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Old 25th May 2017, 11:48 PM   #21
AKSA is offline AKSA  Australia
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Join Date: Sep 2001
Location: Melbourne, Australia
Hi Filipe,

Beautiful implementation of my little babies, you are giving them a great home, Filipe, on the other side of the planet, I am most grateful.....

There is another way to set the quiescent which is a little more accurate. You can measure the entire voltage across all four source resistors, the total is 0.6R from extreme left (near ps cap) to extreme right (near opp. side ps cap).

I let the amp sit for 20 minutes to settle, then measure 75mV across the entire chain. This gives 75/0.6= 125mA. Watch it for a few minutes, and reset it at 75mV if has changed. There is a temp sensor between of the pmos output device and the pcb; it responds if the amp heats up more, pulling the quiescent down to around 110mA. When it cools, it comes back to 125mA. When you first turn the amp from cold, the quiescent rises to about 200mA to warm it up more quickly. Any quiescent settling somewhere between 115mA to 135mA is quite OK and no cause to worry, but nominally I try to set it to around 125mA as a good compromise of good sound and economical use of energy.

Your setting of 40mV across (2x0.18R) is 111mA, a little low. Bump it up to 45mV if you want to set this resistance rather than the entire string. Your values may be a little different to mine because your summer ambient temps are quite a bit higher than Oz at present; my daily ambient here is typically 15C when I set the amps. But it's not important because you have the adjustment to get it precise for your location and mains.

My sincere congratulations, your system is going to be one of the best in your country! I am so happy you regard it as very musical! That is the entire goal in music reproduction.

Ciao,

Hugh
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Aspen Amplifiers P/L (Australia)
www.aksaonline.com

Last edited by AKSA; 25th May 2017 at 11:54 PM.
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Old 26th May 2017, 02:14 PM   #22
saf is offline saf  Portugal
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Join Date: Sep 2009
Location: Porto
Thank you Hugh !
Allways ready to give a helpful answer, your work must really be recognized.

I will try and measure / adjust all 3 channels for 75mv across all resistors.
My chassis is quite hard (impossible really) to make adjustments and check Bias when fully mounted and connected, but i believe i found a way to dismantle the side panel only. This will make thing a whole lot easier.
I will try it later on and give feedback.

Next weekend i will try to assemble the last 2 channels in their chassis.
And finish all the cabling with heatshrink so everything is nice and tidy.

Will let you know the results....but hey....its playin so well now that i dont have the urge to go and mess with bolts and screws !!!

All the best
Filipe
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Old 26th May 2017, 07:21 PM   #23
saf is offline saf  Portugal
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Ok so new update. All 3 channels set at 75mv +- 1mv
I will rest a bit now...very tired and afraid to make stupid mistakes on the last 2 channels...
Sunday will be a good day to finish it

Cheers all
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Old 26th May 2017, 07:57 PM   #24
zman01 is offline zman01  Bangladesh
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Location: Dhaka
Quote:
Originally Posted by saf View Post
I will rest a bit now...very tired and afraid to make stupid mistakes on the last 2 channels...
Now we wouldn't like to see any silly mistakes with these beautiful pieces with Hugh's Maya amps inside!

Quote:
Originally Posted by saf View Post
Sunday will be a good day to finish it
Cheers all
Look forward to the updates!
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Old 28th May 2017, 11:30 AM   #25
AKSA is offline AKSA  Australia
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Filipe,

Have you had a good listen over the weekend? What are your thoughts of the sound quality, particularly bass, midrange, top end, spatial characteristics (imaging) and clarity?

It should be run in by now......

Cheers,

Hugh
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www.aksaonline.com
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Old 29th May 2017, 08:50 AM   #26
saf is offline saf  Portugal
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Hi,

I have been very busy this weekend, but found the time to assemble the last chassis. I now have all 5 channels finished and playing

Here is a quick pic that shows the 2 main channels with the Sonus Faber

Click the image to open in full size.

I must say, from the top of my analysis that i am extremelly happy.

Much has been writen about these amplifiers, and without wanting to be repetitive, i have to say what strikes me obvious with the first few hours of listening.

With all amplifiers i have heard, tested, owned , borrowed.... i normally describe bass, treble , microdynamics , etc with regards to my impression of it. Well this is not the case.
Hugh's amp is not about numbers, or quantity of this and that. It is about music and how it makes you feel.

Almost immediatly upon turn on, you dont start to notice trebles and bass notes, instead, you start noticing violin tones, female mellowing voices or deep cavernous male voices. The feel of engagement is enourmous. One could listen to the amp for hours without fatigue level increasing which is, for me , much to say about an amplifier.
I had friends come over this weekend and all became flabbergasted with the sound. My dad also is a music lover, and has my AKSA100 in his system. I had to litteraly push him out the door last night, as he was GLUED to the couch.

