Can't hear effect of Dreadnought

crcolby

The SDA Handbook describes how to wire up a dreadnought, the isolation transformer in the interconnect that improves sound and enables use of dual monoblocks. The final step is to unplug both negative leads from the amplifier to the speaker inputs, try each of the two ways to match the the pair of interconnect wires transformer’s secondary winding, then choose and permanently use whichever makes the louder and weirder sound. My problem is I don’t get any sound at all. What am I doing wrong?

The speakers are SDA-ICs with serial numbers above 11,000, so they are in the range that the handbook says should work with a dreadnought. Avel Lindberg sent me a Y23 series 630VA transformer, the closest to this forum’s recommended units that wouldn’t involve a likely three-month delay. AL puts wiring diagrams on line.
https://www.avellindberg.com/transformers/y23_range_connections.htm
I wired primary and secondary in series (grey to violet and red to orange), then used an ohm meter to verify near-zero resistance between blue and brown of the primary and between black and yellow of the secondary. Using speaker wire, I joined one of the primary endings to the interconnect point of my left speaker and the other primary ending to that speaker’s negative pole. I made a similar connection from the secondary winding to the right speaker. Upshot: Assuming that series connection is the correct design, I think the transformer is wired in OK.

Some previous owner evidently lost the original pin/blade interconnect, as someone had replaced each speaker’s pin/blade receptor with a barrier strip. One of each barrier strip’s two positions was connected inside the speaker enclosure to the negative pole from the amplifier (I peeked while installing Gimpod boards) and I measured zero ohms from that pole to the position on the barrier strip. The other position on the barrier strip also looked to be wired correctly, and, besides, both before and after messing with the transformer a single wire run between the two speakers’ interconnect positions produced the spacey sound with the negative leads from the amplifier disconnected. Upshot: I think the speakers are wired OK.

With the transformer in place and either radio or CD playing in stereo, here’s what I get:
Disconnect both negative leads from amplifier. No sound from any driver in either speaker. Crank up the volume: still no sound.
Instead, disconnect both leads from amp to left speaker: Right speaker plays OK. Left SDA drivers play what sounds to me like the same as the right speaker, except softer. (This implies there are no open connections in my wiring of the transformer.)
Alternatively, disconnect negative amp lead from one speaker only: All four of its midrange drivers play what sounds just like the speaker with the normal connection, except softer.

Switching the secondary’s black and yellow connections to the right speaker doesn’t change anything. With the isolation transformer in place and everything hooked up, the system sounds fine. I just can’t verify that I am getting the SDA effect.

What’s wrong?

F1nut

Right speaker
Avel red and yellow wires to speaker blue + wire.
Avel black and orange wires to speaker white - wire.

Left speaker
Avel grey and brown wires to speaker blue + wire.
Avel blue and violet wires to speaker white - wire.

crcolby

Wow! And thanks. I wouldn't have guessed that in 100 do-overs. I'l give it a whirl either late tonight or tomorrow morning, depending on how much merriment tonight's (outdoor, distanced) dinner party brings.

F1nut

Did Avel tell you the Y23 series 630VA transformer was audio quality because the only stock one I know of is the 800VA one recommended here.

crcolby

F1nut,

Melanie at Avel said the 800VA transformer recommended on this forum was out of stock and because of COVID would require at least three months to ship to me. She gave the same time to order the special 1000VA transformer. Both would have to come from a factory in Ceylon. I wanted something that would let me use two monoblocks (Schiit Vidars with XLR inputs), so I just got the 630VA item now. Maybe later I'll upgrade.

As I understand your instructions, I should have wired the transformer's primary and secondary each in parallel. With that wiring, music plays. With both amp leads to R disconnected, left plays on left and faintly on R. Same the other way around. To me, this confirms that my wire-nut temporary wiring has connectivity. With both + amplifier leads connected and both negative leads disconnected, no sound emerges from any drive, no matter how I crank the volume up. In other words, no change.

Messing around I found one SDA driver didn't seem to function. I'll be correcting that later today. Thanks for your help so far. If you have any further ideas, I'd appreciate them.

F1nut

Further ideas about what? If you wired things up like I posted then you're good to go.

It doesn't seem like the 625VA transformer is audio grade, so I'd go ahead and order the 800VA version. The 1000VA version is special order with a minimum order of 10, IIRC.

pitdogg2

The 1000VA version is special order with a minimum order of 10, IIRC.

Yes you are correct.

Maybe that 630va isn't a 1:1 like the others we've used.
Maybe that would explain the lack in one side.

F1nut

It appears there is one somewhat suitable 625VA version, Y236856, which is 115V + 115V.

I don't see a 630VA version on my list.

F1nut

Where did he go???

vmaxer

Hopefully still around. I hope it works out for him but it is a bit alarming that you don’t have any record of this model.

F1nut

I doubled checked Avel's site to see if they may have added to the options, definitely no 630VA available.

F1nut

Still nothing. Maybe too embarrassed to admit he bought the wrong model?

pitdogg2

Something happened...

audioluvr

Probably waiting on the 800Va one hopefully.

vmaxer

@crcolby

You still around?

crcolby

Still alive. Details tomorrow.

crcolby

Avel Lindberg's packing slip reads, "Y236856 115v + 115v 2.7A 625VA." Sorry about my 630VA error. I wired the transformer in parallel as F1nut advised. I think, but only think, the dreadnought has improved the sound by mellowing it out some. It's hard for me to isolate the effect of the dreadnought because while putting an ear close to each separate driver to detect any SDA effect I discovered that one SDA driver wasn't playing at all. It had become disconnected inside the cabinet. Fixing that, plus adding a better preamp (Schiit Freya +) to the system, also improved the sound.

Because I wasn't sure the 625VA would be worth keeping, I jerry-rigged it using some wire nuts and the shipping carton wrapped in aluminum foil. Once I confirm that I can use separate amps for each channel, I will need to mount it permanently in a cabinet which has room to substitute an 800VA and maybe a 1000VA in hopes someone organizes another group buy. A-L will specially manufacture and ship its 1000VA of the perfect kind, but that's over $400 if I remember correctly. Fifteen customers would get the best price, but there are advantages to smaller groups as well.

Probably I'll get the 800VA once it is in stock, though nothing in A-L's published specifications shows it more suitable for audio than the 625VA -- it's just bigger.

F1nut

The transformer options were researched by a member here that shall we say, knows what he's doing. He spoke in detail with Avel about it. IIRC, the stock 800VA version has lower noise and a higher saturation point than the other stock offerings. The custom 1000VA improves on that.

dpowell

Something to keep on mind is that the transformers require up to 200 hours of burn-in before they really start to sound good.

crcolby

Trapped indoors with COVID, then Pacific NW wildfires, and a bum hip, I may have 200 hours already. .