Alternatively, you could use a 24v 500mA Class 2 transformer wall wart without a DC-DC stepup. It will drop about 4v across the cap Mx. You can increase the R value of the CRCRC to drop another volt and be at 18v and not have any DC-DC that may be inject high frequency noise (150kHz) into you amp.
Built one with the low bias current values - the amp works (there's sound out), but when measuring voltages they seem all wrong compared the sim (https://www.diyaudio.com/forums/att...gb-bf862-low-bias-irf610-hpa-v1-schematic-jpg)
My Vcc is a hair above 18.2V (18.2x V) Not sure whats going on...?
Voltage measurements are in red, relative to gnd.
My Vcc is a hair above 18.2V (18.2x V) Not sure whats going on...?
Voltage measurements are in red, relative to gnd.
Attachments
This beast is capable of rivaling best tube amps out their . One of my Thai friend own a high end tube amp from schit but i found this amp simply destroys it. As an musician , distortion is not always bad rather second order distortion puts life into your music . . Distortion profile is truly like those of DC Coupled tube amp. I used adapter of my Compaq 620 , it worked flawlessly as power source.
If you are a new to smd , it is better to take help from anyone who repairs SMD boards day in day out like those who repair smartphone , macbook etc for placing JFET on board .
I don't know where xrk971 has fabricated the pcb but they are absolutely top notch as i have used de soldering wig for many time for fixing my stupid mistakes but the board absolutely survived my awful torture . xrk971 always helps you if you have any doubt . Anyway never use Ruby con caps in output stage unless you want some harsh mid range . Vishay BC will give absolutely neutral sound but i will recommend Panasonic FC or Nichicon UFG for clean audio . Use at least 1% resistor from Vishay Dale to archive least distortion . As for film caps use any metallized film like mallory , wima or vishay Roederstein , my favourite .
I actually used every passive components from Vishay as they have excellent supply in india which i cannot say at all for panasonic and wima . I recommend to grab components from Digikey or mouser or farnell to ensure legit components. If you are using 10uf caps in input like Silmic II or Nichicon ues , please kindly give some burn in time before listening . Most importantly , never reverse the supply rail , it will blow your first mosfet in no time .
Lets come to most important thing , how it sounds :
DAC used :: Focusrite Scarlet Solo
Headphone used :: AKG K 240 Semi-Open Studio Headphones
I will compare with OBJECTIVE 2 and OPA1688 based amp of XRK.
Warning : If you have wedding or something important to attend , donot listen to this amp beacuse you cannot stop listening. It literally sings into your ear with awful amount of detail in midrange ,
crystal clear highs with lovely tube like distortion and crisp lows . I have played Yanni Live at the Acropolis [Whole CD] , Skillet Rise [whole album at 24bit ] , Evanescence Synthesis [24 bit ] ,Evanescence Open doors [CD],
Some Metallica[16bit flac ripped from CD] , Enigma Sadness I and II
Yanni Live at the Acropolis [CD] :
First thing i noticed is Piano is quite more profound than any OP AMP based amp i own like OBJECTIVE 2 and OPA1688 based amp of XRK.
In rain must fall , i can feel shout at beginning from different direction which i never heard. I never before distinguished violin in the song properly but this amp did the magic.
Skillet Rise [whole album at 24bit flac] :
In fire and fury , beginning vocal were crystal clear . Objective 2 is crisp but this amp more crystal clear may be due to JFET input stage .
In what i believe , the beginning portion in guitar sounded totally different , man this is not music it is drug . Metal with 2nd order harmonic distortion is totally heaven for those who love rock and role .
Evanescence Synthesis [24 bit]:
In Lithium : In beginning , Vocals of AmyLee were stunning as always but hold on piano never was so crystal clear then the Gothic metal portion enters and this amp blows everything away in distortion profile.
In Bring Me Back to Life : I will call it bring this amp to life , sound quality and timbre of mid range with excellent stereo separation was in another league which objective 2 cannot stand near to it.
Some Metallica[16bit flac ripped from CD]:
In Orion : i cannot say much , this amp is God for listening metal , in orion i heard many stuff first time and i can literally distinguish what kind of effect and type of guitar string they are using . If you play guitar you will
understand what i am saying . I noticed first time the song is on off note .
Enigma Sadness I and II :
In Sadness I, I cannot make much difference between objective 2 , they sounded equally awesome .
In Sadness II , starting was better on DCA but later when beat drop entered both sounded equally well.
In I love you , i will kill : for first time i heard new instruments which felt like Tabla .
My conclusion : if you listen metal , hard rock , soft rock , punk rock or anything like new age instrumental , you will love this amp. This amp is heaven if you love metal .
I am traveling so writing from my phone , Nokia 8 so their may be some typos so forgive me .
If you want to ask me anything , please feel free .
