Lehmannaudio Decade Phono Stage Review

[DSJR]

IT COSTS HOW MUCH???

Terrible 1960's overload levels and awful 'rumble filter' performance for modern turntables (maybe good for my Garrard 401 or Lencos but the monoing function is more useful as bass on vinyl is mono anyway) which WILL have an audible impact if triggered*, not much costly stuff inside by the look of the pics so how can they possibly justify the price apart from dealer margins taking almost half the cost?

This is poor in the audible fundamentals to me and no, I wouldn't recommend it at all as cheaper stages seem to do a far better job! Overload margins and what happens on ticks and splats is VITAL to suspending disbelief when playing records, even though exalted styli and pickup designs can offer low perceived 'vinyl background roar.'



* [Edit] - I was schooled that an 'acceptable' MM phono stage should offer around 70mV overload level and then soft-clip if excited, to minimise audible issues. The phono stage (AVI) that did this once 'warmed up,' helped keep records as quiet as possible and I never had issues with snap, crackle and pop using relatively modest (now vintage) pickups including a Decca Microscanner that I remain eternally fond of although now stored away as my current deck and arm isn't suitable.

 

[KSTR]

That's not the confusion. The confusion is why anyone playing an LP would want to lose their low frequencies. The purpose of such rumble filters is to eliminate infrasonic frequencies that cause extra work for the amplifier and speaker. It is NOT to get rid of audible band frequencies. As such, the proper filter would have a much lower cut off frequency and have a sharp roll off.

Exactly. A proper rumble filter is quite an engineering effort.
Since the bulk of the rumble is out-of phase between channels, one trick is to mix down lower frequencies (<150Hz or so) to mono so that most of the rumble cancels out. Bass is already down-mixed to mono during the vinyl mastering process so not much penalty with regard to stereo soundstage. There is no free lunch, of course, as the second down-mixing typically creates additional phase rotation.

 

[beagleman]

Exactly. A proper rumble filter is quite an engineering effort.
Since the bulk of the rumble is out-of phase between channels, one trick is to mix down lower frequencies (<150Hz or so) to mono so that most of the rumble cancels out. Bass is already down-mixed to mono during the vinyl mastering process so not much penalty with regard to stereo soundstage. There is no free lunch, of course, as the second down-mixing typically creates additional phase rotation.

Finally someone that understands!

I tried bringing up the "out of phase" topic on another forum, and mostly got crickets. Seems a lot of vinylphiles, are not even aware that Rumble and certain surface noise are out of phase to the musical content on a disc....

My implication, was that this out of phase nature of random noise and constant rumble add a pseudo false ambiance to vinyl playback, that at times enhances the sound stage and is one of the primary reasons vinyl playback never sounds like CD or Even Open reel.

 

[phoenixsong]

Whoo wasn't expecting to see this brand featured here! Their black cube linear headphone amp was on my "to buy" list at one point in time XD

 

[KSTR]

One thing to add, @amirm , when you test frequency response do you drive both channels (mono)? If not, you may not get the correct (relevant) response when the phono stage implements a differential high-pass filter.

Below sim is for a simple 1st order differential highpass together with the common-mode highpass.
Green is for mono which is the relevant case for us (as low bass is effectively mono on vinyl), blue is for one channel driven only, and red is for out-of-phase signals (rumble attenuation).

 

[Thomas_A]

The ProJect phono box has literally the same performance for less than half the price
In Addition it offer symmetric in- and outputs on XLR
In my eyes in any case a better choice...

And better performance for $150.

Muffsy phono preamplifier minireview (update)

This review was updated September 21, 2023. Main change was the use of the E1DA Scaler to fix the impedance issues that is evident when using the E1DA ADC alone. This is an attempt to make a small review with measurements of the Muffsy MM phono preamplifier. It is a DIY kit so it is far from...

www.audiosciencereview.com

 

[DrCWO]

And better performance for $150.

But no XLR
I kow Cinch is used with most home devices but as the signal has to travel via the shield it is always prone to mains hum. If a computer is somewhere in the chain you also may get noise from its power supply especially if it is external and grounded.
So I personally dislike Cinch a lot. All the interconnections in my system are XLR
Would be interesting to know which Phono Pre offers XLR…

 

[Frank Dernie]

Low pass filter so bad it makes this useless with a seismic mass cartridge ie all of them

 

[DrCWO]

Exactly. A proper rumble filter is quite an engineering effort.
Since the bulk of the rumble is out-of phase between channels, one trick is to mix down lower frequencies (<150Hz or so) to mono so that most of the rumble cancels out. Bass is already down-mixed to mono during the vinyl mastering process so not much penalty with regard to stereo soundstage. There is no free lunch, of course, as the second down-mixing typically creates additional phase rotation.

