Review and Measurements of Lounge LCR MKIII Phono Amp

[amirm]

No. I got him over a "shock of the new" experience he had. Many of my customers have had similar revelations. The vast majority of vinyl listeners have only heard playback through a standardized set of components. Most phonostage circuits go something like this: low noise opamp(s) with a 20v/us or less slew rate, low cost film resistors or common chip resistors, low cost electrolytic caps in the power supply and often times in other places, power supply rectifier diodes with marginal current rating and slow reverse recovery and the dreaded IMO three terminal preset voltage regulator.... All these things add up to a bloated compressed sound.

Nope. There is no such thing as 'bloated compressed sound." These are the things people imagine but have no basis in fact, engineering or audio research.

Every audio manufacturer claims such things to a different tune. You have a solid state design. There are tons of companies who make tube phono stage who say solid state sounds sterile, non-musical, non-real, etc. As you, they don't have any reliable evidence whatsoever to establish that as a fact.

Fortunately we know what is real hifi and what is not. The former is one that is most faithful to what is recorded. Heaping tons and tons of distortion as your unit does, is not it. No way that much harmonic distortion makes things less compressed or bloated.

 

[Lounge Audio]

How exactly did you determine SMD parts cause smearing?

By building lots of circuits with and without SMD parts and listening to them over the last two and a half decades.

Who says you have to use all SMD parts in a design?

I don't know who says this.

You can just as well use a through-hole capacitor if you feel that is a big deal.

Sure!

SMD designs shorten paths which is greatly helpful in analog designs.

That's one way to lower trace impedance and parasitics.

We have DACs and headphone amplifiers which achieve 50-70 dB better performance than your design

I can lower noise in my design too. One quick way would be to use a low noise op-amp. But slew rate performance of the op-amp will suffer when compared to the device I use. I've tried it and I would rather have a little more noise and a better transient response. That's part of the cleaner, more defined topend that gives customers a "shock of the new" experience.

And both have raving reviews from customers as well.

Maybe that means you treat those manufacturers a little bit better than you treat me since those customers fit in your camp better.

As to feedback and ringing, that only happens with illegal audio signals like square waves with very fast rise times. You have one of those coming from an LP? If so, let's see a measurement graph of such.

How you do find an illegal audio signal? is there a phone number for the audio police?

You don't do SMD design and manufacturing so it must be a bad thing.

I worked a Harman in the Multimedia Department for 7 years. I was an engineering tech. Almost all I did was solder up prototypes of Ipod docking players. It was mostly 0603 but some 0402 parts and chips with no legs and heatsinks on the bottom of the case. Lots of microscope work.

You don't understand the nature of feedback so that becomes a bad thing too.

Every component has a group delay. It may be small, but it's there. When you take that signal and tie it back to the input it is correcting something that has already happened within the component. Put a complex filter network in the feedback loop and the corrective action of the feedback loop slows down even more. It's ringing and overshoot.

You throw out star-trek language at lay customers who can't counter. Please don't use them against us. It only deteriots your position here.

Huh?

 

[Lounge Audio]

I regards to SMD parts and my usage or non usage of them. I do use them now. I use 0.01uf MLCC's right at each opamp power pin to bypass noise to ground. Also 22pf MLCC's are used on both of the feedback loops of the opamps, and for the first gainstage across inverting and non-inverting inputs along with the non-inverting input to ground for stability and RF immunity. I also use the better SMD thin film, low tempco resistors on one position of the Silver and Gold units for voicing as I see fit according to customers listening preferences.

 

[SIY]

Just to make sure I understand correctly, the topology is two flat gain blocks with a passive EQ circuit between them?

 

[Lounge Audio]

The changes on the PCB looks very much like the standard beginner's modded board. If you need to decouple that much all over your PCB, you've designed it wrong. And why do the star grounding with wires? Shouldn't that be done on the PCB when designed? Maybe go to a four-layer board instead? Or does the four-layer board smear the sound and make it less airy? After the SMD comment, I expect any crazy reply.

I fully understand how you see this as a beginners hack job. There is no other way that I know of to use silver wire on a PCB. Point me to a PCB house that does silver foil and copper foil on one board and I will give it a try. I could layout the board to make things look a little neater, but that would take time away from production which is most of what I spend my time doing and it would increase my cost.

The way that things are done now sounds very good with wide open dynamics. No customer has complained. In fact it has been quite the opposite. Type "Lounge LCR Silver" on a search and read on.

 

[Lounge Audio]

Just to make sure I understand correctly, the topology is two flat gain blocks with a passive EQ circuit between them?

