Post pics of your builds.... - Page 235

It is the van-alstein "longhorn" mod.
Its a small u-channel glued to the front of the cart, and partially filled with solder. It is supposed to reduce cartridge "wobble" and adds some mass to the cart.

The biggest downside is that it hits most record clamps/weights. I really liked it on my rega, which I run without a clamp, but I am going to switch to a different cart so I can use a clamp.

Vintage AMB - part 2

After alpha1 and beta1 I had several other projects on the drawing board, most didn't see the light of day. Meanwhile a bunch of friends were begging me to build them stuff, so here is alpha7 and beta7, a preamp and 40W/ch power amp (bridgeable to 120W mono) I built for one of my best friends in junior high and high school. This was around 1979-80.

I used an aluminum enclosure that Radio Shack offered at the time to make the job easier. The boxy shape was a bit odd but it actually turned out looking better than I expected. The preamp was in one box, but the power amp was a two-box configuration because there was no way everything was going to fit in one. As I eluded to in part 1, the front panel was no longer loaded with a million knobs and switches. However, at the request of my friend I retained an LED level meter on the power amp, this time in a more conventional vertical arrangement.

The preamp had a power switch, an input selector, a volume control, a continuously-variable loudness contour knob, and a headphone jack. The power amp had a power switch, level control knob, the aformentioned LED meter, a switch to select normal/standby/bridged modes, and some status indicator LEDs.

The preamp was an all-opamp circuit using NE5534s, which was the audio opamp of its time. The power amp topology was similar to the beta1's (complementary differential input stage, complementary VAS, darlington push-pull output), except for lower rail voltages, smaller power supply, and only one pair of TO-3 output BJTs per channel. No fan-cooling this time, the heatsink was mounted on the rear panel. A relay-based muting delay/DC offset protection circuit similar to the one in beta1 was also used.

Again, sorry about the poor quality photos.







More of my vintage builds to follow soon...

"starving student" build

Defenitely not your style nowadays, but the excellent work of a high school kid almost 30 years ago (with the limited resources at that time) keeps fascinating me.

your early amps are quite interesting amb. I find it strange that you were known as amb at 14 though, how did that come about?

anyway this is a little bit of a strange project that I built that is actually best illustrated through a video. It's my first bit of SMD soldering (that worked) and also my first pcb. I made a few layout mistakes but nothing too serious and surprisingly it worked first time. There are a few design flaws (I overestimated the audio signal amplitude) making it hard to sweet spot on the pot so it actually works:


(caution don't watch the video if STROBE lights cause you problems)
[YOUTUBE][<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/9fngCGdILNM&hl=en&fs=1"></param><param name="allowFullScreen" value="true"></param><embed src="http://www.youtube.com/v/9fngCGdILNM&hl=en&fs=1" type="application/x-shockwave-flash" allowfullscreen="true" width="425" height="344"></embed></object>][/YOUTUBE]
*note the music in the background is not the music input to the device (hence lack of sync ).
anyway an interesting experiment I doubt I will use it due to the before mentioned design flaws and having no need for such things. I have also built a headphone amp:


it's a simple follower but works quite well, I am using my 18V supply I built a while ago to power it.

for my next project I feel like a complete usb>headphones dac amp combo all in one box as I go to uni soon and my current set up is not portable (and my sound card is a POS and I feel like designing a more complex amp). I will probably aim to make all signals in the unit differential and use one PCB.

It's a long story and not all that interesting...

I just love how the '70s style amps perfectly match the '70s style carpet

LOL, how true.

Pimeta + Tread

Just finished my Pimeta for the most part. Waiting on my PCBs from BatchPCB to put in the Monofied Sijosae Buffers.

Pretty standard build. It has OPA2227 as the dual op-amp with OPA227 as the ground amp. Battery power is 12x 800mAh AAA battery (from 4x 3cell telephone battery packs). The power jack is run through the side of the case and the trickle charge sits between the wall of the case one of the capacitors.





Wall power is current coming through a Tread I build on a breadboard. It is regulating down the 48v from a Cisco PoE adaptor down to 20v. You'll notice two capacitors have been cut out of the circuit - I have to replace them. I blew them when I attached the wall power to the wrong end of the Tread.

http://img410.imageshack.us/img410/2...ainsidenf0.jpg
What are the resistor values you are using for R4-R8?

R3=1k
R4=10K
R5=jumper
R6=open
R8=jumper

This makes it a gain of 11. It is the same single feedback loop as Tangent's Cmoy tutorial. When I get my buffers done, I'll replace the R5 jumper and add R6 as per Tangent's schematic

My new Opus DAC w/ IVY output stage. The only thing left to do is build the "convertible" top. I have a servo & gearbox that will open a hole in the top to see inside.

Nothing like a blackberry trackball to clean up the front of a panel Right now it's programmed to switch inputs (toslink, spdif), switch outputs, and adjust lighting brightness.




Nude shot:

That is awesome

What are you using for the control gear?

Thanks It's an Arduino microprocessor (the blue board that's floating around loose in the case) getting inputs from the blackberry trackball and displaying on a 16x2 character serial enabled LCD. It's an open source platform, so there are tons of libraries available for programming, and it ended up being extremely easy to program compared to something like a Motorola HC11 that has to be coded in assembly.

Very cool!