If your car is a sedan then I would not consider this arrangement. The subs would be radiating into two different environments and this could cause all sorts of problems. If your car is a station wagon or hatchback where the trunk and cabin are essentially the same airspace then why not. Wiring the ...

I like Panasonic FC series. They are not original color, but I think the blue/gold color is perfect on the gold circuit board. The big rail caps should only be changed by someone who really knows how to (de)solder and has the appropriate equipment. There is hardly any electrolytic caps in the signal...

I'm not sure about this but I remember hearing that if these amp have been clipped on a regular basis, the clipping light circuit gets damaged and starts causing problems.

You're right, the bias current should show up as some mV across the resistors. Maybe 5mV, I can't recall exactly. The pots on the PCB are for adjusting bias. DC offset at speaker connectors should be 30mV or less. Large values indicate the amp has had a hard life and the output transistors are "...

The red line in the graph looks like a free field frequency response to me. If you build a box according to that, it will sound good in a very large room or outside. If you put that box in a car you will get a huge boost starting about 70 or 60Hz and increasing towards lower bass. It will likely sou...

I'm pretty sure the crossovers in modern HU's are digital and my assumption has always been that digital crossovers don't really sound like anything. I mean different crossover algorithms sound different, but they are in principle "perfect". It's the D/A conversion where you get difference...

I have a ZX450 which has issues with the gain varying on its own in one channel. After switching on, after a few minutes the gain increases suddenly. It might be a pot issue but I don't really know. ZX amps could be better if the crossovers could be removed entirely. The crossovers were state of the...

There was a picture on the PG FB page with a guy holding #1 zen9 amp.

Nice test!

i will only comment that with old amps the sound may or may not be same as new from factory.

The problem has got worse. When I turn up the volume, the channel with the gain fluctuation distorts quite badly.

Last time I checked the price of 4700uF 16V Panasonic caps, I noticed the price had doubled. Don't know If this is related to anything, just saying.

Hmm, I see what someone did there. That's hot-rodding the power supply transformer.
Doubling the primary coils halves the resistive heat losses and allows for a bit more current.

Sure enough if I turn the volume up loud, then the gain settles much faster, maybe less than a minute. And then its fine. But if I turn the stereo off and on again, the right gain is louder again. SO it seems like the amp needs to warm up to settle into its normal operating point. I've never had thi...

I've had a ZX450 in my car for about six months now. When I turn the stereo on, now the right front channel is much louder than the left channel, like 10dB more. After maybe 10 minutes it settles and sounds right. Keep in mind its winter here and temperatures below freezing. It doesn't seem like a g...

Only thing that comes to mind is a MAC500. The specs are similar. Never seen anything like this before.

The biggest difference between the M(P)S amp lineup is the rail voltage. MS2250 +-58V MAC500 +-50V MS2125 +-36V MPS2500+-28V MS2125 and MPS2500 are specced at same power ~500W rms, but at different loads. Since the MPS makes its power at half the ohms, its parasitic power losses are double that of M...

You should know Eric, the MS2250 has bigger power supply toroids and better cooling than the rest of the big MS/MPS amps.

I think the dyno run vids show quite clearly that a MS2250 can do about double RMS and dynamic power compared to the rest.

From memory the rail voltages are 38V vs 30V.
And no , you can't bump up the voltage easily.

Use the same values as you have in there. The values must vary between different revisions of amps.

R9 -R12 100ohm fusible resistors.

When looking at Big D's dyno vids you must keep an eye open for the test frequency. 40Hz vs. 1kHz makes a big difference. MS-2125 got dynoed at 40Hz mostly but MS2250 at 1kHz a lot of the time. The MS-2125 made more than half of MS-2250's power in every comparable test. You just have to compare powe...

I use winISD. You could download it on another puter and transfer the installation program on a memory stick which has been checked for viruses. Its a simple yet sophisticated program which does everething I need. It can even simulate voice coil temp. rise which is handy for estimating real world pe...

Hi guys!

Stumbled upon this:
http://www.ampdoctor.co.uk/more-phoenix ... fications/

What do you think about that?
Zeropoint has mentioned ZX bias issues many times at least.

Obviously that 8 fet power supply can deliver some serious current! Even the buss bars are warped from the heat

From some tests I've read, it's not all about mass. reducing vibration requires a very lossy material between two layers. CLD stands for constrained layer damping. The stuff between your car body and a thin layer of aluminium is usually butyl rubber or equivalent. This stuff is very lossy and does t...