Trigger for sub amp

[subynube]

I have a parts express HPSA 1000 plate amp, that is triggered on through RCA inputs on the amp, when a signal is recieved from the receiver's sub RCA output. I am now using Emotiva UMC-1. I need to have the processor volume up at high volumes to get the sub amp to trigger on. If I listen to music at lower volumes, the amp doesnt get triggered on. Is there some external trigger that can be used to keep the sub on at all times? I remember seeing a post on this recently but I can't find it. Thanks all :T

[maseline_98]

Why would the sub be triggered to be on at only high volume levels? What does the volume have to do with the sub being triggered on?

[subynube]

Why would the sub be triggered to be on at only high volume levels? What does the volume have to do with the sub being triggered on?

I shouldnt use the term "high" volumes, but the processor volume is turned up to about 20. If I play music at lower volumes at about 15 or so, the sub amp turns off again and will only be triggered back on when the volume is turned back up to 20 again. This was true for the last 2 processors I've owned. I think the trigger of the plate amp just needs higher voltage to keep it running.

[Kevin D]

Just looked at the amp. Strange there isn't a 12v trigger or even an option for 'always on'.

The audio level will need to be higher in order to get the proper voltage. The only thing I can suggest is to crank up the sub output of the receiver and then lower the volume on the amp.

Kevin D.

[theblue]

since there is no 12V trigger you will need an outlet that it triggered by 12 volts and able to take a high current.

My panamax conditioner has 2 of such outlets on it. I use one to turn on/off my rotel amp that doesn't have a trigger. The panamax even allows me to set a delay on the outlets so they wait 10 seconds after the processor to turn on to avoid any spikes.

I'm sure there are cheaper triggered outlets if you look around.

[Kevin D]

If you look at the amp, the only options for the power switch is AUTO ON or OFF. So even if he switched AC power to the sub, he will still be in the same boat.

Kevin D.

[theblue]

I see what you're saying... hmmm...

[subynube]

If you look at the amp, the only options for the power switch is AUTO ON or OFF. So even if he switched AC power to the sub, he will still be in the same boat.

Kevin D.

Yes, absolutely true. I wish there was a switch to keep it on all the time, but the main power switch to turn it on is more of a off and "standby" switch, and therefore still needs the trigger input. And there is no 12V option. So I definately am in the same boat. I have tried to put the levels to the sub output a little higher, as to give the plate amp more "juice", and just turned the gains on the plate amp down. This helps a little. However, I would be concerned about overdriving the plate amp and causing distortion. I'll have to try it and see what happens. Thanks for the input so far!!

[Jim Holtz]

I have a parts express HPSA 1000 plate amp, that is triggered on through RCA inputs on the amp, when a signal is recieved from the receiver's sub RCA output. I am now using Emotiva UMC-1. I need to have the processor volume up at high volumes to get the sub amp to trigger on. If I listen to music at lower volumes, the amp doesnt get triggered on. Is there some external trigger that can be used to keep the sub on at all times? I remember seeing a post on this recently but I can't find it. Thanks all :T

Low turn on sensitivity is a known problem with the PE HPSA series plate amps. If you're handy with a soldering iron, PE has instructions about how to replace a resistor which increases sensitivity. Darren created the instructions long ago.

Contact PE and they should be able to send it to you. It's pretty easy to do and the amps turn on perfectly after that.

Jim

[subynube]

Low turn on sensitivity is a known problem with the PE HPSA series plate amps. If you're handy with a soldering iron, PE has instructions about how to replace a resistor which increases sensitivity. Darren created the instructions long ago.

Contact PE and they should be able to send it to you. It's pretty easy to do and the amps turn on perfectly after that.

Jim

Thank you!!!!! This is exactly what I would be looking for. I will give an update here when it is done!

[subynube]

Just a quick update. I contacted PE tech support, and they said only the real old amps were benefitting from the resistor modification, and the newer ons like mine are not. Back to the beginning again

[duketbrd88]

I noticed when using the rca auto sen. turn on that instead of just using the left input or the (LFE), simply using an rca y splitter on the sub seems to turn it on at lower volumes. This is if your not already using right and left rca's. I am not familiar with your setup, so maybe this will help.

[Jim Holtz]

I noticed when using the rca auto sen. turn on that instead of just using the left input or the (LFE), simply using an rca y splitter on the sub seems to turn it on at lower volumes. This is if your not already using right and left rca's. I am not familiar with your setup, so maybe this will help.

This is an excellent point that I forgot to mention. The HPSA amps won't put out full power unless you either use a "Y" cable in the L/R RCA inputs of the HPSA or tie the sub amp into your mains for a full range signal. It should also help with the turn on sensitivity issue.

