Steve Bench's tube crossover - Help needed.

[dipp]

Steve Bench's tube crossover is said to be good sounding and I want to build it.
But how to scale the resistors R4, 5, 6, 9, 10, 11 and 12 for 500 HZ?
I think the caps. are the same as in the 800 HZ schematic.
Can anybody help me with this?

[mashaffer]

The 400 and 800 hz use the same cap values so I would just interpolate the values for the resistors and then check using the spice program of your choice. You can tweak as needed in Spice to get the precise response that you want.

The interpolation factor is 22% so chose values 22% of the way between the 400Hz values and the 850Hz values.

[dipp]

I have tried to estimate, but do not find the interpolation factor to be constant.
Spice is unknown to me. I have been building many amplifiers etc. from schematics, but my theoretical knowledge is very limited. So here it stops.
Still have a hope to avoid spending $4000 on a Marchand crossover.
Anyway all replies are appreciated.

[mashaffer]

Not sure what you mean by inconsistent.

(500-400)/(850-400) = 0.22

R4:
182-(0.22*(182-84.5)) = 160.55k
R5,6:
200-(0.22*(200-93.1)) = 176.5k
R9:
174-(0.22*(174-82.5)) = 153.9k
R10:
36.5-(0.22*(36.5-16.9)) = 32.2k
R11,12:
2.7-(0.22*(2.7-1.2)) = 2.37M

[dipp]

Thank you Mike, I should be able to build the crossover now.
Not quite sure how to balance/attenuate HF-LF.
Is it ok to replace the 1Mohm paralell input resistors with 1Mohm attenuators/potmeters?

[mashaffer]

I would buffer any level controls with a CF to insure that the curves are not distorted by the gain setting or better yet put the gain controls in the following PA section.

[dipp]

Good you mention this as I don't want to introduce distortion.
It's a problem that the schematics I have seen are missing attenuators which should be a natural part of a crossover. I purchased the TCJ Filter Program, but not even there is an attenuator circuit shown.
I have no idea how this shall be done, can you explain?

[Cale06]

You could replace R8 and R14 with pots for separate high and low frequency volume attenuation.

[dipp]

Originally Posted by mashaffer

I would buffer any level controls with a CF to insure that the curves are not distorted by the gain setting or better yet put the gain controls in the following PA section.

What is a CF?
May be it is better that I make a buffered 12dB 500HZ Linkwitz-Riley filter with TCJ Filter Designer.
It suits my Altec Voice of the Theatre better.
Will the signal be attenuated without deterioration with that buffer stage ?

I am now also thinking about making a new tube line amp integrated with a tube crossover.

Any opinions/suggestions?

[dipp]

Originally Posted by Cale06

You could replace R8 and R14 with pots for separate high and low frequency volume attenuation.

Easy solution, but are you sure it doesn't deteriorate the signal.