My_Ref Fremen Edition - Build thread and tutorial

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#2,342
R11 looks fine and measures ok. The solder joints are ok but I'll maybe run the iron over them when I put on the replacement C1 and C2 caps.

T201 is all present and correct - just the way it caught the light when I took the photo.

I'll let you know how it goes when I fix it up.

Thanks everyone.
 
#2,348
AndrewT said:
Any axial 1uF 100V MKP would do.
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Schlumpfpeter,

You are touching on one of those subjects that is long running argument. I have no wish to ignite this discussion, but let me provide an overview. Some say that there is no difference in sound between capacitors while others (me) say that both material and design differences do affect the sound of a capacitor, especially a capacitor in the signal path. Others, perhaps Andrew, would fall in between.

The capacitor you are discussing is a coupling or DC blocking cap at the input of the amp. In my opinion, this capacitor has the biggest effect on the sound of the amp of any component choice you will make. In Andrew's terms, this would be a filter cap.

Andrew's suggestion on appropriate materials for a filter cap is correct. If you want to go farther than that, subjectivists (like me) would be even more specific in our recommendations. I refer you to posts 2317 and 2322. The good thing is that some of the suggested caps don't cost any more than a generic MKP. I am not one of those that believes something is better, just because it costs more.

Jac
 
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#2,349
If you adopt a value of DC blocking cap for the input that is too small, then it could operate as a filter.
If you adopt a value that ensures it never works as a filter of the audio signals, then it does not create any added distortion that can be measured.

It is down to selecting the correct type and value for the duty.
 
#2,350
Schlumpfpeter said:
There is one part not available at the shop, can you pelase reccomend a replacement?
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You can use Mouser code 598-940C6W1K-F from the industrial BOM but I would invest some euros more on the suggested best part, Mundorf MCAP Supreme (plain ones, not the 'oily' variants).

While Andrew is correct, as Jac I think it is one of the most important parts of the amp, soundwise.
 
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#2,355
Joseph K said:
"As we are talking about a 1uf cap, the costs are even for the better ones quite low, so I will go for the one you recommended."

Whoa! Now that is a real man talking!

In this case,me personally would not stop any lower than a CastDccu-30.
In the pdf linked..
And i'm not joking..
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Oh my goodness 😀

Unbelievable! Ok, let me correct myself, 1uf in the "normal" range of parts is not that expensive so that I can choose the better ones 😀
 
#2,356
As far as a search in this thread yielded, no experiences of an active two-way amplifier with the My_Ref_FE (or: FE) have been reported. That is, besides some exploring posts.
One important lesson from others seems the same (type of) amplifier should be used for the various channels, in order to obtain a coherent sound.

In for instance, a two-way system the higher frequencies (hights) require only a modest fraction (10% ?) of the power, compared to the lower frequencies (lows).
When considering an active system, one may follow several routes (I think, never seen such a categorization):
- same FE for both channels, the hights with a preset volume control to balance hi/lo.
- same FE for both channels, with for the hights a separate transformer with lower voltages
- standard FE for the lows, and an FE set for lower gain for the hights
- standard FE for the hights, and a bridged FE for the lows

The various routes each require different sets of FE’s. I ask, because Dario kindly announced a new GB 2016, again with interesting updates, here:
http://www.diyaudio.com/forums/grou...remen-edition-gb-eight-run-v1-6-boards-3.html


Can you please comment?
 
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#2,357
I have built an active system around the MyRef. Do a search on my user name.

I will comment here on a couple things you wrote. I'm certainly not an expert, and there are many other places to get information.

In an active, bi-amped system, the amplifiers for mid/high and low frequencies do not need to be the same type. In fact, one of the primary reasons for bi-amping is lost if one uses the same type of amp for both frequency ranges. The coherence of a bi-amp system is enabled by the active crossover and drivers selected, and has little to do with the amplifiers used. Some amplifiers produce high and midrange frequencies more realistically, others produce low frequencies more accurately. Use these factors to your advantage instead of fighting to get powerful lows out of a tiny chip amp or delicate highs out of a powerful brute. The standard MyRef FE does happen to be very good at low frequencies and excellent at mids and highs, and could be used for both halves of a bi-amp system. That would certainly simplify everything.

The power required for mids and highs can be almost as great as what is needed for lows, depending on the crossover point. At 350hz, there is approximately a 50% split between mids/highs and lows. However, a smaller chip amp probably will be better at controlling smaller drivers such as mids and tweeters than big woofers. The MyRef is simply not as good at the lowest frequencies as a large amplifier, but it will certainly be okay. Of course, if the crossover point is moved from 350hz or the slopes are unequal, then the proportioning of power shifts.

