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Old 6th October 2011, 07:58 PM   #211
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Quote:
Originally Posted by destroyer X View Post
People that feel these 2 small vertical heatsinks too much hot can reduce VAS current in order to reduce heat there.... i have simulated and i found the original schematic fine... with the modification you will have changes in performance, but not that huge.

The 22 ohms resistor that sets the CCS current can be increased to 47ohms in order to reduce current...then you will have these transistors mounted into vertical heatsinks (CCS to VAS and VAS transistor) less hot.

I found power there not that big...the left one is the CCS transistor, CCS to feed VAS (Voltage Amplifier Stage) and it is dissipating 1.65 watt.... the rigth side one is the VAS transistor, the second stage, the most active unit, following the buffer and the power there, dinamic power, will be around 1 watt....not that huge power and the small heatsinks should fit in most of the cases... exception is when people is using higher supply voltage... say... really higher voltage.

You can replace the 22 ohms resistor by a 27 ohms, 33 ohms, 39 ohms or 47 ohms.... i suggest you to go to 47 ohms because will really cool down in order to work fine with tiny vertical heatsinks... with this resistor replaced, the performance when using low impedance output loads will clip earlier.... some loss in power...not that huge, not that important.

Carlos
Hello dear Carlos,

Do you have an estimate on how much less the dissipation would be with a 47R? And do you have the power and distortion figures when using that resistor value?

If you recommend this, I assume you have evaluated that the sonics will remain the same?

Thank you,
Martin.
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Old 6th October 2011, 09:27 PM   #212
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by canonnica View Post
Words from the initial poster on foreign forum:
Thanks ...


Maybe it's better to use bigger heatsinks than reduce CCS current ... ?
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Old 6th October 2011, 10:17 PM   #213
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Default Yes....better to increase heatsinks than to reduce current

As i said.... audio is almost the same...not the same.... while operating high current (low impedance) we have losses when we reduce current increasing that resistor to 47 ohms...it is an option...but not the best option...better is to increase heatsink size.

regards,

Carlos
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Old 7th October 2011, 12:38 AM   #214
a.wayne is offline a.wayne  United States
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Carlos,

What is the optimum voltage for the vas stage ? I'm going to run the outputs at 45v.. What should i run the VAS stage at for best sonics ..?
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Old 7th October 2011, 08:13 AM   #215
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Default -48 volts into the VAS transistor emitter and -922 milivolts into the VAS colector

This is achieved using a 50 Volts supplies.... was the voltage i found the amplifier better sonically...but was not optimized into THD measurements, despite the difference (numbers) was not important.... this voltage was achieved with a 55 volts supply ... when driving the amplifier hard to full power (so, dinamically operating) the supply voltage was dropping to 50..and there was the point it was lovely.

Will it be worse with other voltages?

Not really Wayne, and you wanna know why?..... because you having not listened the unit with 50 volts you will not know how it can perform while operating with this voltage.....and not knowing you will never know....not listening you will not perceive...it is not that easy to perceive...sometimes i have to repeat tests to perceive...difference is so small that sometimes i feel i am crazy.....well....maybe i am.

Using 45 volts supplies you will be working fine too, do not worry too much because this amplifier sounds lovely anyway...hard to kill the sonics...even making mistakes and foolishes i found it always fine.... watch carefully, you will see the Blameless from Doctor Self there...basically it is a Blameless..the topology is almost the same..some touches and retouches, some fine tuning, tips and tricks applies and was listened carefully and tweaked for sonics..but basically..you have the best possible design ever made (till today) by Doctor Self...he made other designs...i tried some...no one (to my musical taste, personnal opinion, subjective feelings) can beat this one.... it is just the best ever wide world ever made design..just that.

Yes...i am proud because i have tweaked, i had courage to publish, i worked alike a workhorse, i am proud i could tune it and have people cooperating..but the honor goes to Self...he is the man...i am just a slave that worked hard to offer you something good and to feel myself great watching people interested to build...happy to share..this is the truth.

Using your supply voltage you will have -43.33 in the VAS emitter (main vas, second VAS, not the small buffer you have in the input) and - 903 milivolts in the Colector....the operation point is nice there, despite the amplifier goes fine from 12 to 70 volts supplies... a little bit worse at 4.5 plus 4.5 volts and i dislike when go over 76 volts.

