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Old 26th June 2003, 02:27 AM   #1
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Default New Preamp, Processor, Speakers (A Culmination of several projects)

First is a picture of the Preamp, processor and DAC:

This I have been working on for about 2 weeks. I built the DAC a while ago, and just switched cases. The PCB in the front is the active crossover from ESP. It is 4th order electrical at 2200Hz. The double decker assembly behind it is the equalization for the dipole roll off, and the 4th order XO to the subwoofer. It is actually only 3rd order, but the first order dipole roll off makes it an acoustic 4th order. I cross to the sub at 100 Hz.

I may add a linkwitz transform circuit after I do my room analysis.
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Old 26th June 2003, 02:32 AM   #2
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Here are the speakers that go with it.

They are called the "Shorties" I designed them to be used on very short stands for maximum SAF. The lobe created by the XO at Fc is angled up at 12 degrees, making a low placement ideal. I will have the tweeter about 24 inches off of the floor.

THe stands have yet to be finished, and the speakers have yet to be finished in that I need to add damping compound to the back of the woofer frames, and stain and laquer the frame (I cant call it a box).

THe driver are the Peerless 850122 7" woofer and the Seas T27TFFC tweeter.

I was wooried about over excursion on the woofer, but because of the 100Hz XO to the sub, this dosnt seem to be an issue, I can play REALLY loud without any clipping or IMD.

The tweeter sounds amazing, I am not sure if is the lack of passive components, or that I have really only ever worked with lower dollar tweeters, but it sounds very good, not quite as extended as the Revel Studio's that I have auditioned for a few hours, but I like their sound better than those darn titanium domes.

I will take some measurements soon, and post them.

-Paul Hilgeman
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Old 26th June 2003, 02:37 AM   #3
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And here is the whole shebang. The small things in the back are the amplifiers. LM3875;s using premium components.

Below everything (out of the picture) is the power supply. Independent suppplies for +/- 12 VDC (Regulated) and +/- 27VDC (After rectification). I will be upgrading all of the briges to MUR860's.

Also out of the picture is the Subwoofer, it uses Dual Peerless 831857 12" woofers in a small sealed enclosure. It has a 380 W amplifier.

I had planned on using a Lnkwitz Transform circuit for it, but it turned out that it really didnt need it, maybe from 30Hz down, but I am not really a bass head anyways. I just wanted to get that super tight bass that only a sealed woofer can make (well dipole too, but I dont know if they could handle it).

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Old 26th June 2003, 05:29 AM   #4
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Frequency Response



Great through the XO reigon (2200 Hz)

Not too sure what the 1Khz is though... possibly the rear chamber, between the 'wings' of the baffle?

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Old 26th June 2003, 06:12 AM   #5
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Can you tell something more about the DAC?
Schematics, costs, comments are welcome.


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Old 26th June 2003, 09:16 AM   #6
Bricolo is offline Bricolo  France
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where did you buy those nice cases?
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Old 26th June 2003, 01:03 PM   #7
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The DAC is the Scott Nixon Non Oversampling DAC. It is just a kit, so I am not all that proud of it, but it sounds excelent.

THe cases are from :

The whole project has cost about:

GC Parts: 20 bucks apiece times 4 including connectors etc
DAC: 120
PCB's and parts for XO and EQ: 100.00 (Using 1% panasonic film resistors and 2% poly caps with Panasonic FC bypass caps)
Transformers and PS stuff: 90.00
Chassis: 14 times 4 for the GC's and I think about 24 for the main chassis

Most of the IC's I got via sample programs - Oh yeah, all of the opamps are BB.

I got the tweeters from eBay for 28 bucks, and I got the woofers from e-bay for about 24.

Wood: 20 bucks

So for the grand total: 542.00 for the main speakers, amplifiers, PS, preamp, EQ, DAC

The subwoofer was 70 per driver x2 and 170 for the amp.

So, about 300 for the sub.

-Paul Hilgeman
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Old 26th June 2003, 02:07 PM   #8
grataku is offline grataku  United States
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Originally posted by Bricolo
where did you buy those nice cases?

For the bostonians in the audience, "You Do It Electronics" has these EXACT cases in the black anodized version which look and feel even better.
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Old 27th June 2003, 11:11 PM   #9
king30 is offline king30  United States
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can you point us to a link for the equalization circuit.

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Old 30th June 2003, 04:57 PM   #10
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Well, it is all custom, but all ideas, forumals, theories came from:

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