diff between LPL44 low level control and sub volume control?

eyesofra · Post by **eyesofra** » Thu Mar 01, 2007 12:08 am

Hi guys,
I need some help with LPL44 ?
This might get a little long but pls help me through ..

I was confused of its real purpose or to be precise what it does ?
So sent an e-mail to PG and got a reply from Tech support . ( They really do have an amazing support, any queries get replied by 48hours max ! )

I've pasted my question and his reply .

My Question :
Hi there, I would like to know what's the real purpose of having the remote low pass level controller in the amp ?? As far as my knowledge extends, the bass level control in my HU attenuates/amplifies signal at 100hz whereas the bass boost/t-bass in the PG amps attenuates/amplifies at 45hz. So what does the LPL44 does then ?? Does it control another fixed low frequency or merely a remote control for the bass boost/t-bass circuitry ( at 45hz ). If yes does it mean that when the remote port is activated the bass boost on the amp itself gets disengaged ?? Pls explain cause i'm completely puzzled whether to get one or not at this point of time. Thank you for the time.

PG Tech Phil's reply :

Hello,

The LPL44 controls output over the entire frequency range up to the roll-off frequency when the amp is set to low-pass mode. It is considered a “secondary” output control, whereas the amplifier’s bass control or head unit EQ affects a certain frequency.

Ok now,
My HU ia Nakamichi CD-400 which has a dedicated output for subwoofer with its own sub volume control.
With this i can increase and decrease my sub's volume level without affecting the overall volume of system and it ranges from off-(-10)-0-(10)

Now based on Phil's reply , does this volume control on the HU and the LPL44 serve the same purpose ??
And does it mean i dont need the LPL44 for my system?

Any replies would be much appreciated.
Thanks a lot in advance

Post by **bdubs767** » Thu Mar 01, 2007 6:03 am

the volume control on your headunit is a 45hz graphic EQ, where as the lpl is your gain.

Post by **stipud** » Thu Mar 01, 2007 8:12 am

I am not sure about your specific headunit.

There is a difference between these two functions on decks that most consumers don't "get":
Bass : 0 - leave it at 0, this is the bass boost at 45Hz. Since the boost on a factory headunit has a fairly wide "Q" (it affects more frequencies above and below 45), then people tend to think that it is a volume control. This is not the case. Artificially boosting a signal can create a lot of noise, plus every 3 decibels boost requires your amplifier to double it's output at the boost frequency. Of course I get into most people's cars and this is completely cranked, because they think it is a volume control. They want to get the full volume out of the subs, so they crank it. This is when I set it at zero, fix their gains, and they immediately realize how clear it sounds without boost... plus lower and higher bass frequencies are played stronger, rather than just 45Hz.

Subwoofer : 0 - if this is separate from the bass boost, most of the time it is to adjust the volume of the subwoofer RCA output from the headunit. As far as I know with Alpine decks you have to bring this level to +15 before your RCA output makes it's full power. On my ooold Sony deck I recall it acted as a boost if you turned it above 0, so it would easily distort.

I really love the LPL though. You just set your headunit to put out as much voltage as possible through the RCAs... then you can set your amps gains and use the LPL as your volume control. What I do then is actually set my gains higher than they should be -- technically overdriving the amplifier, but then I use the LPL as a remote gain knob instead. By doing this, you can adjust the gain for each song... so if something has a weak bassline, you can make it as loud as a pounding rap song if you want to. This just lets you get the full output of your amplifier on any music you want.

The only concern then is that you have to be very careful not to clip your amplifier. Clipping is bad. My rule of thumb is to turn the LPL up until it stops getting louder, and then turn it back a tiny bit. That way you are still playing within the boundaries of your amplifier's capabilities, instead of distorting and risking blowing your speakers and amplifier by clipping it.

Post by **VW337** » Thu Mar 01, 2007 10:33 am

In simple words the LPL44 is a variable level muting control for your amplifier's gain stage. It provides up to 20db of attenuation to the input section of the amp. If the LPL is set to full output it would be the same as not even being plugged in.

eyesofra · Post by **eyesofra** » Thu Mar 01, 2007 10:58 am

hi stipud,
thanks for your elaborate explanation on these.
Now i can see things a little better on how i should set it up.

Can u pls suggest to me on how i should go bout with my system.

My Nakamichi CD-400 HU has 3 Tone controls :
( as in the manual)

1) Bass @ 100Hz +/- 11db
2) Mid @ 1Khz +/- 11db
3) Treble @ 1KHz +/- 11db

Also it has 3 preouts , for front , rear and subwoofer.
Currently ;

1) " front " line level output feeds directly to a stereo amp powering my front rsd6.5's

2)I've got no rear speakers so the rear line level has no conections to it.

3)The subwoofer line level output feeds directly to my mono amp in trunk to drive a single 12" rsd.

Each of these line level output is adjustable , of course faders for the front and back and a dedicated " Subwoofer Volume Control "

The sub out volume control starts at
" turn off - (-10db)-0db-(+10db) "which means +/-20db of attenuation dedicated for the sub .

Now, this is how everything is hooked up, so how should i go bout it.

I've realised the sub sounds good at 0db in the HU , tight at +1db up to +2db and gets somewhat uncontrolled after that onwards.
Shares the same attributes of the Sony HU you decribed i believe.

Should i just leave this at 0db and just use the LPL44 as the gain control as you suggested ??

One last thing , lets say now i have the amp gain set at halfway,does this mean by plugging in the LPL44 i'll be able to control the gain form " zero to halfway ??

Pls advice and i'm very thankful for all the info so far.

Post by **Bfowler** » Thu Mar 01, 2007 11:03 am

you will want to leave your bass gain at zero.

increase the sub fader slightly higher then you would normally, then use the LPL to attenuate the sub from there

One last thing , lets say now i have the amp gain set at halfwit's this mean by plugging in the LPL44 i'll be able to control the gain form " zero to halfway ??

Exactly correct

eyesofra · Post by **eyesofra** » Thu Mar 01, 2007 11:18 am

will it be better and easier if i were to go without the LPL44 and just use the sub out control from the HU ??

Or is it much better to further tailor the sound with both the sub out and LPL44 ??

Thanks again guys

Post by **Bfowler** » Thu Mar 01, 2007 11:22 am

i personally LOVE the LPL

its much easier to attenuate a little bass knob then to go into the menu's on the deck. i refuse to run a sub without a lpl.

but essentially it is doing the same thing, so its really up to you

eyesofra · Post by **eyesofra** » Thu Mar 01, 2007 11:38 am

thanks man...
ill try out both and c which one makes life simpler...
thanks for all the input guys...
this is certainly one of the best "phorums' i've been so far...

Regards,
Amuthan

Post by **fuzzysnuggleduck** » Thu Mar 01, 2007 12:17 pm

I just got my LPL yesterday and I played with it already a bit but I haven't installed it permanently yet.

Great little knob.

I would say go for it. I *much* prefer having a hardware knob that controls low level output instead of going into menus and such... but because my deck only has one RCA set out (kind of wish I paid the extra $43 to get three RCA outputs) I don't have the option of using subwoofer control on the deck because my front stage is also being fed to my amp over the single RCA "subwoofer" out.