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Old 5th July 2007, 09:39 PM   #1
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Cool DIY amp for B&W 805's?

Hi all,

I was just able to finagle my way into a pair of B&W 805's at a great price (It's good to have worked for a dealer!) - I was expecting to get some Rotel equipment to pair them with...but I realistically can't afford $3000 worth of equipment right now. So, my mind got to wandering into the DIY realm. I'm an electrical engineer fresh out of college, with a good amount of high voltage experience and a healthy amount of audio-specific experience too (fixing some old tube stuff, making a great sounding SS headphone amp...I'll likely make another post concerning THAT later).

Anyway I'd like to make myself a good sounding amp to do these speakers justice...I don't think my kenwood HT receiver is going to cut it for very long! I'm not sure if I just want to build a power amp and use the kenwood for a pre for now...or just go for an integrated. Or a separate pre/power. The 805's are not particularly efficient, weighing in at 88 dB, so I would imagine I'd need a design with a fair amount of good power. Maybe somewhere in the realm of 100W? It seems like there are so many good designs out there, it's a bit overwhelming trying to fish through everything.

Does anyone have any ideas/thoughts/suggestions/incoherent ramblings? Any and all help would be much appreciated.

Thanks much,
Bob
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Old 5th July 2007, 09:48 PM   #2
troystg is offline troystg  United States
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Without hesitation....

My "audiophile" LM3886 approach

Edit: I owned the 805 matrix version. They worked well together.

I then recycled the 6.5" mid added the Scan Speak 9900 Revelator tweeters and a LEAP crossover from Meniscus in new enclosures.. Mauro's amp still did it justice.

Only reason I recycled the 805's was because the tweeter pods finally broke after repeated knock overs by children.. What can ya do..
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Old 5th July 2007, 09:54 PM   #3
roger-k is offline roger-k  Norway
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This is a very good amp:
http://users.ece.gatech.edu/~mleach/lowtim/

I have build it and I'm very satisfied.
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Old 5th July 2007, 09:55 PM   #4
troystg is offline troystg  United States
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http://www.twistedpearaudio.com/revc/revc.aspx
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Old 5th July 2007, 10:41 PM   #5
roger-k is offline roger-k  Norway
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The sound is better in amps consist of discrete components compared with chip amps. That is anyhow my opinion.
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Old 6th July 2007, 01:44 AM   #6
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Quote:
The sound is better in amps consist of discrete components compared with chip amps. That is anyhow my opinion.
Yeah...I think I agree with this. I'm certainly open to all ideas right now, but my gut has been telling me that a chip-amp might not offer all the quality I'm looking for. Then again, I've never actually heard one so I could be dead wrong!

As for that leach amp...it's very well documented! I'm going to have to sit down with a cup of coffee tomorrow (or maybe even a beer...it's friday, after all!) and give that site a more thorough read. And actually, a quick search for "Leach" on this site gives quite a staggering set of results. Looks like I have some reading ahead of me!

I do like having options though, any other ideas out there? Thoughts on the Leach?
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Old 6th July 2007, 02:58 AM   #7
troystg is offline troystg  United States
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Mauro's is not a chip amp.

But then again some people know all the answers and have deep pockets.

To also represent the other side, I have four UcD 180AD's sitting idle in a chassis I have not been able to complete as of yet. I can't comment on thier performance with the 805's but you won't find an easier amp to construct that will sound as good.

Jens did a small (6 trannies) and large (10 trannies) version of the Leech amp. Very impressive PCB's if they are still available.
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Old 6th July 2007, 03:27 AM   #8
troystg is offline troystg  United States
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My mistake, 4 transistors on the small. Still would be a good match for the 805's.

http://www.diyaudio.com/forums/showt...615#post585615
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Old 6th July 2007, 02:46 PM   #9
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Haha, I hear ya about the tweeters on the Matrix line, Troy...I just sold my Matrix 804's (to raise money for the new 805's), on which I had to replace one of those tweeter casings. I *am* a bit concerned that the Nautilus tweeter seems rather more fragile...

So, just out of curiosity, what makes mauro's design not a chip amp? Both gain stages are built around ICs...? Not to sound ignorant or anything, I'm just new here.

I also took a gander at Jens's thread...very nice PCB's indeed, but I think that ship may have sailed. I've got no real problem rolling my own though; my new job got me a seat of Altium, and there are plenty of PCB houses with reasonable prices on low volume prototype boards. We've actually also got an LPKF circuit board prototyping machine here that I have access to as well - that might be interesting to play around with.

As for the lower-power version - I know the 805's aren't big speakers but I've heard them paired wonderfully with a 130wpc Rotel amp. Part of me says "better to have extra power, gotta be able to keep up with big transients" - while part of me says "the amp isn't going to sound as good as it can until it's cranked a good bit." Decisions, decisions...
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Old 6th July 2007, 03:20 PM   #10
troystg is offline troystg  United States
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Quote:
Originally posted by orangeshasta
Haha, I hear ya about the tweeters on the Matrix line, Troy...I just sold my Matrix 804's (to raise money for the new 805's), on which I had to replace one of those tweeter casings. I *am* a bit concerned that the Nautilus tweeter seems rather more fragile...

So, just out of curiosity, what makes mauro's design not a chip amp? Both gain stages are built around ICs...? Not to sound ignorant or anything, I'm just new here.

I also took a gander at Jens's thread...very nice PCB's indeed, but I think that ship may have sailed. I've got no real problem rolling my own though; my new job got me a seat of Altium, and there are plenty of PCB houses with reasonable prices on low volume prototype boards. We've actually also got an LPKF circuit board prototyping machine here that I have access to as well - that might be interesting to play around with.

As for the lower-power version - I know the 805's aren't big speakers but I've heard them paired wonderfully with a 130wpc Rotel amp. Part of me says "better to have extra power, gotta be able to keep up with big transients" - while part of me says "the amp isn't going to sound as good as it can until it's cranked a good bit." Decisions, decisions...

I had the Bryston 3B and the Jeff Rowland Model 2 on them. The Bryston / Bi-wire Kimber 4TC/ 805 combo was KILLER. It flat out beat many more costly systems.

Mauro's amp uses the LM3886 as a current pump. The actual amplification "I BELIEVE" was done in the op-amp. It was a closed loop design that made both units "functionally" one. It really sounded great for the money rivaling the big name brands (ML, Krell, JRDG, Audio Research) and bettering the Rotel / Adcom / Parasound types by far. But yes, I think he went direct sales only now.


"If it were me", or "in MY opinion" I'd either do the UcD180x or Leech in mono blocks. I lean to the UcD for the energy efficiency (thinking of the children) and "latest greatest" technology. BUT I have not heard the Leech nor UcD myself.
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