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Old 27th April 2007, 07:18 AM   #1031
Nordic is offline Nordic  South Africa
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I bought my first bag of spade connectors for the DX....Think I'm set for a long time now... 100 spades

And it is called vertical PCB to spade or spade to pcb connectors, i.e. they point up...

I.f you have $20 to $30 you can go out and buy almost all the components for the electronic side of things...
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Old 27th April 2007, 08:09 AM   #1032
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Default Uops....it seems your informed voltage is AC

This way you will have something alike 45 plus 45 volts....hehe..even loosing some volts because of the load, your transistors will hold a lot of energy...you will submit, expose, your transistors to a lot of "stress"....they may result burned.

Forget to use 4 ohms of 6 ohms speakers..for sure you will have smoke.

Using 8 ohms, normal music levels will not be a problem...but if you install a guitar, a sinthetizer or a continuous test signal...hehe..this way will see smoke too.

Use 2.5 amperes in series with your outputs, fast blow fuses, and pray that your supply may help you loosing a lot of volts during dinamic operation.....because if the opposite happens, a huge supply, able to keep the voltage without too much losses...than...boooom!

Your Dx amplifier will not be guaranteed using those output transistors...unless you use those two pairs in parallel to one channel only...using emitter resistances to each one of those output transistors...0.22 ohms will be good enougth.

70 watts over 8 ohms and 140 watts over 4 ohms during the peaks...with the supply condensers charged.... musical introductions of small moments without sound and than a "fortíssimo"...hehe...will kill your transistors if you use a single pair.

Those transistors are not a good idea.... better to find others.

regards,

Carlos
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Power supply; ripple, filter, noise, stability and the use of capacitance multiplier... Portuguese and English; https://www.youtube.com/watch?v=sSm0ku1eIgg
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Old 27th April 2007, 08:47 AM   #1033
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Default My dear friend Phong Vu Tuang disappeared..he dissipated alike smoke

I could not read him once more.... i have found him posting in Symassym, that other model with bigger supply voltage.

The last news he told me was that a Dx amplifier was playing loud into a Restaurant or something alike.

The informs i have, if not wrong, was that the supply was 55 plus 55 volts.... also he informed that had burned transistors with the Dx schematic, well..he burned transistor with his supply schematic.

With this voltage, will be easy to produce 250 watts RMS over 4 ohms...and something alike the half of it when using 8 ohms.

And this is undistorted sound!

Now try to imagine the real conditions, of a restaurant, when the environment is noisy..volume up the limit to distribute sound to the entire room...if people is dancing...well, things goes harder and harder, as they will absorb sound and will block sound alike a wall.

Speakers, even beeing specified as 8 ohms, they are not really that impedance in entire bandwidth..some of them have valleys of impedance, and 3 ohms is not impossible....this may result in more than 300 watts of power.

Under 8 ohms, dissipation will be something near 200 watts....and under 4 ohms will reach 400 watts.

If Phong used a single pair into the output..for sure the amplifier is now a days burned..and this may explain why he disappeared...not to bring bad news....and not to feel ashamed too.

This happens, as people force amplifiers above the limits.

"Dx amplifier is huge and reliable..but cannot hold those excesses"

regards,

Carlos
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Old 27th April 2007, 10:11 AM   #1034
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Not got time to read the whole thread. Can somebody just explain why there is ELINK points -- surely you want decouple those caps all the time? Also how is the zobel grounded?
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Old 27th April 2007, 10:36 AM   #1035
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Default There are discussions about were to ground the Zobel, some people

prefer the transformer center tape ground, others prefer the lifted ground.

To avoid to discuss those things, as this is more a matter of preference than a matter of sonics (tested), we include this Ze points...so you can run your ground wire the way you want.

Doctor Graham Maynard, if i am not wrong, prefer star ground points and zobel connected into the lifted earth point.

So, dear Ritchie...do what you prefer, or what you think that will be better.

regards,

Carlos
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Old 27th April 2007, 10:42 AM   #1036
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Default BillH, i was thinking on you, and i remember that you will have reduced sensitivity

into the input..this is great to avoid overdrive the amplifier...will be another helping hand to you....i mean, the maximum standard pre amplifier output will not be able to drive the power amplifier into it's maximum power...and this maximum power is something you will need to avoid.

The increase of supply voltage compared to original will make the amplifier less sensitive.

The solution to increase the sensitivity to standard value is to decrease R10 value to 1K8 or even 1K5..... better not to have standard sensitivity with those transistors you shown us.

So, keep the R10 as 2K2 as standard.... will be more safe.

But i think your output transistors may short...this way, do not forget the output fuse to avoid to have burned speakers too.

