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Old 12th April 2013, 10:55 AM   #281
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Just be mindful of dissipation. You could look at Allen Wright's SLCF as upgrade to standard buffer topolgy. Automatically deal with bf862 dissipation.
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Old 12th April 2013, 10:57 AM   #282
Floric is offline Floric  Europe
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Quote:
Originally Posted by Itsmee View Post
I don't have enough 2SK170's to build the crossover, would there any disadvantages in building the buffers with BF862 other than fiddeling with SMD.
I have been very successful builduing buffers with j310. I think on semi still produces them as TO-92.

Best regards

floric
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Old 12th April 2013, 11:59 AM   #283
Itsmee is offline Itsmee  England
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Hi buzz and Floric, thank you for the replys.-------------------------------------------------------------------------------------------------------buzz, thanks for the reminder, I should be OK if I pick the ones with the lowest IDSS, I also have some nice little DIL heatsinks that should help to keep things cool.--------------------------------------------------------------------------------------------------------------------------------Floric, I was thinking of using J309's, but I'm going to use Rod Elliots Project 09 boards, it's uses opamps (yuck) so I need to build the buffers onto an 8 pin DIL header, smd seemed to be the answer, I may still go with the J309's if I can find 100 or so.-------------------------------------------------------Sorry about the --------- guys, I hate my work computer, it removes all the spaces and scrunches everything up.

Last edited by Itsmee; 12th April 2013 at 12:06 PM.
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Old 23rd June 2013, 03:37 PM   #284
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Originally Posted by Rodeodave View Post

The final circuit is like the one I posted earlier, but with 221R gate stoppers at each and every gate. And one 2200uF 50V Panasonic FC capacitor per rail for decoupling and peace of mind.
To avoid potential ground loops, the XO's ground is only connected to the DCB1 at one point, namely through the cables coming from the power supply. Since the circuit is biased in class A I see no potential harm in doing so.
Dave, or anyone,

Other than these extra capacitors, does the stock DCB1 power supply need to be altered at all to keep up with the additional buffer circuits?

Looking into a similar build, but my power supply knowledge is lacking.
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Old 23rd June 2013, 04:40 PM   #285
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Hi harmolodics,

Before I had built the DCB1 crossover, I was using the hotrodded Salas DCB1 simply as a preamp (buffered volume control really). When I decided to build the crossover I simply used the DCB1 as a power supply for the circuit. For construction details you can check out my blog entry here at diyAudio: http://www.diyaudio.com/forums/blogs...cb1-build.html.

Like I mentioned in post #269 B1 Active Crossover, the only(!) modification I did to the previously built hotrodded DCB1 was the addition of a 5R1 resistor (10W wirewound iirc) in parallel to the previously installed 10R, effectively creating a 3R3 resistance in the DCB1's current source. The additional resistors are mounted on the underside of the board.
For current draw, simply assume 10mA per JFET pair, sum over all pairs and double or triple the result, depending on xformer and heatsink size, which are the only practical concerns more or less.
For instructions regarding setting up the Hypnotize DCB1 power supply, see Using the HYPNOTIZE as a general shunt reg PCB.

Good luck, and keep us updated on your progress!
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Old 25th June 2013, 04:02 AM   #286
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Thanks Dave! Those are very helpful links. My plan is to use the DCB1 plus 2 additional buffers to make a simple buffered line level crossover. So it might not be considered an "active crossover" like yours, but this way I can make the crossover parts modular so they can be easily swapped out for different values or slopes.

stepped attenuator - B1 < High Pass - B1
.....................................Low Pass - B1

With three JFET pairs per channel at 10mA per pair, I calculate the current draw to be 60mA, multiplied by 3 for headroom gives me 180mA CCS. Plugging this into Salas' equation (CCS=2.2/R) gives a resistor value of around 12R. Does this sound right?

Working on tracking down parts. Looking forward to biamping.

Last edited by harmolodics; 25th June 2013 at 04:04 AM.
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Old 25th June 2013, 07:20 AM   #287
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12R sounds about right. I've had around 150mA with 10R in my DCB1 build. As long as the transformer and the heatsinking can keep up, you can always increase the current.

Are you going for a buffered PLLXO as in TLS.org | Passive Line-Level Crossover ? I built a 12dB/oct version before I finished my B1XO, and it required quite some gain (delivered by BOZ) to make up for the PLLXO's insertion loss, but that was because my amps have a fairly low input impedance (22k and 15k). I can dig up the schematic if you want.
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Old 26th March 2014, 12:14 PM   #288
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Default I've just completed two B1 crossovers.

I have been following this thread for a couple of years, and I have now just completed
two LR4 crossovers based on this design for two of my systems.

System 1. Lowther EX4 front horns with Jensen P15N in corner (rear) horn cabinets crossed over at 180Hz. Used Russian K71 100nF capacitors.

System 2. Fostex F120A in Voigt Pipes, with B&G Neo3PDR dipole tweeter crossed over at 1kHz.Used Russian K73 31nF capacitors.

I am very pleased with these XO solutions for both systems. I used straight forward
variable LM317/337 series regs for +/-10V rails.

I am now looking to build a 3 way version of this LR4 design for my "Orion"
variation of SL loudspeaker. I use cheaper drive units than what SL specifies, and have been using a Behringer DCX2496 as XO, emulating SL analog design in the digital domain. HP and MP should be straightforward with the B1 design ( I won't bother with the Notch Filters), but I'll need a shelving low pass for the bass open baffle drive units.

I don't know yet if the B1 non-inverting design can make a SLP, if not, I may use op-amps for the woofers only.

Any ideas?

Davidkou
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Old 26th March 2014, 02:56 PM   #289
AndrewT is offline AndrewT  Scotland
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Is the shelving low pass (slp?) a passive filter (EQ?)?
If so then all you need to get it to work correctly is for the filter to see the correct source impedance and to see the correct load impedance.

If those "correct" impedances are: zero for source and infinity for load, then use the B1 buffer for both input and output.
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Old 26th March 2014, 03:28 PM   #290
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You could use a B1 buffered passive version with Active Filters and put it in front of the whole x-over. That's what I'm using for baffle step compensation in mine.

And post some pics please :-)
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