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Old

Don't ground your pot

Posted 10th December 2011 at 12:28 AM by jtktam (Newbie audio DIYer)

I always ground my pot to the star ground on my other projects.. seems that for some reason this shuts down the left channel on my sapphire..

went through the whole diagnostic to narrow it down to the pot.. (or so i thought) and replaced it with a new one.. i got it working.. then i grounded it and it didn't work again..

on a hunch i removed the ground wire.. and VIOLA.. sweet sound from both cans!

-joe
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Old

But how does it sound?

Posted 9th December 2011 at 12:42 PM by jtktam (Newbie audio DIYer)

Hard wired the left output to the right side (running mono R on both headphones)

testing the sound of the amp.. it's truly amazing.. nothing i have compares to it..

need to get it to the store to put it on demo.. no time to work on fixing this one.. worked til 2am last night and woke up at 4:30am.. too tired

i will probably end up building another set of boards and swap it out and debug later..

-joe
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Old

bumpy ride

Posted 9th December 2011 at 12:40 PM by jtktam (Newbie audio DIYer)

The sapphire amp is done. I ended up building an external power supply, not enough room in the hammond to put everything.

I had overheated Q3 on one of the boards and the DC output was at 8vdc! luckily I always check offset before I plug headphones in.

Ended up replacing it and it works fine..

I had originally wired the chassis for dual mono output into a Y harness back to stereo.. then my friend suggested that i wire it directly for stereo.. no sense in spending time on the harness..

upon rewiring, the left channel refuse to work.. i didn't even touch it..

i must be jinxed

-joe
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Old

My systems

Posted 4th December 2011 at 11:41 AM by alexcp (My DIY projects)
Updated 12th May 2013 at 07:41 PM by alexcp

Someone pointed out that it's interesting to see all the components in a system, rather than discuss them individually. I liked the idea - I think it also shows what projects ended up actually useful - so here are my systems (I have four with diy components).

The music I listen to is an eclectic mix of classical music (such as Rachmaninov and Tchaikovsky), opera (mostly arias), jazz (Armstrong) and some pop music.

The first system is the one I listen to the most:
  • exposure 2010S CD player with Tentlabs low-jitter clock
  • B1 clone preamp
  • F5 clone
  • Vintage Celestion DITTON 15XR speakers

The second system is the testbed for whatever project I may be working on:
  • Audio Analogue Crescendo CD player
  • B1 clone preamp
  • Zen V4 with SiC power JFET in the gain stage
  • Klipsch Heresy III speakers

The third is the best sounding so far, has the highest WAF and is likely to stay around for some time:...
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Old

RJM Sapphire

Posted 4th December 2011 at 01:58 AM by jtktam (Newbie audio DIYer)

Another weekend, another project.

Started on the RJM sapphire headphone amp this weekend. Having a bit of trouble with the transformer I ordered. According to the BOM they specified a Triad 25VA unit.

I got them from Mouser and it was huge, the wires were unwieldly and I didn't think I would use them

Looking at the pics posted by RJM, they used Amveco, which is my normal brand.. DOH!

So off to digikey to order yet another set of transformers..

Also need to figure out if I would use the bridge rectifiers I already bought, or use Peter Daniels rectifier PCBs and use the MUR280 instead.. the latter will be faster and cost more.. the former might not perform but it's cheap

-joe
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Old

Interesting blog post about fake chips

Posted 3rd December 2011 at 03:27 AM by abraxalito
Updated 5th March 2012 at 02:50 AM by abraxalito

On Counterfeit Chips in US Military Hardware bunnie's blog
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Old

PA speakers for brothers band

Posted 30th November 2011 at 09:42 PM by googlyone

My brother was complaining about his vocals not coming through clearly in his (rather modest / amateur) band. It turned out that he was trying to use some old hifi speakers we had as kids!!!

I had a bunch of Beyma 12G125 bass drivers and some P.Audio PA-D26 compression drivers, so offered to throw some proper speakers together for him.

There were a couple of illustrations of design principles in here that are worth reiterating:
- The horn driver has a massive (and by this I mean both acoustically and electrically) resonant peakj just below 2KHz.

To use this driver and avoid horrible the resultant upper midrange peak, it is essental to put a trap on the tweeter to flatten out the impedance.

this at least gives the crossover a hope of working...

- The horn driver still has a big fat peak at 2KHz.

- The horn was CD - and needed compensation to bring the top end up to "flat".
...
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Old

Matching Stuff

Posted 26th November 2011 at 11:24 PM by Michael Rothacher (Audiohobby.com)

The topic of JFET and MOSFET matching comes up often in the forums, so I thought I'd show you the jigs I use.

First up, is my trusty old JFET IDSS matcher.

Click the image to open in full size.

There's a 9V battery inside, and the meter probes are conneted across a 10 Ohm resistor which is connected to the JFET drain. I included a polarity switch for convenience when testing P channel parts.

It's pretty easy to connect the microclips, count to five, and take a reading.

Click the image to open in full size.

And here's what I use for the big stuff. This is my MOSFET Vgs matcher.

Click the image to open in full size.

First, I install a sample part and let it warm up for about an hour. There's a thermistor hot-glued to the heat sink,...
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Old

new layout

Posted 25th November 2011 at 12:32 PM by jtktam (Newbie audio DIYer)

Click the image to open in full size.
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Old

Ck2iii pics

Posted 25th November 2011 at 12:30 PM by jtktam (Newbie audio DIYer)

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Click the image to open in full size.
Click the image to open in full size.
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