This is why RME ADI-2/4 implements a correct Mono bass DSP

 

[peniku8]

Quite a strange approach to subsonic filtering, to say the least. I wonder if they decided how many db of attenuation they wanted at 10Hz (say 14 or so/5 times) and then worked out what kind of cutoff they'd need with a first order filter to get it (50Hz or so).

Some of the ICs look interesting, though (THAT corp). The overload behaviour reminds me of heavy loading/current limiting on an active filter rather than the usual passive sort that we see. Purely speculation, though... Unfortunately, despite quite a complicated power supply arrangement, which will doubtless have plenty of audiophile appeal, we're not seeing enough voltage output to give us an overload margin of 20dB against 5mV in the final analysis.

The correct term would be infrasonic filter. Subsonic is a speed, no matter how often companies misuse the term
But I agree, the filter isn't steep enough and thus extends far too high. Its -6dB point looks to be 29Hz, which is somewhat reasonable, but it being a 1st order Butterworth makes it unfit for the purpose. A 4th order BW with the same -6 point would be -0,5dB at 43Hz, which would be a much better solution. Maybe they thought a single series capacitor was enough in terms of build complexity.

Regardless, I think @KSTR made a very interesting point here, which I hadn't thought about before and makes a lot of sense. Would be worth looking into, imo!

 

[splitting_ears]

Bass is already down-mixed to mono during the vinyl mastering process so not much penalty with regard to stereo soundstage.

That's generally true, but not always the case. Elliptical filtering (i.e. 'monoing the bass') is common, but not a mandatory step in the disk mastering process. In theory, such filtering is applied only when necessary, depending on the resulting groove geometry. Some material may translate well without it.

An LF crossfeed option makes perfect sense to reduce rumble in a phono preamp, but only if it can be turned off if needed.

 

[DSJR]

That's generally true, but not always the case. Elliptical filtering (i.e. 'monoing the bass') is common, but not a mandatory step in the disk mastering process. In theory, such filtering is applied only when necessary, depending on the resulting groove geometry. Some material may translate well without it.

An LF crossfeed option makes perfect sense to reduce rumble in a phono preamp, but only if it can be turned off if needed.

Sorry to ask or doubt your post gere, but do you cut records for a living? My now retired mastering engineer pal (worked for Polygram as-was) told me that basically every commercial cut done for commercial pressings (and he thought EMI did this too automatically), filtered off content below 40Hz or so and mono-d the rest, this in addition to compression and de-essing in some or many cases. I believe most cuts also go or went through a digital delay so the computer could best ascertain the depth and pitch of the grooves. Once popular DMM cuts remove everything below 60Hz (you can clearly hear this too) to prevent mod noise, the DMM process keeping the crispness on top better I remember.

Now, maybe some audiophile orientated cuts are less heavy handed here, but if you hadn't seen it with your own eyes, you'd never believe what is done to get the music into the grooves in a playable fashion. Sure I have records cut up to the 90's which have been through much of the above and which surprisingly still sound okay without a digital disc or file with which to compare - and a reasonably neutral system that favours neither format

 

[Michael Fidler]

IT COSTS HOW MUCH???

Terrible 1960's overload levels and awful 'rumble filter' performance for modern turntables (maybe good for my Garrard 401 or Lencos but the monoing function is more useful as bass on vinyl is mono anyway) which WILL have an audible impact if triggered*, not much costly stuff inside by the look of the pics so how can they possibly justify the price apart from dealer margins taking almost half the cost?

This is poor in the audible fundamentals to me and no, I wouldn't recommend it at all as cheaper stages seem to do a far better job! Overload margins and what happens on ticks and splats is VITAL to suspending disbelief when playing records, even though exalted styli and pickup designs can offer low perceived 'vinyl background roar.'



* [Edit] - I was schooled that an 'acceptable' MM phono stage should offer around 70mV overload level and then soft-clip if excited, to minimise audible issues. The phono stage (AVI) that did this once 'warmed up,' helped keep records as quiet as possible and I never had issues with snap, crackle and pop using relatively modest (now vintage) pickups including a Decca Microscanner that I remain eternally fond of although now stored away as my current deck and arm isn't suitable.

I think this is a very good example of what we could call 'performative engineering'. In this case we have something that definitely looks to be serious business. The enclosures are well made, full of THT components and heavy-duty large capacitors and heatsinks in the PSU (which is remote to avoid magnetic field disturbances affecting the front end). The internal construction looks very sound, and it's clearly using components that are not cheap (DIP8 THAT ICs). This is enough to make it highly desirable to most of the Audiophile market, but there's actually no need for the company to design a competent circuit to make plenty of sales when you consider the marketing strategy. All that is required is to check the constructional bullet list to signal to the consumer that the performance will be good, based on a series of assumptions that the consensus-based subjectivist zeitgeist has hammered home through decades of marketing.

