FM Acoustics 711 MK 3

ack

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Nice; I love conductive plastic pots.
 

LL21

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anyone heard this one?
 

ack

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GMKF

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Yes, you did not read the contents of the link

OK, found it now. I was looking for a plastic "pot", instead of a plastic potentiometer.
What a stupid idea.
 

ack

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OK, found it now. I was looking for a plastic "pot", instead of a plastic potentiometer.
What a stupid idea.

And FWIW, conductive plastics have been used for decades in high end audio - Spectral and FMA are or had been using them for 25+ years that I am aware of; except that Spectral went out and built their own space-age pot over a decade ago, with a rumored cost to them of $500 a piece
 

Folsom

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Spectral uses relay controlled stepped attenuator now. Why? Because pots are trash even when you though big bucks at them.
 

ack

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Spectral uses relay controlled stepped attenuator now. Why? Because pots are trash even when you though big bucks at them.

Nope, they still use a custom-made linear pot
 

Folsom

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Oops. I wonder where I saw it?

Well, that's reason enough I wouldn't want one.
 

ack

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LL21

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To be fair, it seems that Spectral actually say in their description "no pot or fader currently available is transparent or linear enough for the most critical gain adjustment applications in audio. " From their website below:

The Case for Uncompromising Attenuation

Certain devices in a high-end preamplifier fundamentally determine the ultimate performance possible in the component. Since a preamplifier basically amounts to an adjustable line amplifier, the role of the volume control or gain attenuator system is especially critical and will have a strong influence over the final sonics of the component. Most of today’s high-end preamps incorporate various digital and IC based attenuator systems to control gain, while a minority still use mechanical controls, potentiometers, switches or relay arrays. In our experience all of these approaches have serious compromises which limit signal transparency, dynamic range, step resolution or reliability. Today, digital based IC attenuators are ubiquitous in modern audio design. But even the most exotic of these digital and solid-state attenuators color the sound in various ways. Spectral engineers have long experience researching digital and DAC attenuators and find that none of these gain controls are really up to the demands of high-end preamp use, let alone for critical recording applications. We find the best relay and switch based resistor attenuators to be much better sonically than any digital control. Unfortunately, they in turn suffer from dynamic range and contact life limitations, more importantly they are not a realistic option when continuous gain adjustment is required. Since digital attenuators are not sonically transparent and stepped resistor attenuator controls have step size, contact life and dynamic range limitation, the ultimate gain control would have to be a continuously variable potentiometer or fader. Unfortunately, no pot or fader currently available is transparent or linear enough for the most critical gain adjustment applications in audio.





The Spectral Super Fader Technology

To solve the problems of existing gain control systems Spectral engineers have been working with a leading aerospace contractor. Out of this multi-year effort comes an extraordinary ultra-precision gain control. The Spectral ‘Super Fader’ combines mechanical precision, advanced materials science and unrestricted use of exotic materials to create a level control that behaves like an infinite number of theoretically ideal resistors. Inside, the critical moving parts are precision machined from solid precious metals. These wipers have many surfaces that are spring pressured as a group to contact micro-polished optically flat resistance elements. Exemplary mechanical design and fabrication alignment is used to prevent localized heating from circulating currents. Ultra-pure contact metal eliminates solid-state or junction distortions which occur from plated parts used in other controls. When such precision and material commitments are combined, noise and error in the presence of test signals is immeasurable and other performances are very near to ideal thermal accuracy limits. With polished custom element and ball-bearing construction, there is every indication that this superior performance will remain intact even after 100 million operations. The ‘Super Fader’ potentiometer outperforms all existing gain control systems with virtually infinite service life. We hear a clarity and transparency, as if a wire has been substituted for the control.
 

ack

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To be fair, it seems that Spectral actually say in their description "no pot or fader currently available is transparent or linear enough for the most critical gain adjustment applications in audio. .

Yes this is why they built their own. But plastics are still very good
 

Jon Q

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I just read that, I think these potentiometers are made by "Measurement Specialties, Inc." on request (options/customization) from Spectral. The conductive element remains the plastic, as shown in the data sheet. For photography, the reference (6211-2024-030) also combines with the series (6211-1004-030), see data sheet pag. 3. The difference between 2024 and 1004, I think to be the value of resistance, two individual channel, a third channel, this one works as an encoder, to know where the cursor its , and also be log and not linear.

https://www.whatsbestforum.com/attachments/t5d_9802-jpg.20614/

https://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Data+Sheet6211_Rotary_SeriesA1pdfEnglishENG_DS_6211_Rotary_Series_A1.pdfCAT-RDP0018

jon
 
Last edited:

ack

VIP/Donor & WBF Founding Member
May 6, 2010
6,774
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I just read that, I think these potentiometers are made by "Measurement Specialties, Inc." on request (options/customization) from Spectral. The conductive element remains the plastic, as shown in the data sheet. For photography, the reference (6211-2024-030) also combines with the series (6211-1004-030), see data sheet pag. 3. The difference between 2024 and 1004, I think to be the value of resistance, two individual channel, a third channel, this one works as an encoder, to know where the cursor its , and also be log and not linear.

https://www.whatsbestforum.com/attachments/t5d_9802-jpg.20614/

https://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Data+Sheet6211_Rotary_SeriesA1pdfEnglishENG_DS_6211_Rotary_Series_A1.pdfCAT-RDP0018

jon

Great stuff, thanks
 

Folsom

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Spectral might use those as control, but the signal goes through relays to resistors - much better than plastic.
 

ack

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Well, not exactly. Here's the exact language from http://spectralaudio.com/bulletins/0407.pdf

<<Spectral Develops the Super Fader Technology

To solve the problems of existing gain control systems Spectral engineers have been working with a leading aerospace contractor. Out of this multi-year effort comes an extraordinary ultra-precision gain control.

The Spectral ‘Super Fader’ combines mechanical precision, advanced materials science and unrestricted use of exotic materials to create a level control that behaves like an infinite number of theoretically ideal resistors. Inside, the critical moving parts are precision machined from solid precious metals. These wipers have many surfaces that are spring pressured as a group to contact micro-polished optically flat resistance elements. Exemplary mechanical designand fabrication alignment is used to prevent localized heating from circulating currents. Ultra-pure contact metal eliminates solid-state or junction distortions which occur from plated parts used in other controls.When such precision and material commitments are combined, noise and error in the presence of test signals is immeasurable and other performances are very near to ideal thermal accuracy limits. With polished custom element and ball-bearing construction, there is every indication that this superior performance will remain intact even after 100 million operations. The‘Super Fader’ potentiometer outperforms all existing gain control systems with virtually infinite service life. We hear a clarity and transparency, as if a wire has been substituted for the control.>>
 

Jon Q

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Jun 16, 2019
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Lisbon
Spectral might use those as control, but the signal goes through relays to resistors - much better than plastic.

Dear "Folsom"
Can you indicate where this is written, or send a photograph that proves what you say
 

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