DIY Audio Projects Forum

Elliot Sound Products - P3A 100W Amplifier
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Author:  Suncalc [ 03 Jun 2014, 23:41 ]
Post subject:  Re: Elliot Sound Products - P3A 100W Amplifier

skittle wrote:
Is this operating temperature too high or is this in th normal range.
The real question is, what is the device temperature? Measure the actual temperature of the device or the heat sink DIRECTLY under the device. Then tell us EXACTLY in what package the power devices are housed. Then we can determine the actual junction temperature and we'll see how much headroom you have.

Author:  skittle [ 04 Jun 2014, 05:53 ]
Post subject:  Re: Elliot Sound Products - P3A 100W Amplifier

From the tech data sheet the package is stated as TO-3BPL (TO264) Case 340G-02. Will try and get temperature at device when I get it back together and running again. Trying to fit it to a cabinet and need to rearrange a few connections etc. Should be back up and running in a couple of days.

What sort of maximum temperature would you want at the temperature would you want?

Author:  Ahorn [ 16 Jun 2014, 12:09 ]
Post subject:  Re: Elliot Sound Products - P3A 100W Amplifier

Thank you so much for these very useful explanations and pictures of the P03A. Kind regards Marc

Author:  costi_n [ 23 Feb 2015, 16:34 ]
Post subject:  Re: Elliot Sound Products - P3A 100W Amplifier

Due to very good reviews of Elliot P3A amplifier, I want to experiment a SMD version of this little piece of art. The only problem is a SMD replacement for BD139 / BD140.
I found a DPAK case transistor MJD44H11G / MJD45H11G ... 4H11-D.PDF

I'm not shure if are suitable for this application and if heat dissipation will be a problem for these devices. Any advice will be helpful.
For the power devices I want to use MAG6333 / MAG9413. They are new, fast, powerful and not too expensive

Kind regards

Author:  Rutherberg [ 08 Jul 2015, 16:48 ]
Post subject:  Re: Elliot Sound Products - P3A 100W Amplifier

Hi dtsup1,

Thanks for this awesome review of the amp, you made me ordering the PCBs :-P
I have few questions about this project, some points are differents than on Elliott's project page and I would like to know why.

First of all, PSU : why do you use two rectifier bridges and thus two PSU rails for each side of the amp ? One rail isn't enough ? According to Elliott, one PSU rail can be used for a pair of amps.
Furthermore, the filtering. Way more than announced (4x 22000µF instead of "max" 15000µF total recommended). I know, the more the better, but is it worth it ?

Next question is about preamplification. I plan to use CD player and auxiliary sources like iPod, iPhone, Sonos connect, etc...
Does this amplifier needs a preamplifier in those cases ? If not, can I use a simple 100k stereo pot at the input of the amp for volume control ?
Does the preamplifier have another role than (sometimes) coloring the sound and, you know, preamplifying weak audio signal ?

Please be kind if some questions sounds silly, it is my first SS hifi project !

Thanks in advance,


Author:  ILoveHiFi [ 23 Feb 2017, 17:32 ]
Post subject:  Re: Elliot Sound Products - P3A 100W Amplifier

I went through the first 5 pages of this thread and haven't heard any one talking about fixing the speaker DC voltage to zero volts.

You should achive this by precisly matching your diffrential inputs. ... ching.html I suggest using this method to match your transitors, I had also used this method for mosfets too and it was extremly accurate.

Also to fine tune the voltage to 0mV consider adding a few ohms to the emiter of the diffrential input. No transitors are perfect and you'll always need to do adjustments to set it perfect.
Adding a potential meter 100 or 200 ohms and putting a 50 to 22 ohms in parallel with the pot will allow you to do some fine adjustments.
This may or may not work, its just a guess. I take no repnsiblity if you blow your amp.
This method should work for amps which take both inputs of the diffrential output, but P3A one only takes one output of the diffrential input.

From my exprience speaker dc voltage effects sound quality, amps with large dc voltage have unbalanced power transitor bias.

Author:  Pedja_bg [ 12 May 2017, 13:06 ]
Post subject:  Re: Elliot Sound Products - P3A 100W Amplifier

DC on output in my case is 4 and 10 mv. This is not a issue. Rod says that should be lower then 100mv. With unmached pair I get 16 and 20 mv... Also, input transistors needs to be tighten together, and also led diode and transistor next to it needs to be as close as possible. Do not mount driver transistors and bias sens transistor on same heatsink as output devices. Driver and bias transisstors need to be on moderate heatsink together.

Author:  Shawnstium [ 07 Mar 2019, 10:05 ]
Post subject:  Re: Elliot Sound Products - P3A 100W Amplifier

Which transistors need to be matched? I am guessing Q1 matched to Q2 and Q7 matched to Q8. Are there any others that need to be matched and how closely should they match?

Author:  ILoveHiFi [ 09 Mar 2019, 16:58 ]
Post subject:  Re: Elliot Sound Products - P3A 100W Amplifier

The best way is to change r6 560ohms to a adjustivple pot to adjust dc voltage.
By replacing with multi turn 1k pot in parallel with 1k8 you get about 560ohms.
Second choice is by replacing with 2k pot in prallel with 820ohms to get about 560ohms.

The only transitors that needs to be matched are q1 and q2 match to them self.

Multi turn must be used otherwise single turn normally has poor reliablity and some non sealed exposed to dust will cause plorbems such as pops over time.
single turn also not fine enough adjustment so hard to adjust dc to 0.

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