I am now sure which form this should be posted in, so moderators feel free to move this posting as needed.
For my system pictured below, I recently added an ETA PD11SP 4 step sequential power up/power down conditioned power distribution strip. And I also made a major change in how my high frequency drivers are now protected, which is the real point of this posting.
When I first built this quad amplified system, I just could not bring myself to connecting the high frequency drivers directly to the amplifiers outputs. So, I used the 545 Hz and 3 kHz 12db/octave high pass filters pictured below to provide protection to the 2446 and 2405 drivers. And being new to this multi-amplified world, I once made a very common and stupid mistake of turning off the electronic crossover, before turning off the power amplifiers. Wow, talk about a really very loud bang that little mistake can make! Thankfully, the high pass filters protected the drivers from my own stupidity.
Initially, these filters did not have any damping resistors on their outputs. But, after reading about damping resistors on this site, I experimented and found that the addition of some damping resistance greatly improved the performance of the drivers.
After reading several references on this site, that when a 2405 is directly wired to an amplifier’s output, the performance can only be described as some kind of a religious experience. That got me started looking into the possibility of removing the high pass filters and going to direct drive.
But, one real threat to any high frequency driver that is wired directly to an amplifier's output is any noise that comes from the powering up and shutting it down the system. So, I came up with the relay box pictured below as a solution to this problem.
When the relay box is hooked up to the ETA PD11SP, the system powers up with the following steps:
Step 1: The CD player, pre-amp, and electronic crossover are turned on.
Step 2: The 3 Crown D-75A amplifiers are turned on. But, their outputs are only connected to dummy load resistors at this time.
Step 3: A Crown K1 is turned on.
Step 4: A Crown K2 and a 12 volt wall-wart power supply is turned on. This causes the 2 relays to close their contacts and the 3 Crown D-75A amplifiers are now connected directly to the 2405s and 2446s. (The 2446s are powered by bridged-mono D-75As)
During power down, this sequence is reversed and the 2405s and 2446s are disconnected before D-75s are turned off.
After hooking up the relay box and disabling all of the high pass filters. I then re-balanced my system with a pink noise track and a SPL meter. Here are the results from this little direct drive upgrade:
From listening to the very first note, the difference in how this system now sounds was jaw dropping. The driver's transient response has dramatically improved. And I also noticed that the high pass filters were creating a small amount of notch distortion. So, the system now sounds much cleaner without the filters. And while, I have not run any tests to confirm this, I really do think the 2446 driver's frequency response is now flatter. And surprisingly, even the stereo imaging of this system has improved. This was something that was completely unexpected.
With the exception, of the ETA PD11SP power sequencer, this has been a fairly inexpensive upgrade. And most of the parts for this little project were ordered from Partsexpress. But, I did order the DPDT 12 volts relays and the wall-wart power supply from Mouser Electronics.
Baron030
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