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3 way post #6 - the cabinet

Posted 14th November 2009 at 05:35 PM by relder (Rob's active 3way with transconductance chipamps build blog)

A Wilson type setup - the mid/tweet box is separate from the woofer box. The upper box is open front and back - replaceable baffles on both sides in case I care to change something, either drivers or sealed vs. open back.

The bottom cab is MDF. I had some of that concrete board left over from an outdoor kitchen project and figred I'd laminate it to the front baffle under the woofer. I don't think it was worth the effort. A knuckle rap test on the sides vs. front showed no huge difference.

The top cab is MDF laminated with baltic birch.
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Phono Stage Shoot Out and Conclusions

Posted 14th November 2009 at 05:26 PM by kevinkr

For some time I've had the feeling that there was something not quite right about the sound I was getting out of my most recent phono stage. The phono stage in question had never been compared to anything else, so it was difficult to understand what was going on. To add to the complications I use a Grado Reference Platinum cartridge that has a reputation for being rather laid back - so I was not really sure if the often boring sound was due to the cartridge or a problem with my phono stage design.

The design is a two stage with Lipshitz based passive eq., high transconductance type tubes, and gyrator loads. The tube complement is triode connected D3A in the front end, fixed biased 5842 output stage and gyrator loads based on the 5687.

The problem seemed to center around my choice of cathode bias in the first stage with the D3A. This resulted in a 60 ohm resistor and a 1000uF electrolytic cap shunted by a variety of other caps, after a long succession of problems...
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Old

The problem with wanting to get the best performance

Posted 14th November 2009 at 09:28 AM by wintermute (Wintermutes Rantings)
Updated 25th November 2009 at 11:15 AM by wintermute (added o category misc)

Well for me anyway I think I must be borderline obsessive compulsive! It happens every time I start a project (or even before I start it). I spend hours and hours and hours deliberating on whether this would be better or that would be better. Honestly in some ways I wish I'd never become "aware" of alternatives to the kits that were available from the local electronics shops Dick Smith and Jaycar

I got the jfets for my B1 a few weeks ago. I finally started matching them earlier this week, I hadn't started because I was obsessing over the fact I needed a 100 ohm precision resistor and a transistor socket. I hadn't got those because I wanted to order all the other bits as well and only pay for one lot of shipping. But do you think I could make a decision on what parts to get?

First off I obsessed over the resistors (yeah I know).. wanted vishay RN60D's but local sources are 5 - 10 times the price of mouser, problem with mouser is unless...
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Tweaking

Posted 12th November 2009 at 08:53 AM by aaaron
Updated 12th November 2009 at 09:03 AM by aaaron (wrong word)

Iam into the tweaking of marantz cd 94 MK2 (just repaced the output op amp with OPA 627,and the buffer stage with BUF 634 T and balance output *****(need to mention Special Thanks to Subash from FARNELL INDIA chennai branch for the wonderfull support rendered throughout the tweaking ***can be contacted at subashb@farnell.com for any elctronic components and the related )
the result is good and there is nice improvement in sound and sonic stage.

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Old

Too late

Posted 12th November 2009 at 01:56 AM by relder (Rob's active 3way with transconductance chipamps build blog)

The day or two after I start a blog here they take the blogs off the main diyaudio home page. Figures.
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3 way post #5 - the drivers

Posted 11th November 2009 at 01:37 AM by relder (Rob's active 3way with transconductance chipamps build blog)

The drivers chosen were somewhat dictated by what I had lying around.

Tweeter: Fountek NeoCD3.0 - I've been wanting to use a ribbon for a while. I have fond memories of hearing old Apogees in the 80's. I bought the prior version (JP1?) quite a while ago. (I'm good at buying drivers for projects and then not building them when I get some other bright idea) When I opened them to use them one of the unit's magnets had delaminated/disintegrated. Big bummer. Madisound came through with great service though and gave me the current model at no cost and no hassle.

Mid: Tangband W4-1337S - The Statement guys seemed to have success with this mid with the Fountek, so I figured why not.

Woofer: Peerless 850146 - I bought these a while ago. Supposedly one of the few woofers appropriate for sealed enclosures. One reason to go sealed is the double hump in the impedance for a vented enclosure would cause the frequency response to rise at both...
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Old

Useful link

Posted 10th November 2009 at 11:41 AM by robocow

http://ampslab.com/vifa62.htm
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Blog Starter

Posted 10th November 2009 at 11:22 AM by robocow
Updated 10th November 2009 at 11:23 AM by robocow (Insert Title)

I have been insipred by PMC to create my own Trasmission Line design. I say inspired, as clearly I'm not going to match their acheivement on a private scale!

So to date I have chosen my drivers, the Vifa PL18 WO09 and the SEAS 27TFFC(H0881).

I'd love to hear if any one has had any experience with these drivers!
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3 way post #4 - power supply

Posted 9th November 2009 at 09:27 PM by relder (Rob's active 3way with transconductance chipamps build blog)

Here's the power supply brick for all amps. A toroid with a CLC. -35V-0V-+35V

Note the color coded terminals on the right so I don't roach another LM4780! (see last post)
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Old

3 way post #3 - the circuit boards

Posted 9th November 2009 at 09:20 PM by relder (Rob's active 3way with transconductance chipamps build blog)
Updated 9th November 2009 at 09:28 PM by relder (Update title)

Here are two of the assembled boards. A mono one for the woofer on the left and a stereo on the right for mid and tweet. I designed the PCB to do both.

Originally I did two in point-2-point, which I found tedious, especially for the LM4780 which has tiny pins with little room for error. And after I blew up the LM4780 board (I hooked up the power supply backwards - poof!) I decided to go PCB, since there was no way to replace the chip given how close the pins were to each other.

The ExpressPCB software is pretty easy to use. Eagle, for how often I attempt PCB's, had too many annoyances for me when creating new objects, etc. The service is pretty quick too, ordered on a Tues and received them on a Fri. They give you 3 boards in their low cost service - so I'll use the one P2P LM3886 and 3 PCB boards.
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