It seems the quad op-amp LME4974 used in Ballsie is replaced by a better spec LME49740. Will the new Ballsie kit come with this LME49740 instead?

I am interested to use this Ballsie board as a buffer after the Joshua Tree to drive amps (balanced input) with lower input impedance. When will the Ballsie kit be available again?

Thanks

Hi Brian,

It seems the new Ballsie Lite does not have buffered balanced output. Do I need to go for Ballsie instead?

Thanks

Hi Russ,

Sounds good, so when will the IVY II be available?

Btw, can Counterpoint be used for this buffer application as well?

Hi Russ,

Thanks for the recommendation.

So when using IVY as a JT buffer with unity gain, should I set R1-R4 to 750ohm, and use jumpers for R5-8 & R17-20? What value should I use for C1-C4?

Correct.

R1-4 750R
R5-8 Jumper
R17-20 omit
C1-4 Omit

The rest you can leave alone. :)

Cheers!
Russ

Hi Russ,

I see your point, thanks for the suggestion. (and also wonder if something like R1-4=2K, R5-8=1.24K might be even better ).

I am planning for compatability with other power amps of higher input impedance (e.g. >10K) as well. In those cases direct output from JT is feasible, but perhaps not as good as having IVY to drive a normal length cable (e.g. 1.5m).

Since you have already built and used an IVY buffer, I would like to hear your opinion if there is any noticeable (sound quality-wise) advantage to provide for an additional set of output from JT directly (for high input impedanance load), or I should just save the hassles and connect everything to the IVY buffer output.

Thanks

Russ,

I did some quick studies on the differential opamp in IVY, and found that while termination for the resistive JT output is not very important, assuming a balanced JT config with 750R each leg, perhaps the best value to use for R5-8 is around 750ohm, with the corresponding R1-4 set at around 1.5K for unity gain. Hope this is useful for sharing.

While I will likely adopt IVY as the JT output buffer, I have another requirement to find a good buffer for a source with a high 20K output impedance (again very much resistive like JT) on its +ve and -ve pins relative to ground. I wonder if I can still use IVY for this case, setting R5-8 to 20K and R1-4 to 40K. Do you think IVY is still very suitable or I may encounter noise problem using such high feedback resistance?

Thanks in advance for your advice.

For a high input impedance the best thing to do is to use an instrumentation amplifier in front of the OPA1632.

We have a board that does this. Its called "Mesh" but I don't think we have it for sale yet. I will see if we can rectify that. :)

Sure here is the schematic.

It's a multi-purpose board I created to use as a driver(including headphone amp) and an active filter. So it is marked with some spots as C/R. The reason is that those spots could either be a C or an R depending on if it is used for high or low pass filter. :)

In your case you would simply omit any filter caps and just set it for whatever gain you need.

It a sort of a hard thing to kit, because how you use it is completely up to the user. :)

But if you want a couple PCBs just let Brian know, and he can get you some.

Cheers!
Russ

Edited by user Friday, April 24, 2009 8:42:53 PM(UTC)  | Reason: Not specified

Sure LME49720 is probably what I would use, but there are lots of duals that would be just fine.

You can choose any value of RZ1/2 that suits your needs. I typically use 47K-100K. But you could even omit them if you want.

:)