My_Ref Fremen Edition RC - Build thread

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#121
atupi said:
To me is a bit strange to have that nice metal enclosure and not to benefit of a goos shielding. A will test to see how it sounds with PGNG connected to the enclosure.
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If you connect your chassis to safety earth you're using the shield... 😉

lehmanhill said:
The BOM says they should be 50 V. When I put the part number from the BOM into the Mouser website, it comes up as a 35 V cap.
(...)
Just checking, are these OK at 35 volts?
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The 35V cap will work perfectly, probably it was specified in bom in place of the 50V one (647-UFW1H221MPD) simply because at the time it was not available.
 
#124
Simply, when two bridges are used, the current through each bridge is half of a single bridge for a given load.
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no.
the current in each diode bridge of a dual bridge arrangement is exactly the same as the current through a single bridge arrangement.

I don't think there are any sound differences between the two bridge arrangements.
There is a difference in the grounding schematic between the two bridge arrangements.
 
#125
Double Diode Bridge

AndrewT said:
no.
the current in each diode bridge of a dual bridge arrangement is exactly the same as the current through a single bridge arrangement.

I don't think there are any sound differences between the two bridge arrangements.
There is a difference in the grounding schematic between the two bridge arrangements.
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Hi Andrew,

I bow to your greater experience. Please help me understand the current flow in the single .vs. double bridge.

My understanding was that the current flow out of the smoothing caps was controlled by the demand of the amplifier. The current into the smoothing caps is the amp demand plus or minus some current flowing in and out of the smoothing caps. If I can assume that the two secondary coils operate independently at the same voltage, then isn't the current through each secondary coil in parallel and about half the total? If that statement is correct, then wouldn't the dual bridge approach flow half the current through each bridge? Just trying to understand.

As for a sound difference from single to double bridge, I am also not sure. I respect the earlier work of Subbura and others, but I will experiment a little to try it myself. I will also study the grounding scheme as I hadn't considered that before.

Thanks for your input. I find these questions very interesting.

Jac
 
#130
lehmanhill said:
Please help me understand the current flow in the single .vs. double bridge.
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Hi Jac,

Andrew is right on this, diodes see the same current no matter which way.

I used to be an advocator of dual bridge, but after really thinking it through, analysing it in spice, and finally measuring its properties (a current clamp is a nice tool) I decided for myself there is essentially zero benefit, in the end. It can be even more sensitive to supply noise issues (leakage current paths get chopped, modulated by diode conduction timings, unless one takes special measures) than a single bridge.

As for wiring/layout advantages, think of the PSU as a black box with a break-out cable with a 3 pin plug (pos/neg/gnd) and a socket right at the point of load. It obviously cannot make any difference whether there are three or more than three conductors in the cable, unless I'm missing something... the actual "cable" embodiment is of great importance of course, same for the bridges and caps wiring (strive for lowest loop area, mainly) as well as aditional components (snubbers & filters)
 
#131
Dual Bridge

Hi Klaus,

Thank you for your explanation and experience on dual versus single bridge. With two experts like you and Andrew, I accept the constant current. I will have to play in Spice, as you did, just because it is not obvious. In the end, that is one of the best things about DIY. I learn something every time.

Thank you very much.

Jac
 
#132
Before powering up ...

A preview of my work before connecting to toroids.
 

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#135
bcmbob said:
I see you went for some top choices. Looks great and anxious to hear about your audition.
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Unfortunately i will have some solid impressions after mid september as in the weekend i'm leaving for a two week vacation 😉
But the drilling, putting wires nicely in the case in fun.
Did anyone of you tested MyRef with a low sensitivity speaker ? (under 85db)

PS i having someone for sell two caps ERO Mp1834 10nf ? Unfortunately something strange happened and there is nothing even close to this value available on ebay.
 
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#136
atupi,

I don't know the formal rating but the Sunflower speakers I am using now are much less efficient that others I have owned. My experience is that the combination of the Mundorf AG caps and a larger transformer produce a sufficient SPL for most situations. I have a JC-2 pre at hand for the few occasions it's needed, but I suspect you will be pleasantly surprised with the output of your build, even with just a simple pot.
 
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#137
I have one 200w toroid/channel and a B1 buffer (wich is no gain) but very soon i have in plan to build a volume control/souce selector based on PGA2311/microcontroller wich i also intend to be powered from a Salas shunt. Did you tested Salas shunt on your JC-2 ?
 
#140
Sockets

I got a care package from Mouser today. It should have the bits I need to finish the build.

I ordered some of the sockets suggested earlier in the fine tuning thread. I tried to fit the BG STD caps for C9 into the sockets, but the leads are too thick. For you guys that have used these sockets before, what do you do when the leads are too thick? My thought was to file down a short section of lead to fit. Open for ideas. I am hoping to socket and compare C9 and C13,

Jac
 
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