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My_Ref Fremen Edition - Build thread and tutorial
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Old 11th August 2017, 01:02 PM   #3441
udailey is offline udailey  United States
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My_Ref Fremen Edition - Build thread and tutorial
RN55 are really great musical resistors. Made to mil spec by many manufacturers. You could build your own with manganin wire. Better than just about anything besides an ldr then.
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Old 11th August 2017, 01:13 PM   #3442
ClaveFremen is offline ClaveFremen  Italy
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My_Ref Fremen Edition - Build thread and tutorial
Default Confused...

guys, did you read the build guide or at least the BOM?

Vishay Dale RN55 are the through hole resistors in BOM, available from Mouser...

BOM
Build Guide

BTW I subscribe to this:
Quote:
Originally Posted by madisonears View Post
None of the "boutique" parts priced between V/D and Z-foil were worth the extra money. The Z-foil is worth the extra money if you have it to spend, but it's not essential to get decent sound.
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Old 11th August 2017, 01:20 PM   #3443
Joseph K is offline Joseph K  Hungary
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I was just looking up the BOM.. wanted to note the same. Only was not sure if it's the exact same type.
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Old 11th August 2017, 01:41 PM   #3444
lehmanhill is offline lehmanhill  United States
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While we are talking about resistors, I have been reading up on resistors and their effects. Based on my reading, R13, the input impedance resistor may be worth looking at.

The idea is that, since it runs from input to ground, it sees the entire input signal and any noise or distortion that is introduced will be amplified through the system. Measurements show that resistor noise increases with voltage drop across the resistor and with resistance value of the resistor. Since R13 is 100k, it is likely one of the highest resistor sources in the amplifier.

Of course, some would argue that any noise or distortion from a resistor is small compared to the noise and distortion from active elements and that may be true. But, with the exception of bulk foil resistors, industrial and military resistors are all relatively affordable, choosing a good resistor makes sense to me.

Jac
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Old 11th August 2017, 04:29 PM   #3445
Spartacus is offline Spartacus  United Kingdom
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Quote:
Originally Posted by madisonears View Post
If you don't want to spend the money for Z-foil, and that's perfectly understandable, I suggest Vishay/Dale for the most "even" sound. You don't give up much fidelity and you save a lot. None of the "boutique" parts priced between V/D and Z-foil were worth the extra money. The Z-foil is worth the extra money if you have it to spend, but it's not essential to get decent sound.
Thanks, this is useful. I recently replace the 12K Susumu feedback resistor with a Z foil and was very impressed, but in the other important positions I already have Vishay Dales. I'm currently thinking I'll hold back for a while, and spend my budget on other things, such as some nice NE123W midranges .....
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Old 11th August 2017, 06:36 PM   #3446
madisonears is offline madisonears  United States
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Sorry Dario, I have not read the BOM lately. Nice to see we agree on this "value" part. You specify RN55, but I have found any of the Vishay/Dale series sound good. Mouser stocks thousands.

Spartacus, that NE123W is the midrange I have recently installed in my MTM's. It is an amazing driver, so much better than the poly cones I had in there previously. The voices have finally come "out of the box" and now I can easily discern things like the subtle differences between resistors (and, more importantly, violins!). Like the Z-foils, the NE123W is worth the premium price if you can afford it.

Peace,
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Old 12th August 2017, 01:06 PM   #3447
Spartacus is offline Spartacus  United Kingdom
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Quote:
Originally Posted by madisonears View Post
Spartacus, that NE123W is the midrange I have recently installed in my MTM's. It is an amazing driver, so much better than the poly cones I had in there previously. The voices have finally come "out of the box" and now I can easily discern things like the subtle differences between resistors (and, more importantly, violins!). Like the Z-foils, the NE123W is worth the premium price if you can afford it.
Yes I saw in another thread that you were using these. I'm currently using Tangband W4-1337s as midranges, which are good but have a slightly hard sound due to elevated odd harmonics. The NEs seem good replacements, or possible SB12s.
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Old 12th August 2017, 07:16 PM   #3448
Spartacus is offline Spartacus  United Kingdom
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Quote:
Originally Posted by lehmanhill View Post
While we are talking about resistors, I have been reading up on resistors and their effects. Based on my reading, R13, the input impedance resistor may be worth looking at.

The idea is that, since it runs from input to ground, it sees the entire input signal and any noise or distortion that is introduced will be amplified through the system. Measurements show that resistor noise increases with voltage drop across the resistor and with resistance value of the resistor. Since R13 is 100k, it is likely one of the highest resistor sources in the amplifier.
Whatever impedance that is driving the amp will be in parallel with R13, so should mitigate many effects of the large value of this resistor.

The largest voltage will be across the 12K feedback resistor. Something else, that came out of a chat with George, was that any distortions/noise from the feedback network (R7, R10 and C9) will be amplified by the open loop gain of the amplifier, so in the ball park of 100,000 in this case. Therefore, higher feedback amplifiers such as the MyRef should be more sensitive to the quality of the feedback network than lower feedback amps.
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Old 13th August 2017, 11:52 AM   #3449
lehmanhill is offline lehmanhill  United States
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That's what I love about this forum. I learn something new everyday. Thanks.

Jac
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Old 13th August 2017, 04:09 PM   #3450
soongsc is offline soongsc  Taiwan
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Quote:
Originally Posted by lehmanhill View Post
While we are talking about resistors, I have been reading up on resistors and their effects. Based on my reading, R13, the input impedance resistor may be worth looking at.



The idea is that, since it runs from input to ground, it sees the entire input signal and any noise or distortion that is introduced will be amplified through the system. Measurements show that resistor noise increases with voltage drop across the resistor and with resistance value of the resistor. Since R13 is 100k, it is likely one of the highest resistor sources in the amplifier.



Of course, some would argue that any noise or distortion from a resistor is small compared to the noise and distortion from active elements and that may be true. But, with the exception of bulk foil resistors, industrial and military resistors are all relatively affordable, choosing a good resistor makes sense to me.



Jac
Actually R13, R12, C12 form an input impedance curve. This curve is close to the curve of lots of cable.
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