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Old 30th July 2006, 12:47 PM   #11
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Join Date: Oct 2004
Location: The high-five state
Tweeter: Vifa D27TG-35-06
Sensitivity 90dB (1W, 1m)

Midrange: Vifa PL14WJ-09-08
Sensitivity 86dB (1W, 1m)

Woofer: Orion XTR 8d
Sensitivity 95dB (1W, 1m)

The crossovers were built by a local shop called Meniscus Audio. http://www.meniscusaudio.com/
They are a LEAP design and custom built for my setup.

As far as what I'm seeing for line level voltage, my CD player is producing ~450mV and my MP3 player ~500mV.

Thanks for all the help so far.
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Old 30th July 2006, 03:44 PM   #12
Did it Himself
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I'm not sure why speaker sensitivity is being brought into this. Don't confuse the guy

All you need to do is get a 1kHz sinewave output from whatever source you want. Then hook it up to the amp. Measure the input voltage on your meter. Then measure the output voltage on the amp. There is no need to have a load on the amp for this test.

Then the gain is simply output / input and should be approx 23 times.

I'd be willing to bet money you are simply using the wrong input stimulus to measure with, and your source is too weak.
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Old 30th July 2006, 05:03 PM   #13
AndrewT is online now AndrewT  Scotland
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Hi Richie,
I don't want to confuse anyone, certainly not deliberately.
But our Thread starter is complaining of lack of volume.
This is more likely to be down to inappropriate combinations of equipment rather than faulty equipment.

Bushroot,
I see you are using a range of drivers, the lowest sensitivity of which is 86db. If these are fed from a passive crossover it is likely the overall speaker sensitivity will be in the range 84db to 86db

Now, add the 27.2db of the amp and the SPL comes out at 111db to 113db for each 2V of input.

With only 450mV of input from a CD player the resultant maximum SPL will be about 94db to 96db.
An average signal from compressed CD with a level about -10db below max gives an output from your system of only 85db and that is with the volume turned full up. If you prefer CDs with an average level about 20db below maximum then you have an even lower level of just 75db. A conversation is about as loud as this.
No wonder you are querying max volume.

The solution seems to be a pre-amp with gain. Maybe 6db minimum gain but possibly as much as 20db of gain.

or

speakers with a higher sensitivity, say 90db or Tannoy's Dual concentrics of 94db.

Richie,
sensitivity does enter into a sensible discussion on output SPLs.

Any other suggestions?
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Old 30th July 2006, 05:16 PM   #14
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So, I do need a preamplifier. I was under the impression that I would not. I'll give that a try.
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Old 30th July 2006, 05:41 PM   #15
AndrewT is online now AndrewT  Scotland
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Hi Bushroot,
Just a simple bit of feedback.
Was that too complicated or did you follow the long discussion?
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Old 30th July 2006, 05:43 PM   #16
Did it Himself
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Why not simply measure what kind of voltage out you get from your CD player like I said first before building anything new. Just as a check.
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Old 30th July 2006, 05:55 PM   #17
Geoff is offline Geoff  United Kingdom
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Quote:
Originally posted by bushroot
So, I do need a preamplifier. I was under the impression that I would not.
You definitely need some preamplification, no matter what the sensitivity of your speakers, if you wish to get maximum output from your P101.

You have apparantly built the higher power version and you have indicated that the rail voltage, under load, is +/- 69V. This means a peak output voltage capability in the order of 60V, which equates to 42Vrms.

The gain of the P101 is 22 (not 23 as previously stated, the potential divider formed by R1 & R2 has been overlooked) and so an input voltage of just under 2Vrms is required if the maximum output voltage capability is to be achieved.

Most CD players have a maximum output voltage of around 2Vrms and so a pre-amp would not be required, but if your CD player outputs a little under 0.5Vrms, as you have indicated, then you will need a preamp with a voltage gain of 4 (12dB) if you wish to utilise the full output voltage capability of the P101.
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Old 30th July 2006, 08:18 PM   #18
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Join Date: Oct 2004
Location: The high-five state
Quote:
Originally posted by bushroot
Tweeter: Vifa D27TG-35-06
Sensitivity 90dB (1W, 1m)

Midrange: Vifa PL14WJ-09-08
Sensitivity 86dB (1W, 1m)

Woofer: Orion XTR 8d
Sensitivity 95dB (1W, 1m)

The crossovers were built by a local shop called Meniscus Audio. http://www.meniscusaudio.com/
They are a LEAP design and custom built for my setup.

As far as what I'm seeing for line level voltage, my CD player is producing ~450mV and my MP3 player ~500mV.

Thanks for all the help so far.

Quote:
Originally posted by richie00boy
Why not simply measure what kind of voltage out you get from your CD player like I said first before building anything new. Just as a check.

Thank you Andrew. I did follow. I am actually an electrical engineer by education, although it's been a few years since I've used much of it. I work as a controls engineer. The extent of use of formulas is the occasional use of Ohm's and Watt's laws and possibly calculating voltage drops over long runs of wire. Other than that, I mostly do PLC programming and electrical drawings on CAD.

I should take some pictures of the power supply section of this amplifier. You could arc weld with it if you wanted to. Everything is made of Aluminum and the amplifier still weighs just over 40lbs. I spent a year putting everything together and it bothered me that I didn't have enough output to dislodge the cones from my speakers.

I appreciate everyone's input on this. I was simply unaware of the level of input signal that was required. This was a consideration I had discussed with my friend Steve (he brought over some home brew and helped me set bias and test the amp). Unfortunately, my old Mitsubishi gear doesn't have an output after the preamp. What a terrible thing to have to build another project!...lol

I had been accumulating parts to build a gainclone for my PC. I guess I'll put that on hold and order a preamp board and possibly an EQ from Rod.

Thanks for all the support,
Christopher
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Old 30th July 2006, 10:19 PM   #19
AndrewT is online now AndrewT  Scotland
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Hi,
up the gain of the ESP to +35db.

Then decide if you want to build/buy another project.
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Old 31st July 2006, 01:15 AM   #20
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I was talking about putting the gainclone on hold and building a preamp, but I see where you're going with that statement.
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