Passive Pre between MSB Premier and MSB S202 amp?

[luca.pelliccioli]

I’m a happy owner of MSB Dac + Amp combo. Unfortunately I can’t afford the upgrade to The Reference DAC that sports a pre module (75k euro). When playing digital music I don’t use my PS Audio BHK Pre and I like the result. Unfortunately I need to swap the cables each time I want to listen to a vinyl, because of it requires a preamp in the chain.

I was wondering if a passive pre could help me. I’d like to have a passive pre able to not alter the sound when I’m playing digital music through the Premier DAC (set high level) to the S202 amp (set at 75 ohm). My aim is to keep the BHK Pre (and other pre) out of the chain, because I’m liking much more going direct from MSB DAC to MSB Amp than using a Pre in between that brings its own signature to the sound, And at the same time it should be able to deliver an excellent sound when I’m playing analog music through the phono pre (Stellar Phono PSA) - without the need of swapping cables, of course. I’m too lazy.

Any MSB owner here ever experienced using passive pre? Pros vs cons? Any suggestion?

A smaller one would be appreciate, I need only 2 XLR and 1 RCA inputs and 1 XLR output.

TIA

 

[Bones13]

I do currently use a preamp between my MSB Premier DAC and Atma-Sphere Class D monoblocks, using XLR connections. The Boulder 508 phono is connected similarly. As I use a balanced tubed pre-amp, and not MSB, amps means I can’t directly answer your question. My current system relit’s on the synergy of the Pre-Amp -> Amp. I just happen to use excellent sources.

I’m positive that MSB designed their amps to work best from the volume control present in their DACs. I’m sure you could stick a passive pre-amp in the middle of that system, but could not predict whether you would retain your current sound. There are some not expensive volume/input control devices available that you could experiment with. Needing a balanced device will increase the cost though.

I, personally, am interested to hear if anyone has run an MSB headphone amp from a pre-amp. The MSB site literature says that they can’t. I’m not sure if it’s an electrical thing (impedence/load type of thing) vs a liability thing of a headphone amp lacking volume control being dangerous to hearing when using a source without a volume control. Most headphone amps having built in volume controls of course.

 

[shawnf]

I do currently use a preamp between my MSB Premier DAC and Atma-Sphere Class D monoblocks, using XLR connections. The Boulder 508 phono is connected similarly. As I use a balanced tubed pre-amp, and not MSB, amps means I can’t directly answer your question. My current system relit’s on the synergy of the Pre-Amp -> Amp. I just happen to use excellent sources.

I’m positive that MSB designed their amps to work best from the volume control present in their DACs. I’m sure you could stick a passive pre-amp in the middle of that system, but could not predict whether you would retain your current sound. There are some not expensive volume/input control devices available that you could experiment with. Needing a balanced device will increase the cost though.

I, personally, am interested to hear if anyone has run an MSB headphone amp from a pre-amp. The MSB site literature says that they can’t. I’m not sure if it’s an electrical thing (impedence/load type of thing) vs a liability thing of a headphone amp lacking volume control being dangerous to hearing when using a source without a volume control. Most headphone amps having built in volume controls of course.

Yes - I'd be keen to know too.

My headphone setup consists of plugging my Premier DAC direct to a Benchmark AHB2 and using the DAC's preamp and attenuator for volume control. It's a very powerful solution, especially if you use certain Hifiman headphone modules. But I am keen to also see how the MSB headphone amp performs.

 

[Bones13]

I was informed by MSB the Premier Headphone amplifier had issues with over voltage from some pre-amps. Specifically that my ModWright LS300 could provide enough voltage to fry an expensive part in the Premier Headphone amplifier.

For me, it will come down to a simple decision. When I downsize later this year (retirement + downsizing/moving to Seattle) If I have enough room to keep the vinyl side of my system (TT, phono pre, and the ModWright pre + vinyl storage + record cleaning machine) then I’ll keep either/both of the Blue Hawaii SE + Violectric V281 headphone amps. (the ModWright LS300 has 2 XLR outputs)

If there is not enough room for the vinyl, then it might be MSB stack to amp/speakers, using the MSB Premier DAC volume control. Decision then will be sticking with my BHSE (electrostatic) system, or go full hog MSB using the Premier Headphone amp. The BHSE does have a fully passive XLR pass through. (XLR inputs directly wired to XLR outputs, so it works even if BHSE powered off)

Other concerns involve the fact that we are moving to assist our daughter with child care, and tubes may be a concern. Many factors to consider as things move along.

I love the MSB Premier DAC, and have a Digital Director coming next week (65th BD present) it will form the central axis of my retirement system.

 

[Daniel Francis]

Yes - I'd be keen to know too.

My headphone setup consists of plugging my Premier DAC direct to a Benchmark AHB2 and using the DAC's preamp and attenuator for volume control. It's a very powerful solution, especially if you use certain Hifiman headphone modules. But I am keen to also see how the MSB headphone amp performs.

Shawn,

Sidenote, that Benchmark amp is a remarkable piece of engineering. I used one for a long while before upgrading to the S202. Really nice product, one of the industries best kept secrets. I wish more people knew about it!

