Power amp under development

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#2,481
Re Post #2312 and Post #2313

Samuel,

I noted I could offer some suggestions how to post schematics from your older EWB program running under Windows 98.

Sorry I have been distracted a few times in last weeks and I will have limited time the in the next few weeks due to an injury.

What I like to suggest initially is you install a Postscript printer from your Windows 98 install CD and chose "file" as the default interface, not a LPT or serial device port. Please note that you do not have to have a Postscript printer to install the respective driver. This is implied by the fact "file" can be set as the default interface. My suggestion is to first try an Apple Postscript printer and choose one that is Postscript Level 2. If you do not find a Level 2 Postscript Apple printer then select a HP 4ML Postscript printer. Once the Postscript printer is installed print to the Postscript printer you installed and select print to file if you did not chose file as the default interface during the driver installation. The driver should then open a file selection menu so you can choose the directory and name of the .ps file that will contain the Postscript print file.

If you can try this with your modified quasi NMOS schematic with the VAS bufer and other modifications you have made, then zip the resulting Postscript file hopefully the zip file will be less then the diyAudio 100KB attachment limit. If the zip file is less than 100KB please post it and I will convert it to a PDF document.

Once you have successfully been able to create a Postscript file I will then guide you to the next part that will allow you to create a PDF document. I will also do some more research that may allow you to install a printer driver that will create a PDF document directly using the Windows print function. I know of one such printer driver, but so far is is not clear the driver works in Windows 98.

If you have any questions feel free to as me. I will answer, but it may be a day or two delay depending on medical and other legal related matters to the injury I have to deal with.


Regards,

John L. Males
Willowdale, Ontario
Canada
29 November 2007 06:06
Official Quasi Thread Researcher
 
#2,482
Hi All,

I have some quick questions about the implication of the bias setting.

If one has a 3 output pair device quasi NMOS module and the bias is set to 30ma per device:

1) Does that mean the module output devices operate in Class A for the first 30ma or 90ma with respect to the output?

2) If Vrail is 70 VDC does that mean that the resistive power output into 8 ohms Class A operation is for the first 2.1W or 6.3W before switching to Class B operation of the output stage?

3) If Vrail is 40 VDC does that mean that the resistive power output into 8 ohms Class A operation is for the first 1.2W or 3.6W before switching to Class B operation of the output stage?

If one has a single pair output device module set to 30ma per device:

4) Does that mean the module output device operate in Class A for the first 30ma with respect to the output?

5) If Vrail is 70 VDC (I know this is not likely, but for the sake of example) does that mean that the resistive power output into 8 ohms Class A operation is for the first 2.1W before switching to Class B operation of the output stage?

6) If Vrail is 40 VDC does that mean that the resistive power output into 8 ohms Class A operation is for the first 1.2W before switching to Class B operation of the output stage?


Regards,

John L. Males
Willowdale, Ontario
Canada
29 November 2007 06:26
Official Quasi Thread Researcher
 
#2,483
keypunch said:
Hi All,
I have some quick questions about the implication of the bias setting...
Click to expand...


IF you have 3 pairs set at 30mA per pair, then the total standing current is 90mA and this is what you use to get the class A operation limit, irrespective of rail voltage. Rail voltage would only come into play if it was lower than the voltage required to push the total standing current through your chosen load.
In general, with such calculations you use the standing current as the maximum output current available in class A, but this is not true in most cases. If the output devices were pure converters of input voltage to output current, linearly, you could get up to twice the standing current on the output at the point where one of the devices goes into cut-off and class B begins. In practise, the devices are not linear and there is really no defined cut-off, so if you want a really accurate figure, you would have to measure. Using the standing current is therefore a pessimistic safe bet, but it will give you perhaps unexpectedly low values:

So, for your examples:
With 3 pairs @ 30mA, class A ends at 32.4mW
Single pair @ 30mA, class A ends at 3.6mW.

(P=I*I*R, keep in mind that you need to calculate with RMS values of current, that 90ma standing current is peak current, i.e. 63mA RMS)
 
#2,484
ilimzn,

Thanks so much for simplifying the answer. I am a bit stressed the last few weeks. I had forgotton the simplier reduction of the question as you have so clearly indicated. As always you are clear and concise with your answers and knowledge. Sorry I forgot to state I was referring to P-P and not RMS.

Thanks so much.


Regards,

John L. Males
Willowdale, Ontario
Canada
29 November 2007 07:20
Official Quasi Thread Researcher

P.S. I need some shut eye soon.
 
#2,487
Hi Samuel, john (keypunch)

John if you are trying to print to a pdf file thee is one you can use :

http://pdf995.com/

It installs a printer call PDF995 and you just print whatever you want to it. It will ask you where to save the pdf file and by giving it a folder and file name, you had created yourself a pdf file. Hope that's what I can understand from what you are talking about the postccript printer and all that stuff.
 
#2,491
🙂
 

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#2,492
bigpanda said:
Hi Samuel, john (keypunch)

John if you are trying to print to a pdf file thee is one you can use :

http://pdf995.com/

It installs a printer call PDF995 and you just print whatever you want to it. It will ask you where to save the pdf file and by giving it a folder and file name, you had created yourself a pdf file. Hope that's what I can understand from what you are talking about the postccript printer and all that stuff.
Click to expand...


Hello bigpanda,

Thanks for the link above to PDF995. Perhaps this will be a more complete and simplier solution for Samuel's Windows 98/EWB combination.

With regards to me when I do use a Windows environment at a client I have no problem creating PDFs as I was guiding Samuel. I have been using Linux since 2000, and I have no problem creating PDFs 🙂 There are so many Open Source options and easy ways to create PDFs in a Linux/Unix/BSD environment 🙂)


Regards,

John L. Males
Willowdale, Ontario
Canada
29 November 2007 20:46
Official Quasi Thread Researcher
 
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