Sprague Disc Caps - Problems ?? Poor Quality ??

['67_Plexi]

I've had a batch of Sprague 1000V disc caps recently that start out fine and after about an hour start leaking DC. This is evident because the volume and treble pots become scratchy. Measuring on the DC blocked side, I'm getting between 150 and 300mV DC, which is enough to create a harsh sounding amp. Somewhere between 5 and 20mV leakage is normal on a good quality cap used in a tonestack. If I replace with silver Micas the problem goes away.
I'm going to try some different disc caps, any recommendations ??

Anyone else had this problem ??

[Bob-I]

That's really odd. I use the cheepest garbage ceramics I can find and I've never had a leakage problem. I've had a few caps that went completley bad, shorted or open, but never more than a few mv leakage.

(Note to self:.... self... don't buy Strague ceramics.)

[Obelix]

Never tried silver micas or glass instead of ceramics
BTW, for sprague orange drops, serie 716P is round the half of THD of tthe 715Ps
non-Linearity in capas grows with value and requency...
it's due to the fact that the dielectric doesn't fully loads (or unloads) the capacitors at the frequency of the signal passing thru, so it's better to find the absorbing material with the lesser absorbing dielectric...

For small values, micas and glass are the bests, for higher values, oil, then teflon or polypropylens have the best results in audio...
For electrocchemics capas, prefer aluminium to tantalum...

[keithrick]

Obelix,

I think the ceramics in the tonestack add a little hair,fuzz and airiness that gives the tone a little horn or Sax type vibe. At least that is what my amp is saying it want to sounds like

If you think the treble cap is harsh place it on the switch like the pics Ayan posted, Scott (correct me if I'm wrong) has also suggested this in another post to add some hifi properties. I just implemented this in my amp last night, .002 treble on board and a 330pf on the mid switch and had a chance to turn it up a bit and I am liking the direction my tweaks are heading!

Never tried silver micas or glass instead of ceramics
BTW, for sprague orange drops, serie 716P is round the half of THD of tthe 715Ps
non-Linearity in capas grows with value and requency...
it's due to the fact that the dielectric doesn't fully loads (or unloads) the capacitors at the frequency of the signal passing thru, so it's better to find the absorbing material with the lesser absorbing dielectric...

For small values, micas and glass are the bests, for higher values, oil, then teflon or polypropylens have the best results in audio...
For electrocchemics capas, prefer aluminium to tantalum...