| Romy the Cat wrote:|
There is no aspects of minimization
of the inductor size. You can go to 30K, or 50K, or 100K input LPAD. The LPAD (which
is not inductive switched attenuators with good resistors) anyhow sites behind
the filter, so the input impedance of the attenuators will be “visible” by
other channels only at HF, so the value of the attenuators is semi-irrelevant.
The reasons why I went with 20K is because I would like to keep the value of
the resistors that formed the attenuators lower. If I use S102 resistors that
have no inductance of any kind then the value of the resistors would be absolutely
irrelevant. I use very good resistors for attenuator (RN/CMF55/60), they are
metal film and non-indicative but they still have “some” residual inductance
and my presumption was that higher value the more inductance. I warn you that
this is such an irrelevant minor thins that we can talk about it but I very
confident that it has no practical impact to the sound you will get out of it.
So, in term of the input attenuators for HF you can do anything you want.
Thanks Romy, that is just the information I was after.
I am planning to add an extra power supply just to run the DHT channel. In the course of things this lets me scale down the power transformer and choke for the first stages of Channels A, B, C (that choke is a monster!) and it eliminates the 56R resistor on the DHT B+ which may or may not be affecting things.
Also I am scaling down the power transformer for the second stages of Channels A, B, C to roughly half of the specified current rating. I have a feeling that that trafo is rated 3A because at the beginning of the 6-Channel project there was the potential for 6 x 6C33C, but in the course of development that is now reduced to three. The smaller power transformer should operate closer to its nominal voltage rating as a result and the chokes that follow will probably operate closer to their rating as well.