FWIW, I had three of these amps at one point in my home theater. One powering a 12" AV-15 in each of my line arrays and the third one powering a 15" AV-15 sub. All of them had the same issue. Once corrected, they've worked flawlessly.

Jim

[subynube]

This is an excellent point that I forgot to mention. The HPSA amps won't put out full power unless you either use a "Y" cable in the L/R RCA inputs of the HPSA or tie the sub amp into your mains for a full range signal. It should also help with the turn on sensitivity issue.

FWIW, I had three of these amps at one point in my home theater. One powering a 12" AV-15 in each of my line arrays and the third one powering a 15" AV-15 sub. All of them had the same issue. Once corrected, they've worked flawlessly.

Jim

Thanks Jim. What I have done is kept the input to the amp throught the LFE input and doing the signal processing through the processor and not the parametric EQ on the sub. I have now turned the sub output on the processor to as high as it will go, and turned the gains down on the sub amp. This definately helps a LOT. Not yet perfect, but really much better. My last option will be to do exactly what you said and tie the sub amp into the main outputs of the processor and use the left and right output both to help trigger the amp. That im sure will be the best option. However, I want to make sure I undersand this correctly:
-The LFE output on the processor and the L and R outputs actually put out differrent information? Or is it the same information, but just low passed for LFE and full signal for the L and R mains? Not sure which one is correct. Thanks everyone for your input, as I think this problem is no longer!!

[subynube]

FWIW, I had three of these amps at one point in my home theater. One powering a 12" AV-15 in each of my line arrays and the third one powering a 15" AV-15 sub. All of them had the same issue. Once corrected, they've worked flawlessly.

Jim

Also, Jim, when you say "once corrected, they've worked flawlessly" do you mean you did the resistor modification?

Thanks,
Josh

[Jim Holtz]

Also, Jim, when you say "once corrected, they've worked flawlessly" do you mean you did the resistor modification?

Thanks,
Josh

Hi Josh,

Yes, I did the resistor mod on all three amps. These were the original amps in 2006 IIRC. The resistor trick worked perfectly. I picked up the resistors at Radio Shack for a couple bucks for all three. The newer amps are "supposed" to have this fixed but there are numerous complaints on the PE board about the turn issue. It's a good amp other than the sensitivity and it doesn't meet the power spec.

Some thoughts from other posts in this thread. You do need to use a "Y" cable to connect the LFE out put from your pre/pro or receiver to the sub amp on the sub end. I would use the sub amp crossover in addition to the one in your processor. The crossover in the sub amp is very good and is a 24 db crossover rather than the 12 db offered in lessor amps. The crossover in your processor is 12 db and is designed to combine with the 12 db crossover of cheaper sub amps to sum at 24 db. No problems combining the 24 db + 12 db for a total of 36 db. More is better when it comes to getting your sub out of the mix.

If you've ever heard voices coming from your sub you'll know what I'm talking about.

The only difference between the LFE output and tying into the main L/R RCA output of your processor to drive the sub amp is the LFE is summed to mono and the crossover built into the processor is preventing the high frequency signals from passing to the sub. If you "Y" off the main RCA outputs of your processor to drive the sub L/R inputs, the internal sub crossover will filter the high frequency signals.

BTW, the crossovers in "GOOD" sub amps are much better than the ones offered in processors/receivers, IMHO.

I'm getting wordy! I hope that helps!

Jim

[subynube]

I'm happy to say I just completed the resistor mod. It took about 1.5 hours to do, and real easy. Unfortunately, I don't think it made a difference, but I am fairly happy with it right now as I have the sub volume outputs one the processor all the way up, and it is doing well. The final thing I will try is using the L and R outputs of the processor instead of the LFE output, and see how that does. Thanks again all!

BTW, 1 more question:
Jim, you said the LFE outputs and the L and R outputs dont really play different information, except the LFE is low passed and the L and R play in stereo. I understand this would be true for stereo listening, but is this true for all movie listening also? I really thought that the LFE output played different information in 5.1 than it does in stereo listening. Thanks :T

[Jim Holtz]

BTW, 1 more question:
Jim, you said the LFE outputs and the L and R outputs dont really play different information, except the LFE is low passed and the L and R play in stereo. I understand this would be true for stereo listening, but is this true for all movie listening also? I really thought that the LFE output played different information in 5.1 than it does in stereo listening. Thanks :T

The signal is the same in the LFE channel (just summed to mono) as the L/R mains. The LFE of course has the crossover built in that rolls off the high frequency signal you'd get from the mains. It doesn't make any difference if it's a movie or music.

That said, Dolby Digital does direct different frequencies to each channel depending on how it's coded. If you run the sub from the mains in a home theater system you will want to turn off the LFE channel so the mains will get all the bass.

HTH

Jim