B1 Active Crossover - Page 12 - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 9th January 2010, 08:09 AM   #111
diyAudio Member
 
Join Date: Feb 2004
Location: utrecht
Based on my experience with pre-amps and phono-amps, when the design of the functional part is good most critical is the PSU. I agree with Nigel's PSU first.
I think Salas sym PSU B1 is a very interesting option. Does someone have a clue how many buffers, filter-stages, one could hook up to that specific B-1 design?

Regards
Michiel
  Reply With Quote
Old 9th January 2010, 10:10 AM   #112
njepitt is offline njepitt  United Kingdom
diyAudio Member
 
Join Date: Aug 2008
Location: Maine
Quote:
Originally Posted by earsandeyes View Post
Based on my experience with pre-amps and phono-amps, when the design of the functional part is good most critical is the PSU. I agree with Nigel's PSU first.
I think Salas sym PSU B1 is a very interesting option. Does someone have a clue how many buffers, filter-stages, one could hook up to that specific B-1 design?

Regards
Michiel
Hi Michiel,

I'm using separate regulator circuits for the filters (which will be essentially the Salas circuit from the sym B1 thread) and for the output buffers, which are the ones from juma's BF862 preamp thread. I'm hoping (and expecting) one salas PSU is enough for the filters - if anyone thinks otherwise please let me know while there's still time to adjust the design...

Cheers

Nigel
  Reply With Quote
Old 9th January 2010, 10:39 AM   #113
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
I would be tempted to use a separate pair of regulators for each channel.
Then I would consider using separate regulators for the upper frequency range from the lower frequency range. The input buffer could be run off the lower frequency range.
That's 4 pairs of regulators for a stereo crossover.
__________________
regards Andrew T.
  Reply With Quote
Old 9th January 2010, 11:01 AM   #114
njepitt is offline njepitt  United Kingdom
diyAudio Member
 
Join Date: Aug 2008
Location: Maine
Quote:
Originally Posted by AndrewT View Post
I would be tempted to use a separate pair of regulators for each channel.
Then I would consider using separate regulators for the upper frequency range from the lower frequency range. The input buffer could be run off the lower frequency range.
That's 4 pairs of regulators for a stereo crossover.
Hmmmm... Did you mean four pairs of 7809/7909 regulators, or four pairs of discrete regulator circuits? I'm planning on using the sym B1 discrete regulator circuits; each pair of these uses: 2 IRFP9240, 2 IRFP240, 6 2SK170, 1 BC550, 1 BC560, and 16 LEDs. I don't think doing four of these is really practical in the space I have available. Total heat would probably not be much different from powering it all one from one pair, although I'm almost tempted just to see what 64 LEDs in one case would look like... ) It *might* be possible to fish around for a slightly simpler circuit to use instead, but it isn't clear to me if the benefits of having separate circuits outweigh the disadvantages of a simpler circuit...

Cheers

Nigel
  Reply With Quote
Old 9th January 2010, 11:12 AM   #115
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
builders are reporting very good SQ results for B1s on discrete shunt regulators.
Most are hanging only two B1s on one pair of regulators.

How many B1s will your crossover have?
__________________
regards Andrew T.
  Reply With Quote
Old 9th January 2010, 01:24 PM   #116
njepitt is offline njepitt  United Kingdom
diyAudio Member
 
Join Date: Aug 2008
Location: Maine
I had almost finished a reply when the power went out for a couple of minutes, and internet service took ages to come back... Annoying as all hell; on the other hand every time I moan about bad aspects of life in Brazil I should reflect on the fact that here today it is warm and sunny with a mild breeze, just about perfect (as it is most days, really...), whereas AndrewT and everyone else in the UK has rather different weather....

Quote:
Originally Posted by AndrewT View Post
builders are reporting very good SQ results for B1s on discrete shunt regulators.
Most are hanging only two B1s on one pair of regulators.

How many B1s will your crossover have?
A total of 14. This includes 4 on the output buffers, which have entirely separate regulator circuits, and a total of 10 in the filters, being 1 input buffer and two buffers each in LP and HP, per channel. The BF862s will be running at Idss, about 13mA each, so total current draw in the filters should be about 130mA, which seems to me to be more or less OK with just one pair of regulators, if I heatsink the mosfets well. (If anyone thinks not, please let me know.) This is from a purely electrical point of view, however; if sonically this might be a little too much by raising the noise levels then I could adapt this, maybe, but I'd like to hear suggestions in this case.

