Quick split-n-blend question

[HeavyFog]

So i'm planning on building a tube preamp for bass and i'd like to include a blend control. I know the signals need to be in phase with each other. The plan right now is to have tube preamp>buffer>baxandall tonestack. The tube circuit is very similar to the valvecaster and if i'm not mistaken the output signal of a valvecaster is non inverting. As for the buffer i have no idea. I'd like to have a buffer to keep the tube stage from loading down the tonestack (in place of a cathode follower). Can anyone recommend a simple non inverting buffer? Maybe i would be just fine without a buffer?

[HeavyFog]

Anyone?

[robthequiet]

Could you provide a link to the schematic?

Placing a Baxandall tonestack after a tube preamp does not seem so difficult. How you work the buffer into this is a bit of a question, thus a schematic would help to figure this out.

Here is a site you may have seen already:

https://web.archive.org/web/20090101102631/http://www.beavisaudio.com:80/Projects/ValveCaster/

[PRR]

> recommend a simple non inverting buffer?

Cathode follower?

> in place of a cathode follower

I must be missing a point.

[HeavyFog]

Sorry, maybe i didn't phrase my first post very well. My mistake.

The circuit i'm planning on using is a heavily modified valvecaster. Pretty much with same general design of a standard valvecaster but with cathode bypass caps, an interstage gain control, running at 120-130v, and without the standard valvecaster tone control. As for the tonestack i was planning on using a standard baxandall.

I want to make sure before i build it i would ike to make sure that when mix of the split-n-blend is set to blend both dry and affected signal that i don't get phase cancellation. I think what i should have said was a buffer that doesn't invert signal polarity instead of inverting.

Here's the link to the layout i plan on using
http://tagboardeffects.blogspot.ca/2012/02/split-n-blend.html
The link mentions that pedals like the tube screamer and dyna comp invert the polarity (phase) so i'd like to avoid having this happen. If I'm not mistaken the valvecaster shouldn't invert the phase nor should a passive tonestack like the baxandall.

As for a buffer it was recommended to me in order to fulfill the same role as a cathode follower in a tube amp right before a tonestack. I was told that it would be a general improvement. I know it would work without a buffer since i have built a valvecaster before with a tonestack before but would it really be a noticeable difference? If i do use a buffer i would like for it to be one that doesn't invert signal polarity so phase isn't an issue.

[robthequiet]

If you take your output from the cathode, you're in phase. If you take it from the plate, you're 180^o out of phase. A buffer may be regarded as a unity gain amp, so you're using a 0dB gain stage as an inverter. Why not? The tube experts on the forum can probably elucidate better than I, but a two-stage amp with first stage inverting then second stage inverting lands you in phase, no buffer required, as in the Valvecaster. Two stages would be useful if you need to overcome some drag in the tonestack. Just follow your circuit to determine what phase you end up with at the final output and use a switchable inverter on the blend circuit if you have to. Ultimately it's your ears that will tell you whether or not the sound is good.

I believe the Tweed Bassman and Vox AC-30 preamps might get the result you describe to some degree.

[robthequiet]

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