wave said:Ahh I see now. So the pads marked with an "X" would need to be attached to the ground plane?
If this is the case then I think doing this board double sided would be fairly easy.
Dave
shabtek said:thats close--can that second pole be made available,
and an extra pad per throw--maybe a 3rd row of 0.1" to accommodate daisychaining resistors.
i like where this is going
wave said:Ahh I see now. So the pads marked with an "X" would need to be attached to the ground plane?
If this is the case then I think doing this board double sided would be fairly easy.
Dave
ruffrecords said:Turns out removing the ground plane and tracking the ground normally was quite easy. I even managed to get it on the same side of the PCB as all the other tracks so for home etchers it is a single sided PCB. Attached is a pic and here is a link to the zipped up Gerbers:
Cheers
Ian
shabtek said:can you add the grayhill boards to the group buy; I am in for several (grayhill boards)
shabtek said:can you add the grayhill boards to the group buy; I am in for several (grayhill boards)
ruffrecords said:Are you happy with the new layout??
I have also had a request to do a Lorlin version. Is that of interest to anyone?
Cheers
Ian
wave said:Also,
What inductors would I need to buy? Is it all dependent on how I would build the EQ? Are there any examples of what the different inductors would give me in each position?
DAve
ruffrecords said:...you wrote: ....
As you have discovered, the overall circuit impedance is the key to determining the size of inductors you need to obtain a given Q or bandwidth and the lower the circuit impedance the easier this gets which is one reason I suspect the original EQP1A works at 600 ohms. If people are going to drive this EQ from an op amp then that in itself should not be a problem but for a low cost tube mixer where you would want to perhaps drive it directly from a 10K fader your worst case source impedance is going to be 2.5K or more so you really don't want to load this with more than 10K which is exactly what the poor man's EQP1A tried to do. So if this EQ is going to be fairly universally applicable then that's probably where we need to stay. So yes, I agree with you we should aim fro a 10K bridging input impedance.
bruce0 said:ruffrecords said:...you wrote: ....
As you have discovered, the overall circuit impedance is the key to determining the size of inductors you need to obtain a given Q or bandwidth and the lower the circuit impedance the easier this gets which is one reason I suspect the original EQP1A works at 600 ohms. If people are going to drive this EQ from an op amp then that in itself should not be a problem but for a low cost tube mixer where you would want to perhaps drive it directly from a 10K fader your worst case source impedance is going to be 2.5K or more so you really don't want to load this with more than 10K which is exactly what the poor man's EQP1A tried to do. So if this EQ is going to be fairly universally applicable then that's probably where we need to stay. So yes, I agree with you we should aim fro a 10K bridging input impedance.
Ian:
Sorry I am confused by this, would you mind explaining how I think about overall circuit impedance? Is this the input impedance of the circuit (the input trafo or the input load resistor in parallel with the output impedance of the previous stage)? Or is this the load on the output of the passive circuit.
I am trying to get my head around these passive EQ circuits and would like to understand how these effect the EQ. I understand that the Q of the LC boost circuits is reduced as the impedance there is increased, does this also happen as the input impedance increases?
I have knocked together a point to point Pultec passive section to play around with and for the moment have driving it a really low impedance discrete op-amp based circuit that can drive pretty much any load. I put a load resistor across the input but am trying to understand the effect of that load and what load I should be putting there. On the output makeup gain stage I currently have a 10k load and a very high impedance op-amp input, but again I don't understand the implications of that, and what I should do there.
Any help on this would be appreciated, (I usually can pick things up but I am finding the passive circuits really befuddling)
bruno2000 said:Greetings Ian,
Do you have the Universal Passive EQ boards for sale?
Thanks!
Best,
Bruno2000
bruno2000 said:Greetings Ian,
What are the Carnhill part number(s) for the inductors?
Does ChrioN have these available as well?
Thanks!
Best,
Bruno2000
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