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-   -   Bridgeclone - Rowland Concentraclone (http://www.diyaudio.com/forums/chip-amps/16396-bridgeclone-rowland-concentraclone.html)

ThorstenL 12th June 2003 11:45 PM

Bridgeclone - Rowland Concentraclone
 
Koinichiwa,

I just came across some hi-rez internal shots from the new Cncentra. It may be of interest to those seeking to "clown around" with "Bridges over the River Kwai" and the like....

First the overview:

http://www.image-hifi.com/51/bilder/15110-4.jpg

As can be seen, unlike the other Rowland Amps that use switch mode supplies, the concentra still does it the oldfashioned way...

The inputs are switched by little, very familiar looking relais, goldflash over copper contact IIRC and then you get a nice Jensen Input Transformer:

http://www.image-hifi.com/51/bilder/15110-2.jpg

There is a lot of jiggery pokery and to those who already know, the Concentra uses the CS3310 as volume control.

The following picture shows parts of the PSU, pretty basic, single bridge with ceramic snubber caps, 4 pcs Nichicon PSU Cap's, I'd guess from the looks 10,000uF/63V each:

http://www.image-hifi.com/51/bilder/15110-1.jpg

Now onwards to one of the six Nat Semi LM38XX (we know they are 3886) output chips in bridge/parallel:

http://www.image-hifi.com/51/bilder/15110-3.jpg

No sign of a servo. Dale 0.2R 1% Output Resistor. All else SMD, including the two local decoupling caps which are by the looks X7R or possibly even Z/Y5U Multilayer Ceramics. All the other SMD resistors appear to be tight tolerance (guess) and there is no manual offset correction either. The paucity of passive components suggests BTW inverting mode....

Sayonara

mhennessy 13th June 2003 09:59 AM

Nice!
 
Nice pictures! Where did you find them?

Cheers,

Mark ;)

ThorstenL 13th June 2003 10:03 AM

Re: Nice!
 
Koinichiwa,

Quote:

Originally posted by mhennessy
Nice pictures! Where did you find them?

www.image-hifi.com

Sprechen sie deutsch?

Sayonara

mhennessy 13th June 2003 10:29 AM

Re: Re: Nice!
 
Quote:

Originally posted by Kuei Yang Wang
Koinichiwa,

www.image-hifi.com

Sprechen sie deutsch?

Sayonara

No, but Google does ;)

Circlotron 13th June 2003 11:34 AM

Very nice clamping bar holding the IC's onto the heatsink. It puts the pressure right on the part of the tab that has the most heat. Way better than using the bolt hole that pulls the IC down unevenly. Good method for TO-220's and TO-247's too, especially if you are working them hard.

grataku 13th June 2003 12:17 PM

Quote:

Originally posted by Circlotron
Very nice clamping bar holding the IC's onto the heatsink. It puts the pressure right on the part of the tab that has the most heat. Way better than using the bolt hole that pulls the IC down unevenly. Good method for TO-220's and TO-247's too, especially if you are working them hard.
Don't forget the nice SS fasteners, the only screws I use. ;)

cm961 13th June 2003 12:30 PM

It looks like a very nice amp, I hope mine turns out like that :clown:

As soon as I get a mill machine and start making two sided PCBs, the possibilities will be endless.

Pete

miguel2 14th June 2003 02:20 PM

The signal goes directly from the jensens to the vol control and then to the output chips? No other gain/buffer ICs in between?

Miguel

mothman 14th June 2003 11:32 PM

A beautiful amp indeed and if I had the extra $7000 I'd buy one!
I'd settle for a dozen of the chip insulator pads though at this point.
Anybody know where a fit pad like those can be had?

MWP 15th June 2003 06:08 AM

Quote:

Originally posted by mothman
I'd settle for a dozen of the chip insulator pads though at this point. Anybody know where a fit pad like those can be had?
TO-3 silicon rubber insulators cut in half work well on the LM3876/3886.


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