Another GREAT aspect of this design is its silence. It is the DIY most quiet amplifier i have seen. There is litterally silence coming from the speakers when turned on and not playing music. Not one buzz. And this lack of background noise (noise floor?) shows in quiet passages when playing.

So i must say KUDOS to Hugh, because these amps make me want to sit in the couch and scroll through my music library. They emphasize cord instruments like no other i have heard (ok, maybe the AKSA100 i have too!).

I should also say (without wanting to be too much of a critic here) that i feel what others have noticed and described as "lesser quantity bass notes".
The amp is not bass shy, but comparing it to others previously tested in my system, it does seem to not go so low. On the other hand, the bass is very good, scaled, proportioned i may say and as such i prefer it to any other.

This may be due to the amp only having about 5h of play, or it may be a characteristic of it. On the other hand, i run my amplifiers through a AV processor which has an equalizer in it. I am able to increase bass notes without too much trouble...and as such this is not a problem for me. I may have to explore this better...and try to make a clearer picture.

These are my first impressions, and i must emphasize that i like them a lot and would not want any other amp playing my speakers.
One note regarding matching speakers, the amps do get HOT when pulling a difficult speaker. For example my centre channel Proac does not even make the amp get warm. On the other hand, the rear Sonus Faber Elipsa Auditor makes the amp go very HOT and make me glad i made a proper ventilated chassis !
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Old 29th May 2017, 09:17 AM   #27
saf is offline saf  Portugal
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Forgot to ask :

What is the recommendation for fuses in a 2 channel Maya ?
Should i use 6.3A or 10A ? I just blown a 4A yesterday...too much inrush current i say.
Thanks
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Old 29th May 2017, 11:42 AM   #28
AKSA is offline AKSA  Australia
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Hi Filipe,

Thank you so much for a discursive, analytical, engaging review!! I can see why you are a gun programmer, Filipe, you have a logical, analytical mind - yet you recognise the humanity and culture of music. These amps were specifically design for culture rather than sound.......

I will think about your comments on the bass, but I think it probably has good definition so a reflex speaker with a large motor should be very good for very loud bass notes. Otherwise, as I mentioned, I will think on it!

You mentioned the silence. Silence is often significant in music, and it has to be created without electronic corruption. It took many tries to get the noise level correct over many years. There are complete books written on earthing, it is a black art. But it seems to work very, very well on all my latest amplifiers. I use a 10R ground lift resistor on all the signal earths, down to an ohmic center between the two rail supplies. The chassis is replete with two back to back large diodes to the power amp of each module.

For 220-240Vac mains I use a 10A fuse in the IEC to the transformers.

You captured the spatial characteristics of this amp very well. It throws up a vivid sound field, where it's on the material of course, and it's extremely realistic. Listen to a Diana Krall 'Live in Paris' CD and you will recognise Schmidt's mastery of recording art, it is very good on your excellent speakers, and from memory the Sonus Faber has a shunt crossover, with quite low sensitivity. That will generate quite a bit of heat in the amp, but the heatsinks are indeed generous, at 0.28C/watt for each module. Filipe, you are in summer, I read off the net that day temps in Porto are just over 20C, but in the height of summer it might increase to 25C, a very mild weather pattern. In Oz in summer it can easily be 35C in Melbourne, and I have found my Maya's fine with my relatively efficient speakers at 87dB/watt/metre and series crossovers, easier to drive of course than your Sonus. Even so, be assured that the Maya can cope with this; the output devices are mosfets, rated at 480W each, and fitted with a very effective temperature sensor which pulls the quiescent down if it gets hotter than normal. Music is not usually constant; even heavy metal takes a break from time to time!

Thank you again for the leap of faith! I have my babies on the continent, sub-continent, north America, and quite a few in Oz. Soon will be in Singapore! Let us hope they cry out from the rooftops!

Ciao,

Hugh
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Aspen Amplifiers P/L (Australia)
www.aksaonline.com

Last edited by AKSA; 29th May 2017 at 11:47 AM.
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Old 29th May 2017, 12:49 PM   #29
zman01 is offline zman01  Bangladesh
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Quote:
Originally Posted by AKSA View Post
even heavy metal takes a break from time to time!
Well said Hugh!

Who would have known that heavy metal was part of your musical diet...
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Old 29th May 2017, 01:13 PM   #30
AKSA is offline AKSA  Australia
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Ah yes Zia I admit to some admiration for Ramstein! The fact is there are standouts in all genres - even Rap!

HD
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