MUFF WIGGLER Forum Index
 FAQ & Terms of UseFAQ & Terms Of Use   Wiggler RadioMW Radio   Muff Wiggler TwitterTwitter   Support the site @ PatreonPatreon 
 SearchSearch   RegisterSign up   Log inLog in 
WIGGLING 'LITE' IN GUEST MODE

Why no contact with the temp-co?
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Author Why no contact with the temp-co?
terjewinther
This is probably a question for a more general group, but I noticed in both some Oakley projects as well as in some older synths that sometimes the temp-co resistor is not in physical contact with the exponential converter components (with usually are either an op-amp or some dual-transistor arrangement). I thought the reason for using the temp-co was to gradually change resistance according to the internal heat of the amplifying components. Granted, general external heat will be reflected by the temp-co, but is that enough?
If anyone can explain this, or point me to a good net explanation, it would be appreciated. (No, really, I have tried searching Google).
Synthbuilder
terjewinther wrote:
... I noticed in both some Oakley projects as well as in some older synths that sometimes the temp-co resistor is not in physical contact with the exponential converter components

The best place for the temp co is as you rightly point out is in contact with the transistor pair. Indeed, all three components should be at the same temperature.

In more sensitive modules like the VCOs I will strive to make this so, but for things like filters and EGs then it is less important. This means we can get away with a cheaper temp co resistor, like the 3000ppm/K ones I use, and not have it physically stuck to the transistor pair. It is very likely that the area around the three components will be roughly the same temperature since the board in which they are mounted is usually in an enclosed box.

Tony
terjewinther
Good point!
kecked
Any reason not to mount the tempco resistor on top of the transistor pair? Doing the svf and I heat shrink the transistors together so I could glue the tempco to the top of the joined transistors but it would mean adding leads back to the holes for the resistor. Would the leads be more of a liability than I gain by doing this?
terjewinther
I think this would be an ok solution. I have seen lots of modifications to older synth were exactly this have been done.
But usually this only applies to VCOs and not filters and such, as see Tony´s comment above.

kecked wrote:
Any reason not to mount the tempco resistor on top of the transistor pair? Doing the svf and I heat shrink the transistors together so I could glue the tempco to the top of the joined transistors but it would mean adding leads back to the holes for the resistor. Would the leads be more of a liability than I gain by doing this?
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Page 1 of 1
Powered by phpBB © phpBB Group