Better to find stronger output transistors....80W is not enougth..better if you find 160 watts and up.... but, beeing your supply voltage bigger...good idea to you is to use Sankens (one of the strongest workhorses, an enormous beast, a strongly powerfull transistor for audio..a powerfull heavy duty "panzer" devices")

2SC2922 and its complementary is one of those "hard to kill" units....the image is showing you one of the possible complementary to this NPN above...my personal dream is to obtain more units alike this one.

regards,

Carlos
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Old 27th April 2007, 11:03 AM   #1037
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Default Take a good look at those wonderfull devices.

Compared with 2SC5200 they are more huge, and seems that can reproduce a sligthly higher level of trebles without distortions.

You know...that realistic sonics of a bell...that brigth you may perceive if your amplifier was able to reproduce some harmonics...and metals...in special bells, are rich of harmonics.

But take a look at the size of this working animal...observe the metalic back size...this enormous area will transfer heat in the order of 200 watts very easy...depending how the die is fixed internally to this back metal plate.

It was sanded, waterproof Norton sandpapper, grain 500, to obtain a very flat surface to transfer heat to the heatsink...those ones are not always flat enougth.

Sand them over a glass..because it is flat enougth...install sandpapper with some watter and distribute power using three fingers....do circle movements without strength...more patience than strengh.

And be happy...those transistors are very special.... in my point of view...weathy, rich people, are the ones have those ones.

Enormous, green envy i have related Jacco Vermeullen...he has many of those folks....my God!

To the "fake hunters" i have to say that my transistors were obtained inside a dismounted Pionner power amplifier...i am sure nobody touched this amplifier but the factory..screws made that noise that ensure us that they were fixed using electrical screwdrivers....any signs that someone could ever open it...so...as Pionner do not use fake units...mine units may not be fake too.....well..if fake they had worked with more than 30 amperes and i have surpassed the maximum voltage and maximum dissipation many times...as i use those ones to my amplifiers testings.

regards,

Carlos
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Old 27th April 2007, 11:06 AM   #1038
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Default Re: There are discussions about were to ground the Zobel, some people

Quote:
Originally posted by destroyer X
prefer the transformer center tape ground, others prefer the lifted ground.

To avoid to discuss those things, as this is more a matter of preference than a matter of sonics (tested), we include this Ze points...so you can run your ground wire the way you want.

Doctor Graham Maynard, if i am not wrong, prefer star ground points and zobel connected into the lifted earth point.

So, dear Ritchie...do what you prefer, or what you think that will be better.

regards,

Carlos
I see, so that is for the zobel. But what about the ELINK points?

Technically a star ground is better and each dirty part should have it's own path back to the star. However, I have not had a problem with sharing all grounds on a PCB. Maybe because I keep PSU wires short and thickd and keep to main star grounds for each amps, it is OK.
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Old 27th April 2007, 11:08 AM   #1039
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Quote:
Originally posted by richie00boy
Not got time to read the whole thread. Can somebody just explain why there is ELINK points -- surely you want decouple those caps all the time? Also how is the zobel grounded?
Hi richie00boy,

Thanks for your interest.

Earlier on in the post, there were discussions on proper grounding methods. We've all read Douglas Self's 8 casuses of distortion in amplifier and know incorrect grounding in one of the causes. I made the PCB so you could separate the signal ground from the power ground by cutting one trace at the bottom centre of the PCB and then run two wires back to the star earth. I then added the ELINKs to allow you to run separate earth wires back from each filter cap. It might make a difference (or not).

As Carlos explained, the Zobel earth can be run to where you like. I didn't want a Zobel on the PCB at all, but most people like it there. There were conflicting opinions of were the zobel earth should go and because it was a late addition we came up with this flexible solution.

regards
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Old 27th April 2007, 11:14 AM   #1040
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Default Dear Greg said...i agree..and my signature is under everything my partner Greg says.

Thank you dear Greg.

It is good to have you around.

I do also think that zobel could be splitted..one for speaker terminals (more logical place) and other to the amplifier, to help to drain EMF and also to "suck" oscilations to ground, as fast as it try to start, the zobel "eat" that fluctuations of voltages (AC) or DC unstabilities.

There are never ending discussions.

Yes for zobel
No for zobel
Install it into speaker terminal
Install it into your amplifier board
Split it into two halves.

Also ground we have different ideas...and Dx amplifier, the happy amplifier, will make everyone smile, as it provide options to everyone ideas, feeling, tastes and electronic knowledge development levels.

"Dx amplifier, the real democratic amplifier"

Marketing group; text number E038857773666265653

I have to tell you Ritchie, to make justice to you, that i feel very...very...very happy to have you here...i use to read your posts.

regards,

Carlos
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