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Problem with PE 1000w plate subamp


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#1 of 34 Thomas J. Coyle III

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Posted January 05 2004 - 02:29 PM

To all

I recently ordered and successfully assembled a 15" Titanic subwoofer System with the new 1000w plate amp. When calibrated to the correct level (75-80db SPL) at the Dolby reference of "0" on my Outlaw 950 pre/pro, the subwoofer really rocks. However, at normal listening levels for pop/country music, the subwoofer plate amp will not go from the standby mode to the operate mode when the power switch is in the "auto on position". Also, when in the operate mode, the power light becomes bright green instead of yellow as stated in the amp manual. To achieve a calibration of 75-80db SPL, I have the amp gain set at "5" and the 950 pre/pro output at -5db. To get the amp to turn on, when in the "auto on" mode, at normal listening levels for music, I have to boost the 950 pre/pro output to +8db (the pre/pro trim range is -15 to +10db). Also, the amp turn on point seems to be dependent on the amp gain setting. For this reason, I do not believe that my amp has been adjusted to go from the standby mode to the operate mode upon receiving a 3mv input signal as stated in the product description. Do I have a malfunctioning amp? Has anyone else had a similar problem with this new PE plate amp?
Regards,
TCIII
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#2 of 34 David_P

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Posted January 06 2004 - 03:04 AM

I can't speak to your problem, but I'm very interested in your take on how the driver/amp combo works... is this the kit (box/driver/plate amp)?

I haven't seen much feedback on these plate amps at all, in any forums that I can find.

thanks...

#3 of 34 Jack Gilvey

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Posted January 06 2004 - 04:23 AM

Ditto on David's curiosity. All those new Titanic kits look like real steals.
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#4 of 34 Owen Bartley

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Posted January 06 2004 - 07:50 AM

Actually I have a similar thing happening with my Tempest/AVA250 combo. for movies, which I usually watch fairly loud, no problem. When I switch to TV or quieter music, I sometimes have to turn the sub on myself. Looking at your post... could you adjust the gain on the pre-pro higher, and turn down the gain on the sub and calibrate THAT to be your standard setup? I am thinking about trying it as well.

#5 of 34 Thomas J. Coyle III

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Posted January 06 2004 - 03:44 PM

Hi Owen,

Thanks for your response. I have already done what you have suggested. I originally set the plate amp gain a "5" and adjusted the 950 pre/pro subwoofer output to -5db to achieve a +75db SPL when the 950's volume control was set to the reference level of "0". This combination will reliably cause the plate amp to go from the standby mode to the operate mode when I run the system at home theater sound levels. However, when I listen to music at a much lower level, the plate amp will not turn on unless I raise the subwoofer output of the 950 pre/pro to around +8db with +10db being the maximum. I also did an experiment to determine the affect of the plate amp gain control on the auto-on function. I set the plate amp gain to around "3" and then readjusted the subwoofer output of the 950 pre/pro to 0db to achieve the +75db SPL at the "0" volume reference level. As usual, the plate amp would turn on at home theater volume levels, but would not turn on at music listen levels. While listening to some music, I then began to increase the plate amp gain control beyond the starting "3" position while leaving the the 950 pre/pro subwoofer output at 0db. Low and behold, the plate amp turned on at a gain control setting of between "5" and "6". This little experiment indicates that the PE 1000w plate amp auto turn-on feature is dependent not only on the level of the LFE input signal from the preamp, but also on the level of the plate amp gain setting. Because of this anomaly, I doubt that it will be possible to achieve a combination of plate amp gain and preamp LFE output that will accomodate both home theater and music level volumes and result in the plate amp turning on automatically.
At this point in time, I would not recommend buying the PE 1000w plate amp until PE resolves this auto turn-on issue. It could be that I have a malfunctioning plate amp as PE advertises that the plate amp will turn-on if it receives a signal greater than 3mv and I believe that my preamp is putting out a LFE signal greater than 3mv at normal music listening levels. After all, the PSB Sub Sonic 6 that I used to have in my system would auto turn-on at any volume level be it music or home theater.
I have emailed PE's tech support, but have yet to receive an answer and it has been longer than 24 hours.
Regards,
TCIII
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#6 of 34 David_P

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Posted January 07 2004 - 02:33 AM

but aside from the issue with auto turn on, how does the combination work?

