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Tube amp progress

Posted 21st September 2012 at 03:19 AM by wlowes

In the past few weeks I have made progress on by OTL amps. The wooden bases are finished, and I am very happy with the finish.

I reformed and tested all the big can caps. The Nippon Chemi Caps are fine. The big old Samgmo caps make me too nervous to consider using them. They may be serviceable, but have a high leakage current compared to the Nippons and do not seem to hold a charge. Perhaps I'll use them in some other project. I will buy 2 x 2200 caps for each rail. 4 per mono and 8 in total. This caused yet another redesign of the top plate. I have now got room to place a big heat sink on top. It will disipate heat from bridge rectifiers and big resistors used for soft start.

Finally I started to build. While all point to point wired, the amps will be modular. I am using wood blocks as the base for each power supply circuit. I laid out the supply for the small tube anodes and wired them up. This way the caps are well supported and vibration damped....
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My 6c33c OTL project

Posted 21st September 2012 at 03:03 AM by wlowes

I am starting this blog to create a record of my first tube amp project. The project is to build a pair of 110W 6c33c OTL monoblocks based on Bruce Rosenblit's patent. I am starting the blog at the stage that I am well into the project. I started planning and collecting parts well over a year ago and am at the stage where execution is under way.

So how did I end up with this choice? My DIY audio experience got under way with a Peter Daniel chip amp which I enjoy to this day. Along the way I discovered the Lampizator site leading to the creation of a 1541A DAC with 6np2 tube output. When this sprang to life I was hooked on the idea of building a tube amp. I have never actually heard a tube amp. The look is very fundamental. I want to experience the additional nuances in the music reported by tube amp fans.

I wanted to start with something simple but good quality for my first project. I also wanted to keep costs in check. I figured that good quality...
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Akihabara, lost to the maids.

Posted 20th September 2012 at 11:51 PM by rjm (RJM Audio Blog)
Updated 23rd September 2012 at 11:24 PM by rjm

A maid cafe is, as far as I can make out - and wikipedia confirms - a cafe/light restaurant staffed by girls who dress up as anime characters or doll-like maid costumes. Chatting with customers is encouraged, so the atmosphere is more social than a regular cafe. Its also more expensive, and the food worse. (from what I can judge from the menus: its what my nine year old daughter might make if left alone in the kitchen...) They advertise by by having the staff stand around - in costume - on busy street corners nearby handing out small cards.

This is a phenomena that started about 5-6 years ago, or at least started to go mainstream then. Ground zero for maid cafes is the "nerd districts" where computers, comic books, and video games were sold: Akihabara in Tokyo, Nipponbashi in Osaka.

Growth appears to be exponential: every time I visit either region (I'm in Tokyo right now, staying near Akihabara) the number of maid cafes (and therefore maids on the street)...
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Finally packaged up "new" ADAU1442 DSP

Posted 2nd September 2012 at 08:11 AM by googlyone
Updated 15th September 2012 at 08:10 AM by googlyone

Wow - it has taken me months to finally get around to packaging up my latest DSP. With work, travel and holidays I have a huge bag of excuses, but I guess the actual reason is that my old DSP using the Analog Devices AD1940 actually works just fine.

The results are I think pretty neat:

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The case was made from leftover bits from the last set I built - the sides are simply timber with a groove routed for the top and bottom panels to sit in, and the front and rear panels screw into the timber sides. It makes a change from the multitude of "all metal" cases that litter my workroom and playroom.

The implementation here has one analogue to digital converter and four digital to analogue converter cards.

These can be seen here:

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Where the ADC is the first vertically mounted bard on the left with the slightly scruffy IDC cable. The four DACS...
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