Author Topic: Need some power amp help (Read 349 times)

tsosboom · « **on:** January 29, 2007, 10:26:17 AM »

I have used an Alembic F1-X preamp for about 7 or 8 years now, running it through a USA 900 power amp into various cabinets over the years. I finally picked up an Ampeg SVT810 (800w at 8 ohms per side, I think) and hooked it up and knew I found my setup.

Well, as I was loading my gear to play a gig the other day, I dropped the hardcase containing the power amp and it fell from the top of the cabinet. As you can imagine, the power amp didn't fare too well. Channel 2 is shorted out and Channel 1 is providing only intermittent power. It's got to be fixed or replaced, and the bench fee to even crack open the power amp has me wondering if I shouldn't just pick up a new or new to me (used) power amp.

So, since about all I know is that I like the ability to run the output of the preamp into two separate channels of the power amp, which in turn drive the separate 4x10s so I get two distinct tones, I'm seeking advice on a suitable power amp to accomplish this task. I love the Alembic preamp, my cabinet and my bass. The power amp, not so much.

What kind of power amp do I need to properly drive the 8x10, to handle the distinct signals from the full range and high pass outputs of the preamp and to give me plenty of volume for some of the sub-par venues my band plays?

cozmik_cowboy · « **Reply #1 on:** January 29, 2007, 10:46:53 AM »

Hi, Ryan - welcome!
I would suggest that you look into Yamaha power amps - they give clear, uncolored sound, they aren't overly pricey, they come in a wide enough range of power ratings that you can no doubt find one to meet your needs, and, based my experience with them, a Yamaha probably would have survived that fall with no ill effects (they're the most reliable amp I've ever used.)

Peter

kmh364 · « **Reply #2 on:** January 29, 2007, 11:47:58 AM »

QSC. Durable, American-made, readily available parts/service, reasonably priced. They're the choice of most pro sound services for the above reasons. Oh yeah, and they sound good!

Lots of Alembic Club memebers use 'em...myself included.

kmh364 · « **Reply #3 on:** January 29, 2007, 11:48:40 AM »

Sorry, duplicate post

(Message edited by kmh364 on January 29, 2007)

dannobasso · « **Reply #4 on:** January 29, 2007, 02:24:15 PM »

I too have a number of qsc's (5 in fact) and they are backed by a great service dept. I did just order for a school pa install, a crown xti 4000. They make a 1000, 2000 as well specs:

Output Power (1 kHz, 0.5% THD)
    Stereo   Bridge-Mono
8 Ohm   4 Ohm   2 Ohm   8 Ohm   4 Ohm
XTi 4000   650W   1200W   1600W*   2400W   3200W*
XTi 2000   475W   800W   1000W*   1600W   2000W*
XTi 1000   275W   500W   700W*   1000W   1400W*
*With 1% THD.
Voltage Gain at 1kHz, 8 ohm rated output:

XTi 1000: 30.5 dB
XTi 2000: 32.9 dB
XTi 4000: 34.2 dB

Frequency Response: +0/-1 dB from 20 Hz to 20 kHz at 1 watt into 4 ohms.

Load Impedance: Safe with all types of loads. Rated for 2 to 8 ohms in Stereo mode, 4 to 16 ohms in Bridge-Mono mode.

Sensitivity: 1.4V

Signal to Noise Ratio (below rated 1 kHz power at 8 ohms):
100 dB (A weighted).

Damping Factor: Better than 500 from 20 Hz to 400 Hz.

Crosstalk: > 70 dB below rated power, 20 Hz to 1 kHz.

Input Stage: Input is electronically balanced and employs precision 1% resistors.

Input Impedance (nominal): 20 k ohms, balanced;10 k ohms, unbalanced.

Maximum Input Signal: +22 dBu typical.

AC Line Voltage and Frequency Configurations Available: 100V, 120V, 220-240V
50/60 Hz.