#7 of 34 ThomasW

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Posted January 07 2004 - 04:41 AM

Quote:
I have emailed PE's tech support, but have yet to receive an answer and it has been longer than 24 hours.

Call their standard toll-free number and ask to speak with someone in tech support.

#8 of 34 Owen Bartley

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Posted January 07 2004 - 07:47 AM

Wow, you were way ahead of me Thomas. I would have thought that the signal coming from the source (receiver, pre/pro, whatever) would be the only one that determined the voltage going to the auto-on sensor. Worth a try I guess. I hope you find something that does work.

#9 of 34 Thomas J. Coyle III

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Posted January 07 2004 - 03:20 PM

Okay everyone,

Here is how it sounds. The 15" MKIII Subwoofer System really shakes our townhouse and I am sure that it is suitable for large home theaters since its sports a 1000w plate amp.
I have a True Audio RTA that I used to characterize the subwoofer in our home theater / living room. I drove the LFE input of the plate amp directly from the RTA and used a Behringer ECM8000 mic coupled to a SHARK preamp to track the SPL with the RTA. The RTA has a frequency calibration curve for the mic and I used a very accurate sound level meter to calibrate the mic's SPL response. I started at 103Hz with 88db, hit the F3 point at round 35Hz with 86db and was able to get 78db at 24Hz. The response fell to 60db at 20Hz. I plan to crank up the starting SPL this weekend to 105db and will let you know how the subwoofer acts at the higher output level. I found a room induced peak of +6db around 40Hz and used the plate amp's single channel parametric equalizer to bring it down 6db which seemed to make the sub sound smoother and less boomy. I plan to use my BFD to really dial in the frequency response once I get the auto turn-on anomaly taken care of.
Regards,
TCIII
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#10 of 34 David_P

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Posted January 08 2004 - 02:31 AM

thanks...

Please be sure to post back as to what resolution was forthcoming WRT the autoturnon problem.

David

#11 of 34 Thomas J. Coyle III

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Posted January 08 2004 - 12:48 PM

Hi David_P

I have exchanged a number of emails with the PE tech support staff. The conclusion is that this is the way that this plate amp works. I am an electrical engineer so I know my way around electrical circuits and because the amp gain control affects the auto on turn-on level, I would say that there is a design anomaly here.
I have reviewed the schematics of several of the popular 250w plate amps and the auto turn-on circuit is ahead of the amp gain control so that the setting of the gain control will not affect the input level to the auto turn-on circuit. Whoever in China designed this particular plate amp used the signal level that comes off of the gain control as the input to the auto turn-on circuit. Therefore the auto turn-on input level is dependent upon both the amp gain control setting and the LFE input level from the preamp. I believe that my experiments with the amp gain control settings and the LFE preamp drive signal support this conclusion.
I asked the tech support staff if they could email me a copy of the schematic (I hate to reverse engineer electronic hardware, but I will if there is no other recourse) so that I might figure out (I have the resources of Raytheon Company at my disposal) a way to improve the sensitivity of the LFE input. This could possibly allow the plate amp to auto turn-on at a very low input level and then it would be useful for both music and home theater sound levels. I have received emails from other plate amp users indicating that this is not an uncommon problem where the subwoofer is used for both music and home theater listening. My original PSB Sub Sonic 6 subwoofer would auto turn-on the instant my pre/pro turned on and its turn on level was independent of the plate amp gain control. So, I think that that PE might sell more of these new plate amps and have less returns if this anomaly is corrected either by changing the circuit in new production runs or by advertising a fix on your tech talk form that can be implemented by DIYs who know what they are doing. Comments?
Regards,
TCIII
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#12 of 34 Wayne Ernst

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Posted January 08 2004 - 02:23 PM

Thomas,

Is Parts Express allowing you to return the amp? If so, have you considered something like the Keiga 52100?

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#13 of 34 Baldemar Garcia

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Posted January 09 2004 - 01:54 AM

Thomas,

You're obviously on top of this, but I just thought I'd add a little. IMO, your remark about this being a common problem with plate amps is a little misleading. And I think it comes from advice that was given in a mag a while back, that being the recommendation of running the receiver's sub output highly attenuated, and making the adjustments using the subamp's level control. With this setup (and considering that most people probably listen to movies at higher levels than music), it isn't hard to see how it would appear that plate amps have a problem with auto turnon when listening to music.