I ensure you that you can make the mess you want...using other transistors, other voltages, other capacitors (exception is the Miller one) and you will beat almost 90 percent of other amplifiers you may have around...this design Wayne, even bad developed, bad applied, using bad solutions, is the winner... after 51 years searching and researching and assembling amplifiers (more than 6400 units built) i could not listen anything better.... Self Blameless is the one, and all Blameless style amplifiers are good, you have several options around..all them if fine.

regards,

Carlos
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Last edited by destroyer X; 7th October 2011 at 08:17 AM.
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Old 7th October 2011, 07:20 PM   #216
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Default to soft start or not to soft start?

I was hoping to avoid purchasing a soft-start module, but I keep blowing my 5-amp slo-blo mains fuses. This is with only 1 of my 2 power supplies hooked up. Is it safe to increase my mains fuses? Should I be blowing 5 amp slo-blo fuses, or is this an indication something is wrong. One option is to remove a pair of filter caps, which I think are excessive anyway. I have 10,000uFX4 + 2,700uFX4 per channel (I have dual mono PS). I've also not increased the value of my 2K bleeder resistors yet, which I know needs to be done.

I guess the question is: with two 56V power supplies with either 50800uF or 30800uF of filter capacitance, am I doomed to need a soft start, or should I wait and see if I need one?

-Byron
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Old 7th October 2011, 07:36 PM   #217
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Not excessive Byron , actual that's pretty small for such an powerful amp, a soft start is always desirable and i would suggest 80,000uf /ch at a min ...





Quote:
Originally Posted by destroyer X View Post
I ensure you that you can make the mess you want...using other transistors, other voltages, other capacitors (exception is the Miller one) and you will beat almost 90 percent of other amplifiers you may have around...this design Wayne, even bad developed, bad applied, using bad solutions, is the winner... after 51 years searching and researching and assembling amplifiers (more than 6400 units built) i could not listen anything better.... Self Blameless is the one, and all Blameless style amplifiers are good, you have several options around..all them if fine.

regards,

Carlos

We will see...... Senor Blameless,

This one will be big and heavy( 50Kilos)....lots of heatsink, fans , Humongous transformers ...

Blame who ...?

Last edited by a.wayne; 7th October 2011 at 07:41 PM.
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Old 8th October 2011, 07:57 AM   #218
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Default Soft start is a very good idea.

If you can use it.

regards,

Carlos
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Old 8th October 2011, 08:35 AM   #219
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Byron,

I strongly recommend you to use a light-bulb tester when you power an AMP for the first time.

Click the image to open in full size.

http://www.abload.de/img/joe0044br3.jpg

I use a 30 Watt high-voltage halogen light that I have connected in series with the mains hot wire.

In the test phase the light bulb tester does not only limit the transformer's inrush current, it also limits the current dissipated by your AMP,
thus protecting your transformer, if you did a mistake (f.e. a short on the PCB).

After the 1.st power on, when you feel that the AMP behaves as it should, remove the bulb tester and do the adjustment.

But: with a big transformer like yours, you still need a "Soft-Power-On" circuit.
The inrush current into your transformer with blow your fuses otherwise.

Best regards - Rudi_Ratlos

P.S. On the picture above you see my "Soft-Power-On" PCB being switched on for the 1st time.
And: my light bulb-tester is in use.

Last edited by Rudi_Ratlos; 8th October 2011 at 08:47 AM.
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Old 8th October 2011, 10:40 AM   #220
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Gentlemen,

since I wrote my last post, I have been asked by 2 of you, if I can sell you my "Soft-Power-On" - PCB.

No - I can't. I ordered a lot of them 2 weeks ago, but I have none of them left.

But: since Byron organized the DX Blame HX AMP PCB's group-buy, I will send him the EAGLE-files of my circuit
and it is up to him to offer you the PCB / Kit or not.

Byron: do you want to have the EAGLE files?

This is how my "Soft-Power-On" works: Posts #58 and #69 of the TO-3 SYMASYM group-buy.

If Byron agrees and offers you the PCB / kit, this will of course take some time.

In the meanwhile I suggest you to use the highest possible - power light bulb that you can get (here in Germany: 200 W)
and connect it in series with the mains hot wire.
This will of course delimit the current being drawn by your AMP, but will prevent your house's-fuse from being blown
during power-on due to the inrush-current.

Best regards - Rudi_Ratlos
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