A few weeks ago, I was wondering in a post about the reason why such buffers are almost never seen on schematics, at leat on the recent ones. No answer at all.
Is there some rebuttal towards single ended buffers ? In that case, why not to use a White buffer (with a clean power supply) which has the nice feature of a well defined quiescent current.
Is there some rebuttal towards single ended buffers ? In that case, why not to use a White buffer (with a clean power supply) which has the nice feature of a well defined quiescent current.
Guillermo,
I like 2SC1845 for VAS (110MHz, Cob 1.6pF, beta 600, super low noise, 50mA but watch the dissipation, only 500mW, don't run it over about 150mW), and 2SC1360 for the buffer. However, since the buffer is an EF, and intrinsically fast, you could use any relatively high voltage device here, such as a 2SA1837, BF470, or even a cheap BD140 if operating at low voltage.
Cheers,
Hugh
I like 2SC1845 for VAS (110MHz, Cob 1.6pF, beta 600, super low noise, 50mA but watch the dissipation, only 500mW, don't run it over about 150mW), and 2SC1360 for the buffer. However, since the buffer is an EF, and intrinsically fast, you could use any relatively high voltage device here, such as a 2SA1837, BF470, or even a cheap BD140 if operating at low voltage.
Cheers,
Hugh
Not at all. Because you don't give the slightest idea of harm it could introduce and some very good reasons have already been mentionned wihout any caution in D. Self's litterature.
Lumba,
With respect, you are wrong. I support Sebastien. The buffer makes the VAS act as a voltage, not a current source, and this makes for less correction as it negotiates the erratic load of the output stage.
I notice better sonics, too, a stronger performance all round, and more resolution.
Hugh
With respect, you are wrong. I support Sebastien. The buffer makes the VAS act as a voltage, not a current source, and this makes for less correction as it negotiates the erratic load of the output stage.
I notice better sonics, too, a stronger performance all round, and more resolution.
Hugh
Hi Hugh,
Thanks for your advice.
However my main question still remains : why is a VAS follower loaded by a CCS is almost not used, even in the D. Self's published schematics ?
In his 5th edition book, Self praised the White follower. Its default of having a low PSRR (my simulation shows about 30 dB for single transistors and 50 dB for Szilkai pairs) can probably adequately got around using a clean power supply and/or a lot of low frequency NFB. What do you think ?
Hi Lumba Ogir,
Could you tell what are the negative factors as the positive ones are already known ?
Thanks for your advice.
However my main question still remains : why is a VAS follower loaded by a CCS is almost not used, even in the D. Self's published schematics ?
In his 5th edition book, Self praised the White follower. Its default of having a low PSRR (my simulation shows about 30 dB for single transistors and 50 dB for Szilkai pairs) can probably adequately got around using a clean power supply and/or a lot of low frequency NFB. What do you think ?
Hi Lumba Ogir,
Could you tell what are the negative factors as the positive ones are already known ?
Lovely amplifier... awsome circuit solutions, interesting protection
Nice bootstrapp uncalibrated...there are several interesting solutions applied.
I will assemble.... will be the next to be tweaked for sonics.
This one is a promisse of high quality, excelency in measurements, for sure..we gonna see the sonics.
thank you Geirin.
regards,
Carlos
Nice bootstrapp uncalibrated...there are several interesting solutions applied.
I will assemble.... will be the next to be tweaked for sonics.
This one is a promisse of high quality, excelency in measurements, for sure..we gonna see the sonics.
thank you Geirin.
regards,
Carlos
Attachments
Yes...i am already using the Dx Amplifier output into the simulator
I felt in love by this circuit...it looks better than mine.... maybe will sound better, and this i want to know.
If really sounded better..hehehehe..new Dx will born..will be Grundig by Dx.... Grundex!... will migrate from Aksadex to Grundex..ahahahahahah!
Interesting solutions applied, double bootstrapp, but with different values related positive and negative side...this may be because selecting harmonic distortions to fell into nicer frequencies.....well, there are a lot of things i loved in this unit.
Passion..... i will try to find this unit in Brasil.... i would like to buy the unit.... i think this amplifier is impeccable.... about the sound..only listening and tweaking.
regards,
Carlos
I felt in love by this circuit...it looks better than mine.... maybe will sound better, and this i want to know.
If really sounded better..hehehehe..new Dx will born..will be Grundig by Dx.... Grundex!... will migrate from Aksadex to Grundex..ahahahahahah!
Interesting solutions applied, double bootstrapp, but with different values related positive and negative side...this may be because selecting harmonic distortions to fell into nicer frequencies.....well, there are a lot of things i loved in this unit.
Passion..... i will try to find this unit in Brasil.... i would like to buy the unit.... i think this amplifier is impeccable.... about the sound..only listening and tweaking.
regards,
Carlos
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