astrodt wrote:Trying to work carefully, I did the "ohm it out" checks from the manual. Shouldn't the J6 and J7 pin 1 resistance measurements be more like 517k ohms? (the series of R2+R4 or R1+R3) The manual says it should be >10M ohm.
Nice catch! You are correct, sir. Starting with the new Rev D, I've removed the DC blocking cap, which would have made it appear as an open. Thanks for the heads up.
astrodt wrote:Also, the board has some un-utilized features (or anachronisms):
C14/R48 and C15/R47 are not required, but would seem to be an RC from the plates of V1 to ground. Under what circumstances would these components be included and to what benefit?
This is an undocumented low pass filter that is new to the Rev D. I have plans to use it in an officially released triode design, but haven't messed with it yet.
astrodt wrote:What is the purpose of the three holes under R20/R21, R17/R18, R23/R24 and R26/R27?
These are also an undocumented footprint for a CCS, like a LM317. We were just talking about this in an earlier thread, if interested.
astrodt wrote:If there are potential uses to these, perhaps they could be mentioned in the "Modifications" section of the manual.
The difference between 'undocumented' and 'modification', is a lot of testing. I want to make sure that a certain mod is worthwhile (and actually works). Personally, I'm still trying to grasp what makes a good trioded EL84 amp. Also, I need to see if the CCS method is useful in an ultralinear mode.
astrodt wrote:Thanks, this is an excellent product and I'm having great fun putting it together!
- Andy
Andy, thanks for the praise. This is a great hobby!
Shannon