In this case, we have something that looks very good, and clearly has plenty of money invested, but the overall result is rather poor indeed when we measure it holistically. The design choices have been made to signal quality, rather than realising it as part of a complete system. Audio seems to be a field that particularly suffers from this, but I've seen it in avionics as well.

 

[fullspeed]

Nippon LXZ low esr caps!!! Is it right for audio and this cirquit?

 

[splitting_ears]

Sorry to ask or doubt your post gere, but do you cut records for a living? My now retired mastering engineer pal (worked for Polygram as-was) told me that basically every commercial cut done for commercial pressings (and he thought EMI did this too automatically), filtered off content below 40Hz or so and mono-d the rest, this in addition to compression and de-essing in some or many cases. I believe most cuts also go or went through a digital delay so the computer could best ascertain the depth and pitch of the grooves. Once popular DMM cuts remove everything below 60Hz (you can clearly hear this too) to prevent mod noise, the DMM process keeping the crispness on top better I remember.

Now, maybe some audiophile orientated cuts are less heavy handed here, but if you hadn't seen it with your own eyes, you'd never believe what is done to get the music into the grooves in a playable fashion. Sure I have records cut up to the 90's which have been through much of the above and which surprisingly still sound okay without a digital disc or file with which to compare - and a reasonably neutral system that favours neither format

Unfortunately, I do not cut records myself, but I regularly supply pre-masters to cutting engineers, so I have a bit of knowledge and experience of the whole process. I am also well aware that some of the things done in the cutting room would horrify many people here. LPFs set as low as 16kHz with really bright mixes being one of many possible examples

To be honest, I wouldn't be surprised to see an elliptical filter (or HPF) enabled by default at around 40Hz in any factory to make easier cuts, especially during the heyday of vinyl production and its mass consumption. However, some artists and labels still go to the trouble (and expense!) of working with established cutting engineers, whose main advantage is that they have time to do test cuts with different settings to find the best combination. In this case, some mixes may not benefit from much (or any) filtering at all.

Which brings us back to the review: a $2,000 phono preamp better be able to reproduce all audible content perfectly, especially when so much effort may have gone into getting it onto a record!

 

[KSTR]

The correct term would be infrasonic filter. Subsonic is a speed, no matter how often companies misuse the term

That's wrong.
The latin prefixes sub- and infra- mean the same thing and can be interchanged. Same with ultra- and super-.
When used with an adjective like -sonic you also need a subject to which is it applied, which in our case it is frequency.
The subject is often omitted when it is clear from the context, similar to frequency response which needs a subject, the frequency response of which quantity. Sound pressure level, mostly.

You are referring to speed of sound, though.

English tends to be a somewhat sloppy language when it comes to properly describe things, compared to German at least.

 

[KSTR]

That's generally true, but not always the case. Elliptical filtering (i.e. 'monoing the bass') is common, but not a mandatory step in the disk mastering process. In theory, such filtering is applied only when necessary, depending on the resulting groove geometry. Some material may translate well without it.

An LF crossfeed option makes perfect sense to reduce rumble in a phono preamp, but only if it can be turned off if needed.

Agreed. The groove can only take so much vertical modulation so it all depends on the level.
IMHO it strongly depends on the exact type of crossfeed whether there is any advantage from making it optional. The simple types do affect stereo width at low mid frequencies quite a bit.

Just for grins, elliptical filtering is again one sloppy term in my view. An elliptic (or Cauer) filter usually refers to one class of filters, similar like Butterworth etc, but that's not what it actually means here.
IIRC, originally it comes from the pronounced ellipses (one example of a Lissajous pattern) you see on a goniometer (o'scope in X-Y mode) once the bass isn't mono enough. And the filter tries to flatten the ellipses.

 

[JDS]

Ouch... cheers for the testing though;

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JSmith

Weird to see such a beefy power supply, and real heat sinks for output devices, and yet have headroom be the limiting factor.

 

[LTig]

[..] The overload behaviour reminds me of heavy loading/current limiting on an active filter rather than the usual passive sort that we see. Purely speculation, though... Unfortunately, despite quite a complicated power supply arrangement, which will doubtless have plenty of audiophile appeal, we're not seeing enough voltage output to give us an overload margin of 20dB against 5mV in the final analysis.

The bad overload behaviour certainly is caused by the passive RIAA filter - a stupid design decision to cater audiophool believes.

 

[LTig]

@amirm: could you run a dashboard with MC in high gain mode? Somehow I feel this is missing ...