Dual mono amps and SDA SRS 2.3TL

70hemicuda · January 12

So been running my 2.3 TL's on a single Yamaha pc2002m and everything worked great. Just picked up another amp and set everything up for running them bridged. As soon as I turned them on I got a horrible popping from the speakers and immediately powered down. No smoke, no fireworks. Checked my connections and thought it had to be the SDA cable causing a ground issue. Disconnected it and tried again and everything works perfectly fine. Did some research and turns out mono with the SDA is no good. Hopefully I didn't destroy anything, it all seems okay. Amps have protection relays built in.

Anyway, is it okay to run this with the interconnect cable disconnected? and is there a way to make this system work? Yamaha c-80, dual mono pc2002, SDA SRS 2.3TL

boston1450 · January 12

Yes you can use them without IC cord. I've never done mono, just 2 channel amplifier. I'm sure someone will chime in

Gardenstater · January 12

The manual says 16 to 32 ohms speaker impedance for manual mode operation. Even if it would be OK, which you need to verify, to bind the chassis grounds together it would seem that it isn't rated to run your speakers in mono mode.

F1nut · January 12

You need to build a Dreadnought isolation transformer. Plenty of info here on what to buy and how to build one. Just do it, you'll thank me later.

70hemicuda · January 12

Gardenstater wrote: »

The manual says 16 to 32 ohms speaker impedance for manual mode operation. Even if it would be OK, which you need to verify, to bind the chassis grounds together it would seem that it isn't rated to run your speakers in mono mode.

I've been reading and seems like plenty of people are running it with speakers below that ohm rating with no issues.

F1nut wrote: »

You need to build a Dreadnought isolation transformer. Plenty of info here on what to buy and how to build one. Just do it, you'll thank me later.

Yeah, I'm just starting to read up on all that tonight.

Gardenstater · January 13

Always weird how manufacturers choose to underrate their products sometimes isn't it? Maybe since this was a professional amp they are trying to protect themselves for warranty purposes by saying on the back of the amp 8 to 16 ohms and not giving a rating for 4 ohms at all. And then in the manual they say 16 to 32 ohms for mono mode, although in the specs they do say 350W @ less than 0.01% THD for 8 ohms in mono mode! So I bet in stereo mode it can do 4 ohms. In reading the manual for a NAD 2200PE amplifier, they say that in mono mode the impedance of the speakers "as seen" by the amplifier is effectively halved so probably the same would be true for your Yamaha. Those 2.3tl were never reviewed by Stereo Review as far as I can tell but they raised the impedance to "compatible with 8 ohms", vs the 2.3 6 ohms. The 2.3 could dip to 3 ohms but ranged between 5 and 8 ohms.

The manual for your amp says that in mono mode you would use the terminals for A Channel + and B Channel + for outputs to speakers. Makes me wonder if in mono mode both + and - are hot (need to verify)? That would probably mean you have to have a Dreadknought and can't ground the effective minus terminals in mono mode.

invalid · January 13

If you are bridging these amps, the amp will see half of the impedance that the speakers are rated at. I also think that with the SDA cable it seems as though it's even harder on amps.

Schurkey · January 17

Gardenstater wrote: »

Always weird how manufacturers choose to underrate their products sometimes isn't it?

Amplifiers are "underrated" because they don't have the heat sink, the power supply, or the output devices--or a combination--to get through the FTC rating protocol.

In other words...they may be able to drive a low-impedance load at low-to-moderate volume, but pushed hard they'll overheat or prematurely clip, or both.

The last thing low-impedance speakers need is an amplifier that's crippled at low impedance; and lacking a 4-ohm FTC rating is telling you something.

Then the amplifier manufacturer either gives you a (lying/cheating, exaggerated) non-FTC rating (or no rating at all) for the lower impedance, or they put a power-supply strangulation switch on the back panel.

Gardenstater wrote: »

The manual for your amp says that in mono mode you would use the terminals for A Channel + and B Channel + for outputs to speakers. Makes me wonder if in mono mode both + and - are hot (need to verify)? That would probably mean you have to have a Dreadknought and can't ground the effective minus terminals in mono mode.

Correct. You're not going to tie the negative terminals together, or reference them to chassis ground.
He could remove the SDA interconnect cable. But then the magic of the SDA is obliterated. The speakers still sound pretty good, in a conventional sense.

Gardenstater · January 18

Schurkey wrote: »

Gardenstater wrote: »

Always weird how manufacturers choose to underrate their products sometimes isn't it?

Amplifiers are "underrated" because they don't have the heat sink, the power supply, or the output devices--or a combination--to get through the FTC rating protocol.

In other words...they may be able to drive a low-impedance load at low-to-moderate volume, but pushed hard they'll overheat or prematurely clip, or both.

