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Old 24th April 2012, 12:37 PM   #251
Rush is offline Rush  United States
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Quote:
Originally Posted by johngalt47 View Post
Whatever happened to this design?
If you are referring to me, I am busy with other projects, but will get to this project this year. I hope.

Rush
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Old 1st October 2012, 02:03 AM   #252
Rush is offline Rush  United States
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Default Phono Pre Amp B1 Crossover Complete

Quote:
Originally Posted by Rush View Post
I am trying to put together a stereo 2 way 4th order crossover with preamp source switching (2 sources) and overall volume control.

I have a pair of Snell E with a crossover point of 2700 Hz.

To configure the values for this cross point I referred to the Grey Rollins' article: The Xenover - Part II Article And Design By Grey Rollins

The resister and capacitor numbers corresponds to Grey's Schematics as indicated. I don't have a way to change the values on the attached PDF.
Butterworth high pass (Schematic 7)

C = C1 = C2 = C3 = C4 =.002

1st section: R5 = 0.9239/(2*Π*F*C) = 27.2k

1st section to ground: R6 = 1.0824/(2*Π*F*C) = 32k

2nd section: R11 = 0.3827/(2*Π*F*C) = 11.3k

2nd section to ground: R12 = 2.6130/(2*Π*F*C) = 77k



Butterworth low pass (Schematic 8)

R = R5 = R6 = R12 = R13 = 22k

1st section: C1 = 1.0824/(2*Π*F*R) = .0029 uF

1st section to ground: C2 = 0.9239/(2*Π*F*R) = .00247 uF

2nd section: C3 = 2.6130/(2*Π*F*R) = .007 uF

2nd section to ground: C4 = 0.3827/(2*Π*F*R) = .001 uF

As I proceed with buying the resisters and capacitors I would like confirmation that those calculations will work for the B1 buffer crossover using 2SK170BL devises. I may use a discrete opamp for the preamp gain stage.
Finally finished the 2 Hypnotize regulators for the 2 way stereo crossover, had to cut off the B1 part of the boards to save space. I populated the bread board crossover 6 months ago, the Salas Simple phono pre amp and regulators were finished 2 months ago along with the Mesmerize DCB1. Put it all in the box, cranked it up on the bench and noted the DC offset of around .2 volts on each output. I chose to cap couple the output and not deal with rematching jfets. The high pass was a small .02 uF styrene cap, the low pass I used a 7 uF Kimber cap that was lying around, I may change this later as I only need a 1 uF and can afford a better cap in this value.
Hooked up the bench tube amp and crappy speaker and found a loud buzz on all the crossover outputs. So I took a .22 uF cap, attached one end to ground and started poking around the crossover. Found that when I touched the top leg (plus rail) of the top jfet on the input buffer, the buzz went away completely. That was easy, needed a little decoupling. Soldered them in and it is pretty quiet.
Listening now for the last hour or so and it sounds great! I am sure the parts will break-in over the next few weeks. I will leave it on.
I have a separate box for the 2 power transformers each is switched so if I don't want to listen to records, I can leave that transformer off and reduce heat and electricity consumption. Needed 2 transformers as the voltages were completely different.
I wired the transformer box to the pre amp with a 4 conductor cord and 4 pin XLR, each rectified raw voltage (48 VC and 17 VDC +/-) shares the same ground wire. Wasn't sure that was going to work and I worried about how I was going to ground all that in one pre amp box.
Worked it out with some fiddling.

Thank you Jacques Merde for all the help. This thread has given me a great sounding crossover.
I will also thank Salas for his regulators are everywhere, 8 of them in one box! (5 positive and 3 negative)

Rush
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Last edited by Rush; 1st October 2012 at 02:10 AM.
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Old 1st October 2012, 02:32 AM   #253
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Congratulations!
That one looks not easy to build.

Thank you for the tip about buzz exorcism

Enjoy it.
M.
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Old 1st October 2012, 02:45 AM   #254
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Rush, got a breadboard version of B4 wired up now. Temporarily using the B1 as a FE until I go to complimentary input. Looks great and I bet it sounds great too. Congrats. Now if you only had i nice amp to run it through
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Old 2nd October 2012, 12:48 AM   #255
Rush is offline Rush  United States
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Default Removed the output caps

I was in a hurry to finally listen to the pre amp/crossover after debugging it. I threw those caps on the output and did some listening.
But of course I can't leave well enough alone. I remeasured the DC offset and found none, .001, .003, .002, .000 and said what? I must have measured wrong or after 24 hours of burn in it settled out? Naw, I must have measured wrong. I didn't remeasure the offset after I added the caps to the plus rail, could be that, or?
Anyway, took the coupling caps out and hooked it back up. Sounds even more better without the caps. I guess you can hear caps.

I am an amateur after all.

That saved me a ton of money. The V-Caps TFTF were going to set me back a couple of large ones!
Might still buy them for the phono pre, but not at this time. I'll wait for Christmas, buy them tell the wife they cost half what they did and she can give them to me for Christmas. Then I won't have to buy her so large a present in return.
That has served me well for 19 years of marriage.

Rush
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Old 14th February 2013, 10:33 PM   #256
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How does the attached circuit look like?

It's a Bride of Zen feeding a passive RC shelving lowpass followed a 3rd (cascaded 1st and 2nd) order high-/lowpass network employing unity gain DCB1 buffers.

I have the BOZ, a ready-made DCB1 blue edition, a DCB1 Mezmerize pcb and numerous pairs of matched 2SK170BLs. The additional JFET buffers would thus be fed from the DCB1s' shunt regulators.

With the present values the passive BSC should give a pot-adjustable attenuation past 500Hz for baffle step equalization.

The part values of the crossover that follows the BSC are based on matched capacitor values I happen to have on hands, and it's supposed to be a spread frequency crossover at 2500 and 3500 Hz. Level setting pots are provided for each branch.

What would you change, add, ditch? More gate stoppers perhaps? Supply decoupling caps I would certainly add in the real design then. Something else?
I also have one of those red JBOZ pcbs from ebay, which means i could build enough amp and buffer stages to move the gain stages to the output. JBOZ for highs, BOZ for lows, with JFET input buffer. Would that be preferable?

And does anyone have a link to that version of the JBOZ with the bipolar supply, please? I can't seem to find it.


Thanks for your critique,
Dave
Attached Images
File Type: jpg BOZ_B1_XO.jpg (71.4 KB, 471 views)
File Type: jpg BOZ_B1_XO_f.ckt.jpg (40.5 KB, 453 views)
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Old 15th February 2013, 10:04 AM   #257
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Default 2sk170 gain stage

I managed to find the 2sk170 gain stage myself:

BF862 Preamp and BF862 Preamp

Maybe I'll mod the DCB1's shunts to produce the appropriate voltages and use one of these circuits as a gain stage.
Now the question...gain stages at the input or the output?
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Old 27th March 2013, 09:59 PM   #258
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Almost done
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Old 28th March 2013, 01:03 AM   #259
Rixsta is offline Rixsta  United Kingdom
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Hi, Is there a 3-way version of this Crossover ?
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Old 28th March 2013, 01:48 AM   #260
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easy to make , reading post #247
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