If you are a new to smd , it is better to take help from anyone who repairs SMD boards day in day out like those who repair smartphone , macbook etc for placing JFET on board .
I don't know where xrk971 has fabricated the pcb but they are absolutely top notch as i have used de soldering wig for many time for fixing my stupid mistakes but the board absolutely survived my awful torture . xrk971 always helps you if you have any doubt . Anyway never use Ruby con caps in output stage unless you want some harsh mid range . Vishay BC will give absolutely neutral sound but i will recommend Panasonic FC or Nichicon UFG for clean audio . Use at least 1% resistor from Vishay Dale to archive least distortion . As for film caps use any metallized film like mallory , wima or vishay Roederstein , my favourite .
I actually used every passive components from Vishay as they have excellent supply in india which i cannot say at all for panasonic and wima . I recommend to grab components from Digikey or mouser or farnell to ensure legit components. If you are using 10uf caps in input like Silmic II or Nichicon ues , please kindly give some burn in time before listening . Most importantly , never reverse the supply rail , it will blow your first mosfet in no time .
Lets come to most important thing , how it sounds :
DAC used :: Focusrite Scarlet Solo
Headphone used :: AKG K 240 Semi-Open Studio Headphones
I will compare with OBJECTIVE 2 and OPA1688 based amp of XRK.
Warning : If you have wedding or something important to attend , donot listen to this amp beacuse you cannot stop listening. It literally sings into your ear with awful amount of detail in midrange ,
crystal clear highs with lovely tube like distortion and crisp lows . I have played Yanni Live at the Acropolis [Whole CD] , Skillet Rise [whole album at 24bit ] , Evanescence Synthesis [24 bit ] ,Evanescence Open doors [CD],
Some Metallica[16bit flac ripped from CD] , Enigma Sadness I and II
Yanni Live at the Acropolis [CD] :
First thing i noticed is Piano is quite more profound than any OP AMP based amp i own like OBJECTIVE 2 and OPA1688 based amp of XRK.
In rain must fall , i can feel shout at beginning from different direction which i never heard. I never before distinguished violin in the song properly but this amp did the magic.
Skillet Rise [whole album at 24bit flac] :
In fire and fury , beginning vocal were crystal clear . Objective 2 is crisp but this amp more crystal clear may be due to JFET input stage .
In what i believe , the beginning portion in guitar sounded totally different , man this is not music it is drug . Metal with 2nd order harmonic distortion is totally heaven for those who love rock and role .
Evanescence Synthesis [24 bit]:
In Lithium : In beginning , Vocals of AmyLee were stunning as always but hold on piano never was so crystal clear then the Gothic metal portion enters and this amp blows everything away in distortion profile.
In Bring Me Back to Life : I will call it bring this amp to life , sound quality and timbre of mid range with excellent stereo separation was in another league which objective 2 cannot stand near to it.
Some Metallica[16bit flac ripped from CD]:
In Orion : i cannot say much , this amp is God for listening metal , in orion i heard many stuff first time and i can literally distinguish what kind of effect and type of guitar string they are using . If you play guitar you will
understand what i am saying . I noticed first time the song is on off note .
Enigma Sadness I and II :
In Sadness I, I cannot make much difference between objective 2 , they sounded equally awesome .
In Sadness II , starting was better on DCA but later when beat drop entered both sounded equally well.
In I love you , i will kill : for first time i heard new instruments which felt like Tabla .
My conclusion : if you listen metal , hard rock , soft rock , punk rock or anything like new age instrumental , you will love this amp. This amp is heaven if you love metal .
I am traveling so writing from my phone , Nokia 8 so their may be some typos so forgive me .
If you want to ask me anything , please feel free .
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A new DCA is about to be born - this one by Vunce, will power his new ESS 422H hybrid AMT cans.
Looking forward to the new open chassis amp on a plank but with real aluminum front panel.
Looking forward to the new open chassis amp on a plank but with real aluminum front panel.
I have what may be a bunch of dumb questions. Could someone explain the formatting of the BOM on pg 2? Or is there another version that's in more like layman's terms (or at least terms that a non-EE can understand)?
I.E. For C101, what is CPOL-EUE3.5-8? I googled that and put it into Mouser & Digikey’s search and found nothing. I’m assuming 10µ0 means 10.0 µF, correct?
Similarly, for C101A, what is C22/10 C22.5B10?
I’m used to seeing capacitor types and dimensions.
Also, can I assume that anything labelled as “polarized capacitor” is an electrolytic, and anything just labelled as “capacitor” is a film cap?
Finally, is it possible to build this amp with switchable high/low gain?
I.E. For C101, what is CPOL-EUE3.5-8? I googled that and put it into Mouser & Digikey’s search and found nothing. I’m assuming 10µ0 means 10.0 µF, correct?
Similarly, for C101A, what is C22/10 C22.5B10?
