split load vs this idea

[uneumann]

However, this idea brings yet another question....i said 500k pot because it more closely mimics the 220k plus the 100k. But any reason a 1M pot might be better considering that right now with the total of 320k i'm really liking the tone as is?

The difference in circuit behavior due to pot resistance 500k vs 1M will be minimal. There is nothing magic about the values in my example - they're just examples. Sure use a pot to dial in the behavior you prefer.

There is another stage coupling option you mentioned in the thread title - the split load resistor. I added it in the figure below to round out the discussion. In case E, the gain is reduced again - this time due to the split load divider. The difference is that the split load resistor lowers the stage output impedance, while the series resistors in cases C and D increase the effective stage output impedance. This impacts the overdrive character of the second (right) tube. Lower drive impedance rounds (softens) clipping on positive signal swings. You may like it or not, but it makes a difference. This Low-Impedance Overdrive (LIO) coupling to an overdriven stage is relatively rare, but you may want to try it if you're open to something different. I've used LIO variants in several amps with good results.

[daz]

Then again, I think what you are experiencing may not be blocking distortion at all because you report that it's affecting the top end. Blocking is a consequence of capacitor loading and manifests to a much greater degree in the LF. It usually sounds like a mushy clamping of the signal and/or a choppy sort of cut off. Some ugliness in the top end wouldn't lead me to suspect blocking distortion.

No, it's just semantics. You can't really base it on what someone;s description of tone is because words are a poor substitute for hearing. Your description is more accurate so i believe it;s blocking. Plus i know it was because with the gain on 10 before i changed the values it was locking to the point of the signal cutting out completely. And yes, circuit D.

I tried 2 pots just now, a 1M then a 400k. (yes, 400....a 500k pot that measures low) The I like the ability to tweak it, and in some cases, i believe with the 1M pot, i had a better clean tone when i rolled the guitar back. That is, it retained a more percussive attack than usual with a strats bridge/middle quack position which i like. But the on 10 gain tone was sacrificed and sounded a bit too spiky. In fact, neither pot gave me as good a full on gain the as the 220k and 100k resistors did. Thats of course speaks to you twin pots idea. But i really don't want to complicate things that much. I'll play with this for a bit and see how i feel once fully used to it, then go back to the set resistors and see if they indeed sound better. I think they did tho, and if so that might also speak to the notion there IS a difference with the resistor before the cap.

EDIT: just realized D is not quite right....i have a 47k grid blocker so the 220k doesn't go directly to the grid but to the other end of the 47k.

[daz]

One reason i didn't use a split load (i DID however try it but they never seem to sound good to me) is because you can't have the series resistor from plate to cap as big as i wanted without increasing the overall plate load. In your example there are 2 100k's, but what if i want to retain 100k plate load? I first had a 470k in series with the cap, so i;d have had to have a huge plate load to do that and i like 100k for the plate. When i tried it i used two 100k's like your example i didn't like it.

The difference in circuit behavior due to pot resistance 500k vs 1M will be minimal. There is nothing magic about the values in my example - they're just examples. Sure use a pot to dial in the behavior you prefer.

There is another stage coupling option you mentioned in the thread title - the split load resistor. I added it in the figure below to round out the discussion. In case E, the gain is reduced again - this time due to the split load divider. The difference is that the split load resistor lowers the stage output impedance, while the series resistors in cases C and D increase the effective stage output impedance. This impacts the overdrive character of the second (right) tube. Lower drive impedance rounds (softens) clipping on positive signal swings. You may like it or not, but it makes a difference. This Low-Impedance Overdrive (LIO) coupling to an overdriven stage is relatively rare, but you may want to try it if you're open to something different. I've used LIO variants in several amps with good results.

[ATTACH=CONFIG]40916[/ATTACH]

[Dave H]

...i like 100k for the plate. When i tried it i used two 100k's like your example i didn't like it.

To retain the 100k plate load with a split load the two resistors should add up to 100k so you would use two 51k resistors. You could leave the plate load as a single 100k and just disconnect the cathode bypass capacitor. The attenuation will be about the same.

[daz]

To retain the 100k plate load with a split load the two resistors should add up to 100k so you would use two 51k resistors. You could leave the plate load as a single 100k and just disconnect the cathode bypass capacitor. The attenuation will be about the same.

I know that, but as i said if i retain 100k for the plate load split or not, i can't have more than 100k for the series R coming off the plate to the coupling cap. In other words, no way for that series resistance to the cap to b for example 220k while retaining a 100k plate load. As for removing the cathode cap, no way. I long ago came to use .68uf/1.5k for the cathodes and nothing else is quite satisfying regardless of the rest of the circuit. But more than that, no cap at all just destroys the tone and makes the amp unusable for my tastes. And while there may be ways to counter that, now we're talking about redesigning the entire circuit and i don't wanna go there. What i'm doing right now is fine tuning a area that was good as it was but just experimenting out of curiosity because the values i had might not be as optimal to my ear as i thought. Turns out tho it's looking more and more like they were, but i'm still playing with it.

[Dave H]

I know that, but as i said if i retain 100k for the plate load split or not, i can't have more than 100k for the series R coming off the plate to the coupling cap. In other words, no way for that series resistance to the cap to b for example 220k while retaining a 100k plate load.

As for removing the cathode cap, no way. I long ago came to use .68uf/1.5k for the cathodes and nothing else is quite satisfying

You could have more than 100k. For example use circuit B) with a 51k/51k split load and make the 100k in series with the grid 470k which will make it -3dB at about 3.5kHz if that's what you need.

Well, I didn't know you had a 0.68u cathode cap because we don't have your schematic so I was working with the 25u on uneumann's schematics which gives a flat frequency response.