Phase inversion for Push Pull in this Hammond Pre amp

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scott2000

scott2000

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Trying to learn ......  ;D


Looking at this Hammond Pre amp, as a push pull  ....if the high impedance input is grounded when not in use, how would that 6SJ7 receive its inverted signal??


Does the inversion come from the cathodes being tied to ground and that is the signal reference???? Or, am I just too lost in the theory behind it and there isn't anything like this happening in the unbalanced scenario???

I know screen grids can do this but, I'm not sure if that's the case here????



I really would appreciate any insight.... or extra thoughts...... I'm just not getting it ......


Thanks!

 

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Thanks so much!!!

So looking at the 6sj7 screen grids that are coupled, what is the purpose of this? Why would a signal be coupled here?? I understand the screen grid voltage somewhat in relation to the plate and control grid but, I don't understand what this coupling part is doing???????

Is it sending an inverted signal to the screen grid of 6sj7 that has it's control grid grounded and how would it affect it's output and  phase in relation to the 6sj7 receiving it's control grid signal from the source???????

I hope this makes sense...

I really appreciate the help!!

 
scott2000 said:
Thanks so much!!!

So looking at the 6sj7 screen grids that are coupled, what is the purpose of this? Why would a signal be coupled here?? I understand the screen grid voltage somewhat in relation to the plate and control grid but, I don't understand what this coupling part is doing???????
Click to expand...
Look with sharp eyes; screens are tied to cathodes. Capacitors C1 & C3 are just treble-bleed.
 
?

I may have this wrong or not understanding but, c1 and3 are from G3??? I was talking about c9 I think it says.....The G2s are coupled? 

I'm just curious , because I read that the signals there at g2 are out of phase with control grids and just a bit smaller than the plate output, what is going on there??

And what affect the g2 plate resistor values have in this scenario with the single ended set up to push pull 6sn7.........

and what increasing or decreasing those resistor values would have because of the way they are coupled....Does it mess with the 6sj7 who's control grid is grounded differently than it would the other's????

I noticed the schematic looks like it has numbered the cathode and suppressor screen  backwards too......... but I'm talking about pins 6???

I removed some of the drawing to better explain how I'm looking at it.....

Thanks !!

 
scott2000 said:
I may have this wrong or not understanding but, c1 and3 are from G3???
Click to expand...
Well, you mentioned screen grids... C1 & C3 (missing in the 2nd schemo) are treble-bleed caps connected between G1 and K; since screens (G3) are connected to K, there is indeed a connection of these caps to teh screens.

  I was talking about c9 I think it says.....
Click to expand...
C9 is the coupling cap to G1 of V4.

The G2s are coupled? 
Click to expand...
Since only V1 and V2 have active G2's (V4 doesn't count cause triode connected), I surmise you mean C4.

I'm just curious , because I read that the signals there at g2 are out of phase with control grids and just a bit smaller than the plate output
Click to expand...
That's right...

what is going on there??
Click to expand...
...by coupling them together, the effect of variations are eliminated, since they are out-of-phase, which linearize their operation.

And what affect the g2 plate resistor values have in this scenario with the single ended set up to push pull 6sn7.........
Click to expand...
Please rephrase. What is a "g2 plate resistor"? What is a "single ended set up to push pull"?

Does it mess with the 6sj7 who's control grid is grounded differently than it would the other's????
Click to expand...
Both 6SJ7 have identical bias. Do you mean the 6J7? Please be accurate.

I noticed the schematic looks like it has numbered the cathode and suppressor screen  backwards too...
Click to expand...
That's correct.
 
abbey road d enfer said:
abbey road d enfer said:
C9 is the coupling cap to G1 of V4.
Click to expand...

Sorry.... I meant C4....I'm just looking at the input section before it heads out to the vibrato......

abbey road d enfer said:
  Since only V1 and V2 have active G2's  I surmise you mean C4.

...by coupling them together, the effect of variations are eliminated, since they are out-of-phase, which linearize their operation.
Click to expand...

Neat...Thanks!!....

abbey road d enfer said:
What is a "g2 plate resistor"
Click to expand...


Sorry...,,I meant the G2 resistors...... I was curious if changing the values here would affect anything other than gain because of the way one of the 6sj7 has  it's control grid grounded........and the screens from both 6sj7s are coupled

abbey road d enfer said:
What is a "single ended set up to push pull"?
Click to expand...

I don't know.... lol...... Sorry.... I was looking at the 6SN7 as push pull sort of...... if the transformer was 2 secondaries and center tap..... Forget I asked....... I'm just confusing matters more than I can explain my way out of.....

abbey road d enfer said:
Both 6SJ7 have identical bias. Do you mean the 6J7?
Click to expand...

I was just asking about the 6sj7s.....my main question was to find out what affect changing the G2 resistor values would have outside of gain..... I was just confused because it doesn't make sense to me how a tube (6sj7) with it's control grid getting it's signal from ground wouldn't be affected in other ways because of the G2 coupling.......like messing with the inversion in respect to the other 6sj7 .....Just trying to learn..and you answered my question.......

.Sorry for the confusion and thanks again!!! I'll make sure I get a few more slugs of coffee in before I try to ask in the future..... :)
Click to expand...
 
scott2000 said:
Sorry...,,I meant the G2 resistors...... I was curious if changing the values here would affect anything other than gain because of the way one of the 6sj7 has  it's control grid grounded...
Click to expand...
No, the fact that the Hi-Z input is grounded does not change the operation of the LTP.

I don't know.... lol...... Sorry.... I was looking at the 6SN7 as push pull sort of...
Click to expand...
Not "sort of", it's a real push-pull stage.

I was just asking about the 6sj7s.....my main question was to find out what affect changing the G2 resistor values would have outside of gain.
Click to expand...
Actually, the gain change is minimal. Altering the G2 resistors have some effect on distortion and headroom, but it's an undocumented effect, so, if you want to know, you have to make a test jig and experiment.
 

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