They are both close to
-1.5+mhz UG
-70-80+ degree PM
-52-53 db CLG - 1hz- 10k+
Very similar , slightly over- compensated.
They are a good match VFA --- >CFA.
You would need to reduce Cdom in each to 1/2 value to
get ringing.
Below , you can see many similarities. Both are new designs (to me) ..
I have not had much experience with them.
OS
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That's right my friend!!!!!!
The only way to answer the question(CFA vs CFA) is if we can listen these(with our friends) on expensive top loudspeakers.
I haven't these top loudspeakers.🙁
Nattawa (post 1242) did the "maggies" with them (his spookies).
That literally exposes all sonic weaknesses.
He said there were none.
As the NAD simulates nearly exactly -SW/slew/CLG/THD ....
I would say it also has (none).
PS - I spent the most time on these 2 symmetric topologies ...
I already have built many (blameless/symasym types).
OS
That literally exposes all sonic weaknesses.
He said there were none.
As the NAD simulates nearly exactly -SW/slew/CLG/THD ....
I would say it also has (none).
PS - I spent the most time on these 2 symmetric topologies ...
I already have built many (blameless/symasym types).
OS
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I forgot to mention that I changed the resistor value R27 FROM 47K TO 22K. for +/-44V .
Is this in the right way?
Is this in the right way?
You forced more juice through the LED's.
(both LED strings could benefit at your low rails with a lower R)...
The way to know you are "there" is to see where
the optimum bias is on the OPS.
4.5-5ma VAS puts you right in the middle... 225-235R (500R).
The post resistors get you close ... if you are close ... let it
be.
If you need more VAS I reduction/increase , R27 can go from
22-56K , depending on rail V's and VAS dissipation.
PS - best distortion profile is with 1/3 I through the LED's , 2/3 to the Cascode's.
OS
Hello OS,
I have 2sa992/sc1845 taken from a gutted amplifier, but they are different hfe rank.
For nad input trannies I have 2sa1045/2sc1815 both Y rank.
For Vas devices a have 2sb1109/2sd1609 which should be good enough. I do not have any other small trannies that hace collector as mid pin.
Rest of the components for the amp should be on my desk on monday.
I´ll continue my search.
J
I have 2sa992/sc1845 taken from a gutted amplifier, but they are different hfe rank.
For nad input trannies I have 2sa1045/2sc1815 both Y rank.
For Vas devices a have 2sb1109/2sd1609 which should be good enough. I do not have any other small trannies that hace collector as mid pin.
Rest of the components for the amp should be on my desk on monday.
I´ll continue my search.
J
2sb1109/2sd1609 - very nice... 5p Cob/ 160V - they will "sing" !!
Servo's on both should compensate for rank , but ... performance would
be better with similar devices.
OS
Servo's on both should compensate for rank , but ... performance would
be better with similar devices.
OS
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Pay attention please i have a mistake AT SHEMATIC on post #1267
The right is:
V R20=1.43V
V R29=0.78V (VAS undercurrent), not the opposite!
Sorry for this.
Thimios.
This time with +/-50V.
So new trim resistors(R10,R19 FROM 68R TO 22R & R22 FROM 47K TO 23K) FOR +/-50V are here.
Please Pete look at this.🙂
Thimios.
So new trim resistors(R10,R19 FROM 68R TO 22R & R22 FROM 47K TO 23K) FOR +/-50V are here.
Please Pete look at this.🙂
Thimios.
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Hi OS,
One issue we never seemed to get to is --- does slew rate matter? Since you have been able to get thd of VFA and CFA to be nearly the same and you could do same with Slew Rate (SR)... then the sound is similar/same. But, if just slew rate was .5 to 1v per peak volt output (the standard recommended) was compared to 200-300v/usec+ SR, do they sound different??
THx-RNMarsh
One issue we never seemed to get to is --- does slew rate matter? Since you have been able to get thd of VFA and CFA to be nearly the same and you could do same with Slew Rate (SR)... then the sound is similar/same. But, if just slew rate was .5 to 1v per peak volt output (the standard recommended) was compared to 200-300v/usec+ SR, do they sound different??
THx-RNMarsh
That looks good... 1.7mA from the LTP cascodes producing 7.15mA at the
VAS re's.
Real close to spec.
The real way to see is to observe where your final OPS bias point ends
up.
OS
With modern devices , I can't conceive of an amp that slow.
A simple blameless (lin) .... is the slowest, at 30-40V /uS.
The "honey badger" does about 50-60+ V/us.
So .... a good comparison would be my "wolverine" IPS with a
big, fat, single 100pF miller as compensation (30V/uS) , up
against the NAD/spooky at 200V+/us.
ALL the IPS's are 28X gain , run the same EF3 .... can't think
of a more level "playing field" than this ?
OS
I find Wavebourn's ideas interesting:
http://www.diyaudio.com/forums/tube...ower-iii-high-end-hybrid-amp.html#post1886619
Os,
That's just what we need, a vacuum tube to go along with the led's and light up a front panel ! 😀
That's just what we need, a vacuum tube to go along with the led's and light up a front panel ! 😀
Thanks OS ,but i can't understand this"The real way to see is to observe where your final OPS bias point ends up"
Can you explain more?
Sorry my bad English
I see that if amp. is on hard clipping U.V leds comes dimmed (if that helps).
Regards.
Thimios
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At 4.5 -5ma VAS , the Vbe circuit's trimmer should be 180-225R for
60ma OPS current.
I you have to much or too little current , you might "run out of trimmer".
This can be changed ,however. The resistor in series with the trimmer
can be changed for a different VAS current.
This is normal (dim UV/BLUE) - the hawksford is saturating and
"stealing" the LED's current .... 😀
PS - you could even use this side effect as a protection trigger node!!
OS
Thanks again
I have used 1K multi.trimmer and ,as i see, it is posible to trim bias very well as recommended.
Protection via optocupler // U.V led? Good idea!
Thimios.
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