AC Line Current:

XTi 1000: 6.5A
XTi 2000: 6.9A
XTi 4000: 8.0A

At Idle: Draws no more than 90 watts.

Operating Temperature: 0? C to 40? C at 95% relative humidity (non-condensing).

DSP Section

EQ: 4-band paragraphic per channel, boost/cut ?12 dB. Also adjustable high and low shelving filters.

Filters: Highpass and lowpass per channel. Butterworth 6/12/18/24 dB per octave. High and low shelving filters, one per channel.

Delay: For signal alignment of driver; 50 mS total delay.

Subharmonic Synthesizer: Adds low-frequency content.

Output Limiter: Prevents clipping.

Presets: 10 user speaker presets.

Front Panel Controls and Indicators

Level: Detented rotary level control, one per channel.

Power Switch: On/off switch applies AC power to the amplifier.

Sel/Prev/Next Buttons: Three buttons near the LCD screen are used to access menu items.

LCD Screen: Backlit liquid crystal display shows speaker presets.

Signal Indicator: Green LED, one per channel, flashes when a very low-level signal is present at input. May be used for troubleshooting cable runs.

?10 Indicator: Green LED flashes when output signal exceeds ?10 dB below clip.

?20 Indicator: Green LED flashes when output signal level exceeds ?20 dB below clip.

Ready Indicator: Green LED, one per channel, illuminates when the amplifier is ready to produce audio.

Clip Indicator: Red LED, one per channel, turns on at the threshold of audible distortion.

Temp/Fault Indicator: Red LED, one per channel, illuminates under Fault or excessive temperature conditions.

Power Indicator: Blue LED illuminates when the amplifier has been turned on and has power.

Rear Panel Controls and Connectors

AC Line Connector: NEMA 5-15P (15A).

Input Connector: XLR, one per channel.

Link/Out Connector: Loop-thru signal from input connector for linking to another amplifier, one per channel.

Output Connectors: Two Neutrik? Speakon? NL4MP (mates with NL4FC) output connectors. Channel-1 Speakon? is wired with Ch. 1 and Ch. 2 outputs for use with optional single 4-conductor cable. Two binding post outputs (in parallel with Speakon? connectors).

HiQnet USB Connector: Type B, connects to a HiQnet network.

Protection

XTi-Series amplifiers are protected against shorted, open or mismatched loads; overloaded power supplies; excessive temperature; chain destruction phenomena; excessive output current, input overload damage; and high-frequency blowups. They also protect loudspeakers from input/output DC, large or dangerous DC offsets and turn-on/turn-off transients.

Construction

Chassis: Steel.

Cooling: Proportional speed fan with front-to-rear airflow.

Dimensions: EIA Standard 19-in. rack mount width (EIA RS-310-B), 3.5 in. (8.9 cm) high and 12.25 in. (31.11 cm) deep behind mounting surface.

Net Weight:
18.5 lb (8.4 kg)

tsosboom · « **Reply #5 on:** January 29, 2007, 06:07:17 PM »

Thanks for the help, folks. I'm going to see what I can scout out around here for used gear, paying particular attention to Yamaha power amps. I don't know if I communicated well that I have been using a QSC amp, which I like, but since all the specs and stuff are like white noise to my eyes (hey, I just play the bass - I'm no electrician) I thought I'd see if I'd been using the wrong setup.

Oh, and I took a look at my cabinet. It's a SVT-810EN. I can't seem to find any documentation for that particular model, only the SVT-810E and SVT-810AV. Anyone have any thoughts on how to get some kind of manual to make sure everything is as it's supposed to be from the factory? I have a feeling the previous owner may have done something creative with the wiring inside.

Thanks again.

worldfamousandy · « **Reply #6 on:** January 31, 2007, 06:59:34 AM »

What is paragraphic eq? I'm surprised to see any eq on a power. Low-pass filters, and features like that have become common, but adjustable eq is something I have not seen.

