Ok, I got a problem. Fired one channel and tried to adjust the bias¸ monitoring voltage drop on 100R . voltage (+ side) 0.68V , turning trim pot to get 5V .and nothing happened voltage the same 0.68V, Checked (– side) voltage 11V . Turned of power. And start to search mistake. Could not find it. The only difference is that output transistors are MG6330/MG9410. Suggestions?
For sure you have errors in your board
When bias does not adjust, also when output off set is high, or when you have NPN driver burning, all these things and other strange things too, means errors, human natural mistakes.
There's no way to say exactly what you have made wrong..but it is easy to know that there's something wrong on that.
We have hundreds of possible mistakes that can result this problem, but it seems the bias circuit is the stronger suspect.
First check solder....clean flux (Kerozene, the aviation fuel) and observe, then ressolder and clean once again..check part's position, inverted transistors can be found...check if NPN is in it's correct place and if PNP is in it's correct place...check part's values, diodes polarity, your supply polarity too...well..... search of a mistake...as no doubt there is a mistake or more than one mistake..and this happens from time to time.... mistakes, errors building is human, a natural thing we do everyday.
Check transistors insulators, measure from colector to ground (conductivity) and cannot read low resistances this way.... well....observe each component and compare it with the schematic, check polarity and values.
Good luck,
Carlos
When bias does not adjust, also when output off set is high, or when you have NPN driver burning, all these things and other strange things too, means errors, human natural mistakes.
There's no way to say exactly what you have made wrong..but it is easy to know that there's something wrong on that.
We have hundreds of possible mistakes that can result this problem, but it seems the bias circuit is the stronger suspect.
First check solder....clean flux (Kerozene, the aviation fuel) and observe, then ressolder and clean once again..check part's position, inverted transistors can be found...check if NPN is in it's correct place and if PNP is in it's correct place...check part's values, diodes polarity, your supply polarity too...well..... search of a mistake...as no doubt there is a mistake or more than one mistake..and this happens from time to time.... mistakes, errors building is human, a natural thing we do everyday.
Check transistors insulators, measure from colector to ground (conductivity) and cannot read low resistances this way.... well....observe each component and compare it with the schematic, check polarity and values.
Good luck,
Carlos
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Not a real problem...factories use to tweak to force off set to be less than 25
milivolts....after factories assemble the make some tests, if they find more than 25 mV then they adjust....if not they give their OK and the equipment goes to packing and delivery.
25 milivolts represents less than a hundred microwatts of waste of power...for sure this will not mess with your amplifier...not an important thing... let it be the way it is.
regards,
Carlos
milivolts....after factories assemble the make some tests, if they find more than 25 mV then they adjust....if not they give their OK and the equipment goes to packing and delivery.
25 milivolts represents less than a hundred microwatts of waste of power...for sure this will not mess with your amplifier...not an important thing... let it be the way it is.
regards,
Carlos
DESTROYER VS ALBARRY
I purchased the cards in the right Blame super but they are too large, then I'm forced to build the destroyer ES - What should I change to power with 40 volts DC??
thanks so much for your work
I purchased the cards in the right Blame super but they are too large, then I'm forced to build the destroyer ES - What should I change to power with 40 volts DC??
thanks so much for your work
DX Blame up and running and sounding good.
Carlos - please could you tell me the purpose of C24, the 100pF cap across C-B of Q3.
Carlos - please could you tell me the purpose of C24, the 100pF cap across C-B of Q3.
A safety against oscilations..it can go from base to ground too
It was installed in the earlier stages of testings, when some strange intermitent oscilations appeared superimposed to the square wave positive DC flat top when 25 Khz signal (square wave) was injected in a such level that was driven the input to saturation.... was a 500 milivolts peak to peak high frequency signal i had from time to time, only at the positive flat top.
Latter on i found the transformer was the one was creating unstabilities, that toroidal was to the trash box and i have never faced such kind of oscilations once again.
I do think you can supress it, in the reality doing nothing now a days.
regards,
Carlos
It was installed in the earlier stages of testings, when some strange intermitent oscilations appeared superimposed to the square wave positive DC flat top when 25 Khz signal (square wave) was injected in a such level that was driven the input to saturation.... was a 500 milivolts peak to peak high frequency signal i had from time to time, only at the positive flat top.
Latter on i found the transformer was the one was creating unstabilities, that toroidal was to the trash box and i have never faced such kind of oscilations once again.
I do think you can supress it, in the reality doing nothing now a days.
regards,
Carlos
Thanks Carlos!
I could not measure any sort of difference with/without it. Along with your comments, therefore I will leave it out.
