Working on understanding my valvecaster project. It's operating at 12 volts with a 7812 regulator. Other than the regulator it is currently stock.
Wondering what gives with pin #6? It ranges from 4-6 volts dependent on what 12AU7 tube I am using. "Healthy and Suggested" readings are in the 8 volt range. What gives?
Here are the pins:
1 3.12
2 -0.38
3 0
4 0
5 11.89
6 4
7 -0.28
8 0
9 5.94
I am a noob and could really use some knowledge.
Also any ideas on how to lower the noise floor? And to reduce farty bass. I have tried cathode cap in parallel, and lowering cap to grid to .022uf
Thanks in advance.
Can't see the schematic.
Pin 1 is plate, shouldn't this be close to the V+ supply voltage ?
Pin 6 is also a plate [anode of the second triode].
there is most likkely a miswire...
Adressing the noise floor after the tube is biased is suggested.
As far as bass mud, a triode like the 12a_7 @ such a small voltage potential may have troubles producing linear bass response.
Thank you so much for your time. I am unsure why the readings on the plates are so far a away from V+ value of 12 volts. The resistors present are 220K plate 1, and 100K to plate 2.
Here's the schematic I was using from BA.....
http://www.diystompboxes.com/smfforum/index.php?topic=63479.msg500470#msg500470
Could it just be bread board anomaly????????
> ranges from 4-6 volts dependent on what 12AU7
Yes. A well-fed tube circuit's plate will vary +/-20%. This under-fed 12V scheme is even more likely to vary. 2V-3V would be wrong; 4V-6V seems acceptable to me.
You could try reducing R3 to 50K.
> why the readings on the plates are so far a away from V+ value of 12 volts.
That's the supply voltage. The tube and the plate resistor tug-of-war against each other. As a general thing, the plate should sit at "about half" of supply, 1/3rd to 2/3rd, or 4V to 8V in a 12V system. To get large gain on very small signals, you give the tube the short end of the rope, 1/4 to 1/2 or 3V in a 12V system; that's how the first tube runs when gain pot is full-short. If you watch while you dial some resistance into VR1, the plate voltage rises from 3V to 6V, 8V, or maybe more.
> lower the noise floor?
It should not have excess hiss, just a normal tube (which is comparable to a TL072 like we use everywhere). It IS a HIGH-gain circuit so any noise will be loud.
Thanks so much! I felt my brain getting bigger. Oh wait! That was just happiness that it is within characteristic. Fun circuit with a simple soul!!!!!