Lab Gruppen FP14000 clone amplifiers - Page 168 - AVS | Home Theater Discussions And Reviews
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post #5011 of 5021 Old 04-06-2015, 11:45 PM
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Quote:
Originally Posted by GizzeGutten View Post
Been talking with Mr Johnson and he says they've been working on their own version of FP20000Q for a long time. They want to launch it in October. He also says they will employ a simple integrated DSP which is great news.

I remember chatting with him about the Fp20K 3 years ago. Hopefully he is successful and it becomes a great piece like the Fp14k has been for most.

I dont know why anyone would want a Fp14 for their mains as someone stated earlier. I am really liking the DCM specs and videos from QSC for mains. They have a lower RMS but are able to peak very high. For me the go to will be a pair of 4 channel 4.2's. 4.3's would work also if I had more money but not needed for my speakers. And the 4.5 provides more constant RMS power which is intended for subs. The 4.3 and 4.5 peak the same amount of power. BUT this is just my 2 cents.

There are many other options out there that may be cheaper or more expensive. These are just what options I will be using. Sorry for the derail Not.
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post #5012 of 5021 Old 04-07-2015, 09:35 AM
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The potentiometers on the front of FP14k and many other PA-amplifiers, how exactly do they work?

Does it attenuate the input signal so that if you have an amplifier that has an input sensitivity of 1vrms and you give it 1vrms but lower the attenuator by 50 % then it will only give out 50 % of the power capacity when seeing 1vrms at the input?

Asking because I've seen people say that even if you turn those down the full amplifier output is available. Is that because if you set it to 50 %, then it will still output 100 % of it's capacity when seeing 2vrms at the input? (again, when the input sensitivity is 1vrms)

When should and shouldn't you use those attenuators?

Just want to make sure I understand this. I've been using those attenuators to level the gain between different components.

Quote:
Originally Posted by chrapladm View Post
I remember chatting with him about the Fp20K 3 years ago. Hopefully he is successful and it becomes a great piece like the Fp14k has been for most.
Yeah, Johnson said they had been working at it for years but had trouble reverse engineering the Lake DSP. I'm not sure what I'd do personally though. 2xFP14k are just a little more pricey compared to the current FP20kQ offerings, it gives you some redundancy and you can run separate lines with individual breakers for each so in a home environment I think I'd rather pick a pair of those.

DAC/Preamp: miniDSP 4x10 HD
Speakers: JBL 4343B, JBL 4430 and JBL 120Ti
Amplifiers: Emotiva XPR-1, Denon POA 1500, QSC GX5 and Sanway's LabGruppen FP14000 clone
Midbass modules: 4x DIY JBL 2226
Sub: 4x DIY LMS Ultra 5400
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post #5013 of 5021 Old 04-15-2015, 05:30 AM
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Question

I need someone to PLEASE tell/explain to me where I am going wrong.
I have been looking at trying to calculate the correct gain structure to use with my FP10kQ.
I remember reading somewhere that we needed to account for -6db attenuation but no sure where to build that into the equation.

This is what I came up with so far.

Power = Voltage^2/Load Resistance
Eg
2000 watts = Voltage^2/4ohms
(2000x4) = Voltage^2
8000 = 89 volts

Voltage Gain = 20 * log (Voltage Out / Voltage in)
Eg
10^(Vgain/20) = Vout/Vin
10^(44/20) = 158.5
89/158.5 = 0.56 VRMS required
@44db gain the FP10kQ needs 0.56 vrms in to order to provide 2000w into 4ohms.

10^(VG/20) = Vout/Vin
10^(35/20) = 56
89/56 = 1.59 VRMS required
@35db gain the FP10kQ needs 1.59 vrms in to order to provide 2000w into 4ohms.

10^(VG/20) = Vout/Vin
10^(32/20) = 39.8
89/39.8 = 2.24 VRMS required
@32db gain the FP10kQ needs 2.24 vrms in to order to provide 2000w into 4ohms.

I have a 2x4 Balanced minidsp feeding my FP10k.

Taking into account the following factors:
> 2vrms output of the 2x4
> -6 attentuation I need to account for somewhere
> Significant EQ on the minidsp
> Headroom?

What is the suggested gain setting I should use?

Not very smart so please dumb it down for me. Thanks.

Last edited by Nuno C; 04-15-2015 at 06:35 AM.
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post #5014 of 5021 Old 04-15-2015, 07:27 PM
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Don't understand where you get -6dB from?

If you boost 6dB you need to subtract 6dB from the overall signal to leave yourself with headroom in the digital domain for your boost filter.

If you EQ with miniDSP its max output will still be 2Vrms when the EQ'ed digital signal is 0dBFS.

Optimally 2Vrms in will yield 2kW out.

If you have your gain too high you will clip the amp (if you've set the VPL) or output a ton of power unintentionally sending a high signal to the amp.

If you have too low gain you will not be able to drive the amp into 2kW @ 4 ohms.

This chart is from the original FP10000Q.



Seems like you should set the VPL at 89*sqrt(2) = 125.87V which we see doesn't exist, so you're left to limit it above or below.

Then calculate gain based on 2Vrms input from miniDSP to amp.

Voltage gain = 20 * log (Vout/Vin)
=> 20 * log (89/2) = 32.97 dB gain

to get 2kW out into 4 Ohms.

PS: This assumes you have not bridged the amp!

DAC/Preamp: miniDSP 4x10 HD
Speakers: JBL 4343B, JBL 4430 and JBL 120Ti
Amplifiers: Emotiva XPR-1, Denon POA 1500, QSC GX5 and Sanway's LabGruppen FP14000 clone
Midbass modules: 4x DIY JBL 2226
Sub: 4x DIY LMS Ultra 5400

Last edited by GizzeGutten; 04-15-2015 at 07:31 PM.
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post #5015 of 5021 Old 04-15-2015, 07:34 PM
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The miniDSP balanced 2x4 can output more than 2Vrms. When I tested mine it maxed out at 4.7Vrms when it started clipping.
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post #5016 of 5021 Old 04-15-2015, 07:43 PM
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Maybe that's where he gets the -6dB from then?

