A Chiara in memory to JLH (56K)
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maxdamage

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These last few weeks I have been building a "Chiara" head amp to compare and possibly replace my original John Linsley Hood discrete design. Given Johns recent sad passing away I wanted to make this project something of a tribute to the man who has given me and many others so much pleasure with his superlative designs.

I would like to share my efforts with you. The case is scratch built from two metal boxes from Maplin.co.uk mounted on a piece of MDF. The front panel is 6mm smoked plexi and the case sleeve is also made from MDF.

Using the two boxes, which are physically separated, allows the original grounding design to be used whilst allowing a "single box" finished case. It also helps to keep supply induced hum and noise to a minimum. The extra PCB in the amp section is an input switching circuit. The only thing left to do is add the remote control circuitry which is still under development.



With lighting in place.




The finished unit switched off.


Switched on. The light around the volume control looks bright in this pic but it is really quite subdued. My digicam is not too good at shooting lit leds or black mirror shiny surfaces either.


This is no ordinary power light. The writing only appears when the amp is powered on. J L Hood - the man who inspired this project.


I am thinking of giving my JLH mono blocks the same treatment.
 
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Megaptera

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That is a very classy amp. Nice work
 
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Dan the audioman

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Nice Job! I really like the "in-writing" power indicator. That was a very creative idea.


Regards,
Dan
 
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IMEP

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Very impressive case work! I really like the signature power light.
 
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ProFingerSk8er

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very cool!

where did you get that knob?
 
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Sewer Guy

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Very innovative front panel. I think you will like the amp, after it has about 250-300 hours on it. Be sure to try a national semi LM 6172 op amp; but be sure to change c3 to 20pf, when you do. It is very fast but unity gain stable. The sound is clean & uncolored,unlike BB 627 & 37. I am using it in my Chiara, the highs are very smooth & extended, mids untouched & the low end is as strong as the original source material. The detail & soundstaging are excellent. With most classical recordngs I do not need a crossfeed circuit but I use Pink Floyds when it is needed.

I am using the LM 6172 in my Chiara, with no instability or oscillation; just clean clear sound.

Goodluck from Team Chiara,U.S.
 
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maxdamage

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Thanks for the comments guys.

ProFingerSk8er - The knob is the standard one that came with the Chiara kit from williamshart. It is just a plain black anodised aluminium knob. I drilled out the knob to fit the red position indicator led. (Incase you thought it came fitted).

Sewerguy - Thanks for the tip I will give it a try. The amp has had about 50hrs running time and seems to be slightly more dynamic than the full discrete version which I have had for quite a few years, although it is probably too early to tell. I don't know how to say this but I can't remember what op amp is in it right now. I did some initial testing using the top three recommended on Pinkfloyds site and I can't recall which one I decided on.
 
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ProFingerSk8er

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the red led does make it very cool, the finish on the knob is exactly what i want on my future project, anyone know where can i get that knob alone?
thanks!
 
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ProFingerSk8er

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thanks for the link maxdamage, however im in US and shipping fee for a knob would kill me
 
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PinkFloyd

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Whoaaaa! that looks fabulous Max, it's pretty amazing what you've managed to do with those Maplins cases... really classy stuff!

The Led in the knob is a great idea as is the lit J L Hood signature on the fascia. The op amp list on my site is not up to date and I'm using 2 x BB OPA 627's on a browndog adaptor at the moment which sound pretty good, the AD 823 also sounds great in the Chiarra.

I also found that changing the 2 "dubilier" 470uF caps for ELNA Silmic 470uF caps brought about quite a noticeable improvement to the sound but that's something you can experiment with once the amp has fully settled in


Superb job Max
 
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maxdamage

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Thanks, I'm pleased you like it. I took the lid off - I currently have the 823 in it but I have also tried a pair of 843's on a browndog. Not sure what I prefer yet, the 843's produce a more open sound.

I am currently using the passive output to my JLH mono blocks and I have noticed running the amp switched off produces a significant drop in volume. The op amp obviously has a detrimental loading on the input when powered down. I had hoped to be able to run this amp passively when not using phones - I think I will add another relay which disconnects the electronics from the pot when the unit is powered down to produce a purely passive preamp.
 
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PinkFloyd

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Quote:

Originally Posted by maxdamage
Thanks, I'm pleased you like it. I took the lid off - I currently have the 823 in it but I have also tried a pair of 843's on a browndog. Not sure what I prefer yet, the 843's produce a more open sound.

I am currently using the passive output to my JLH mono blocks and I have noticed running the amp switched off produces a significant drop in volume. The op amp obviously has a detrimental loading on the input when powered down. I had hoped to be able to run this amp passively when not using phones - I think I will add another relay which disconnects the electronics from the pot when the unit is powered down to produce a purely passive preamp.



Try connecting it like this Max..... the instructions don't make it clear but if you connect like this you'll be sorted
http://www.rock-grotto.co.uk/tweaks.htm

Look at it closely.......... R goes to 4 (Pads 3 & 4) and then R goes to 1 (pads 1 & 2)

All the best.

Pinkie.
 
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maxdamage

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Thanks Pinkie but the problem is caused by the fact the opamp is still connected to the pot and even though the output signal is not passing through it, the opamp is still having an effect on the sound. It is a minor quibble and one I can easily remedy with a relay. (I am a big fan of relay switching
)
 
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