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Old 27th April 2010, 04:50 PM   #21
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Default Very good performance Sakis..the way Rodd Elliot use to say

This should have a good sound too ... by the waveforms ... observing them..seems a promise of good performance ... sometimes good waveforms gives a good indication of sound quality... sometimes, not always.

By your interest in this amplifier, seems this is the case.... once again...a simple amplifier with good looking waveforms... and may sound good, as you are skilled daily listening good brands...so..you know how to compare and has the needed tools and skills.

regards,

Carlos
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Old 28th April 2010, 11:15 PM   #22
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Default Dear Current flow.... i think something was misunderstood about BD139/140

These transistors can face 100 volts from coletor to emitter
These transistors can operate above 100 Megahertz
The gain use to be from 90 to 220

Widely used, since the seventies...hundreds of factories used, now a days some designers still use them.... observe they are survivers, good and reliable within their limits of course.

More modern ones, alike Sakis has told us (BD829/830) can be better in dissipation (metal tab).... also can work in higher frequencies (higher Ft)....but observe have even smaller voltage from colector to emitter...and BD139/140 having a metalic tab alike the new ones have, can also dissipate 2 watts as i use them here..... i have build more than thousand amplifiers using it.... hundreds of brazilian factories still using them...when i was Radio Amateur (from 1970 to 2002) i used them to repair HF transceivers... the transistor worked as output drivers at 30 megahertz beating others transistors dedicated to Radio Frequency (2SC1971)...i have used in FM (98 to 108 Megahertz) transceivers and worked fine with very small losses compared to expensive units costing 12 times more!.

Designers still use them...even now a days.... people that has not prejudice because old (means tested, reliable) accept them because good ones.

I would like, my dear friends, to spend some time observing the datasheet...also observe the modern ones dear Sakis is introducing to us (2002 transistors... already old)...and do that in respect to thousands designers that have used and are still using...this way you gonna notice these designers are not stupid nor menthaly retarded..if they made that choice is because the transistor has good performance, as they have a brain inside the skull alike everyone of us.

regards,

Carlos
Attached Files
File Type: pdf BD140.pdf (195.0 KB, 168 views)
File Type: pdf BD829-839.pdf (64.0 KB, 167 views)
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Last edited by destroyer X; 28th April 2010 at 11:17 PM.
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Old 29th April 2010, 03:34 AM   #23
Bigun is offline Bigun  Canada
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Quote:
Originally Posted by sakis View Post
i wasnt expecting a noticable diference but even though the bias is quiet low since size of the box and heatsink i didnt want to create high temperature inside still it plays by far better than the 139-140 or 15030-31

can anyone explain why ????
can any one double check this and provide an opinion ???

thanks sakis
You have a new baby - this might make all things more wonderful than they were before !

One difference you made was the bias. Before you had 120mA and now you have only 30mA. Perhaps it is now optimally biassed and before it was not. If you reduce bias in the bigger amplifier to the same level do you perceive a difference ?
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Old 29th April 2010, 07:05 AM   #24
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Default An explanation about depends the evaluator's goodwill

If the evaluator like you, then he will think you have "tuned" your amplifier to an optimized setting.... and reduced the power consumption creating a green amplifiers.

If the evaluator does not like you, and want to burn your amplifier image, also your personnal image, then he will say the reduction of bias is dangerous, because will make the ouput transistors work very near the crossover region area, and this may drive them to produce crossover noises while changing state of conduction to non conduction.

So, you see that the same reality can be evaluated, and view, from 2 or more point of views

As i believe in Sakis.... mine evaluation is the first one.... and i will test these transistors he said are excelent.

regards,

Carlos
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Old 29th April 2010, 07:30 AM   #25
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Quote:
Originally Posted by Bigun View Post
You have a new baby - this might make all things more wonderful than they were before !

One difference you made was the bias. Before you had 120mA and now you have only 30mA. Perhaps it is now optimally biassed and before it was not. If you reduce bias in the bigger amplifier to the same level do you perceive a difference ?

thanks for your wishes about our new baby ... but the P3a as was with all the small mods presented in the thread is standing on my bench almost 3 years now .....it is my standard listening system for the times i am in my shop normally from 9.00 till 21.00 and i listen from the same sources all the time and for testing perpus always the same music


now 3 years is a lot of time to listen to this amp also in the past three years i have bulited almost 20 of these amps while trying new pcb versions making other style of cooling but never tested so far with these drivers

in between in these three years i repaired about 250 amplifiers or more so standard procedure is to listen to them compaired to the P3A as is

so belive me i know this amlifier by far very well .....
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Old 29th April 2010, 10:14 AM   #26
tinitus is offline tinitus  Europe
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P3A is specced to use BC546

But BC549/550 are the low noise versions, but also lower voltage

Might be good options for a low voltage version

Any comments to that ?
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Old 29th April 2010, 10:46 AM   #27
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i will take this in mind but add down under that i found dramatic improovement also at any time i used matched pairs
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Old 29th April 2010, 10:47 AM   #28
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Use 2SA970/2SC2240 the are also low noise and the voltage is 120V
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Old 29th April 2010, 10:51 AM   #29
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there is also many others ... but trying various types of ltp will end up in a ghost chase i try to keep the project as close as the original is

some other ltp may better or not
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Old 29th April 2010, 11:43 AM   #30
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Quote:
Originally Posted by destroyer X View Post
These transistors can face 100 volts from coletor to emitter
These transistors can operate above 100 Megahertz
The gain use to be from 90 to 220

Carlos
Hi Carlos,

You're absolutely right for the transition frequency. It appears that the datasheet origin for the BD139 I quoted was unreliable. Many manufacturers don't quote this parameter, with the exception of Philips and Siemens.

I have no doubt that the BD139/140 pair are good performers in audio applications, although you may now be tempted to try the BD829/830 in your DX Blame ES to see if the effect is as marked as Sakis found in his P3A

Regards,
Steve
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