[tranhieu]

Quote:

Or wait for LCDuino1 + δ1, which has constant input Z. 

Might be a bit off topic here, but when will the first batch come out? Hopefully by October?

 

[amb]

Quote:

 
Might be a bit off topic here, but when will the first batch come out? Hopefully by October?

Sorry, I can't promise a date, or even give an estimate.  But we are making every effort to make it as soon as possible, but no sooner than when we feel that it's ready.

 

[ujamerstand]

Take your time. 

 and please let us know when you need more people testing out the system. 

 

[Lil' Knight]

Well, if I want to go with the buffer solution, what'd be the simplest one that would do the job? I'd prefer the SS one, no more tube for me.

 

[amb]

 
Quote:

Well, if I want to go with the buffer solution, what'd be the simplest one that would do the job? I'd prefer the SS one, no more tube for me.

I would've recommended the JISBOS if there were any left, but not so.
 
An IC opamp wired as an unity-gain voltage follower would be the simplest solution, but consider this -- you're talking about the β22 here, which was deliberately designed to be all-discrete, fully-complementary, cascoded in every stage, etc., it just seems thematically wrong by adding such buffer circuitry into the path.  Not to mention that the signal would have to go through more electronics which isn't a good thing.  In effect, you're applying band-aids to make the JT work between your tube source and the β22, and the result is not exactly pretty.

 

[Lil' Knight]

Yes, I did think that the JISBOS is an option and sent GlassJar an email asking about the availability.
 
Would you say the JISBOS won't do any harm to the signal because it's totally discrete?

 

[amb]

Quote:

Would you say the JISBOS won't do any harm to the signal because it's totally discrete?

No, I wouldn't say that.  It's still extra circuitry, and there is no such thing as an active circuit that "does no harm", even though some come pretty close.  But why are you so hell-bent on using that JT?  Not that the JT is itself bad, but in this case the combination of your tube stage and the JT forces you to make unnecessary and undesirable compromises.
 
I say save the JT for another project, and use a 50K constant input-Z attenuator or pot here.

 

[bada bing]

 
Quote:

I would've recommended the JISBOS if there were any left, but not so.
 

 
Any chance there will be another run of boards of the last JISBO version ?
I for one would step up for 8 boards worth of a run.
 
I have a 4 board B22 with an original version 4 channel JT installed for volume control. I've been happy with it,
but knew of the variable & low input impedance from the beginning. I  don't have any sources that don't play
nice with it. It seems as though a set of JISBOS would be a worthwhile addition for someone like me who
already has the JT installed. There appear to be several potential wiring schemes that would add value and
there is no requirement that the JISBOS have to be used. Easy enough to wire buffered and unbuffered input jacks to
the JT. The JISBOS could also provide a buffered loop out as well impedance matching input for finicky sources.
It seems that by socketing R2 on the JISBOs, it would be possible to easily tune the load impedance seen by any source.
 
I'm seeing more advantages and less disadvantage with the JT + JISBO than a lot of the posts here imply.

 

 

[MisterX]

 
Quote:

 I for one would step up for 8 boards worth of a run.

 
8 is exactly how many I have left in my junk drawer, pm me your address and I will drop them in the mail for free.

 

[Lil' Knight]

Quote:

I say save the JT for another project, and use a 50K constant input-Z attenuator or pot here.

I will take your advice to save (or sell?) the JT for later use. Maybe after I change to a new source
 

 

[ujamerstand]

Hey, if you're still interested in getting the JT to produce a constant input z, here's how: jumper R2A/B, cut traces that links ground to pin 2 and 5 on the first relay, place R2A/B to where those connection would've been, and put a termination resistor between the output terminal and the ground. The value of the termination resistor is roughly the same as the desired input impedance. AMB describes the precise calculation here. Then voila, you should be getting constant Zi.

 

[Lil' Knight]

Interesting ...
 
So it means that the Zin is only affected by a resistor and I don't have to change all the remaining resistors?

 

[amb]

Quote:

So it means that the Zin is only affected by a resistor and I don't have to change all the remaining resistors?

No, all resistor values will have to change.

 

[ujamerstand]

Quote:

No, all resistor values will have to change.

Yep, but its a 20 dollars order shipped from mouser or digikey, so its not too bad, right?

 

[Lil' Knight]

Well, surely I don't mind about ordering new set of resistors.
 
ujamerstand, did you find a calculator somewhere?