Lampizator Valve / Tube Rolling Review Thread

[abeidrov]

A lot depends on a source (music server / renderer) and a software which you run on it. In my case the difference between Aurender and my older server was more pronounced, than the change of dac. Maybe it’s system dependent, but in my case the server matters more, than the dac.

 

[godofwealth]

There’s a very long thread on head-fi.org on the Chord Dave DAC that Rob Watts, Dave’s chief designer, contributes to. Here’s part of what he had to say on the subject of comparing USB to SPDIF. You should read the whole thread, but in a nutshell, USB has very serious noise issues that are very difficult to control. It was never intended as a high resolution low noise audio interface (in the pro world, no one uses USB to my knowledge):

So firstly there is no master clock to be recovered from the SPDIF - but I digitally convert the SPDIF format into a parallel I2s like format - that is word clock, data left and data right. The word clock is extracted directly from the pre-amble, this word clock extraction only works on the fixed pre-amble so has no possibility of data related jitter, unlike using a conventional PLL based clock extraction, which relies on all transitions, pre-amble and data.

The extracted word clock then is fed to the DPLL. I should not call it a DPLL, (DFLL is more appropriate term) as phase locking is only applied initially; once initial lock is obtained, it works upon frequency only and is frequency locked to the incoming word clock - so the phase (and hence jitter) of the incoming word clock has zero influence on the generated word clock, which is generated from the local low jitter 104.25MHz fixed frequency oscillator. The DPLL ensures that the generated word clock is frequency locked to the incoming word clock, and it has a time constant of many seconds.

Meanwhile the data is fed into a micro buffer, and the data is read out from the buffer via the generated word clock, which is synchronous to the 104.25MHz low jitter fixed clock.

But I can talk as much technicalities as I like - ultimately it does not matter. The fact is that using my MSI lap-top I got identical sound quality from using optical SPDIF as using USB with Dave. USB of course is asynchronous, the data is fed to the DAC with an integer count of the 104.25 MHz low jitter clock, so no clock generation is done at all, nor any conversions from SPDIF to parallel data either. So I know the DPLL system is innately transparent. This does not mean that all USB sources sound the same as optical, as the galvanic isolation on the USB is not perfect - some RF noise can leak into the DACs ground plane from noisy USB sources via the 2pF isolation capacitance on the USB interface. But you can treat the optical input as the SQ reference, with USB either sounding identical to optical or worse, depending upon the cables and the source and how much RF noise is fed into the DAC.

Is this a really complicated way to say chord uses spdif to i2s conversion using ASRC? An ASRC block does solve the clock jitter/noise issue.

Last edited: Mar 28, 2022
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Mar 28, 2022 at 8:48 PMPost #19,640 of 20,205
[IMG alt="Rob Watts"]https://cdn.head-fi.org/avatars/m/394/394072.jpg?1397540867[/IMG]

Rob Watts​

Member of the Trade: Chord Electronics​

JoinedApr 1, 2014Posts2,833Likes9,654

The Jester said:
So there’s no possibility of USB sounding any better than optical unless the optical output of the source is inferior to its USB implementation, leaving the only reason for using a USB input down to the 96k (sometimes 192k) limit of optical cables ?

There is no possibility of USB performing better than optical (excepting opticals 192k limit). And I use the term performing rather than sounding better as "sounding" depends upon the ear and taste of the beholder - and there is no accounting for that!

Ideally, it would be better if all USB bit perfect sources sounded identical to all bit perfect optical sources, then the source arguments would cease - in the same way when you used a noisy RF linear PSU it sounded identical to the supplied SMPS (power delivery the same) then the linear arguments would cease. It's my goal to have DACs in the future being able to accomplish this - but this actually is a very much bigger challenge than one might think at first - as the ear/brain is extremely sensitive to minute and immeasurable levels of noise floor modulation. And its changes in noise floor modulation in the analogue portion of the DAC that accounts for the SQ changes one hears from PSUs and digital sources.

No doubt after spending many years (or decades?) in the future creating such a stupendous DAC that was completely immune to RF noise from the source and the PSU, some audiophile would then criticise this DAC for not being "transparent" because they can't hear differences from sources... C'est la vie, or you can't please all the people all the time!

 

[dminches]

Maybe this topic should be taken elsewhere since this is the Lampizator tube rolling thread.

 

[godofwealth]

Yes, agreed . Back to tube rolling…

 

[christoph]

Interesting. I find the USB input on the Pac to be pretty awful sounding compared to the sound I get from playing back CDs on my CEC TL0 transport, which is still hands down the best digital front end I’ve heard in 30+ years of owning dozens of digital products. USB was never designed for high fidelity audio. It’s a jury rigged contrived solution. Chord’s lead designer, Rob Watts, says that USB is the very worst transmission medium for digital audio. His preferred connector is optical due to its hugely better RF properties.

I’m not sure if it’s Roon that’s at fault here. Generally, the higher the resolution the bitstream in Roon, the worse it sounds to my ears. There are of course mathematical reasons why this might be true. DSD injects an enormous amount of ultrasonic noise into replay. About the worst thing you can do to is upsample to DSD, which is a guaranteed way to increase noise. There could be other factors. Modern digital recordings seem to have greatly reduced dynamic range, which I suspect is because of the huge compression engineers seem to like.