But as you've noted, the most popular models are designed correctly, with the auto turnon being solely dependant on input signal level. There is definitely a design problem with the model you've purchased from PE.
bgarcia

#14 of 34 Thomas J. Coyle III

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Posted January 09 2004 - 01:59 AM

Hi Wayne,

Yes PE has given me the option of returning the plate amp. However, I do not think that returning the amp will resolve the problem. The plate amp cut out in the back of the subwoofer cabinet is made specifically for the 1000w plate amp and I would have to modify it to use any other plate amp. Also, I have read of problems with the Keiga plate amps that are not encouraging.
I think the solution to the problem is to modify the auto turn-on circuit to either have a lower turn-on threshold or move its input from after the plate amp gain control to before the plate amp gain control like other plate amps are designed.
The PE plate amp is very good and very powerful and works quite well in my home theater setup. If anyone is going to buy this plate amp, just be aware that you might have problems with it turning on automatically at low listening levels. If the plate amp had an always on mode, that would negate the auto turn-on problem without having to modify the plate amp circuitry.
Regards,
TCIII
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#15 of 34 Thomas J. Coyle III

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Posted January 13 2004 - 01:42 PM

Hi all,

If you were thinking about purchasing the new PE 500w plate amp, think again. I just received an email from a fellow audio enthusiast and he is having the same LFE low level turn-on problem that I have being having with the PE 1000w plate amp. Sounds like they both have the same auto turn-on circuit configuration.
Sean, at tech support for PE, told me that they will mail me a copy of the schematic of the new 1000w plate amp as soon as they get it from the manufacturer. Hopefully I can modify the auto turn-on circuit to a configuration that closely duplicates the auto turn-on circuit design of PE's popular 250w plate amp.
Regards,
TCIII
Before you send someone to save the world, you better make sure they like it the way it is.

#16 of 34 Joseph Sabato

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Posted January 14 2004 - 01:12 PM

If the amp has a manual on position, another work around is to put together an outlet box with a small high amperage rated relay in line with it (normally open) and run the coil to a switched outlet on your pre/pro outlet so the amp turns on with the preamp.

Since I have passive subs with a separate power amp, there is no signal sensing auto turn on. The relay I use has a 12V coil with a small draw, so I used a "power adapter" as the source and run thin wire to the coil. This has worked great for the last 5 yrs; beats getting up to manually turn them on.

Really should not have to do that with a plate amp though.

#17 of 34 David_P

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Posted January 15 2004 - 03:03 AM

I don't think the PE 500/1000W plate amps even have a manual turn-on option.

#18 of 34 Thomas J. Coyle III

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Posted January 15 2004 - 07:24 AM

Hi David,

You are right! These two new PE plate amps have a power switch that can be either "OFF" or "Auto Turn-On". There is no "Manual Turn-on". When the plate amp is in the auto turn-on mode, it is electrically energized and is waiting for an input signal on either the LFE input or the two low level stereo inputs in order to start playing. If the plate amp actually adhered to the PE advertised spec of a 3mv signal turn-on sensitivity, there would be no issue at all. However, this plate amp takes alot more input signal than 3mv to start playing.
Regards,
TCIII
Before you send someone to save the world, you better make sure they like it the way it is.

#19 of 34 Chris Carswell

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Posted January 15 2004 - 11:38 AM

.
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#20 of 34 LanceEAR

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Posted January 16 2004 - 07:13 AM

Quote:
Hi all,

If you were thinking about purchasing the new PE 500w plate amp, think again. I just received an email from a fellow audio enthusiast and he is having the same LFE low level turn-on problem that I have being having with the PE 1000w plate amp. Sounds like they both have the same auto turn-on circuit configuration.
Sean, at tech support for PE, told me that they will mail me a copy of the schematic of the new 1000w plate amp as soon as they get it from the manufacturer. Hopefully I can modify the auto turn-on circuit to a configuration that closely duplicates the auto turn-on circuit design of PE's popular 250w plate amp.
Regards,
TCIII

That shoots down my AV15/PE500 amp plan. Any idea from PE if they will actually attempt to resolve the issue? Since it is not functioning as advertised I would imagine they would want it fixed ASAP. Or perhaps they are waiting on some kind soul to fix it for them...

Maybe I should just buy a tempest and a PE250 amp for about the same price as the 500watt and sell my AV15 when/if it ever arrives...

Good luck with your efforts.

-Lance





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