FWIW I think I perceive a tiny improvement in sound by leaving out C18 (charge suckout cap), although maybe I am influenced by removal of this cap in a similar circuit some time ago where I heard a noticeable improvment in treble clarty?
I could not measure any sort of difference with/without it. Along with your comments, therefore I will leave it out.
FWIW I think I perceive a tiny improvement in sound by leaving out C18 (charge suckout cap), although maybe I am influenced by removal of this cap in a similar circuit some time ago where I heard a noticeable improvment in treble clarty?
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A real DIY job dear Rei Momo.
Thank you very much by these pictures.
I am happy watching a real DIY product.
regards,
Carlos
Thank you very much by these pictures.
I am happy watching a real DIY product.
regards,
Carlos
2SA970 & 2SA1064 (+2SC2564) !!!
DX Blame amps deserve these beauties!😎
They also work VERY well with 2sa992/sc1845. 2sa970 is about to be discontinued. 🙁
Cool seeing a full power amp on a breadboard ...
OS
Cool seeing a full power amp on a breadboard ...
OS
Yea, I forgot to say that I used low noise transistors for input stage.
the outputs are Toshiba 2SA1094/Nec 2SD745, Q5 is 2SC1845
I have been mounting other amps on this bredboard since 2007.
the outputs are Toshiba 2SA1094/Nec 2SD745, Q5 is 2SC1845
I have been mounting other amps on this bredboard since 2007.
Nice...you have taken the risk to use substitutes
These transistors you're using are nice...i am glad you had good results.
I hope you're enjoying this nice amplifier...it is just the best in my opinion.
It is better to say that clear..not only mine ones are the best...i do think all blameless style amplifiers sounds great and also measures great...they are all very good..i do prefere mine bootstrapped one...because the bootstrapp sonics by itself.... well... this is personnal, subjective...some may agreed, others not.
When you use CCS (constant current source) feeding VAS (voltage amplifier stage) you have other advantages, numbers are usually better... the difference in between them, say, audible, is not that big...i have tried switches and relays replacing the bootstrap by a CCS, same current..absolutelly same current.......man!.... it is not that easy to notice the difference...and you have to listen several times..different musics, different loudness levels...and finally in the first 3 seconds of each music played one way or other, you can perceive the difference..... but cannot delay too much as our ears + brain adjust...if you let brain adjust, then you will be listening your brain processing, not the real audio.
regards,
Carlos
These transistors you're using are nice...i am glad you had good results.
I hope you're enjoying this nice amplifier...it is just the best in my opinion.
It is better to say that clear..not only mine ones are the best...i do think all blameless style amplifiers sounds great and also measures great...they are all very good..i do prefere mine bootstrapped one...because the bootstrapp sonics by itself.... well... this is personnal, subjective...some may agreed, others not.
When you use CCS (constant current source) feeding VAS (voltage amplifier stage) you have other advantages, numbers are usually better... the difference in between them, say, audible, is not that big...i have tried switches and relays replacing the bootstrap by a CCS, same current..absolutelly same current.......man!.... it is not that easy to notice the difference...and you have to listen several times..different musics, different loudness levels...and finally in the first 3 seconds of each music played one way or other, you can perceive the difference..... but cannot delay too much as our ears + brain adjust...if you let brain adjust, then you will be listening your brain processing, not the real audio.
regards,
Carlos
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I agree , Dr. Self's "blameless" is the "most for the least" (8-9 parts). "Evil CCS's" are at least good for universal voltage (EXACTLY 6.14mA from 15V to 80V 🙂 ) To make a "CCS'ed" blameless sound better , add resistor at LTP "tail" to "soften" it's CCS. 😀 . "Trial and error" (the DX way) to the rest of the amp's values , and even the "EVIL CCS" version can be VERY good sounding (below) and will never fail ( 48 hours of 60V square wave - VERY HOT!! )
OS
Attachments
Yep..this trick you use works fine...the resistance
It keeps current but modulates voltage because voltage drop...this is interesting effect that ressembles the bootstrap in a such way.
regards,
Carlos
It keeps current but modulates voltage because voltage drop...this is interesting effect that ressembles the bootstrap in a such way.
regards,
Carlos
But this trick will not emulate the loudspeaker impedance variations being fed back to the VAS through a bootstrap , A "true blameless" with TMC (CCS VAS) tries to do so. Bootstrap does have a certain "magic" , but this is dependent on the speaker and output stage used/auditioned. Both versions of the blameless are very defined and can be "tweaked" to be almost identical.
The resistor on the LTP does add a few PPM to distortion , but at .0002-3% ... who cares ?
OS
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