I’m used to seeing capacitor types and dimensions.
Also, can I assume that anything labelled as “polarized capacitor” is an electrolytic, and anything just labelled as “capacitor” is a film cap?
Finally, is it possible to build this amp with switchable high/low gain?
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Hi PinkFloyd4Ever:
The BOM was created automatically from Eagle and uses European notation. Typically, on the film caps and electrolytic caps, the first number following the "E" is the pitch between the leads in mm (sometimes a comma is used as a decimal), then the next number is diamter or width dimension in mm. So for example,
C102 10µ0 CPOL-EUE3.5-8 E3,5-8 POLARIZED CAPACITOR, European symbol
means component label (silkscreen) C102, 10.0uF, cap-polarized-European 3.5mm pitch by 8mm wide.
another example is: C143 1µ0 C5/5 C5B5 CAPACITOR
C143, 1.0uF, capacitor 5mm pitch by 5mm wide.
As far as the connectors go, there are qnty 5x 2-pin Molex KK 0.1in pitch (or JST 0.1in or 2.5mm pitch). There is a single 2-pin 10mm screw terminal for power input.
Resistors labeled CMF55 or CMF60 refer to Dale series resisors (0.5w and 1w) I think.
Attached is a revised version with more useful info. Funny, but you are the first person to ask for this clarification - I guess it was not always so obvious.
Use this stuffing diagram, not all parts are labeled on the PCB:
The BOM was created automatically from Eagle and uses European notation. Typically, on the film caps and electrolytic caps, the first number following the "E" is the pitch between the leads in mm (sometimes a comma is used as a decimal), then the next number is diamter or width dimension in mm. So for example,
C102 10µ0 CPOL-EUE3.5-8 E3,5-8 POLARIZED CAPACITOR, European symbol
means component label (silkscreen) C102, 10.0uF, cap-polarized-European 3.5mm pitch by 8mm wide.
another example is: C143 1µ0 C5/5 C5B5 CAPACITOR
C143, 1.0uF, capacitor 5mm pitch by 5mm wide.
As far as the connectors go, there are qnty 5x 2-pin Molex KK 0.1in pitch (or JST 0.1in or 2.5mm pitch). There is a single 2-pin 10mm screw terminal for power input.
Resistors labeled CMF55 or CMF60 refer to Dale series resisors (0.5w and 1w) I think.
Attached is a revised version with more useful info. Funny, but you are the first person to ask for this clarification - I guess it was not always so obvious.
Use this stuffing diagram, not all parts are labeled on the PCB:
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25v caps is good. You can vary the gain, but it is a function of the resistor above the JFET and below the JFET. And they have to be adjusted in such a way that keeps the source voltage about midway of Vcc. Plus you have to look at the harmonic profile while adjusting it. In fact, that’s where the experience of a designer comes in - to get the gain about right and the distortion low with a good profile and balanced output. Use a volume pot to reduce gain!
Ok cool thanks so much again XRK. Ok one more...for now...
What's the deal with C111(A/B) and C112(A/B)? I see they're parallelled with C113(A) and C114(A), which I read you said should be of high quality. So am I right to assume that you'd benefit by using something fancy here as well, such as Sonicaps, Vitamin Qs, Mundorf, etc?
What's the deal with C111(A/B) and C112(A/B)? I see they're parallelled with C113(A) and C114(A), which I read you said should be of high quality. So am I right to assume that you'd benefit by using something fancy here as well, such as Sonicaps, Vitamin Qs, Mundorf, etc?
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Right, I figured as much. But I was just wondering if it's worth using a more expensive film cap for C111 and C112. But I think I may have just answered my own question, because that usually is the case on DIY designs where the designers have made provisions for multiple cap sizes & shapes.
One of the best sounding input caps is the Elna Silmic II 10uF 35v electrolytic. 35 cents. Not kidding.
For output caps, you can also use larger Elna Silmic II but they are huge if you want 1000uF or larger.
Nichicon Muse is good as well as Panasonic SEPF OSCON.
I also find Panasonic FC very good.
For output caps, you can also use larger Elna Silmic II but they are huge if you want 1000uF or larger.
Nichicon Muse is good as well as Panasonic SEPF OSCON.
I also find Panasonic FC very good.
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Alrighy, thanks again xrk.
Shoot, looks like the 10uF 35v Silmic II is only available with 2mm lead spacing. I guess I could always bend them outward and lay the cap down on its side...not sure I'm a fan of the look of that though. I'll figure something out. I'm still very much in the preliminary planning stages of this build...as you can tell, haha.
Shoot, looks like the 10uF 35v Silmic II is only available with 2mm lead spacing. I guess I could always bend them outward and lay the cap down on its side...not sure I'm a fan of the look of that though. I'll figure something out. I'm still very much in the preliminary planning stages of this build...as you can tell, haha.