Volume Control Relay Attenuator passive preamp

[serglobo]

A stepwise volume control is implemented with a set of tiny relays and resistors. In a high-end audio system, a noticable sound improvement over potentiomeneters is obtained, also compared to 'audio grade' potentiometers. Its IR remote control provides convenience over solutions with stepped attenuator rotary switches. The sealed relays will maintain contact quality over a practically endless lifetime. The design represents a audio 'preamplifier' of top-class sonic quality, in a compact and affordable implementation.
The design uses high quality Fujitsu FTR-B4CB4.5Z bistable relays, as well as mil-grade audio grade resistors RN55D, RLR07, CMF55 from Vishay-Dale, which have an excellent reputation in the audio field. The circuit is designed for high-quality audio applications.
The input impedance is constant 10K, 22K, 50K, 100K.
The 1.5 dB adjustment step covers a sound attenuation range of 94.7 dB, 63 steps. By eliminating any active electronics, a very clear and open sound is maintained. There are no clicks when adjusting the volume in the speakers. Encoder for control from the panel.
The IR receiver allows remote control. When the power is turned off, the last volume position is remembered.
The circuit operates from a stabilized voltage source of 5 V.

The input impedance is constant 10K, 22K, 50K, 100K.

Payment is possible via Payoneer or to a bank card. It is also possible to buy on Ebay.

Stereo controller kit (2 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver - 70€
https://sgaudioua.etsy.com/listing/1798144856
Stereo controller kit (2 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver - 70€
Input selector for 4 stereo channels - 20€
https://sgaudioua.etsy.com/listing/1825237975

https://www.ebay.com/itm/267119803938
https://www.ebay.com/itm/266863103276
https://www.ebay.com/itm/266932731942

Stereo controller kit XLR (2 channels XLR), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver - 98€
Input selector for 4 stereo XLR channels - 35€
https://sgaudioua.etsy.com/listing/1824028825
https://www.ebay.com/itm/266918250389
https://www.ebay.com/itm/266936692441

Stereo controller kit (8 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver - 154€
https://www.ebay.com/itm/266863035366

Stereo controller kit (6 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver - 126€

 

[von Ah]

Cool project! This probably should be moved to the Analog Line Level forum (unless you got your project slated for the Store).

 

[serglobo]

The simplest option is a stereo controller with encoder control and IR remote control. For convenience, an indicator is connected, but it can be used without an indicator. Different types of indication will be shown later.

 

[Zatopek]

Even though not brand new, yes, of course this is a function everybody has thought about. I am using a 24 position rotary switch and sure would like to make it either a 48 position switch or a relay attenuator such as the one you have crafted. Let's see how many fans you might convince for that solution. A group delay might help to limit the efforts

 

[Zatopek]

... sorry, a group BUY...

 

[serglobo]

I have been making this product for about 7 years now and during this time it has been brought to almost perfection. Everyone notes the very high quality of sound, plus quite high flexibility in manufacturing and assembly.

 

[rayma]

Thread moved to vendors' bazaar.

 

[serglobo]

Stereo controller kit (2 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver - 70€
Input selector for 4 stereo channels - 20€

 

[kouiky]

Very nice! I have a few questions. What are the physical dimensions of the 2-channel main/relay boards? What is the current usage during idle and during relay switching? Is it 300 degrees of control knob rotation for the 64 steps? Thank you in advance.

 

[serglobo]

The size of the boards is 100*40 mm. The consumption in idle mode is about 100 mA, in switching mode 300 mA maximum. The switching handle is an encoder, in this case 12 steps per revolution, 5 revolutions of the encoder are needed.

 

[maravedis]

Will you share details of the control code? I'd be interested in integrating it with a different controller
What is the price of extra modules? Is there a limit to the number of modules that can be used?
Thanks
.

 

[serglobo]

The number of inputs can be increased to 8 stereo channels. The number of controller boards is not limited. The price of an additional controller board is 28€. Integration with another controller is possible upon your request.

 

[serglobo]

This regulator can be used for both RCA and XLR. The number of modules and the cost change.

 

[maravedis]

Integration with another controller is possible upon your request

I've always wanted to implement a 100mm slider pot remote volume control - reflected by a large bar display on the receiver. I think this is would be so much more communicative than a -db numeric display. It can't be that hard with esp32/bluetooth pair can it? But I've not quite got the skills myself - without a large investment in time...
I wonder if there would be any interest on here in this idea?

 

[Ludus Tonalis]

The links in posts #1 & 8 don't seem to link to anything.

 

[kouiky]

The size of the boards is 100*40 mm. The consumption in idle mode is about 100 mA, in switching mode 300 mA maximum. The switching handle is an encoder, in this case 12 steps per revolution, 5 revolutions of the encoder are needed.

Thank you for this explanation. Very appreciated.

I see 64 PPR quadrature rotary encoders (Bourns EM14A0B-C24-L064S for example), and I wonder if they could work to get more steps per revolution?

 

[serglobo]

It will work.

 

[SRMcGee]

serglobo:

Other display options?

Regards.

 

[serglobo]

Other display options?

https://www.diyaudio.com/community/threads/volume-control-relay-attenuator-passive-preamp.415990/ post 13

 

[SRMcGee]

serglobo:

Thanks! Can the encoder change both the input and attenuation, or just the attenuation? If the latter, is there a way to change the input without using the remote?

Regards.