What is important with two amplifiers is matching the sensitivity and the gain, which is how much output is produced from the same input. Level controls in the crossover can usually account for a difference in sensitivity and power output, but if two amplifiers get louder at a significantly different rate (gain), then the sound will become unbalanced at different listening levels, which is almost impossible to solve. A very small difference will be hardly noticeable.

Peace,
Tom E
 
#2,358
av-trouvaille said:
As far as a search in this thread yielded, no experiences of an active two-way amplifier with the My_Ref_FE (or: FE) have been reported. That is, besides some exploring posts.
One important lesson from others seems the same (type of) amplifier should be used for the various channels, in order to obtain a coherent sound.

In for instance, a two-way system the higher frequencies (hights) require only a modest fraction (10% ?) of the power, compared to the lower frequencies (lows).

Can you please comment?
Click to expand...

I don't see why it would be important to have identical amps in both freq ranges. I could see the need for different amps for highs and low/mids. You probably would want both to have the same peak output power to be able to drive each speaker without clipping. But the tweeter amp doesn't need to provide as much average power as the mid/low amp so the tweet amp can save a bit on power supply capacitance and heatsink capacity.
It may be that in practise it's not really worth enough to make two different amps and people just go with two identical but that is then not because it is required.

Another thing is that it could be an idea to use a lower power amp for the tweet channel but optimised for transparency at higher frequencies. Less massive, more precise, so to say. I've tried that a few times with a tweeter amp based on parallelled and bridged AD815's, but couldn't really hear a lot of difference - but that may be just me.

Tom E also says sensible things above.

Jan
 
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#2,359
madisonears said:
Haven't had much to write about lately, but here a few recent developments.

One of the big attractions of monoblocks, at least for me, is the opportunity to put amps very near speakers and use short speaker cables. One of the risks of doing so is that the amplifiers will be close enough to the speakers to be subjected to increased vibration, both airborne and through whatever the amp rests on. Especially with these lightweight chip amps, that can introduce distortion that a heavier amplifier might not produce. My amps rest directly on the wood floor directly behind the speakers. Originally, I incorporated some damping material into the amp enclosures to reduce airborne vibes, but the whole enclosure is free to shake about as the floor vibrates. I just built a couple of amp stands out of plywood and pieces of stone countertop, and putting them under the amps seems to have increased transparency and dynamics. The stands are nearly twice the weight of the amps alone, so it is a substantial increase in mass. The stone material is mounted onto 3/4" plywood with a thick layer of silicone adhesive to damp the stone from ringing and form a sort of CLD structure, and the plywood rests on spikes with tips ground down a bit so it doesn't wreck the floor. Seems to be eminently stable.

I also changed the leadout wires inside the amp for the third time. Some will scoff that only those few inches of wire can make a difference, but now I believe it does. Strictly subjective, so I may be fooling myself but I have no motivation to do so. I tried to make my investigation legitimate. All the wire I've used is solid core copper, OCC with teflon insulation. I have found this to be the most musical and accurate type of wire. What impresses me now is that the gauge can make such a difference in the tone of the amp. I started with 16ga, and that seemed to flatten the highs and the image, dull but very full-bodied. I switched that out for 18ga which put more life and bounce into the music, but the highs still seemed slightly recessed. Since my amps run only the highs and mids of my system, I thought 20ga would be adequate to carry the current and possibly provide even more sparkle. It did, but it seemed to reduce the body of the midrange, as well. So now I have just finished installing a parallel run of 16ga and 20ga (for each leg of the signal), and that really seems perfectly balanced between detail and fullness. I never would have expected a few inches of wire to make that much difference, but I have now demonstrated, at least to myself, that it does.

Add mass. Play with wire. There is always more to be gained.

Peace,
Tom E
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I agree have been doing this for some time now short output leads can and do change the sound of your system using the same cables...it seems that short lead out sets the sound and the speaker cables carry that sound all the way to your speakers....🙂
 
#2,360
back for holiday, last time i finished building the My ref one channel is working prefectly but one is not due to faulty diode ( two U820 burnt)

today I replaced the diode, the led light turns on but the relay kept on clicking, and very high frequency noise coming out from the speaker
Test the other channel have poping noise then deicde not to work. Any advise to check the problem ?
 
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