 

[Daniel Francis]

I was informed by MSB the Premier Headphone amplifier had issues with over voltage from some pre-amps. Specifically that my ModWright LS300 could provide enough voltage to fry an expensive part in the Premier Headphone amplifier.

I love the MSB Premier DAC, and have a Digital Director coming next week (65th BD present) it will form the central axis of my retirement system.

You are correct on the headphone amp. It isn't designed to work with a large variety of gear, mainly for focused MSB systems. Overvoltaging is a sad day for the amp :/ I think the specs are listed under it tech specs on the website for what it can work with.

Congrats on the Director! I hope to hear your feedback after you get it settled in for a while.

 

[rrobz]

I'm a bit late to the party, but have used multiple passive preamps between my MSB Select DAC and various amps (Kraft 300 monos, VTL Sigfried IIs, CJ ART 300s and Premier 11A).

A passive preamp can work fantastically well with your MSB DAC. However, I am not sure its a good pairing for your amp due to the input impedance. I assume the 75Ohm setting is with the intent of an impedance matching between input and output. As the Sstage review of the S202 states: "MSB recommends the 1.2k ohms setting for any non-MSB component connected to the S202, 300 ohms for use with MSB’s Discrete DAC, and 75 ohms for when the S202 is driven by MSB’s Select, Reference, or Premier DAC."

If you are still interested in going this route,1.2 kOhm is REALLY low for an amplifier input impedance, and not a good match for a passive preamp. Your only realistic option given your configuration is a transformer based passive (which is what I generally use). What kind of budget do you have, and what functions do you need? If you have 10-15k Euro, I'd get a used Ypsilon PST-100Mk2 (I have used both the Copper and Silver versions with the MSB), and I anticipate that would work quite well. I really enjoyed the Promitheus Signature TVC and it is much more affordable, but has limited inputs and outputs.

Honestly, though, I'd ditch the amp and then the preamp questions becomes much simpler- love the DACs, but not a fan of MSB amps.

 

[Dustin Symanski]

1.2 kOhm is REALLY low for an amplifier input impedance, and not a good match for a passive preamp.

You are right that this is a low impedance for a typical audio amplifier input. However 75 Ohms is much lower and 75 Ohms is actually nearly the ideal impedance for any passive preamp. The Reference, Select and Cascade all have fully passive preamps with absolutely no amplifiers of any kind and they ideally drive the 75Ohm Input setting of our amplifiers. This is due to the necessity of cabling between a preamp/DAC/source and the amplifier. Realistic geometries of the dielectric and conductors in cables mean that 35-150 Ohms is the range realistic impedances that can be manufactured. If you have radically different impedances on either end of the cable (eg. 5ohm source and 100K input) the majority of the input energy is reflected and trapped on the cable leading to significantly decreased sound quality. Having impedances that roughly match the cable impedance will allow dissipation of the energy on the cable at the source and endpoint. If only one end of the cable has an impedance that roughly matches the cable then energy may still be drained away at that end which is the second best scenario but not ideal. Simply adding a termination to an amplifier input does not solve the situation however because of the loss of signal power, and if there is an active amplification stage probably an increase in distortion of its output due to energy adsorption and increased load in the termination impedance. It is much better not to throw away that signal power. If the amplifier can use the signal power for a useful purpose then significant performance can be gained, such as all of our current amplifiers.

If you limit your concept of a passive preamp to the simple resistive divider you are correct that this is not a good match any cabling solution. This simple architecture is only useful as part of a small geometry local circuit inside a piece of equipment. The primary problem is that the impedance of the attenuator changes radically with setting, often leading to a drastic change of sound for every volume setting, or an extremely undynamic soft sound if the impedance of the divider is high. But only an idiot designer would limit their imagination to a single naïve implementation such as this. There are tens of other passive attenuator architectures that are far superior, but more complex. You mentioned one example such as transformer based preamp, but I believe electrically tapered, lossy transmission lines are even better. They result in zero impedance change with setting and allow distributed adsorption of excess signal energy resulting in ultra low signal distortion regardless of setting.

The second misunderstanding you seem to have about our amplifiers is that they are similar to others in the industry but have some additional defective design choices (low input impedance). I assure you this is not the case. First the design is radically different. Most (if not all) other audio amplifiers only amplify the input voltage, ours do not. They actually amplify the power present at the input, similar to a typical low noise figure RF amplifier. This means that the source impedance is actually completely irrelevant to the amplifier at all. If the source has a 100KOhm output impedance, but can provide sufficient power, the amplifier will not have any different performance than if the source has a 0.1Ohm output or 50Ohm output impedance that provides the same amount of input power. This power amplification results in a much much lower noise floor, lower distortion and the ability to more closely match the physical cable impedance. In addition all our amplifiers have extremely low distortion without the need of any local or global feedback at all (besides emitter degeneration of some specific transistors). This is achieved through feed forward curvature correction, huge intermediate signal stage power (achievable due to the low loss of input power, unlike the majority of other amplifiers), an ultra low noise figure, and massive dynamic range up to 24db more than most other audio amplifiers.

 

[Socrates428]

The Benchmark LA4 preamp is at home in such a system. I've used one in multiple six-figure systems. It is a straight-wire with gain, perfect if you like what your DAC and amps are doing and want attenuation with the preamp getting out of the way. It's also cheap and has a 30-day trial period from most sellers.