The way I see it,it adds an extra layer of safety being analog right before the amps.
)
The lack of a clear big-ish level indicator other than the dot on the encoder (not sure about it thought,encoders usually don't have marks) doesn't help either.
Exactly. Or a simple operator’s mistake. It happened to me that after testing I left 100% volume on the DAC and the other day I turned on one of my big amps with this setting … almost deaf, but hopefully the speakers survived.
) directly to [email protected] or here on this fantastic forum!
Stupid idea.
Dear all,
I am Karl Lundahl, owner and founder of Lundahl Sound Systems, which manufactures the volume control reviewed by Amir (thanks again for the nice and comprehensive review Amir!).
Thank you all ASR members for your contributions in this thread, it is really interesteing to follow! Below, I will try to address some of the many questions/concerns that have been raised:
Some background:
As someone correctly mentioned, this device was originally developed to be used in an audio system that my company offers where analogue signals are fed from a multichannel DSP/DAC to the volume control which attenuates the signal in an active 2*3 stereo set-up. I would say that this is a typical use-case for this volume control. However, use-cases may not be limited to this. Therefore, we have decided to offer the VC2361 multi-channel volume control as a stand-alone product to anyone that seeks full transparency in any multi-channel volume control application.
Something about the design:
The volume control is a classic stepped attenuator (6 channels simultaneously attenuated) using relays to connect and disconnect metal films resistors (from Vishay) for the required attenuation of the audio signal levels. The relays are activated by a microcontroller either by turning the volume know (which is attached to a rotary encoder) or by using the remote. Hence, there are no potentiostats in use anywhere in the design (this would be detrimental for channel balance and transparency). The audio signal only sees a passive analogue signal- path, passing through a network of connectors, PCB traces, relays and resistors.
Passive vs Active Attenuation:
Related to passive versus active attenuation, I would argue that the main benefit with a passive relay-based attenuator vs an active one is that it is a simpler and more cost- effective design. The drawback is (as someone also mentioned…) the low input impedance at low attenuation levels, and the higher output impedance. The lower input impedance is however not a problem for most modern signal sources to drive and if adequate power is provided in the signal source this design provides 100% transparency, as evident from Amir’s measurements. Downstream, I would recommend using power-amps with input impedances >20kOhm (that should leave you with plenty to choose from) and to refrain from long cable in excess of 3 meters. Personally, I think we can only observe similar performance in active volume controls that are extremely well engineered like e.g. the excellent Benchmark HPA4 (although only HPA4 is “only” 2 channels). However, for multi-channel attenuation, the combination of active and balanced design will significantly add to the COGS, due to more engineering hours in design as well as component and assembly cost. Hence, with appropriate selection of signal-source and power-amps, the VC2361 may be a good choice for anyone that wants to keep 100% bit-depth and transparency when attenuation of multiple channels is needed.
As a side note, in the reference sound system here at Lundahl Sound Systems, we use the VC2361 volume control in combination with power amplification from Benchmark AHB2 for mid, Topping LA90D for tweeters and a Purify class D amp for the bass. Our combined DSP and multichannel DAC is delivering 7Vrms on all six channels to the VC2361 and we can drive this sound system well above 100dB without any additional amplification except for what’s in the power-amps (I run the AHB2 in low gain mode which is around 9dB gain). For those of you who are familiar with the above power-amps, and now seen the measurements of the VC2361, I trust you can understand when I say that the sound is Transparent with capital T …
My apologies for the massive text, I got a bit carried away, this is the first time someone has reviewed our products, so great fun!
Please do not hesitate to ask more questions (or why not orders...
//Karl
PS. My company is not the same, or even affiliated to, the famous Swedish company Lundahl Transformers. We only happen to share the same family name…sorry for any confusion caused…
Thank you, wish more manufacturers would respond to testing threads in the way that you did. Now tell some details (secrets) about BBQ.Dear all,
I am Karl Lundahl, owner and founder of Lundahl Sound Systems, which manufactures the volume control reviewed by Amir (thanks again for the nice and comprehensive review Amir!).
Thank you all ASR members for your contributions in this thread, it is really interesteing to follow! Below, I will try to address some of the many questions/concerns that have been raised:
Some background:
As someone correctly mentioned, this device was originally developed to be used in an audio system that my company offers where analogue signals are fed from a multichannel DSP/DAC to the volume control which attenuates the signal in an active 2*3 stereo set-up. I would say that this is a typical use-case for this volume control. However, use-cases may not be limited to this. Therefore, we have decided to offer the VC2361 multi-channel volume control as a stand-alone product to anyone that seeks full transparency in any multi-channel volume control application.
Something about the design:
The volume control is a classic stepped attenuator (6 channels simultaneously attenuated) using relays to connect and disconnect metal films resistors (from Vishay) for the required attenuation of the audio signal levels. The relays are activated by a microcontroller either by turning the volume know (which is attached to a rotary encoder) or by using the remote. Hence, there are no potentiostats in use anywhere in the design (this would be detrimental for channel balance and transparency). The audio signal only sees a passive analogue signal- path, passing through a network of connectors, PCB traces, relays and resistors.
Passive vs Active Attenuation:
Related to passive versus active attenuation, I would argue that the main benefit with a passive relay-based attenuator vs an active one is that it is a simpler and more cost- effective design. The drawback is (as someone also mentioned…) the low input impedance at low attenuation levels, and the higher output impedance. The lower input impedance is however not a problem for most modern signal sources to drive and if adequate power is provided in the signal source this design provides 100% transparency, as evident from Amir’s measurements. Downstream, I would recommend using power-amps with input impedances >20kOhm (that should leave you with plenty to choose from) and to refrain from long cable in excess of 3 meters. Personally, I think we can only observe similar performance in active volume controls that are extremely well engineered like e.g. the excellent Benchmark HPA4 (although only HPA4 is “only” 2 channels). However, for multi-channel attenuation, the combination of active and balanced design will significantly add to the COGS, due to more engineering hours in design as well as component and assembly cost. Hence, with appropriate selection of signal-source and power-amps, the VC2361 may be a good choice for anyone that wants to keep 100% bit-depth and transparency when attenuation of multiple channels is needed.
As a side note, in the reference sound system here at Lundahl Sound Systems, we use the VC2361 volume control in combination with power amplification from Benchmark AHB2 for mid, Topping LA90D for tweeters and a Purify class D amp for the bass. Our combined DSP and multichannel DAC is delivering 7Vrms on all six channels to the VC2361 and we can drive this sound system well above 100dB without any additional amplification except for what’s in the power-amps (I run the AHB2 in low gain mode which is around 9dB gain). For those of you who are familiar with the above power-amps, and now seen the measurements of the VC2361, I trust you can understand when I say that the sound is Transparent with capital T …
My apologies for the massive text, I got a bit carried away, this is the first time someone has reviewed our products, so great fun!
Please do not hesitate to ask more questions (or why not orders...
//Karl
PS. My company is not the same, or even affiliated to, the famous Swedish company Lundahl Transformers. We only happen to share the same family name…sorry for any confusion caused…
Hehe, well, not all things in life are related to hifi. There is also BBQ. And sailing, of course...Thank you, wish more manufacturers would respond to testing threads in the way that you did. Now tell some details (secrets) about BBQ.
Out of curiosity because of the dot,is it an absolute or an incremental rotary encoder used?
Thank you for the welcome!
).
It's all answered during the thread but the short version:
Ok, but what's the advantage on digital volume adjustment?
The microcontroller is to connect and disconnect the relays either by using the rotary encoder or the remote.