Andy Calder
www.andycalderbass.com

keith_h · « **Reply #7 on:** January 31, 2007, 10:33:04 AM »

Paragraphic eq
Would that be a spell checker?

Keith

essenceman · « **Reply #8 on:** February 01, 2007, 09:04:51 AM »

Hi guys,

I recently changed to a F1-X, SF-2 Yamaha P5000S rig, which sounds great through my baby (2x8 & 1x10) Euphonic Audio cabs. So I can certainly recommend Yamaha power amps.

Also with regard to Keith's post about spell checkers, some of you might have seen this before.

[color=aa00aa]A Little Poem Regarding Computer Spell Checkers...

Eye halve a spelling chequer
It came with my pea sea
It plainly marques four my revue
Miss steaks eye kin knot sea.

Eye strike a key and type a word
And weight four it two say
Weather eye am wrong oar write
It shows me strait a weigh.

As soon as a mist ache is maid
It nose bee fore two long
And eye can put the error rite
Its rare lea ever wrong.

Eye have run this poem threw it
I am shore your pleased two no
Its letter perfect awl the weigh
My chequer tolled me sew.[/color]

I liked it!

Rob

dannobasso · « **Reply #9 on:** February 01, 2007, 09:45:59 AM »

Paragraphic eq
Would that be a spell checker?

That is direct from Crown's website. www.crownaudio.com

keith_h · « **Reply #10 on:** February 01, 2007, 10:17:10 AM »

Well you learn something new everyday. ;-)

Googled this explanation:
Paragraphic Equalizer
Basically this is an EQ that combines the user interface of a graphic equalizer with the functionality of a parametric equalizer. The EQ adjustments are made with sliders (so you get a visual graphic representation of your settings), but each band has adjustable frequency and Q like a parametric. Plus there are often other attributes that can be set. Very few hardware based paragraphic EQ's have been built over the years because they require a lot of components (thus are expensive) and space to lay them out in a usable fashion (especially if long throw faders are employed). However, in software based systems, the paragraphic EQ doesn't need to cost much more than any other type and are more popular, though they still can take up a lot of space on screen.

Keith

kmh364 · « **Reply #11 on:** February 01, 2007, 11:02:20 AM »

This is nothing new: ADC offered paragraphic analogue eq's for home use back in the '70's. The difference now is with today's cheap DSP chips, this and virtually any other sound processing function can be done in the digital domain. I believe this is what the Crown amps, mentioned by Danno above, offer.

somatic · « **Reply #12 on:** March 01, 2007, 04:56:56 AM »

I agree with cosmic cowboy. I have a Yamaha P7000S (2 x 700W @ 8R: 12kg) and whilst the others mentioned (QSC, Crown etc) are very well priced in the US, outside there, the Yamaha's are much better value. In 20 years I've never killed a Yamaha poweramp, and for these two reasons they're my first choice.

You'll never hear the difference between to well designed and made SS poweramps within their envelopes, so buy what you can get locally for the best price and weight.

lothartu · « **Reply #13 on:** March 01, 2007, 01:46:17 PM »

I'm personally using a QSC RMX series power amp (1850HD). The PLX and PLX2 series are the nice lightweight power amps. The RMX series isn't too heavy but it's not the new fancy PLX line so the RMX series amps can normally be found for a very good price.

I picked up my QSC RMX 1850HD for about $325 brand new a couple of years ago. It's heavier than the PLX series but I don't mind at all when I look at the cost difference.

- Jim

tsosboom · « **Reply #14 on:** March 02, 2007, 05:17:36 PM »

Thanks for the additional information, guys. As far as the Yamaha power amps are concerned, I'm not finding any in my area (probably just not looking enough).

At the music shop the other day, I spied some Mackie power amps, and the price is right, but are their amps durable? I've used their mixing boards, but I never had to move one and depend on it working after transport...