I found an amp?

zingo

I have been looking for a great 2-channel amp for a while, and tried a number of offerings, but finally found one that made me do a double take because I could get it at a good price. It has everything I've been looking for (high current, 2 ohm stable, high power, auto-on trigger, tested design, XLR inputs, good reviews) and seems like a great pairing with my speakers, but it has 7 channels! If this was the exact same amp only stereo, I would have no hesitation, but I feel weird having unused amp channels. Wouldn't that mean more power supply available for the two used channels?

Anyway, it's a Sunfire TGA-7400, and I'm having a bugger of a time figuring out if I want to try it on my stereo, 4 ohm speakers...

unc2701

Biamp your speakers- use current source for the tweeters and voltage source for the mid/woofs and you've used 4 channels. And Sunfire amps would probably benefit from less channels being used for their power specs to be realistic. 7x400w=2800w=23a, but it's fused at 10a, IIRC. Claims to put out more power than it takes in anyway. Which isn't to say their power specs are complete fabrications: you're not going to be pumping out identical 60hz sine waves at 400w on all channels at the same time.

So the high current Sunfires are typically power-supply limited, so leaving a few channels idle isn't a bad thing.

zingo

I assumed that allowing the PS to have a smaller load would be a benefit, and the fuse it rated at 15A says the attached manual. I can't bi-wire my speakers, but 800w at 4 ohms is probably enough power too...

BlueFox

I have the TGA-5400 in my HT, and it works fine when I use it in stereo mode. With that said, I am moving my old 2 channel amps, Cambridge-Audio 840W (800W @ 4 ohm) into the HT, and will use the Sunfire for the center and surrounds.

FTGV

You had/have one in that Hypex/Dodd build that checked most of the boxes on your wish list.

zingo

But it's not 800wpc at 4ohm Fred...

zingo

The amp is a claimed 400wpc x 7 using Carvers tracking down-converter power supply, with output power doubling with half the impedance down to 2 ohms; manual states 56.6Vrms output before clipping and 120A maximum current. With the possibility of only running two channels, that should maximize the output for those channels and ensure power is not limited by the power supply.

FTGV

zingo wrote: »

But it's not 800wpc at 4ohm Fred...

Yeah only a measly 400wpc, assuming appropriate supply voltage.

With those power requirements your certainly not driving horns...:)

zingo

If it can push that much current to seven LSis, that amp can handle anything on two channels!

zingo

Nice looking transformer with a CD for reference.

EndersShadow

You buy it then I take it? Its a MONSTER of an amp!

zingo

Yes, I am going to try it as a stereo amp with a Parasound P3.

zingo

What if I used one of the channels of the amp to power my subwoofer? It would provide more power than the plate amp, and I'm already running an external crossover after the preamp. Any downside to running one channel as an external amp?

unc2701

Are you the one with the minidsp and the DIY sub? If so, go for it! Three channels driven is not going to cut into the overhead.

On the other hand, of you have a retail sub, it's likely that there's some boosting/ tuning incorporated into the design of the plate amp and you'll lose that going to an external amp.

EndersShadow

zingo wrote: »

What if I used one of the channels of the amp to power my subwoofer? It would provide more power than the plate amp, and I'm already running an external crossover after the preamp. Any downside to running one channel as an external amp?

No real issue IMHO.

unc2701 wrote: »

Are you the one with the minidsp and the DIY sub? If so, go for it! Three channels driven is not going to cut into the overhead.

On the other hand, of you have a retail sub, it's likely that there's some boosting/ tuning incorporated into the design of the plate amp and you'll lose that going to an external amp.

Thats me, but Zingo is likely running something similar....

zingo

It is an Elemental Designs A3-300 with a few hundred watt plate amp, but no on-board boost or processing. However, my NHT X1 does provide every needed feature for an dedicated amp, so I think I'll try it. I'm currently not using the controls on the plate amp anyway with the X1, so it'll clean things up a little and provide over twice the power to the 12", 4ohm driver.

zingo

I wired up the subwoofer last night:

-Pulled the plate amp, disconnected the internal wiring to the speaker-level input
-Removed the wiring between the plate amp and the driver
-Ran new 12AWG wire to the voice coils wired in parallel for a 4ohm load
-Attached the new wire to the binding posts of the plate amp

I then ran new XLR cables from the mono subwoofer output on the NHT X1 to channel seven on the amp, and ran 12AWG speaker wire from the amp to the subwoofer. Turning on the system, I noticed that the overall gain is a little lower than with the plate amp, but that means running the volume know on the X1 at 12 o'clock instead of 10 o'clock. The sound does seem to be a little cleaner and more punchy with higher quality electronics, and I'm sure the 800wpc available doesn't hurt either. A big problem that seems to be solved is that the plate amp had a lower trigger sensitivity, which meant it didn't turn on with low volume listening. Now since all three speakers are playing off the same amp, that's no longer an issue with a single trigger.



