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DX Blame Group Buy

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#142
Yes, I did misunderstand something, Rudi. I thought it is a combination of high output level and 50khz square wave. Thanks for the correction.

Wouldn't most input devices have low-pass filters to filter out such high frequencies anyway? Plus, I am guessing the likelihood of such waveforms appearing in music is very slim. Square waves are mostly digital signal, aren't they?

Regards,
Nikolay
 
#143
Hello Nikolay,

the DX Blame (like every (?) other AMP) has a high-pass filter on the input (consisting of C1/C2 and R2) to decouple from DC.

A 50 Khz rectangular square wave is normally (!) not on any CD or music-track you listen to.

But Carlos, as the owner and mentor of the DX Blame schematics, is responsible for the fail-proof operation of the DX Blame under every situation.
That is why he discontinued the EX version of the DX Blame, which has a tendency to oscillate when applying fast square wave signals to its input,
and modified it to run stable even with these input signals.

He called the modified AMP version the DX BlameST.

If you are sure that you will never apply an "unusual" input to the DX Blame, you can build the ES version of the DX Blame.
In my ears the ES version is playing with even a little more emotion and musicality than the ST version.


Best regards - Rudi_Ratlos
 
#145
Also i had an strange and defective toroidal transformer that was the big killer

i had in my home...it made me replace 12 pairs of power transistors and several Q9...sometimes the first VAS was burned..... i could not discover the reason why, i have made some tests, i have followed some sugestions people gave me about, till i give up and sent the "animal" to the garbage can.

That transformer was coiled by a friend, in his shop...was a gift.... not a happy gift i must say..i do not know if he made it correctly or not... and i have suspection the toroidal piece felt down and was broken and glued.... the employee that made the job said anything. (did not confess the crime)

As soon as i have replaced that transformer, everything returned to normal, even the ES was reliable, but showing some strange behavior, an intermitent sinusoidal oscilation superimposed to the positive DC portion of a 50 Khz square wave..a high level, already clipping, signal.....that bad trafo. was partially dismounted to check solders and construction and anything wrong (clearly wrong) was found...maybe it was broken and glued, as i have found some traces of Epoxi glue on it.

It gave me a really hard time.

Also, there are non acadhemical solutions applied to the ES that created a lot of mess in the thread, people landed to criticise.... those ones that usually behaves alike birds of prey (5)...they came to say gonna explode, to say would not work, to say was wrong... when the amplifier worked fine after that transformer removal...i decided to create the ST, and point it as standard, with an acceptable circuit for the technocrats to shut their big mouthes and to send them to fly away of me.

But, i use to say..also Rudi, the one sounds better in our point of view is the ES, but i use to point it is not guaranteed as we should offer the best audio and the best technicall solutions to forum members... the construction is under your own risk..the Corporation does not take responsability about amplifiers pointed as not entirelly stable.

That intermitent (comes and go, and sometimes does not appear at all) signal superimposed is low level...500 milivolts peak to peak...the frequency is higher than the 50 Kilohertz (non audible frequencies)...and the power is around 15 MILIWATTS of disturbance....so.... anything dangerous.

That transformer, the hell one.... used to make the amplifier oscilate as soon as you switch the power on..... was a hell, in microseconds you had fuses burned and output transistors damaged... cold and damaged...shorted!...and no leakage from primary to secondary, no strange waveform inspected in the scope...very strange thing....i have tested some small resistances (0.22 ohms) in series with the primary to the rectifier..also from the rectifier to the filter condensers..and they burned instantaneously when we switch power on...

If you are interested, my dear friend, read the Dx Blame ES thread and you gonna see the "adventure" we have faced there... and here the terrible transformer "hell effect" working:

YouTube - Aaaagh, that transformer again!

About the Dx Blame i have made several videos, inspecting waveforms and a lot of other details you can find typing at YouTube search bar the word "destroyersoueu"

regards,

Carlos
 
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#146
Dear Carlos and Rudi,

Thank you very much for the explanations. I'll have another pass a the DX Blame ES thread when I get a chance.

There is one thing I still don't understand though, if the 50khz square wave is not in music and the chances of getting the unstable conditions are very little, what is the concern when we will use the amp to play music?

I may be completely off, but to me, this is something like saying: "If you put diesel in a petrol car, the engine will not run"... and the simple and obvious answer is: "I will never put diesel in my petrol car". Is it that simple, or am I missing something?

Thanks again,
Nikolay

ps @Rudi: Beautiful manual you've put together, Rudi. It will definitely make my first DIY project go as smoothly as possible. Thank you!
 
#147
I see that BC556 input transistors do not have any additional sign as A or B type...is there any recomnedation what to use here?


For C1 I will use some good MKP cap, however 10 uF caps are quite big...could C1 be decreased in value without degradation in bass?


P.S.: Great job Rudi🙂
 
#149
supernet said:
For C1 I will use some good MKP cap, however 10 uF caps are quite big...could C1 be decreased in value without degradation in bass?
Click to expand...
you can substitute a 4u7F with almost no difference in very low bass output quality and/or quantity.
Using 2u2F may show a slight reduction in low bass quantity. This has F(-1dB)@~14Hz (RC=22ms)

C1=4u7F is a better match to the 220uF NFB cap.
C1=10uF really needs a 330uF or 470uF NFB cap.
 
#153
Sorry, dear DX Blame friends,

DHL tried and delivered the PCBs at 1:20 pm today.

An externally hosted image should be here but it was not working when we last tested it.


but I was not at home.

I have a job, like most of you and work in my office from 07:00 am to 5:00 pm.

I asked DHL to deliver the PCBs tomorrow again, after 6:00 pm.

Best regards - Rudi_Ratlos

P.S. What makes me very sad is: it takes 3 days to deliver a parcel from China to Germany.
I sent a parcel to my dear friend Joseph in Canada with PCBs, resistors, ..., 8 weeks ago. It didn't arrive up to now.
 
#158
The PCBs are beautiful, Rudi. Excellent work!

@supernet: The BC 556/546 A/B classification refers to the transistors' DC current gain (hFE). 'A' is between 110 and 220 and 'B' is between 200 and 450. I remember reading somewhere in the DX Blame ES thread (Carlos, please correct me if I am wrong) that the typical value is between 100 and 200. 'A' will definitely work, but I am guessing 'B' will work just as fine. Maybe you can get both and test it out?

Regards,
Nikolay
 
#160
Rudi said i will be the last one..the last group of letters

Well..it is fair...customer first!

No problems..i am sooooo happy that i will send him a gift back.

Kidding folks..no problems....i support Rudi decisions....but my money has the same value and colour.....grrrrrrr!

regards,

Carlos
 

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