In that case I'd start with VPL below the power limit of 2kW and see where a gain of about 20 * log (89/4.7) = 25.6 dB would put me by measuring the output voltage from the amp.

DAC/Preamp: miniDSP 4x10 HD
Speakers: JBL 4343B, JBL 4430 and JBL 120Ti
Amplifiers: Emotiva XPR-1, Denon POA 1500, QSC GX5 and Sanway's LabGruppen FP14000 clone
Midbass modules: 4x DIY JBL 2226
Sub: 4x DIY LMS Ultra 5400
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post #5017 of 5021 Old Yesterday, 07:28 AM
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I have finally decided on my stereo setup, and its all on order now. Just need to decide on what Sanway clone to get. 10k or 14k. The pair of elements the amp needs to run have 1700w rms each 8ohm and roughly twice expected peak (they say 6800w peak but that's one tiny burst). So the question is, 10k or 14k? The 10k in bridged mode I think would be better than a single 14k, but how does the bridging work on the 10k? Can't find clear pictures of the rear where there's somewhat of a guide written beneath the output channels.
EDIT: Found a picture, but can't say I understand it. http://i00.i.aliimg.com/img/pb/273/2...244273_388.jpg
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post #5018 of 5021 Old Today, 03:27 AM
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I am thinking I will move this discussion to the minidsp thread going forward.

So I went and did some digging and found these threads regarding the dB loss with minidsp 2x4.

-7db loss between input and output
http://www.minidsp.com/forum/hardwar...of-minidsp-2x4

-7.5db loss
http://www.minidsp.com/forum/hardwar...volume-voltage

-8db loss
http://www.hometheatershack.com/foru...er-output.html

Reading this again (properly) I see where I made a mistake. I am not bridging my FP10kQ. Appears there is -6db loss in the amp if you bridge.
Lab Gruppen FP14000 clone amplifiers

Regarding EQ this thread seems to indicate it has no effect on the voltage.That is good news.
MiniDSP

Even old hands that really know their stuff have different views.
Popalock says yes
Lab Gruppen FP14000 clone amplifiers

Not says not for me.
Lab Gruppen FP14000 clone amplifiers

Busy reading the minidsp thread at the moment as well and good discussion around clipping and voltage currently ongoing. Time for me to bust out the voltmeter this weekend.

This quote from Stereodude has me believe it is indeed possible to clip the minidsp especially with 7.1. Given sine wave vs real world material is vastly different.
Quote:
So, if you have up to 1.2Vrms (sine wave non-clipping) from the LFE output when listening to 2 channel stereo, you should have up to 1.956Vrms (sine wave non-clipping) from the LFE output when listening to 5.0 content, and up to 4.908Vrms (sine wave non-clipping) from the LFE output when listening to 5.1 content. You don't adjust for the different voltages. They reflect the difference in possible volume output for each different scenario
So as always it is not a clear cut answer. The minidsp 2x4 balanced is probably okay for most scenarios unless you are starting off with a pretty high voltage.
Reading online one guy tested clipping at around 2.2vrms. Stereodude has tested to 4.7vrms before clipping. Hoping the later is closer to norm for most units.
My concern has now changed to input voltage as output voltage is sufficient to drive a FP10kQ to max.

I have been running my 2x4 balanced into a FP10kQ and it has performed well. I have not heard any distress or weird noises coming from the subs and although
the lights on the clone light up I just barely touch the red in 'demo mode'. Will run some tests this weekend and see if I am just over complicating things for myself.

Last edited by Nuno C; Today at 03:32 AM. Reason: Add a link
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post #5019 of 5021 Old Today, 05:11 AM
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Quote:
Originally Posted by Nuno C View Post
I am thinking I will move this discussion to the minidsp thread going forward.

So I went and did some digging and found these threads regarding the dB loss with minidsp 2x4.

-7db loss between input and output
http://www.minidsp.com/forum/hardwar...of-minidsp-2x4

-7.5db loss
http://www.minidsp.com/forum/hardwar...volume-voltage

-8db loss
http://www.hometheatershack.com/foru...er-output.html
The balanced unit has a 6dB loss across it if you don't use the balanced output. I don't know for sure about the unbalanced model. I don't have one and haven't had the occasion to measure one. My guess is you get a loss if the jumper for the input side is set to 2Vrms (because the output is 0.9Vrms). If you configure the input for 0.9Vrms there shouldn't be a loss, but you're bound to easily clip the input.

Quote:
This quote from Stereodude has me believe it is indeed possible to clip the minidsp especially with 7.1. Given sine wave vs real world material is vastly different.
So as always it is not a clear cut answer. The minidsp 2x4 balanced is probably okay for most scenarios unless you are starting off with a pretty high voltage.
Reading online one guy tested clipping at around 2.2vrms. Stereodude has tested to 4.7vrms before clipping. Hoping the later is closer to norm for most units.
I think I read the posts from the guy who clipped at 2.2Vrms (with sine waves). I'm not sure if he had a balanced or unbalanced unit. My guess is the latter. I tested a balanced 2x4. UPS is supposed to deliver my oscilloscope today so I will update my 2nd miniDSP to the latest software / firmware and measure how the levels in the miniDSP GUI match up with the input voltages and if they levels are now peak (since they supposedly fixed that).
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Lab Gruppen Fp 14000 , Sanway Fp 10000q
Gear in this thread - 10000q by PriceGrabber.com

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