Any one want two Elemental Designs LT.200 plate amps with upgraded capacitors? :P

Hermitism

zingo wrote: »

I wired up the subwoofer last night:

-Pulled the plate amp, disconnected the internal wiring to the speaker-level input
-Removed the wiring between the plate amp and the driver
-Ran new 12AWG wire to the voice coils wired in parallel for a 4ohm load
-Attached the new wire to the binding posts of the plate amp

When you guys replace internal wires inside a speaker or sub, do you use slip on connectors like I've seen inside my Polks, or do you permanently solder the connections?

bikerboy

I could possibly use that. The amp for my sub died. I would use it upstairs with the speakerlab sub and the lsim 703s. LMK what you want for it.

zingo

Hermitism wrote: »

When you guys replace internal wires inside a speaker or sub, do you use slip on connectors like I've seen inside my Polks, or do you permanently solder the connections?

This sub has spring loaded connections so it's not applicable, but most use the connectors as soldering inside a cabinet is a pain.

zingo

How about $60? It measure 8 1/4" x 8 1/4", is class D, and offer 200wpc at 4ohms.

bikerboy

Sounds great! Sold.

Polkie2009

That's a great price on the plate amp Jake. I don't think bikerboy will find a better price anywhere. Do you have any subeq or does the X1 do that?

zingo

I do have one more plate amp if you're interested...

The NHT X1 Active Crossover does provide all the adjustment and EQ features I need.

unc2701

I got curious what the Boundary EQ knob does on that NHT and saw this:

NOTE: The X1 contains special equalization circuitry specifically designed for Evolution sub-woofers and tower bass modules only. It is not recommended with non-Evolution subwoofers.

Looking at the subwoofer spec in that manual the -3 db is 26hz, and the -6db is 24hz, so the X1 is definitely doing a little boost to get the bottom end response up. If your sub's rolloff is in the same general vicinity, it doesn't matter, but you might want to take a minidsp for a whirl as an alternative (and it might even be cheaper)

My only complaint with the minidsp is that there's no bigass volume knob to twist down when the wife comes in the room all pissed off.

zingo

The X1 may have been marketed for NHT use only, and may be tuned towards those woofers, but it seems to work great with my subwoofer as well which has a claimed -3db at 18Hz. The Boundary EQ which I usually keep flat, is designed to be adjusted based on room placement of the subwoofer: 0 for against the wall, < 0 for corner placement, and > 0 for freestanding in the room. One thing I really like about it is that all the main controls are on the front of the unit, so no trying to look between the wall and the subwoofer cabinet with a flashlight to tweak the settings.

[Deleted User]

"My only complaint with the minidsp is that there's no bigass volume knob to twist down when the wife comes in the room all pissed off."
Brilliant. What someone needs to do is develop a BA override box to be placed near the doorway.

EndersShadow

unc2701 wrote: »

My only complaint with the minidsp is that there's no bigass volume knob to twist down when the wife comes in the room all pissed off.

LOL... there is one. Its called wire your subs amps to a switched outlet by your seat/door.... she comes in the room (or you hear her coming down the stairs with a ferocity that equals death by words) hit the switch and save yourself lol...

Or heck wire the outlet to a motion sensor lol...... that would make for some fun... every time she gets close, poof it goes off hehehehe

unc2701

zingo wrote: »

The X1 may have been marketed for NHT use only, and may be tuned towards those woofers, but it seems to work great with my subwoofer as well which has a claimed -3db at 18Hz.

Huh- Actually, that X1 might be oddly suited to that sub. -3db @ 18hz and the size make me think the sub might be an EBS alignment- So there would be a dip in the 30s followed by a hump in the low 20's before it rolls off. The X1 is likely boosting in the same range as that dip to give you a nice flat response across that range. Clearly the ultimate evaluation is your ears. Carry on!

unc2701

EndersShadow wrote: »

Or heck wire the outlet to a motion sensor lol...... that would make for some fun... every time she gets close, poof it goes off hehehehe

THAT is genius. Put it in the hallway she has to come through, but I can still get to the kitchen for a beverage. Use a 3 way switch so that it flips off the sub and turns on a warning light for me.