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Post by Deleted on Jan 5, 2015 6:24:31 GMT
Hi - just chanced on this forum!
Other interesting audio forums I'm a member of are LencoHeaven (although I own a Garrard 401!), UK Vintage Radio, and the Orion forum (for builders of Siegfried Linkwitz's loudspeaker designs).
Based in South Oxfordshire, I have been interested in audio and building my own amps and speakers since the age of 16, which is now over half a century ago (pass the zimmer frame...), and high end audio for 20-odd years.
I subscribe to Linear Audio and The Audio Critic.
Looking forward to browsing and contributing to the forum!
Craig
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Post by John on Jan 5, 2015 6:29:24 GMT
Hi Craig
Great to have you on board be great to hear about some of your DIY builds (I presume due to some of the forums you use) I o like the look and approach of Linkwintz latest Open baffles
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Post by Deleted on Jan 5, 2015 6:54:38 GMT
Hi John I built the LX521, Siegfied's latest super high end dipole. The pictures of my build are here www.linkwitzlab.com/LX521/PhotoGallery.htm , 3rd picture down. Active crossover built and tested. Since the speakers need four channels of power amplification each side, I decided to go for Douglas Self's blameless design. There are opinions about Douglas one way and another, but his approach of designing out non-linear distortion seems sound. The main problem I have been fighting for quite some time is something that plagues just about all commercial and DIY power amps - induction distortion. The + and - power rails carry half wave rectified currents (at least for Class B and AB), and these couple into bits of circuitry. It causes distortion to rise at high frequency by 6dB per octave, since it is a di/dt phenomenon. So getting down to the residual distortion of the amps themselves, is a matter of very careful attention to power supply/amplifier wiring, and fine tuning. It is not uncommon for distortion at 20kHz to be a factor of 5-10 times more than the residual distortion of the amps as a result of this effect. At last I seem to be winning, with distortion at 50W into 8 ohms being below or comparable to my equipment residual of 0.003%, rising to 0.008% at 20kHz. The fact that this is an endemic distortion mechanism, the vast majority of power amp manufacturers quote distortion only at 1kHz, which is at a too-low frequency for induction distortion to kick in. The only power amp manufacturers that quote over a wider range are class D switching amps, which can give exceptionally low distortion up to 20kHz. I have an aversion to this approach though, although if you have deep enough pockets (many k to 10s of k pounds) they seem to be quite well received. Once I have completed the first 4-amp chassis (imminent now) it should simply be a matter of replicating the wiring precisely in the second chassis. Fingers crossed! Craig |
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Post by ChrisB on Jan 5, 2015 7:00:20 GMT
Hi Craig and welcome to TAS, it's great that you have found us!
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Post by MartinT on Jan 5, 2015 7:16:27 GMT
Hello Craig and welcome to TAS! You come from august forums, hope you enjoy it here.
Thank goodness for someone who rates PSRR as important!
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Post by Eduardo Wobblechops on Jan 5, 2015 8:01:05 GMT
Hi, welcome from another 401 user. I use active DIY open baffles as my speaker of choice at the moment.
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Post by MikeMusic on Jan 5, 2015 8:25:43 GMT
Hi Craig
Welcome to TAS
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Post by John on Jan 5, 2015 9:54:52 GMT
Nice work on the Baffle I would love to hear the LX521 as I really like the design approach. I gone done the Hawthorne route myself and gone active with DSP crossover in the bass but use passive in the mid and treble. I gone Direct digital amplification as this helps when using digital music, less getting in the way of the sound.
Keep us informed about how the amp build goes..... sounds fascinating!
Great to have another Open baffle user
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