B1 Buffer Preamp

[mantisory]

Since I was too late to buy the board (oops!) I decided to build it p2p.
Lesson learned - don't attempt p2p layout/soldering when dog tired - mistakes abound, and i have given up for tonite!

Byron

 

[merlin2069er]

Oops, I didn't match any of my LSK170's.

Will that be a problem?

 

[AndrewT]

Hi,
the sk170s don't need to be matched in that they do not form a balanced LTP stage.
However, it seems that much of the reported excellent performance comes from operating the stages at the correct Id and this requires that the CCS allows the upper device to stay within it's optimum range.
Some minor tuning of the lower CCS resistor could bring the upper device back to it's sweet spot.

The easy way is to select sk170s that are close to each other to get what Pass is recommending.

 

[merlin2069er]

Ok, thanks.

I ordered my parts before a pcb board was available (and overpaid for my jfets - but i did get a few a free samples from linear).

I'll get it working before I decide to get some matched jfets from NP.

 

[BradJudy]

I finally finished hooking up my B1 and everything seems to be working well.

Pretty standard stuff. The extra switch in the back is for a home theater by-pass (yes, I know the switch is overkill, but it was sitting in my parts bin and made for clean wiring).

 

[Melon Head]

Great to see you have completed yours. I am still half way done.
Anyway what are your initial impressions on how it performs?
What were you using beforoe the B1 and how does it compare?

 

[Salas]

I know its for main system use, but because its easy and cheap to make, I report that it helps a lot in my PC too when I don't need it for other checks. Because its unity gain, I push the digital faders near max, hence not losing bits, and control nicely the active sub and sat PC speaker combo. Along with a listening position EQ with my calibrated mic and ARTA, it gives good quality for near field listening of all the stuff that can go on in a PC. I.e. Everything. Recommended use.

 

[mantisory]

Hi Nelson,
Is there any word on when the next batch of boards will be available?
thanks,
Byron

 

[BradJudy]

Great to see you have completed yours. I am still half way done.
Anyway what are your initial impressions on how it performs?
What were you using beforoe the B1 and how does it compare?

I'm not a good basis for comparison since it's really my first dedicated two channel pre-amp. At the moment, it's in front of a Trends TA-10.1 (the Trends has internal jumpers to by-pass the built-in pot).

It's sounding clear and detailed to me.

 

[merlin2069er]

I was at a couple of electronic surplus shops this past weekend looking for a couple of 18v dc walwarts, but came up empty handed.

They had plenty of 24v ones for about ~ $9. But I figured I should look further.

I'll check ebay for a pair...

 

[Zen Mod]

I was at a couple of electronic surplus shops this past weekend looking for a couple of 18v dc walwarts, but came up empty handed.

They had plenty of 24v ones for about ~ $9. But I figured I should look further.

I'll check ebay for a pair...

why don't you use 24V , with any 3-legged reg chip ?

 

[Magura]

why don't you use 24V , with any 3-legged reg chip ?

It might even turn out to be better


Magura

 

[merlin2069er]

I could do that...

but I found this on ebay.
18v dc adapter

That should be sufficient.

 

[dejanm]

merlin,

there is a guy on this forum (actually he posted it in this post only a couple of pages before this one) who measured distorsion depending on the value of this voltage. According to his measurement you get better distorsion value with 25 V than with 18V ... So do not be afraid ...

 

[sandyhooker]

LSK389 suitability

I have 4 LSK389A devices which are listed as IDSS 2.5- 6.5.Are these suitable for the B1 ??? Or am I better with matched 2sk170BL???

 

[AndrewT]

Hi Sandy,
you will need to measure all eight FETs in those 389s.
The B1 does not need exactly matched FETs, but close Idss is desirable.
If you find that all your 389s are at the top end of the A grade range then they will work in the B1.

The big and only advantage of the 389 is the thermal coupling.
It is a waste to use these pairs for this B1 duty.

 

[sandstorm33]

Hi Sandy,
.
It is a waste to use these pairs for this B1 duty.

Thanks Andrew.....Too bad I did'nt request the "B" variety from Linear Systems. I will order matched 170's from Tech-DIY.


JTP

 

[Zen Mod]

Poor Serbian Man B1

Thanks Andrew.....Too bad I did'nt request the "B" variety from Linear Systems. I will order matched 170's from Tech-DIY.


JTP

you can try this

 

[Babowana]

If you find that all your 389s are at the top end of the A grade range then they will work in the B1.

Otherwise no work? Why not?


>> <<

 

[AndrewT]

Why not?

because the designer says to use BL grade.