i have attached a file from post 20. is it ok? size is 80X77.5 mm
Attachments
oh ok I see 500mA transformer got it, yes this layout is actually the one that goes with the first post I think I'm gonna make this one but sadly those BF245A are obsolete and hard to find unless a equivalent can change this part number 
this layout goes with this schematic yes
I found this part number BF256B is this one can be use instead of BF245A?
one more thing the original schematic does not show the pins identification I assume that is like this right
this layout goes with this schematic yes
I found this part number BF256B is this one can be use instead of BF245A?
one more thing the original schematic does not show the pins identification I assume that is like this right
Attachments
Last edited:
Those JFETs are just used as a current source, so you don't need anything exotic, but you do want a similar Idss and low-noise. The BF256B meets the first criteria, but the datasheet makes no mention of noise.
What about a 2n5457?
(Note: you'll need to compare pinouts of any replacements as they aren't all the same.)
What about a 2n5457?
(Note: you'll need to compare pinouts of any replacements as they aren't all the same.)
oh ok I'm gonna check the 2N5457 and yes I'm aware of pins can be different if I clone this layout and avoid errors
I know Mr. Miles must be occupied I hope he can identified the pins of those BF245A on the schematic so then I can modified the layout to accept ones that are available to purchase
you gotta be kidding...there's no need for any regulator in a class a preamp...a very simplistic capacitor multiplier will do the job equally well for any high end audio preamplifier.The most complicated design needed will probably have 6 transistors for both rails, but nothing else , no matter how complicated it may be, can do a better job as long as you're making use of capacitors to filter, decouple and stabilize that exquisite regulator anyway.Audio world is not full of CERN's photon or nuclear measuring systems.Topics like these make me really mad because when i started electronics i thought that electronics designers do anything they do for a reason, a TECHNICAL reason...It took me more than a decade to find out how many hoaxes i fully believed at start are floating around disguised in technical subtilty clothes.
Class A amplification means almost constant current draw. no real transients are found in a class A amp , no matter the power..
Class A amplification means almost constant current draw. no real transients are found in a class A amp , no matter the power..
Last edited:
do you have a circuit that can then I follow? if not regulation is need it then I can go for that option too
A simplistic capacitance multiplier has issues too (for instance, when the supply voltage drops). And you're never going to get the output impedance you can with a regulator.
(The class-A constant-current-draw argument only holds for single-rail topologies. While the total current draw is nearly constant for a dual-rail design, the draw from each individual rail has twice the variance of a class-B design.)
You can get better ripple rejection and output impedance from a regulator. Yes, it will be more complex. And it will have feedback, so stability needs to be ensured. A series regulator will also need to dump a lot more heat -- and if it's a shunt then bucket loads more heat.
What will work best depends on what your design goals are.
There's a good discussion here: Supply Filtering and why Capacitance Multipliers are NOT the Answer.
(The class-A constant-current-draw argument only holds for single-rail topologies. While the total current draw is nearly constant for a dual-rail design, the draw from each individual rail has twice the variance of a class-B design.)
You can get better ripple rejection and output impedance from a regulator. Yes, it will be more complex. And it will have feedback, so stability needs to be ensured. A series regulator will also need to dump a lot more heat -- and if it's a shunt then bucket loads more heat.
What will work best depends on what your design goals are.
There's a good discussion here: Supply Filtering and why Capacitance Multipliers are NOT the Answer.
Yeah right...and the first two guys talking there are some of the the most expensive sellers of "high endish" useless toys in the diy world...today, if you have an Audio Precision to back your designs you can tell anything as a rule of thumb, but the rules of thumbs are many!
Well I just posted the most advanced phono preamp inside the most advanced integrated receiver ever made commercial by the same team that gave birth to Accuphase(Kenwood+ Kensonic). The input differential section by itself takes 34ma...
I'm talking about this:
Kenwood L-02A on thevintageknob.org
L-02A KENWOOD - HiFi-Do McIntosh/JBL/audio-technica/Jeff Rowland/Accuphase
Yeah, i saw it's full of cascodes with not so great PSRR while placed into a 2x 170w RMS class ab power amp ...
Is it up to you expectation?
Attachments
Last edited:
Check out the circuit they're driving the cascodes from. Is that some sort of current-mirror voltage stabiliser?
So it's a very basic one!!!
That was my answer for you ...the previous post had the capacitor multiplier article on ESP site. I can't count the number of low noise preamps supplied by a simple c-multiplier i saw in real life high quality equipment where they measure less than 0.003thd+IMD distortions over the full audio spectrum...
Now you have the most complicated c-multiplier i have ever seen following a faster regulator
Attachments
Last edited: