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Old 10th September 2012, 11:09 AM   #301
AndrewT is offline AndrewT  Scotland
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Put my paint comment in context.
What way around does the painting machine orient the unpainted resistor?

If you and the machine are synchronised then maybe you get the resistor/s the same way around.

What effect do the different pigments have on the resistance and the parasitics attached to that resistance?
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Old 10th September 2012, 11:29 AM   #302
bcmbob is offline bcmbob  United States
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All good points Andrew. I can only offer the possibility of a consistency within the reports of many socket users describing what they hear as validation.

As much as I hate bringing up the subject, it is starting to look like many of the changes in sound could be emulated with a graphic equalizer. Even if someone took that path (which I strongly resist) it IMHO, is still worth the trial process at the RC stage to develop the "best" base unit possible.

I think we are all anticipating some good information from RC builders who have propper lab equipment to present a more technical picture/explanation of what is changing. Though not highly sophisticated, I hope to make some progress later this week on the Visual Analyzer setup mentioned earlier in this thread.
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Last edited by bcmbob; 10th September 2012 at 11:37 AM.
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Old 10th September 2012, 12:38 PM   #303
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Quote:
Originally Posted by bcmbob View Post
I think the beta pieces Dario did for his brother were socket free. Maybe he can report on the significance here.
When socket are removed it always sound better, it was so for the Rev C and it's so for the FE.

Quote:
Originally Posted by AndrewT View Post
What way around does the painting machine orient the unpainted resistor?

If you and the machine are synchronised then maybe you get the resistor/s the same way around.
So far markings seems consistent (orientation wise) between batches but, in general, we dont have any guarantee on it.

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What effect do the different pigments have on the resistance and the parasitics attached to that resistance?
I know, Andrew, it seem absurd considering resistors orientation and pigments on resistors could be the next 'logical' step...

I refused to trust it for years but I've had to accept it (at least in my reality... )
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Old 11th September 2012, 12:17 AM   #304
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Talking Knee-O-Bee-Ummmmm

I am in the process of comparing unusual choices of capacitors for C9, 220 uF. Good news, Soongsc's CapXon NP caps arrived today. I'll give them time to burn in, but the first impression was promising.

The other cap I am playing with is an AVX Oxi-Cap, low ESR, Niobium Oxide. This is a larger than most, surface mount capacitor that could be soldered directly to the through hole pads at C9 on the FE RC board. Since I want to compare them to the Black Gate PK (early favorites) and to the CapXon, I am soldering on leads that will work with sockets.

Is it worth the trouble? I think so. My impression is that the Niobium cap is competitive with the BG PK. I won't say any more at this point, but would like to invite other builders to try them and give their impressions. For obvious reasons, that especially means you, Dario and Bob (check your PM please).

A short note on Niobium Oxide caps. Niobium is a cousin of tantalum. In oxide form, the cap is made of sintered material in a plastic case. The sintered material can absorb humidity. This causes a problem as the water can expand quickly during soldering and cause the cap to fail. For that reason, the caps are shipped in a sealed bag at low humidity. They should be soldered soon after opening the bag. Alternatively, they can be baked to dry them out.

Also, they have a polarity with the anode or plus denoted by a black stripe on one end of the cap. Here is the Mouser page;

NOME227M006R0040 AVX | Mouser

And here is how I added leads for socket comparison. First, using tacky solder and normal surface soldering technique, solder on a lead.

Click the image to open in full size.

Then, cut out the lead in the middle to separate the two side of the cap.

Click the image to open in full size.

After filing the leads to fit, this is the cap with leads on the board.

Click the image to open in full size.

Jac

Last edited by lehmanhill; 11th September 2012 at 12:25 AM.
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Old 11th September 2012, 09:10 PM   #305
atupi is offline atupi  Romania
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I have attached picture of my 15nf polistirene caps without yellow dot. Where should be the dot ?

I have tested my new MyRef with some low sensitivity speakers small standmounter 8ohm 85db (Spendor SA1) and Spike protection was activated very soon. The same is happening with some test speakers that i have home also not so sensitive (Sony Sb1000) also 8ohm. Unfortunately i dont have anymore (sold) the speakers used when testing RevC amplifier.
Should i be worried about this Spike protection that activates so soon ?
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Old 11th September 2012, 09:41 PM   #306
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Atupi,

The yellow dot is on the top of the capacitor. Look closely at the pictures in post #25 of this thread. The yellow dot looks like a messy paint mark on the end.

Also, I have 4 ohm speakers (22V transformers) with about the same sensitivity. The heatsinks get slightly warmer than hand warm, but no SPIKE protection, even after some loud playing. You may have an issue. Did you use thermal grease between the 3886 and the heatsink? I tried it briefly without grease and the chip got hot very quickly.

Beyond that, I'm no help. Hopefully Dario and others can help.

Jac
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Old 11th September 2012, 09:43 PM   #307
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Regarding if C9 capacitors change the sound level.

I did a little experiment. I measured the sound level with a cheap Radio Shack sound level meter. Playing the same music, but different caps, the sound level was the same within my ability to read it. So far, Dario is right. The sound may seem louder, but it is probably something like improved bass rather than an overall sound level change.

Jac
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Old 11th September 2012, 10:17 PM   #308
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Quote:
Originally Posted by atupi View Post
I have attached picture of my 15nf polistirene caps without yellow dot. Where should be the dot ?
They're for C7, right?

If they're 15nF they don't have any yellow dot.

The KP1834 marking shoud go toward the LM3886 but I would try it using sockets (the right side is the sweeter and fuller one)

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Should i be worried about this Spike protection that activates so soon ?
It depends... sensitivity is important (better >=87db) but it the dinamic impedance goes under 4 ohm (it could be the case) it could be a worse problem.
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Old 12th September 2012, 07:19 AM   #309
atupi is offline atupi  Romania
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I will try also to change the termal paste to a more advanced one as i'm using a generic one now. The heatsink and chip are heated but to too much as i can keep my fingers on them. My heatsink is Heat Sink A4291-60 :: Heat Sinks :: Electromechanical :: Electronic Parts :: Banzai Music 60x165x35mm

I read that the Spike protection is related to temperature but i think a hungry (ineficient) speaker can heat up too much the chip.

What confuses me is that on RevC i used two computer heatsinks with almost no termal paste and had no problems with Spike.

Last edited by atupi; 12th September 2012 at 07:26 AM.
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Old 12th September 2012, 09:32 AM   #310
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by ClaveFremen View Post
.........The KP1834 marking shoud go toward the LM3886 ............
This is a return to the paint affecting the parasitics.
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