Critique My Schematic

[lowell]

ok huh... I'm downloading switcher cad... I have ltspice but not switchercad. I'll run the simulation too and see what happens.

How do you think it could be that the 4v after the first gain stage becomes 800mv after the tone stack? Does the tone stack drop that much voltage??

[Suusi M]

ok huh... I'm downloading switcher cad... I have ltspice but not switchercad. I'll run the simulation too and see what happens.

How do you think it could be that the 4v after the first gain stage becomes 800mv after the tone stack? Does the tone stack drop that much voltage??

yep -

if you go to to the valves and tubes section you will get my version of the koren tubes libruary http://groups.yahoo.com/group/LTspice/

I can email you a copy of the pots lib and push pull transformers libs as well if that helps

[lowell]

yes please email me those that'd be great... any chance you have an input jack and dpdt switch symbol as well? I cannot figure out how to incorporate my own symbols. Well I drew them and added nodes but when I run the simulation it says "cannot find these schematics - input_jack and dpdt"

[lowell]

Hi can someone help w/ this? I've made some symbols/components and added nodes to them and inserted them into the schem... they are the dpdt and input jack symbols. I get that error message though when I "run" the simulation. I must be missing a step or doing something in the wrong order.

[Suusi M]

Hi can someone help w/ this? I've made some symbols/components and added nodes to them and inserted them into the schem... they are the dpdt and input jack symbols. I get that error message though when I "run" the simulation. I must be missing a step or doing something in the wrong order.

email them to me and I will see if I can fix them

[lowell]

Ok here's an updated schem of this amp. I'm wondering if the 1k splitter resistors after the PI coupling caps are the correct value to split the signal so the 6V6 and 6L6 signals are separate.

[lowell]

[*]As a general rule noise is proportional to gain and temperature. 12AX7's use hum canceling heater windings so by doubling the overdrive valves is probably adding something called shott noise[/LIST]

Thanks for the input!

So you think parallel triodes cause MORE noise? The stage is VERY quiet to me. With gain and vol cranked there's NO hum, but there IS decent amount of "hiss" or airy noise. Is that shot noise and do you think it'd be reduced w/o parallel triodes?

[mooreamps]

So you think parallel triodes cause MORE noise? The stage is VERY quiet to me. With gain and vol cranked there's NO hum, but there IS decent amount of "hiss" or airy noise. Is that shot noise and do you think it'd be reduced w/o parallel triodes?

No. The hiss content is generated by the cathode resistor. I know this because I just finished writing a paper on it. I can be reduced, in this application, two ways.

1. replace with low noise metal film resistor
2. switch to fixed bias in the pre-amp.

-g

[lowell]

cool! I'll try 1watt mf resistors and report back. Also, here's an updated schem if anyone's interested.

[mooreamps]

cool! I'll try 1watt mf resistors and report back. Also, here's an updated schem if anyone's interested.

1/4 watt is fine.


-g

[mooreamps]

cool! I'll try 1watt mf resistors and report back. Also, here's an updated schem if anyone's interested.

1/4 watt is fine.


-g

[lowell]

Ok guys so here's an updated schem of this amp. I'm having trouble w/ the 2nd stage of the OD. I get 10v of signal out of the plate of V4 but the grid of V2 clips hard at 5v of signal with the gain cranked. I've tried up 13k on cathode of V2 w/ no change. Well the cathode voltage goes up to 4.5v w/ 13k but the clipping remains at that point. I thought that maybe the Ra of V4 was too low and the plate supply was clipping but obviously its not if the plate signal after the coupling cap is 10v. Can someone shed some light on what I'm missing here? I'd like for it not to clip that early on the grid of V2. FYI the negative portion of the signal is fine - no clipping. Oh and V4's plate is at 240vdc and V2's at 260vdc.