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Old 1st March 2012, 07:06 PM   #1
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Default Vitrohm RG Tantalum/Tungsten series, the unknown audiophile small signal resistor ?!

I just got me some NOS Vitrohm RG520 0.7Watts resistors.

See the datasheet here:

http://www.vitrohm.com/download/series/41/

These guys combine some very sought-after features:

- Metal Glaze, Tantalum/Tungsten resistive element
- Tinned pure copper leads soldered directly to the resistive element (capless, non-magnetic)
- Brown moulded phenolic case like classic Riken Ohm or Allen-Bradley
- Technically far superior to the above mentioned resistor types
- A mature quality product, with a long track record, robustness and low drift etc.
- Still in production and RoHS compatible !
- German brand, production most likely still in Europe

I'm asking myself, why this interesting resistor seems to be entirely ignored by the audio community, while in meantime obsolete Shinkoh Tantalum, Holco, Riken Ohm etc. have a very loyal and almost hype following.

Too expensive ? Not really, at production quantities they are $0.20/pc. if one takes 1000pcs.
Probably Vitrohm is only well-known for their el-cheapo wire-wound power resistors, but these small signal resistors are a completely different class of device and almost same price category as their power resistors ...

Any experience here with these fine resistors ? I'll try them soon in a DAC mod and let's see ...

Please take a look at the appended photograph, it shows the internal construction and the capless resistive element.
Attached Images
File Type: jpg Vitrohm RG520.jpg (43.8 KB, 284 views)
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Last edited by Jon Lord; 2nd March 2012 at 10:43 AM.
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Old 1st March 2012, 07:16 PM   #2
klewis is offline klewis  United States
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where do you buy them?
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Old 1st March 2012, 07:34 PM   #3
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I got them from a German Vitrohm wholesale distributor. It was their complete non-RoHS surplus, so one needs to ask for current production and multiples of 1000, if one wants to buy these resistors from them ...

You can actually buy them from Buerklin in Germany in 10x quantities, but Buerklin obviously stocks only the RGU Series, which is the radial (!!) version with the same electrical properties and internal construction.

See here:

https://www.buerklin.com/default.asp...vitrohm+rgu%29

The RGU series was btw. marketed by Vitrohm in Hifi magazines (!!) in the early 80ies as an Audio resistor. They were then used in some European Hifi equipment for quite a short time and then disappeared again, probably due to cost reasons.

Nevertheless this resistor series was in production all the time ...
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Last edited by Jon Lord; 1st March 2012 at 08:00 PM. Reason: radial, not axial
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Old 1st April 2012, 07:45 PM   #4
StevieK is offline StevieK  Germany
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Default Hello jon lord,

I found myself Vitrohm-R ´s named rg515 and I am intested who they sound
compared to other resistors.
Thanks
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Old 1st April 2012, 08:24 PM   #5
KSTR is offline KSTR  Germany
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Don't know about sound, but in industrial apps Vitrohm ZC series (SMD MELF) have a reputation. Looks they have better specs compared to the RG(U) types, see voltage coefficient, by a factor of 25. Better noise spec, too.
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Old 1st July 2012, 05:38 PM   #6
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Hi,

Did any of you try these? Any opinions?
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Old 1st July 2012, 06:35 PM   #7
KSTR is offline KSTR  Germany
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I will try some ZC MELF's in an upcoming amp build to replace the typical 1206 SMT chip film resistors which are known to be more noisy and more non-linear than any good metal film type.

But, typically I'm not a "best component junkie" having sleepless nights about what resistor brand is "absolutly best", I just choose what seems to be technically appropriate and affordable for the task.
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Old 2nd July 2012, 11:57 AM   #8
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Default Phase Noise in Resistors ?

Hello guys,

the test is still to be done ...

Judging a resistor by listening to it might be anyhow rather unsatisfying, because the differences are so small, that even if there is a difference, one can't easily say, which one is better.

Voltage coefficient is rarely specified and most of the time a maximum value (pretty safely set far above the real value, because it is not tested in production). So comparing manufacturers specs doesn't help a lot.

In Jan Didden's Linear Audio, there was an article published, testing several brands of resistors.

Here clearly thermal distortion could be measured (but still way below inaudible levels for non Carbon types).

The two main distortion effects (temperature and voltage) can be easily cancelled in voltage divider networks by using the same resistor over the whole chain (e.g. attenuation -20dB, take a chain of 9x "unity resistors" for the upper resistor and 1x "unity resistor" for the lower resistor). This type of matching works extremely well in IC design, so it should work in Audio even better ... ;-) Using such smart approaches allows to select the resistors for other parameters (like noise, parasitic capacitances), so this can lead to an overall better performance.

Anyhow, another very interesting effect I saw in the article in "Linear Audio", that some resistors, especially the carbon types, but also some film types show a broadening of the FFT peak width of the fundamental (not only a rise in noise under signal, but also a local rise of noise around the fundamental). This is certainly again well below normal audible levels, but if this is a real effect it could be expressed as resistor phase noise, which I find quite fascinating, especially since such an effect can easily lead into phase intermodulation (Which in other areas would be called Jitter) ...

Anyone ever heard about phase noise in resistors in relation to audio ?
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