LSK pre - BAF 2013

[bern]

Thanks guys,
@ juma: Nice switches but I'm concerned about running long wires (possible noises) to the switch and back again.
@Itsmee: I think I found solution. I will try to buy on ebay/aliexpress NAIS (currently Pannasonic) MBB (Form D) TXD2-2M relay:
TXD2

 

[marconi118]

Hi Juma,
Thanks a lot for the great bjt cascode version implementation of the PASS BAF2013 LSK preamp.
I came up with an idea and hope that you do not mind my using photoshop to merge several of your schematics of LSK Preamp, F5 meets Buzquito and addition of 2x150R at (R23 & R24) for an integrated with no global NFB. Any comments or suggestions for a build with sk/sj pair at idss about 10ma?
Thanks in advance.

Was this setup ever tested or simulated?
It should be a killer amplifier?
Mosfet buffer output
No negative feedback
Jfet imput gain stage
Maybe slightly low damping factor
Kind of a Ba3 preamp on steroids?

 

[juma]

Yes, it was prototyped and tested as proof of concept, but it's far from final version - that one is not recommended to build

 

[marconi118]

Not recommended because it doesn't sound nice?
Is there a final version of this Amp with laterals PP buffer?

 

[juma]

No, it's just not finished - bias arrangement etc...

 

[marconi118]

Ofset is not stable as it is?
But maybe cap coupled output could be usable?

Hope to see updates soon 😀

 

[juma]

No updates for that one - it went into another direction...

 

[marconi118]

Do you have a post number of the last version schema?

 

[juma]

No, it's not meant for publishing

 

[qwertyl]

Not recommended because it doesn't sound nice?
Is there a final version of this Amp with laterals PP buffer?

Perhaps you could consider Cubie2 instead? It is absolutely brilliant little amp.

 

[marconi118]

Found your schema of post 118 with bjt and one on post
354

What performs better as CSS for the jfet input? The 1k 2w resistor?
The k309 jfet CCS or the one with LM317?

In general LM317 is not advised in audio circuits but maybe in this aplication it is good?

 

[juma]

if you know how and why LM317 is to be avoided than the rest should be easy...

 

[marconi118]

I don't know why it has to be avoided or not depending on the usage.
Maybe at low current it is fine but not at higher current?

Maybe you can enlight me?

 

[juma]

IME the LM317 makes a nice CCS - there was even a paper from Walt Jung about it.

Find it, read it, test it - or believe anything anyone writes on the internet...


just for the record:

 

[marconi118]

I am here to learn, will read the paper about the 317
It is difficult to distinguish between ral and fake info in the net.

Will give a try to the 317 ccs being temperature stable do avoid ofset drift.

Thanks a lot for all your advice

 

[marconi118]

Hi Juma I need some info about 2 preamps you designed
firs is one of the first BJT version of the LSK pre, as I understood it is a cascode
LSK pre - BAF 2013

the second is a version in preamp ideas for F5 tread post 53
Preamp ideas for F5

it is similar, with negative feedback but output BJTs are not cascoding? they are amplifying? it is more like an F5?

Does the first have lower output impedance?
Which one sounds best?

 

[juma]

yes
yes
yes
yes
post #485

 

[marconi118]

I really would like to avoid the complexity of #485 because of various reasons (time, transistor matching etc)
Therefore I would like to stay on the 4 transistor configuration, maybe just adding the LM317 or JFET CCS on the input stage.
Would you then advise to use the first or second topology I just posted?

 

[juma]

second

 

[marconi118]

since I mixed the links you mean the second schema the one without PSU regulators, the original LSK preamp with BJT output