BOSOZ & ZEN V4 Transformers

[Brad Kizer]

I'm in the process of gathering parts for a BOSOZ and ZEN V4. In reading various posts it has been made clear that both of these designs are relatively insensitive to to a wide variety of rail voltages, within reason of course. *My question is what are the advantages and disadvantages of using transformers with higher voltage ratings vs lower in these two designs from a sonics standpoint?* The speakers I'm building for this project are Klipshorn-clone bass cabs with a different midrange and tweeter...8ohm and 100+ spl. Having owned a "real" pair of K-Horns in the past I found that 15 to 30 watts is plenty for my musical tastes.

Thanks,
Brad

[jh6you]

I would use the original rail voltages of Nelson Pass.
And, considering the speaker of 8 ohm 100+ spl, I would make 1.32 amp Zen V4, and adjust BOSOZ gain to 0dB. The original Pass articles give us detailed explanation about the 1.32 amp ZV4 and the gain control of BOSOZ.

[Roberto Amato]

Originally posted by Brad Kizer
*My question is what are the advantages and disadvantages of using transformers with higher voltage ratings vs lower in these two designs from a sonics standpoint?*
Thanks,
Brad

I could not comment on Zen V4 as I have no direct experience with it. But with the BOSOZ definately you hear more distortion with a lower supply rail... it also depends how MUCH lower. The gain (value of R15) of the BOSOZ also influences it's quality. The lower the gain the better the sound. Going from 16.5 db gain down to 10 (50v rails) as I recently did, polishes the sound a great deal. In case of BOSOZ I would go for the highest voltage and the lowest gain, in this conditions this pre really shines.

ciao,
Roberto Amato

[2Bak]

Roberto

What was your value of R15 (with lowest gain)?

Thanks
Jan

[Roberto Amato]

Originally posted by 2Bak
Roberto

What was your value of R15 (with lowest gain)?

Thanks
Jan

That was 447ohm... official (Nelson) value is 430. I just happened to have 447 at hand.

ciao,
Roberto Amato

[2Bak]

official (Nelson) value is 430

In the construction article Nelsons R15 value is 124R with the 500R pot.
Mine r15 is 430R and no pot.

[Roberto Amato]

Originally posted by 2Bak
In the construction article Nelsons R15 value is 124R with the 500R pot.
Mine r15 is 430R and no pot.

Jan, this is an excerpt from the original Nelson article (1997). As
you see, it clearly states 430 ohm for 10db gain. I didn't use the
500ohm pot either, just the pots at the input.

"The gain of 10 (20 dB) reflects the 1500 ohms divided by the 150
ohms. You can adjust the gain of the circuit arbitrarily by
adjusting the value of R15 without affecting the quiescent DC
values of the circuit. As you decrease the value of R15 to 0 ohms,
the gain will approach 50 (34 dB). As you increase the value of
R15, the gain decreases, with 430 ohms giving 10 dB of gain.
Some of the performance curves presented later
will reflect both 10 and 20 dB gain settings."

ciao,
Roberto Amato

[2Bak]

Sorry Roberto, I was looking at the circuit in fig. 3, so I missed this paragraph.
Ciao

[Brad Kizer]

Thanks for all of the helpful replies. You guys are great!

Brad