Chasis + GC complete. First listening tests...

[Vikash]

Phew, what an effort - but worth it! I'm on top of the world at the moment. My first chasis (hell, first metal working project), and first fully working two channel GC is complete!

This one uses Brian's basic PCB with a 300VA toroid (2x 20v) and Sfernice P11 10k linear pot.

After running it for a couple of hours, I took it to a friends this evening and hooked it up to his Martin Logan Ascent's and Shanling CDT-100 to see what it could do. It didn't appear to have any problems driving the Logans at moderate levels. There was clearly more bass, perhaps a touch more clarity noticeable on the highs, and better overall imaging than the Denon AVC-A1SR that we used as reference.

Still many tweaks to go, but so far I'm a very happy bunny.

(Must thank PD et al. in the metal working thread for all the help and advice, and of course Brian. )

A bit of a David and Goliath thing going on here...

[Peter Daniel]

I have to point out that proper placing of the amp (feet, supporting platform, etc.) is quite influencial on the sound. Putting it on top of Denon is not optimal solution, I would think.

I did some further experiments with a chassis, and it seems like tightening the bolt on transformer is important too. I preferred to tight it only slightly, only as much as needed for firm support.

You might also notice that removing top cover from the amp, has more influence than removing plastic jackets from electrolytics. The sound is smoother and seemingly more air can be perceived. I still keep the top on, but don't tight the screws at all.

Nicely done, BTW. I like the centrally positioned knob and warmth of side panels.

[jleaman]

Originally posted by Peter Daniel
I have to point out that proper placing of the amp (feet, supporting platform, etc.) is quite influencial on the sound. Putting it on top of Denon is not optimal solution, I would think.

that is not a amp that would be a cd player / dvd player : O)

[Vikash]

The feet are 40mm square blocks of acrylic roughly 15mm thick. I plan to put the LED's inside the feet, I just hope they don't melt. I don't believe my ears will tell me any different if I remove/loosen the cover, adjust the toroid bolt, or remove the cap jackets - but I'll give it a go nonetheless I'm looking forward to a thorough listening comparissons once the premium kit version has been finished.

A shot of the internals:

[Taco]

Very nice chasis.

PD: are those chips so sensitive for microphonics, that feet/ support platform/ transformer mounting has influence on the sound?

[Nuuk]

Yes, nice work Vikash. That's a pro job allround!

Just one thought though!

You measured all your resistors to a decimal place to ensure that you balanced the channels and then you used a pot instead of a stepped attenuator!

[Upupa Epops]

To Nuuk : How big is error ( difference of gain between channels ) by using 1 % resistors ?

[Vikash]

You measured all your resistors to a decimal place to ensure that you balanced the channels and then you used a pot instead of a stepped attenuator!

Very true but I felt I was taking on enough for a fist amp without adding diy attenuators to the list. I took some quick measurements of the channel difference on the pot and and it was not good, so I will almost certainly need to change this down the line. At least the pot will be easier to change than the resistors though

In fact I found an odd quirk whereby you could only hear output in one speaker until you reach a certain volume. This was still at a low volume but I haven't traced the cause yet.

On a last thought, I don't know if there's enough space in the chasis for an attenuator

[MikeB]

Originally posted by Peter Daniel

You might also notice that removing top cover from the amp, has more influence than removing plastic jackets from electrolytics. The sound is smoother and seemingly more air can be perceived. I still keep the top on, but don't tight the screws at all.

Hmm, if your amp is that sensitive to such details, maybe you should
consider that your amp is slightly oscillating ?

I never experienced these details having impact on the sound with
stable circuits. Only the unstable ones showed such symptoms...

Or you have incredible detailed ears compared to mine ?

Mike

[Nuuk]

In fact I found an odd quirk whereby you could only hear output in one speaker until you reach a certain volume. This was still at a low volume but I haven't traced the cause yet.

Is that linear pot law-faked, and of so, with what value resistor?

I believe that law-faked pots can be a bit tempermental at the 'ends'.