Is my amp the problem?


I recently decided to bi-amp my speakers so I purchased a crown xls 1002. (225w 8 ohm). I am driving a 10 woofer. It sounds horrible. I can't seem to get it to put out much power despite its rating even when I make all the right adjustments. Its a class D amp. Is that my problem? It just doesn't seem to have any Ba**s. Lol. Advice is appreciated.
jimbones

The Bryston 10B (that I mentioned above) is likely your best choice for active analog crossover to keep the resolution of your preamp. It has fully discrete analog circuits (probably running in Class A mode) and an excellent power supply. Input impedance is 15k. There’s one on audiogon for $995. They typically sell for well over a thousand.

There’s a Krell KBX for $1360 on ebay. It will probably sound more relaxed than the Bryston, but would probably need to be recapped. Also, the front dials do not show crossover frequency steps, so it will be impossible to determine actual crossover frequency without some sort of mic or line measurement device.

If you want to go cheaper, you could look at a new Ashly XR-1001, but you’d have to use some special cables (either XLR or 1/4" TRS). It is a pro audio crossover, but it is still fully analog (as opposed to digital/dsp like most of the pro audio crossovers nowadays). Input impedance is 20k ohms balanced (this is probably 10k ohms single ended as I can see a 10k ohm resistor on the input of each XLR leg). You can pick it up for $250 at many musician websites (sweetwater, parts express, etc.).

http://s298.photobucket.com/user/maryna1109/media/music/DSCN8468.jpg.html?t=1254515907

The Ashly is not going to be anywhere near the resolution/quality of the Bryston. If I did the Ashly, I would be making significant mods to it. First, Ashly likes to supply power at +/-18V, which is on the high side for normal op amp circuits, but they use normal 7818/7918 regulators. I would be doing the following:

- replace the 7818/7918 monolithic regulators with Sparkos Labs discrete regulators and drop the voltage down to +/-15V.

- Put in the largest power supply capacitors I could fit in the board/chassis (currently they are only 2 x 1000uf).

- Swap out all the op amps with AD797 on dual-channel DIP8 adapters.

- Solder 47uf Muse + 0.01uf metallized poly directly to the power pins on each op amp.

- Replace all the op amp negative feedback caps with film/foil or silver mica.

This is probably $450 worth of components (not including labor).


I’ve seen dbx, Ashly and other analog pro audio crossovers.

Another good x/o is the First Watt B4. All discrete (no opamps), zero feedback. More flexible than the Bryston, with far more available frequencies, and the highly-desirable 4th order-24dB/octave slope, which the Bryston does not provide. $1250 retail, often on sale at Reno Hi-Fi for less.

Yep, saw that one.  There's a B4 on audiogon/reno-hi-fi for $995.  I didn't mention it because it actually has a lower input impedance of 10k ohms.  Also, I'm highly suspect about the power supply -- it looks like a basic laptop power supply, so you may have to buy/build a high-quality high-current linear DC power supply to get any sort of performance out of it.    I also read that is uses bare JFET transistors with zero feedback instead of full op-amp circuits.  The JFETS are biased into Class A, so this crossover will definitely draw some power supply current.  I can't comment on the performance of this specific device, but I have seen instances where a bare JFET will sound nice but not have enough brute force to provide enough gain for bass/midbass punch, especially without negative feedback.  JFETs in preamp circuits can sound nice - they tend to have a nice rich/lush type of sonic signature, but they are not as crisp/clear as bipolar devices (this is largely a personal preference on sound signature here).

The Bryston power supply provides +/-24V (for a total of 48 volts), so the analog circuits definitely have a lot of current to play with for good bass/midbass power.  And I confirmed that the circuits are all Class A discrete and use bipolar devices instead of FET based.

There's always the Pass XVR-1, which is probably the best of the best, but at $5k+, I suspect it is out of range here.

Okay, further research on the Krell KBX.  It looks like this thing has the crossover frequency/slope hard-coded into the unit by Krell factory and cannot be modified.  Krell no longer services these things (possibly), so it may be difficult to impossible to change this KBX to work with you system.  And there is no way to "experiment" with different frequencies/slopes, so I'm going to give this KBX a big NO on the recommendation.
Oh, if you do decide to look at the Bryston, be aware they come in several variations.  Some have RCA inputs/outputs. Some have XLR.  Also, some models have a hard-wired power cord and others have IEC inlet so that you can upgrade the power cord.  The $900 agon is hard-wired power with RCA.  There is another that's on auction with RCA and IEC power cord.