Yes, almost. Because of anomalies in the unit I use as an inductor there needs to be a pole of LF cut at about 220hz and a LF boost at a lower frequency. All that is done in the first gainstage. It's some hammer and anvil correction but it works.

 

[SIY]

Thanks. Is that correction done in the feedback circuit or ahead of the gain block?

 

[amirm]

Maybe that means you treat those manufacturers a little bit better than you treat me since those customers fit in your camp better.

I am emotionless when it comes to manufacturers. Their product either complies with what engineering and science says is right or not. Yours is in the latter category. It is a world created around unverified, unpublished, folk stories about sound and its reproduction. Everyone in your camp has a different idea of what creates good sound. It is a chaotic made up world that takes advantage of non-technical customers.

Build a product based on proper science and engineering and you will get my praise. That is what those other companies have done.

No different than if we were a bunch of doctors and you came here and said taking megadoses of vitamins cures every kind of cancer. We are not guided by random ideas not grounded in real and provable science and engineering.

 

[Lounge Audio]

Thanks. Is that correction done in the feedback circuit or ahead of the gain block?

Oh sorry, the bass boost is active. It’s in the feedback loop of the first gain stage. The bass cut is passive. It’s a coupling cap on the output of the first gainstage that uses a combination of the resistive load of the LCR network and a shunt resistor in-line with a trim pot.

 

[SIY]

Many thanks for the explanation!

 

[patient_ot]

I can lower noise in my design too. One quick way would be to use a low noise op-amp. But slew rate performance of the op-amp will suffer when compared to the device I use.

I'm not qualified to comment on this from a technical standpoint, but I have heard other manufacturers mention this as a type of design trade off FWIW.

 

[SIY]

I'm not qualified to comment on this from a technical standpoint, but I have heard other manufacturers mention this as a type of design trade off FWIW.

TBH, slew rate just isn't very important in this application beyond a relatively moderate minimum. Noise is, but as I mentioned before, as long as it's below the cartridge thermal noise, it rapidly becomes insignificant. Not the trade-off I'd make, but testing will reveal much.

 

[March Audio]

Before we get too pointy with the commentary, let's not forget that a) Lounge is a one-man shop, so design rework involving pull-and-respin would probably be too expensive relative to revenue, and b) these units are only $300. If after all is said and done, Robert finds and implements areas of both objective and subjective improvement based on our input, both he and his customers will benefit. It doesn't have to be one school of thought vs another - there's substantial overlap (and, I'd argue, cross-association between objective measurements and subjective observation).

Whilst that is true, you have to account for that in your design planning. I have had to respin my headphone amp board after testing the first batch. That's why I only made a very small number initially for development purposes. You sort of expect something unforseen to bite you in the ass and plan accordingly. You expect to be able to improve something and plan accordingly. You design, build and veryfy, adjust accordingly then retest.

FWIW my experience is that if it measures well it will sound good. However you can get away with many measurement anomalies that many people won't hear.

 

[Lounge Audio]

TBH, slew rate just isn't very important in this application beyond a relatively moderate minimum. Noise is, but as I mentioned before, as long as it's below the cartridge thermal noise, it rapidly becomes insignificant. Not the trade-off I'd make, but testing will reveal much.

Life would have been much easier with something like an LM4562. I tried it in the LCR, swapped it back and forth with LT1358. At first it seemed ok. Then, after extended playing of different source content, I could hear loss of low level detail. Especially with busy material, things like a plate reverb or room echo would be drowned out a bit in complex passages.

 

[SIY]

That would not be my first choice, either- without some VERY specific attention, the 4562 is notorious for turning into an unintentional shortwave signal generator.

 

[Lounge Audio]

That would not be my first choice, either- without some VERY specific attention, the 4562 is notorious for turning into an unintentional shortwave signal generator.

The LCR MKI had op275. The change to LT1358 is part of what made the MKII.

 

[Lounge Audio]

FWIW my experience is that if it measures well it will sound good.

I have not had the same experience.

 

[March Audio]

I have not had the same experience.

Do you perform blind controlled listening tests?

Whenever I have asked for specific examples of kit that measures well but sounds bad there has always been stony silence or the claiment has not performed blind and controlled testing.

 

[Lounge Audio]

Do you perform blind controlled listening tests?

Not much any more. Used to quite a bit in the past. Usually just blind a/b not many a/b/x tests.

 

[Lounge Audio]

Once I built a SRPP gainstage with 11HM7 pentodes wired as triodes. They are stratospherically high gm tubes. High perveance too. All looked good. one of the most linear sine waves I had ever seen coming from a tube. dynamics to burn. Ran music through it; sounded like cellophane. One of the most one dimensional sounds I had ever heard.