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On distortion by Bob C

Posted 25th March 2011 at 08:30 PM by klewis

I don't find it hard to believe that very low levels of certain kinds of distortion are detectable when at the same time virtually un-measurable differences between passive elements like cables and capacitors are widely believed to be audible.

THD-20 does not tell the whole story on amplifier behavior, but it has also been given a bad rap because single-number usage of THD-20 can obscure the real story. If you have THD-20 with a full-spectral analysis out to the 7th or 9th harmonic, it tells a lot more, but most THD analyzers start cutting off at 80 kHz. One should always take note of the waveshape of the THD-20 distortion residual as well. If it is rather sinusoidal, that is often not too bad. If it is spikey, that is potentially very bad.

CCIF 19+20KHz with full spectral analysis is much better because the IM products lie in-band.

At the same time, moderate levels of benign THD, like mostly 2nd and 3rd, may not bother anyone very much. This...
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Mountain Biking

Posted 25th March 2011 at 08:27 AM by chris661

Many years ago, (when I was 11, now 17), I got a bike for my birthday/Christmas combined present, I got a mountain bike. It was good for what it was: V-brakes, 21 gears, front suspension etc.
So, I enjoyed the bike for about a year, then decided the forks weren't great, and that upgrading them would make everything much better. Now, knowing nothing about bike geometry, I fitted some longer forks. Lovely, I could go over all sorts, land jumps and the front wheel always stayed attached to the ground. Being young and adventurous, I started doing drops - onto concrete. Needless to say the wheels that came attached to a £150 bike didn't hold up particularly well.
So, a little re-speccing later, the bike got some new wheels. These were heavy duty jump wheels that are designed for grown men to jump off stuff. A 13 year old would be fine. Due to the different hubs, I also had to fit a new rear cassette, and all the deraileurs and shifters that come with.
Seeing they were disc...
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New pair of power amps for the my subs

Posted 19th March 2011 at 08:48 AM by googlyone

In the process of upgrading the subs in the play room. The aim was to deliver in the 1kW region into 8 Ohms. Discretion (and common sense - if that ever entered the equation) led me to shoot for something closer to 650 watts (measued 73vrms, or 666 watts on a sine wave into an 8 ohm load, which brought a wry smile to my face).

I chose to use a bridged configuration, as this allowed the use of supply rails at sensible levels (+/-65V) odd. It also allowed me to use a heap of capacitors that I had laying around.

The transformers are ANTEK units, which much to my disgust cost less to buy and ship from the US than to buy locally made. (Sorry about being parochial, but shipping a two 20lb lumps of steel to Australia is expensive - what is with our local businesses???)

No surprise that I was worried about:
- Power supply - needs to be big
- Cooling - an awful lot of heat to get rid of
- Safety - don't want to be melting my speakers,...
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Old

NAD705

Posted 14th March 2011 at 02:17 AM by damith74

Controller board malfunctioned..
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Blogspot

Posted 13th March 2011 at 12:19 PM by ferynov
Updated 17th March 2011 at 02:25 PM by ferynov (edit)

Diy Woody "grado wanna be" inside driver is KSC75. cheap and sweet sounding.

Click the image to open in full size.
http://hobbyaudios.blogspot.com/2011...teak-wood.html

another my audio blog

http://hobbyaudios.blogspot.com/
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Philips CD 880

Posted 10th March 2011 at 05:12 PM by Ronnmaui

I have a Philips CD 880 which I purchased in the 80's and had it modified by Soloist Audio and have enjoyed the machine all these years, until the last year. It stopped playing CD's altogether. The mechanism would open and it would spin, but no sound or no control. I am not a tech as you can tell. I sent the player to Atlas Audio in Pittsburgh and they claimed they could fix it and they returned it in a month. It worked great for one weekend, then stopped again.
I sent it back to them and they spent another 3 months trying to figure out what to do. They said it was repaired and sent it back to me a second time. In the process of shipping it to me the second time the player got "dented" on the rear of the chassis and when I plugged it in, it did not work at all. I got Fedex involved since they insured it and they sent it back to Atlas and gave them 50% of the insurance money. Again they kept the player a couple more months and could not fix it. They finally returned...
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Size Matters! Posting images to the forum

Posted 26th February 2011 at 06:03 PM by Pano

OK, just because you own the latest Whizbang-3000 15 megapixel camera, does NOT mean you know how to use it. Sure, you may take pretty pictures, but posting them here, or elsewhere on the web, requires some thought and effort.

See my comments below for more info. Click on "comments" down here.
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Hello everybody

Posted 21st February 2011 at 07:34 AM by tecosand

hi all i have an early grundig stereo that has a tm45 reel to reel a record player an radio...The radio has 4 columns with differnt numbers that run from top to bottom.... i think it was made in 1961 an im curious to see if they have an elictrical diagram manual that is possibly in english.... an where the fuses are located
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Sharing thoughts

Posted 20th February 2011 at 03:40 PM by Antoni D

Hello,
I'm a new member and I'm still trying to figure out how to use this site. I came upon it when I was googling the net trying to find Fostex x-15 or x-18 4 tracker for sale. diyAudio address popped up among other hits, so I signed up. I don't know why it popped up, because I couldn't find anything related to Fostex x-15 or x-18 here. So I posted a message on Forum if someone has x-15 or x-18 for sale. To my surprise I had only one response, from a member who joined right after I posted my message. Talk about checking credentials here. As far as introduction goes, I'm a musician, I compose my original music, then I record it on computer software and upload it to YouTube. Please visit me here:
<www.youtube.com/user/TosiekDegutis> and
<www.youtube.com/user/biTVToni>
Enjoy!
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Rating: 2 votes, 5.00 average.

PCBs for Dummies

Posted 18th February 2011 at 11:49 PM by NYCOne

WARNING:


The following method uses deadly, strong chemicals. Do not proceed as you could die, or lose a part of your body you value (eyes, face, hands, other). The following is for entertainment purposes ONLY. Following this method is taking extraordinary risk and you could get gravely injured, or die.

Yes, I was a dummy when it came to PCBs. In fact, I was a dummy when I came to anything DIY Audio a few months ago. Of course, now I’m an expert in all things.

All the information you could ever want is in the forum – “Just search the forum…”

It really irks me when people post that. “Hey, I already searched the forum, and now I’m asking…” As a newbie, I knew NOTHING about circuits, PCBs, soldering, resistors, you name it. I always wonder if the “experts” realize that new people enter the hobby now and again.

After trying lots of things, buying lots things, and running some experiments, I know a little bit about...
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