I just completed my ESP P101. It sounds great other than a bit of rectifier hum on the left channel which I'll be taking care of this evening (bad routing). The problem I'm having is that even though I've set the bias to Rod's maximum settings, it's still very underpowered. Loaded, I'm still producing 138VDC. I don't think it's a power issue. I've contacted Rod, but I understand he's a busy guy, so here I am.
I've fed it now with the line level output from my CD player (adjustable line level out) and with the line level from my MP3 player. I don't think input voltage is the issue, but I'm rather new at all of this.
I should be producing roughly 180 watts per channel RMS. That would put my output voltage somewhere around 37 Volts on the output right? I'm seeing peak values of only 9-10 V!
Something is wonky here.
I've fed it now with the line level output from my CD player (adjustable line level out) and with the line level from my MP3 player. I don't think input voltage is the issue, but I'm rather new at all of this.
I should be producing roughly 180 watts per channel RMS. That would put my output voltage somewhere around 37 Volts on the output right? I'm seeing peak values of only 9-10 V!
Something is wonky here.
Hi,
your gain has little to do with your output power nor with your supply rail voltages.
Since you mentioned 37V I assume you have quoted 180W into 4r.
Measuring peaks of 9V to 10V, again I am jumping to the assumption you have measured rms on a DMM, rather than actual peaks from an oscilloscope, indicates you are driving your amplifier hard.
Music signals usually have a true peak voltage about 10db to 20db above the average music level.
If you are measuring rms peaks then you have probably added about 6db to your average.
10V is only 11.5db below maximum power. adding that 6db guess indicates your average level is only 17.5db below maximum.
With the power you have available and the sensitivity of your speakers you have little margin to increase the SPL much higher. If you do, you are moving into the realms of PA and disco that often overdrive their amps to try and produce excessive SPL at the expense of terrible distortion.
Now back to your gain problem. It has much to do with the input signal voltage and the amplifier gain.
Can you identify the gain setting resistors in the ESP amp and confirm their values?
Please also confirm the average voltage level coming from your source. Not the maximum level. eg CD has a maximum level of about 2Vac to 2.2Vac, but average level will be between 200mV and 600mV.
We can then advise.
your gain has little to do with your output power nor with your supply rail voltages.
Since you mentioned 37V I assume you have quoted 180W into 4r.
Measuring peaks of 9V to 10V, again I am jumping to the assumption you have measured rms on a DMM, rather than actual peaks from an oscilloscope, indicates you are driving your amplifier hard.
Music signals usually have a true peak voltage about 10db to 20db above the average music level.
If you are measuring rms peaks then you have probably added about 6db to your average.
10V is only 11.5db below maximum power. adding that 6db guess indicates your average level is only 17.5db below maximum.
With the power you have available and the sensitivity of your speakers you have little margin to increase the SPL much higher. If you do, you are moving into the realms of PA and disco that often overdrive their amps to try and produce excessive SPL at the expense of terrible distortion.
Now back to your gain problem. It has much to do with the input signal voltage and the amplifier gain.
Can you identify the gain setting resistors in the ESP amp and confirm their values?
Please also confirm the average voltage level coming from your source. Not the maximum level. eg CD has a maximum level of about 2Vac to 2.2Vac, but average level will be between 200mV and 600mV.
We can then advise.
I should have 37V into 8r. At least that's what I'm thinking when I do the math. I don't have immediate access to a scope and yes those were true RMS measurements on an Extech DMM.
Here is the schematic on Rod's site. Since it's on the regular site and not on the secure site, I hope he doesn't mind.
I'm not sure which are the gain resistors, but gain is set with VR1, so I'm assuming R7 and R8
Here is the schematic on Rod's site. Since it's on the regular site and not on the secure site, I hope he doesn't mind.
I'm not sure which are the gain resistors, but gain is set with VR1, so I'm assuming R7 and R8
An externally hosted image should be here but it was not working when we last tested it.
Tim__x said:
jaycee said:
I guess I was wrong about the nomenclature. Which is why I put the schematic up. The amps are both adjusted correctly according to Rod's specs (bias). Again, this is all very new to me and this is my first project. All the part values are correct. I've taken it apart to verify that and I also did so when the boards were complete.
Oh and R4 is 1k and R9 is 22k.
Hi,
the ESP gain is = 22k / 1k +1 = 23times. = +27.2db.
What is your speaker sensitivity?
Let's do an example to show where I am going.
Assume you have 87db speakers.
Add 87 + 27.2 = 114.2db.
Input 100mVac into your amplifier. Out comes 88.2db SPL.
But where is the correlation between 88.2db and 114.2db?
Let's do another calculation.
To produce 1W into 4ohm speakers you need 2Vac from the amplifier.
100mVac divided by 2.00Vac, 0.1 /2 = 0.05 = -26db
Now we have some numbers to work with.
Input a 100mVac (-26db relative to 1W into 4ohm) into amplifier with 27.2db gain then into 87db speakers gives an output of (-26+27.2+87)= 88.2db SPL.
For each doubling of input voltage you will gain 6db until you overload either the speakers or the amplfier.
So using our 114.2 db SPL per equivalent watt input
200mV is -20db >= 94.2db
400mV>=100.2db
800mV>=106.2db
1600mV>=112.2db, we are now close to overloading the amp. and the speakers are probably producing gross distortion.
Give us a bit more info:- source output voltage and speaker sensitivity and we can advise.
Maybe you can follow my explanation and try the numbers for yourself.
the ESP gain is = 22k / 1k +1 = 23times. = +27.2db.
What is your speaker sensitivity?
Let's do an example to show where I am going.
Assume you have 87db speakers.
Add 87 + 27.2 = 114.2db.
Input 100mVac into your amplifier. Out comes 88.2db SPL.
But where is the correlation between 88.2db and 114.2db?
Let's do another calculation.
To produce 1W into 4ohm speakers you need 2Vac from the amplifier.
100mVac divided by 2.00Vac, 0.1 /2 = 0.05 = -26db
Now we have some numbers to work with.
Input a 100mVac (-26db relative to 1W into 4ohm) into amplifier with 27.2db gain then into 87db speakers gives an output of (-26+27.2+87)= 88.2db SPL.
For each doubling of input voltage you will gain 6db until you overload either the speakers or the amplfier.
So using our 114.2 db SPL per equivalent watt input
200mV is -20db >= 94.2db
400mV>=100.2db
800mV>=106.2db
1600mV>=112.2db, we are now close to overloading the amp. and the speakers are probably producing gross distortion.
Give us a bit more info:- source output voltage and speaker sensitivity and we can advise.
Maybe you can follow my explanation and try the numbers for yourself.
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.
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.
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.
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.
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?
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?
bushroot said:
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.
bushroot said:
richie00boy said:
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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