The last thing low-impedance speakers need is an amplifier that's crippled at low impedance; and lacking a 4-ohm FTC rating is telling you something.

Then the amplifier manufacturer either gives you a (lying/cheating, exaggerated) non-FTC rating (or no rating at all) for the lower impedance, or they put a power-supply strangulation switch on the back panel.

Gardenstater wrote: »

The manual for your amp says that in mono mode you would use the terminals for A Channel + and B Channel + for outputs to speakers. Makes me wonder if in mono mode both + and - are hot (need to verify)? That would probably mean you have to have a Dreadknought and can't ground the effective minus terminals in mono mode.

Correct. You're not going to tie the negative terminals together, or reference them to chassis ground.
He could remove the SDA interconnect cable. But then the magic of the SDA is obliterated. The speakers still sound pretty good, in a conventional sense.

From what I can tell, the FTC Ratings Regulations only apply to amplifiers marketed for home entertainment purposes so this amp doesn't have to reveal all about its capabilities/limitations. They "might" do that for the purposes of not having to pay out on warranty claims. Yeah I'm a cynic.

https://www.ecfr.gov/current/title-16/chapter-I/subchapter-D/part-432

F1nut · January 18

Told y'all the boy could dig.

70hemicuda · January 22

So emailed avel lindberg about a transformer. Going with the 800 because apparently it's an off the shelf one and shouldn't be an issue getting. Looking into aluminum boxes and binding posts on Amazon now too.

I have a aftermarket interconnect cable I bought not too long ago. Says it's 16 gauge. Would that be okay to splice into and use?

pitdogg2 · January 22

You'd be better off using speakon connection and at least 14ga.

Binding post are way to easy to mis-wire and let the magic smoke out.

70hemicuda · January 28

Transformer and other parts should be here tomorrow, then the fun begins.

70hemicuda · January 30

Dreadnaught is built. Tried to keep it as small as a footprint as possible. Before I hook it up, and I've triple checked the wiring, is there anything that sticks out as no go? I'm thinking about heat shrinking the blades, but otherwise seems okay to me.

Gardenstater · January 31

Looks pretty sweet pending proper wiring verification (the one side I can see looks to be proper parallel wiring). Did you use a non ferromagnetic bolt and nut in the center of the toroid?

70hemicuda · January 31

The bolt, nut, and washers are stainless which from what I found is good to go.

Verified it last night and it all works! Only got a couple minutes of play time so going to have a good burn in session soon.

xschop · January 31

I like the gold-plated faston approach, I'll follow suit for ease of assembly.
I can't believe there is not an actual schematic on the forum of how this torroidal interfaces with the PIN/Blade circuit to help others looking into this.

I see that you have your binding posts' +,- alternated from each other.

Gardenstater · January 31

Not all stainless is non ferromagnetic but can easily be checked with a magnet.

70hemicuda · January 31

Yeah the binding posts are supposed to be horizontal but I had to rotate them to fit, so it's staggered. Just had to be mindful when hooking it all up.

It was a non magnetic bolt.

I hate that the box is blue and white but it's actually pretty nice. I have a full aluminum enclosure coming but it's a lot bigger and this one fits nicely behind my TV so probably keeping this one.

michaeljhsda2 · January 31

What I don't understand is why does Avel Lindberg ship a magnetic bolt, washer and nut with their 800 VA transformers?

F1nut · January 31

You could always ask them.

xschop · January 31

Cuda's top plate looks like powder-coated steel.

Gardenstater · February 1

michaeljhsda2 wrote: »

What I don't understand is why does Avel Lindberg ship a magnetic bolt, washer and nut with their 800 VA transformers?

Maybe it has something to do with the fact that toroidal transformers are self shielding and keep the magnetic flux within the core.

xschop · February 1

Is it ok to run a large diameter alum. round through this transformer?

70hemicuda · February 1

Any reason I should move the transformer to the new box? It's full aluminum and definitely looks better but trying to decide if it's worth it.

xschop · February 1

Put your cell-phone in the blue box and call it, do the same for the all-aluminum one, then report back.

70hemicuda · February 1

Phone rings in both.

xschop · February 1

Wouldn't waste my time then.

pitdogg2 · February 1

FWIW our electrical genius here determined that the dreadnought is better standing up and not laying on its side.
Once again FWIW.

xschop · February 1

pitdogg2 wrote: »

FWIW our electrical genius here determined that the dreadnought is better standing up and not laying on its side.
Once again FWIW.

I thought DK originated the mod?

70hemicuda · February 1

I caved and used the aluminum box. Just looks better and is alot stronger. Super easy, just drilled a center hole, mounted some feet and hole sawed out for the connections. Way happier with this box.

Dual mono amps and SDA SRS 2.3TL

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