Dr nEon
Well-known member
Hi folks..
I have a Soundcraft question which I can't find the answer to anywhere, despite endless googling...
In the Soundcraft 2400 circuit (and other related models), there are little 100pF ceramics in the transistor buffers within the EQ circuit, between collector and base - these are the Cdom or miller caps, right? In my desk, these are all orange tipped ceramic plate types, meaning that they have a negative tempco, N150.
On one of my spare channels, I noticed that one of these ceramics is physically cracked in half , and I need to replace it. So my question is, is it OK in this circuit to replace it with a modern little multilayer c0g type, or must it be N150?
This has got me thinking...there are other ceramics elsewhere in the channels that are black tipped NP0 , but always, in these buffers, are the N150 type. So why would that be? I've read about how negative tempco types are sometimes utilised to take advantage of the neg temp effect, stabilising RF and IF stages, tuned circuits for drift etc... up in radio land. Would Soundcraft have particularly specified the use of N150 types for this reason, or is it more likely that they used them because they were close to 'ideal' , and dirt cheap?
I'd be interested to hear some opinions from some of you gurus as to whether I can ignore the tempco spec.
Cheers,
nEon.
I have a Soundcraft question which I can't find the answer to anywhere, despite endless googling...
In the Soundcraft 2400 circuit (and other related models), there are little 100pF ceramics in the transistor buffers within the EQ circuit, between collector and base - these are the Cdom or miller caps, right? In my desk, these are all orange tipped ceramic plate types, meaning that they have a negative tempco, N150.
On one of my spare channels, I noticed that one of these ceramics is physically cracked in half , and I need to replace it. So my question is, is it OK in this circuit to replace it with a modern little multilayer c0g type, or must it be N150?
This has got me thinking...there are other ceramics elsewhere in the channels that are black tipped NP0 , but always, in these buffers, are the N150 type. So why would that be? I've read about how negative tempco types are sometimes utilised to take advantage of the neg temp effect, stabilising RF and IF stages, tuned circuits for drift etc... up in radio land. Would Soundcraft have particularly specified the use of N150 types for this reason, or is it more likely that they used them because they were close to 'ideal' , and dirt cheap?
I'd be interested to hear some opinions from some of you gurus as to whether I can ignore the tempco spec.
Cheers,
nEon.
