Cheap garage audio using leftovers, low signal to subwoofer power amp

[92saturnsl2]

I have a Sony 5.1 receiver (STR-DE985) that I need to hook up to subwoofer(s) via a power amp.

The receiver has a subwoofer pre-out w/ the requisite low pass filter. It's currently connected to a Carver WCA-400 power amp (400W @ 8 ohm bridged) which is in turn connected to a 12" sub. That has worked just fine.

Purchased another power amp (Gemini XGA-4000, 700W @ 8ohm bridged) and there's simply not enough gain on this amp to get any usable output. The old amp does fine; this amp, the gain control simply runs out of room before I get any sort of decent volume.

I'm hooking the same signal and sub from old amp vs new. Old one kicks it pretty good, new one, hardly anything.

Is there a pre-amp sort of device I can use to boost the signal to the new amp? Please recommend one if so. I need to get both these amps running together at a parallel level of volume (or as close as I can get) so that I can add another sub.

 

[SubieRubyRoo]

Gain isn’t a volume control. Also, mixing sizes and types of subs is almost sure to result in weird harmonics, especially when in the terrible acoustic environment of the average home.

What’s the voltage output of the Sony? You’d need to find an amp that has an appropriate gain voltage, and also understand that splitting a mono subwoofer output to multiple subs via a Y/splitter isn’t going to deliver optimal signal to either sub.

 

[92saturnsl2]

Gain isn’t a volume control. Also, mixing sizes and types of subs is almost sure to result in weird harmonics, especially when in the terrible acoustic environment of the average home.

What’s the voltage output of the Sony? You’d need to find an amp that has an appropriate gain voltage, and also understand that splitting a mono subwoofer output to multiple subs via a Y/splitter isn’t going to deliver optimal signal to either sub.

I'm no stranger to setting up sound systems, but realize this is a 30x50 garage/shop where my primary concern is not sound quality, which isn't a particularly big issue with subs anyway. Subs will be the same, just the amps will be different.

The Sony receiver outputs 2V @ the sub pre-out. The old amp handles this fine and does rated power, and will clip if you try to overdrive it via the gain control as one would expect. The new one, the gain control cannot go high enough to get any decent output. I haven't even split the signal yet (which shouldn't be an issue due to amps' high input impedance), I'm just going from one amp to the other using the same sub.

 

[Nukeman7]

I wonder if this pre-amp will get your desired results?

Mini Stereo Pre-Amp

 

[92saturnsl2]

I found this with some Googling on an audio forum:

"A consumer audio output or input, has an unbalanced connection and is usually in the form of an RCA. It does not matter how much actual voltage measures, It will always be a consumer audio output. Any consumer audio output, regardless of what it measures, is going to require 4 times the voltage, to operate any amplifier that has a PRO AUDIO balanced input. These inputs are usually in the form of XLR. Should one wish to power a PRO audio input, with a consumer audio output, One should first use a matchbox, such as the ART CLEANBOX PRO. or APHEX 124a etc. The matchbox will correct the both the output voltage, and well as the impedance LOSS, thus allowing full and proper use of pro audio equipment with consumer audio gear."

That's pretty much my scenario, the "old" amp takes an unbalanced signal (two wires). The new amp takes an XLR connector (3 wires) or a 1/4" TRS (3 wires).

Naturally, the subwoofer output on the receiver is a standard RCA plug (2 wires).

 

[Drifter]

I have an ART that I use to connect RCA preouts from a NAD rcvr to a Behringer KM1700 power amp to 15 in 3-way spekers. Worked for my set up. I got more power from the Behringer.