Cheers

Nigel
  Reply With Quote
Old 9th January 2010, 02:01 PM   #117
njepitt is offline njepitt  United Kingdom
diyAudio Member
 
Join Date: Aug 2008
Location: Maine
Sorry ! Total of 18, not 14... The schematic I am planning is posted on post #82, except for some component values.. So total current in the filter section should be around 182mA, not 130...

Cheers

Nigel
  Reply With Quote
Old 13th January 2010, 08:28 AM   #118
dviswa is offline dviswa  United States
diyAudio Member
 
Join Date: Oct 2004
Quote:
Originally Posted by njepitt View Post
Hi Dinesh,
In the photo I can see three jfets pairs on the board; are these the parts after the attenuator? I guess you have the earlier Buffer in your list as
part of some different board. (Maybe in a preamp?) In any event, you are doing the 12db/octave original version, right?
Its been too busy with my day job lately.
The picture shows only a part of the board. I started building the second channel, when the first buffer stage was finishedm out of curiosity I thought how would it sound if I bufferred the output from my Twisted Pear Sabre DAC before hitting the 10K stepped attenuator. The improvement was so much, I decided to leave it there, so I will add back another B1 stage into the channel shown.

Quote:
Originally Posted by njepitt View Post
I'll be very interested to hear how it sounds. How are you planning to fit this into your system? I'm being nosy - what crossover point, amps, speakers et cetera.... Do you plan on doing a more sophisticated PSU later?

My build is proceeding OK. I have a habit of always building the PSU first, and in this case I plan on getting the output buffers working next, to give a functional BF862 preamp, then do the filter section last. So it'll be a while before I can hear how it sounds....

Cheers,

Nigel
The speakers are Eminence Alpha 15 and a Fostex FF85KeN in OB. The crossover point is not a Linkwitz-Riley, but actually spread apart a little bit. I am still playing with the components. It is very difficult to decide, because different crossover points bring out different characteristics. I am glad I put in that 16 pin DIP socket. Right now the tweeters are cutting in at 480Hz while the woofer is cutting out at 200Hz. Yes it is simple 12 db/octave filters. These are driving a Pavek Dudel's PA-03 amp based on LM4780, it was a GB right here at DIYA.

I plan to build a shunt regulator later on, probably rebuild the whole thing on PCB. I will be housing it in an old cabinet, I have lying around from another project from a couple of years back.

Sound wise, the first thing the strikes you is that the sound stage moved forward, like going from 15th row to something closer to the performance. Given that I do not yet have the second channel built, I cannot be too sure of this. The articulation improved a lot and so now I can play it at lower levels than I used to. Of course, last few days nothing is playing, because the power amp is getting a make over. I am adding a second board to the power amp so that I can drive 4 drivers independantly. Once the second PA-03 board is complete, I will get back to building the rest of the cross-over.

I am convinced that this is a very worthy project despite the effort it takes to build it P-P.

I would be a great thing to design a small PCB that can take 2 channels single filters. Then you can just use these as building blocks. One for buffer, one for LP, one for HP and on and on, just chaining them as needed. I don't have the software tools for PCB design, but we'll see.

Regards,
Dinesh
  Reply With Quote
Old 13th January 2010, 01:27 PM   #119
udailey is offline udailey  United States
diyAudio Member
 
Join Date: Mar 2008
Dinesh,
Look for Dip Trace. Its a very good pcb software and you can use it for free.
Uriah
__________________
purchase LDRs anytime Also try my Resistor Replacers or LDR based Input Selector Email me. diyldr@gmail.com
  Reply With Quote
Old 13th January 2010, 03:06 PM   #120
cviller is offline cviller  Denmark
diyAudio Member
 
cviller's Avatar
 
Join Date: Dec 2005
Location: Copenhagen
Blog Entries: 2
I think this project looks really interesting. I am toying with the discrete x-over idea myself, but you guys are way in front of me. After having played with an XVR1 at a delayed "after-party" to the burning amp festival I must say that I'm really into this way of doing speaker designs!

If you want me to, I would love to design a PCB for this B1 based crossover since I would probably be doing it anyway.

The XVR1 uses jumpers, which I find really nice when testing - you can select the frequency and Q. DIP switches can also be used and may be easier to work with. It does require a lot of different resistors, but you get a really versatile tool for future projects.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
MOX - active crossover moamps Analog Line Level 234 11th June 2011 06:44 PM
MOX active crossover buy tiroth Group Buys 261 25th March 2010 07:30 PM
Passive crossover into active crossover hahfran Multi-Way 16 10th February 2008 06:16 PM
XVR1 active crossover, discrete active stage promitheus Pass Labs 18 22nd July 2002 01:29 AM


New To Site? Need Help?

All times are GMT. The time now is 05:26 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2