Now that I have the amps back I did the "Atomic Ear" test. with the Mini 2496 dac connected and the bare pot at max, absolutely no sound of any type from the 8" woofer and the two 5" mids. There is a pure airy "S" sound from the tweeter at max pot rotation that completely disappears at normal settings.
With the DAC switched off and FE on, still not a trace of hum and the "S" sound is gone. With nothing attached to the FEs I get a soft Mini-Moog tone appropriate for the sound track for a thriller movie.
Super clean - deadly silent indeed !!
With the DAC switched off and FE on, still not a trace of hum and the "S" sound is gone. With nothing attached to the FEs I get a soft Mini-Moog tone appropriate for the sound track for a thriller movie.
Super clean - deadly silent indeed !!
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So you confirm my experience... fine!
In a couple of hours we should have Suburra's results with 97dB sensitivity speakers.
Race update:
- BMCBob
- SoIL4x4
- Lehmanhill
- b.veneri
- billo44
- arthur
- StefanoSan73
- Suburra
- KSTR
- Randytsuch
- diymax62
- mrsavage
- badrisuper
- pmeade
Yes, same results. I'll add that these are the new Antek toroids with the magnetic shield ring and an extra (purple) ground lead. The amps are still on a piece of plywood with the grounds attached to a small piece of aluminum. Don't know if moving to an all metal case is going to effect things.
Also checking to see if I can hear a difference between a standard power cable and the style I made. DIY Belden 83803 Mains Power Cable - Audiophile Power Cord
Also checking to see if I can hear a difference between a standard power cable and the style I made. DIY Belden 83803 Mains Power Cable - Audiophile Power Cord
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With the RevC difference between power cables were obvious with the FE not so.
The FE seems much less sensitive to power cables.
Possible bad news...
Suburrra heard a very faint hum with 97dB speakers that can be heard from half a meter from them.
With 92dB ones he had to be at some centimeters (3-5) from the woofer.
With 89 dB ones (like mines) he's not sure he can hear it and with ears in direct contact to the membrane.
BTW, just for comparison, a McIntosh present at the store where the test has been done were much more noisy than the FE...
We will see, thanks to KSTR's measures, how serious is the problem and if it can be solved simply insulating C14 ground return.
Suburra will also try connecting the heatsink to safety ground, a 'trick' that for some My_Refs fixes this sort if problems.
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I do agree that, if heatsink grounding doesn't rule it out, is a problem the vast majority of builders will not perceive.
Nevertheless if we can fix it with a simple cutout more on the groundplane... why not?
I've already did the mod to the PCB. it look gorgeous and I don't expect problems with it.
In fact this way is more coherent, also big smoothing caps are alredy separated in the same manner.
PS
The Google folder has been update with the new files.
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I would think simple wiring issues can have much of an influence, too. It is very easy to have some siginificant magnetic pickup (from mains transformer and its wiring) in any loop area formed by the speaker leads. In the MyRef the speaker attach points are spaced apart so this can easily go wrong (I will try illustrate that). Personally I think that a subtle 50Hz-only hum is benign, but when you have higher order components it can be annoying, notably with high eff speakers.
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Yes, I'm as curious as anyone to see how the basic MyRef concept works out... and I already have a bag full of ideas for topological/circuit and layout refinements -- things like discarding C9, balancing pin impedances, using the offset trim option, bootstrapping the LM318 supply, circumventing PSRR issues of the LM3886, moving the relay inside the feedback loop, even using different opamps/chips (eg 5534 and TDA7294) etc... I tend to believe more in conceptual improvements than in the hunt for the best sounding boutique passive components (that still can be had then, of course).
Even more interesting.
Penasa started with TDA chips but only with the LM3886 found what he was seeking.
Me too, after optimizing the My_Ref BOM I've started this project for this reason.
The BOM is important for optimizing circuit performance but can't transform a bad circuit in a good one...
The low frequency magnetic field usually requires iron shield to redirect the field. Other metals that are non-magnetic are good for high frequency shielding. I think for simple testing of prototypes, one can use existing cookie/candy cans to cover it up and see of there is a difference or not.
I have received several inquiries about the actual value/quality of the Audyn True Copper caps for C13. Those who have heard them think they are great and well worth the price. The only way to know for sure is to hear what improvement they offer. At $79 for the caps, and another $15 - $20 in shipping/service charges, (I paid a total ~ $97) builders have just cause for reservations on that purchase.
I've made this suggestion often but nobody has posted it - so I will. If several builders in a country go together to get one pair, and swap them around, each person can audition them before making the purchase. This would of course require the use of quick connects, which is safe, convenient and easy to install/uninstall. This also avoids the need for repetitive soldering of the caps. No doubt about that first pair quickly finding a happy home at the end of the process. And remember - the caps just get better the more they are used.
Such an approach could be done by private PMs/eMails, or could be a sub-group buy here on the FE forum.
Just a thought
I've made this suggestion often but nobody has posted it - so I will. If several builders in a country go together to get one pair, and swap them around, each person can audition them before making the purchase. This would of course require the use of quick connects, which is safe, convenient and easy to install/uninstall. This also avoids the need for repetitive soldering of the caps. No doubt about that first pair quickly finding a happy home at the end of the process. And remember - the caps just get better the more they are used.
Such an approach could be done by private PMs/eMails, or could be a sub-group buy here on the FE forum.
Just a thought
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Those caps are great quality ones and the best I've auditioned.
Suburra, who's auditioning my FE modules (including the True Copper), find them gorgeous.
Nevertheless don't think the FEs needs them to sound great.
Start with confidence the build with the Vishay/Sprague in BOM, they sound very good for the price.
This is a great idea so that builders can upgrade their modules after actually auditioning the True Copper.
No doubt the BOM will sound great. In fact my second choice (for my style of music & my system) is the flat out best value Sonicap Gen I @ ~ $8. Price is not always the determinative factor.
IMHO, many similar choices must also be made with consideration of the capabilities of the speakers used. The sub-group buy idea just reduces the "gamble" aspect of buying higher priced components.
IMHO, many similar choices must also be made with consideration of the capabilities of the speakers used. The sub-group buy idea just reduces the "gamble" aspect of buying higher priced components.
Another great cap for builders on a budget is the russian polystirene K71-4(film/foil).
Not as good as the Audyns but incredibly good for the price.
They're quite big though, they will not fit perfectly on board.
Not as good as the Audyns but incredibly good for the price.
They're quite big though, they will not fit perfectly on board.
IMHO, better.
Much more clean, refined and detailed.
Sonicaps, thought, may be a bit more musical.
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