Passive Volume Control for DACs/Sources

Bespoke Audio and Music First pre's fascinate me like exotic cars. IIRC Steve Hoffman preferred the newer Baby Reference 2, citing something along the lines of it has sins of commission that bring something beneficial to the experience where the Bespoke Audio has no sins of omission but brings nothing to the experience.

 

Then the Bespoke sounds better to me, based on that. I would like to hear one next to my DIY Slagle AVC just for shits and grins. But I suspect any difference is going to be minutiae. If I have to strain to hear the difference between the Slagle and literally nothing (no preamp), then there's not much left in terms of transparency. Big price tag too, but I can appreciate the extreme handmade old school aspect of the Bespoke. And supposedly, they claim to have quite a backlog of orders. Horses for courses.

 

For $7,000 USD it better bring me the experience of Emily Ratajkowski

 

Perfect fit to any $140k system which, I am sure, would sound like shit without this valuable $7k addition.
When SA1x-47 costs $628 and is as transparent as any volume control can be, how did they spend $6372 extra?

 

Hand craft. Bespoke Audio can run you up over $10k for that matter. And perhaps an oversimplification to equate to SA1X. Think of it as audio jewellery that sounds good too.

Edit - you can mod an Evo all you like and it may beat a Ferrari, but it will never be a Ferrari.

 

Actually since mention of the SA1 I have a rando question.

If I had a balanced dac -> SA1 -> active monitors....would the output impedance of the dac carry through or is there a different output impedance from the SA1?

 

You want sins of some other category, then.

 

Have absolutely no experience with their products, but was looking up information on EC Designs (https://www.ecdesigns.nl/en/) out of the Netherlands due to their MOS 16 DAC that @purr1n is currently playing with and noticed that they have a passive volume controller called the "SVC" that looks interesting - https://www.ecdesigns.nl/en/shop/svc. Uses "two studio quality motorised servo slider potentiometers" and is battery powered, while also having a remote. Did a quick search and didn't see any mention of it in this thread, so thought I'd bring it up if anyone's interested. Cheers

 

The output impedance of the dac does not carry through. The amp or whatever is downstream now sees the preamp.


I'm rather curious how the Goldpoint preamps stack up vs the Khozmo preamps. The Goldpoints are a bit more expensive than Khozmo overall.

 

I’ve never really liked Saga or Freya in passive mode. Definite softness and soundstage collapse IMO. Active mode/tubes are much better if you can find the right tube(s).

I have a Sys here that I bought late last year but haven’t used yet - will have to give it a try and compare.

 

I think you'll be quite happy with the Sys when you try it. Due to my ears/gear I couldn't tell if it was audible in my chain or not. My wife's nagging about having to turn a small knob next to the TV to control sound was quite audible though.

 

Apologies if this was answered somewhere before, I'm trying to learn more myself about pre-amps or line stages as their role in the system building process seems often taken for granted. I'm wondering if there are factors other than impedance matching to respect when making a choice between an active vs. passive line stage, or if it really comes down to trial and error per your source and amplifier?

For example your typical modern DAC or CD player with a ~2-2.2V RCA output into a line stage which then feeds the capacitor-coupled input of the average tube amplifier. How much does the design of the input stage in the amplifier play a part versus what comes in one end of the pre-amp (the source) and out the other (the output stage of the pre-amp)? What if gain isn't a factor with really efficient transducers? I would really love if anyone here could educate me about this because it doesn't seem to be a topic that's often brought up in audio discussions!

 

Nope, but I'd give it a go nonetheless. I've seen this product in Munich and was amazed how well it's put together. Besides, I've never heard a passive at my place and I'd do this just for my own education, to know how these sound like in comparison to regular preamps. My guess is that potential difference isn't small.

 

Looking at the specs for SYS it says:

Output Impedance: 5k ohms maximum​

Going into 22k Vidar, this is just a little over 4 for damping factor, which is not exactly high I take it. I assume that maybe this is the Zout when the pot is all the way in one direction (lowest volume/max attentuation?) and that it would typically be a lower Zout than this through the middle or top of the volume range?

 

I was curious about this concept myself for a related but different application (iem attenuation adapter). I put together a quick spreadsheet using the definition of output impedance [given on this page]. For a source with a 75 ohm output impedance (like Bifrost) running into a SYS (10k pot) and then Vidar (22k input impedance), I get the output impedance curve shown below as a function of attenuation. Kind of an interesting curve with an impedance going to zero at both ends of the pot. Note that Z_out peaks at 2.5k, so at worst you'd have a damping factor around 10. But the right third of the plot corresponds to volumes that are probably pretty phucking loud. Interestingly, the output impedance only ever approaches 5k when the source impedance is really high (also around ~10k), so I think the specs are conservative. With modern DACs I think a max of 2.5k is closer to reality. [Disclaimer: I didn't design the SYS and I just did this out of curiosity and for my own small project, so take it with a grain of salt.]

 

This is cool. So if this is correct, and I’m reading it correctly, the Zout actually tracks the opposite of what I suggested - with less attenuation, the Zout increases (except at the upper extreme end of the volume range).

 

Very well put together. But it's a luxury item with wood veneer options, custom wound trafos, an option for gold plated transformer covers, lol. Nothing they're doing is sensible insofar as cost goes, and it's not going to improve sound vs the Slagle wound AVCs. I also don't like how they bundle the L+R channels untwisted and unshielded to travel across the chassis. . If you're really curious, go the DIY route.