking care of that for me, sans speaker. It's Magic! I do have a Bose AV center channel speaker directly in front of the listening position for my Oppo SACD player. You can see it in the middle of the shelf over the monitor.



It's fun asking folk what they thought of the center speaker when playing just the quad w/quadraptor with the H9-AV engaged - wOw, that's nice, gotta get me one of those, and then I tell them the speaker isn't even on.

PS ... in case anyone is wondering - you can't see the Quadraptor in the pic as it's behind the monitor. Once it's set, forget it. There's also a Carver Cube amp back there to drive the center speaker directly from the Oppo. The Technics parametric EQ next to the turntable will get shuffled down to where the BSR graphic eq is now, directly above the Big Mac, and the Maverick TubeMagic DAC will fit in where the Carver H9-AV is now, directly on top of the dbx 3BX, and the H9-AV will fit in on top of the HTPC, leaving the spot next to the turntable open for the ST-120 when it's done. The typical "new box" shuffle, made a bit more interesting by the ST-120's requirement to "see the sky". The McIntosh MC-2205 amp will be staying exactly where it is ... at 90 pounds I'd need a fork lift to move it anyway. Besides, that will give me an excuse to A/B it with the ST-120 just to see how they compare.

But I digress ... again.

I'm not in need of a center channel myself either I was just asking because I was only able to find one QD-1 II L on ebay in germany.
but I much prefer the way the original quadaptor looks, so I'll keep looking...

They pop up on ebay from time to time, but I expect most are located here in the States and not in Europe. As I said before, I find the quadaptor does a pleasent job of expanding the stereo sound stage when set up right. I may have an extra unit if you are interested and want to deal with shipping from California?

I'd definitely be interested! I'll send you a PM as to not clutter this thread.

Sounds good. I'll keep my eye open for an incoming PM.

sKiZo wrote:
Maybe someone else can answer whether the ST70 can handle a center channel tap directly off the main outputs?

Dynaco itself published a data sheet for doing that with ANY of their amplifiers. However, it confused some people because at around the same time, other manufacturers (I think EICO, in its ST-40 and ST-70, was one) had connections for deriving a center channel which was a SUM of the left and right channels...i.e., a MONO channel. Dynaco's, rather than a sum (L+R) was a DIFFERENCE channel (L-R), quite a different animal.

Connecting a loudspeaker between the two hot outputs of a Stereo 70 to derive the simulated rear channel DIFFERENCE signal is perfectly safe.

Good to know ...

L+R, L-R ... then again, there's folk that could never quite make up their minds and left it up to the individual to decide ... here's the back of a Carver H9-AV ...



Their version is a bit more complicated than just a simple internal bridge or reroute, but give you the same basic effects. Manual recommends the L+R for a true center, and the L-R for driving a sub. I don't use them as they're line out and would require an outboard amp. Besides, with well balanced holography, who needs a center channel anyway?

I was so happy to see this series of messages. New to the forum and soon to own a VTA ST-120. I have been running four Klipsch, 2 cornwalls and 2 Chorus rear, through a Mac SS using a Dynaco Quadadaptor. All my tube friends said to ditch the quadadaptor and drop to two speakers to enjoy the real sound of tube. I'll try both ways but suspect I'll continue to enjoy the quadadaptor. Look forward to future discussions.

GP49; (and all) so it would be safe to connect a center spkr across the hot outs of the ST-120?? Dale

Wow, stacked A-35s. I've been running stacked Advents on my solid state system for years, and have A-25s in the front room on my tube system. If stacking the A-35s has anywhere near the synergistic effect it has with the Advents, it should be wonderful.

I've had a Quadaptor since I was a kid. I used it regularly until I got a sonic hologram generator. Later after moving around a bit and having issues with speaker placement I ended up going back to simple two channel and I think I've been the better for it. This thread makes me wonder if I shouldn't break out the Quadaptor (the sonic hologram machine got sold somewhere along the line) and see what it can do in these digs.

I didn't see this mentioned, perhaps I missed it. Here are photos from an album Dynaco sold in the 70s explaining their quadraphonic connection, and providing music that demonstrates its capability. I can scan it to improve the image if necessary.

If you're running two speakers in parallel definitely take the 4 ohm taps. The impedance can pretty quickly drop to 2 ohms, not exactly a short but pretty close.
As to Dynaco A-35 speakers, they are, IMHO, the finest book-shelf speaks ever made -- better even than the old AR-3s and KLHs and step-level superior to the A-25s. I was gonna re-cap mine but hear no need to.