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Old 17th March 2009, 04:27 PM   #1501
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by Pendergast
Hi!

Here is my contribution:

B1 in a box

It was mounted p2p on plexiglass. Fun project. I use it between an audiosector DAC and a SEX integrated amp from Bottlehead.

Really cool. Merci Monsieur Pass!

fugly!!

now you need just 3 layers of any organic oil ..... or Dammar ;

that box is 10 times worthier than DACT

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Old 17th March 2009, 04:28 PM   #1502
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I know. The DACT is recycled from another project.

;o)

Thank you!
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Old 18th March 2009, 04:06 AM   #1503
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Default B1 with SSM2135 Subwoofer Filter on output

I'm in the process of putting a B1 after my volume control and source selector and my Pearl Phono boards to drive my amp, (Hafler 9505 now, Bridged F5 later). Right now I am using an Outlaw ICBM to split the low pass to my Vandersteen V2W subwoofer. The ICBM has both parametric X-over frequency selection and gain control to match the subwoofer output to the main speakers, (3A Signatures now, Quatros soon), but is overkill unless you use it in a 5.1 system.

I am looking at building a fixed 60hz 3-pole X-over with 12 dB of gain using an Analog Devices SSM2135 op amp. The beauty of the SSM2135 is that it can run from a single supply, like the B1 and the Pearl boards, and I can get one from Digikey for 6 bucks. Input would come from the output of the B1 buffer. Output would run into a 10K trim pot and then onto the V2W. The circuit is attached.

This chip is used in IO circuits of PC sound boards and reportedly sounds pretty good - probably good enough for a subwoofer. Have any of you guys tried one of these in any of your circuits ??
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Old 18th March 2009, 10:16 AM   #1504
AndrewT is offline AndrewT  Scotland
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Hi,
have you tried putting those filter values into a filter simulator?

What is the Q of the filter?

Does the single supply opamp require DC blocking caps on the input and output?
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Old 18th March 2009, 05:48 PM   #1505
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salas:

Thanks for share your projects in this forum

Is that Antek 10VA trafo, AN-0120, too tiny to power your 28V DC shunt reg PSU.

http://www.antekinc.com/AN-01xx.pdf

Thanks
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Old 18th March 2009, 06:46 PM   #1506
BFNY is offline BFNY  United States
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Quote:
Originally posted by AndrewT
Hi,
Does the single supply opamp require DC blocking caps on the input and output?
May also need a blocking cap a the bottom of the 10k / 30K connection to gnd, and usually needs a method provide b+/2 to the + input, usually done with 2 large resistors, or as is done in the B1 (more parts= better)
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Old 18th March 2009, 06:58 PM   #1507
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Default B1

BFNY-
I've been wondering about the effect of resistance and capacitance to ground. You just mentioned that it might be an advantage in the x-over schematic- what is the basis of this design feature and can you point me to more info on the subject- I found varied resistance in the various gound leggs of my star grounded b-1 had positive effcts on general noise levels but don't understand the mechanism-
some light at "the mouth of this cave" would be appreciated-
thanks
rob
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Old 18th March 2009, 09:19 PM   #1508
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Default Blocking Caps

Gents, the B1 already has a blocking cap for the input. I would use a 220 Silmic electrolytic and 0.1 mfd film on the output prior to the trimmer - not sure if I need to put it AHEAD of the feedback path, though. (BTW, the input impedance of the Vandy V2W is 100K ohms - I MIGHT be able to just use a big film cap on the output, given a higher valued trimmer pot. )

The SSM2135 application notes don't show this for a single supply headphone amp - see Fig. 31.
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Old 18th March 2009, 09:50 PM   #1509
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Default Re: B1 with SSM2135 Subwoofer Filter on output

Quote:
Originally posted by dcbingaman
The beauty of the SSM2135 is that it can run from a single supply, like the B1 circuit
Is single supply beauty ? Dual supplies can cancel out caps which comes closer to beauty IMO
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Old 19th March 2009, 02:24 AM   #1510
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Default The Beauty of Single Supply

From scratch, dual supply allows direct coupling and so is preferred. Since I am adding this to an existing Pearl Phono, I've already go a nice 2A / 40VDC remote power supply which I can tap from. I can drop this to 25V with an LT1085CT IC voltage regulator for the B1 buffer board and the low pass filter without much pain or perturbation of the Pearl regulators.

Adding another +[/U] raw power supply and negative voltage regulator is a much bigger pain-in-the @#$. Hence, single-supply for this application is very attractive.

I'm not crazy about the SSM2135 SOIC package....my 54-year old eyeballs may not be up to the challenge of soldering this little dude to my prototype board pins....any of you modketeers have any tips on how to do this, (besides buying three of them to account for "F-ups" ??)
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