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3 way post #9 - tweeter distortion measurements

Posted 16th November 2009 at 01:50 AM by relder (Rob's active 3way with transconductance chipamps build blog)

Unlike the mid and woofer - the tweeter doesn't seem to show any gains under current drive.
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3 way post #8 - mid distortion measurements

Posted 16th November 2009 at 01:45 AM by relder (Rob's active 3way with transconductance chipamps build blog)

Some decent reductions in 3rd harmonic.
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3 way post #7 - woofer distortion measurements

Posted 15th November 2009 at 07:36 PM by relder (Rob's active 3way with transconductance chipamps build blog)

So - I setup Soundeasy to take some distortion measurements. I don't claim to be a wizard at taking these measurements and balancing the various factors (overloading the mic, etc.) so take 'em with some grains of salt but they are interesting.

Taken with a Behringer ECM8000 mic (uncalibrated) via a UB802 to a M-audio 410 PCI card.

You can pretty clearly see my noise floor. Taken in a living room with computers/fridges turned off, noisy computer in another room.

Mic was nearfield.

There's some clear differences between the plots when driven with current vs. voltage. Ignore the nasty bits around resonance for the current driven one - I clipped the soundcard input with the resonance peak.
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hello, world!

Posted 15th November 2009 at 07:10 AM by davygrvy

OMG, I'm now a blogger!
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iPods 'n Things

Posted 14th November 2009 at 11:23 PM by kevinkr
Updated 14th November 2009 at 11:28 PM by kevinkr

Went to the gym this afternoon with my iPod (Classic 160GB) as usual - about 15 minutes into a torturous session on the elliptical the left channel just died. PANIC.. I had a further 45 minutes of time to reflect on the meaning of music in my life - in this case it really helps me to get through what I find to be an exceedingly tedious activity. Sonic wall paper to my life outside of my house??

Got home and quickly checked with another set of headphones and determined that my iPod was just fine.The aftermarket JVC folding headphones I purchased a couple of years ago just before this iPod apparently have an open connection somewhere. They never entirely pleased me so I am not too sad to see them go.

Have ordered a set of the folding PX100 made by Sennheiser to replace them - should be a lot better sounding than the failed JVC headphones.

It does rather make me realize just how important a role music plays in my daily life.

As an aside...
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Output tubes's CCS's (bias blocks) completed.

Posted 14th November 2009 at 11:14 PM by Bas Horneman (Bas Horneman's diyAudio.com blog)

sans bypass cap.

Measure 380mV accross a 10R resistors. Therefore the CCS is set to 38mA.
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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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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.

Aaron
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