To this day, the most dynamic sounding classical music albums I have in my 10,000+ collection at home are the 60 year old Mercury Living Presence series, which used simple minimal miking and no compression. About the worst recordings are the newest DSD ones. I attend the San Francisco symphony concerts regularly and have listened to many Michael Tilson Thomas conducted performances (all the Mahler symphonies). The SACD DSD albums of SFO Mahler are an utter travesty of the sound you hear in Davies Symphony Hall. I noticed often when they record live that they label the mike feeds by the DSD channel numbers, and they use hundreds of microphones, all going into a giant compressor/mixer operated by a recording engineer. The resulting sound bears no resemblance to the beauty of live sound. If you want true high fidelity, look no further than the concert hall!

I couldn't care less about what the designer of gear says that I would never ever be able to enjoy listening to

 

[godofwealth]

Sure, I get that. But I always wondered why I never liked USB sourced playback, both with my Chord Dave DAC, and with the Lampi PAC. In fact, I like the LAN input better. Chord‘s Rob Watts is the only designer I know who has extensively written on this topic. I’m not certain his explanation is the primary reason for my dissatisfaction with USB. Obviously if you like USB playback, you have nothing to be concerned about. If, like me, you don’t find it as good as the alternatives, then perhaps his explanation might be of interest.

Back to tube rolling….

 

[christoph]

Sure, I get that. But I always wondered why I never liked USB sourced playback, both with my Chord Dave DAC, and with the Lampi PAC. In fact, I like the LAN input better. Chord‘s Rob Watts is the only designer I know who has extensively written on this topic. I’m not certain his explanation is the primary reason for my dissatisfaction with USB. Obviously if you like USB playback, you have nothing to be concerned about. If, like me, you don’t find it as good as the alternatives, then perhaps his explanation might be of interest.

Back to tube rolling….

If you prefer the LAN input over the USB you should probably use the one you like better

 

[Zero000]

Never buy a Lampi dac without built in VC! That should be strong advice to all potential Lampi customers from a good and knowledgeable dealer. I blame my dealer for all the gain issues I have .

Interestingly enough, I do not hear any distortion from my vinyl rig, which plays at more or less the same level using the highest phono gain setting as my dac with PX25 tubes. Go figure…

For overloading issues to be solved with ease and physical space reasons yes, I agree.

That said, any attenuation method seems to differ in terms of perceived SQ. So some external passive options may actually work better and if it is stuck inside the DAC you will never know. Unless you don't mind fucking around.

I am definitely into heater voltage and having the ability to manually adjust it. I just thought it would be a sensible thing get implemented. And it was.

Heater voltage control allows you to match volume output and balance older NOS and new poorly matched tubes channel balance with ease by ear so long as you don't exceed +/- 10% of the spec'd running voltage. You can do more than that percentage wise if you don't give a shit how long the tubes you are running live. Or use your preamp's balance control. Solving the issue closest to the point of source seems to work best sonically, though.

It's not for the mass market. People without a clue will cause damage to things they shouldn't. But if you really are an enthusiast with some basic understanding it is a great thing to have.

In fact multitudes of differing test points and the ability to dynamically control them would be cool. But we gotta get real in terms of practicality.

 

[cpcat]

An external passive pre will always have the slight disadvantage of added capacitance for the cable run vs an integral VC. Whether you make up for this with better parts/design in the passive pre I guess is the question. The VC even on the B7 MKII is very good IMO and I’d say most would get better performance with the integral VC.

 

[godofwealth]

One of the unanticipated discoveries for me is how good the Pacific sounds run direct into a JJ SET amplifier that has a built in ALPS potentiometer for gain adjustment. Till now, I was a firm believer in using a high quality preamplifier such as my ARC Ref 3. Not any more. The purity of sound I get from running direct into the JJ is so enticing to me that both my ARC Ref 3 and the massive ARC Ref 210 tube monoblocks sit idle and unused for the past few months. It’s hard to give up the purity of a simple DHT signal path with a simple gain device for the much more complex gain path of a preamplifier and amplifier with many more stages. My Quad 2905s have never sounded better and I’ve spent years looking for the right combo to drive them. At last I have found the promised land. Of course, I have to live with an amplification device that produces only 20 watts. But with my Quads, and my listening preferences, that’s no issue.

 

[Sampajanna]

fully loaded Pac on the way now. It has the RK PX25 and 5U rec. I am excited! Should arrive this coming week!

 

[Sampajanna]

Anyone try these: https://www.nosaudiotubes.com/produ...osram-globe-dht-made-in-gt-britainl6119k9893/

 

[Golum]

I believe you can’t go wrong with these…

 

[bonzo75]

Anyone try these: https://www.nosaudiotubes.com/produ...osram-globe-dht-made-in-gt-britainl6119k9893/

Osram are excellent tried them in an amp not Lampi

 

[Sampajanna]

And GZ34 metal rectifier is ideal?

 

[dminches]

And GZ34 metal rectifier is ideal?

There is no “ideal.” You have to try multiple tubes to see what sounds best to you. I preferred the the 274B variants over 5U4Gs and GZ34s. But that’s just my ears.

 

[Zero000]

Anyone try these: https://www.nosaudiotubes.com/produ...osram-globe-dht-made-in-gt-britainl6119k9893/

Yeah I posted about them a while ago. I have a pair that measure tipperty top. Look back or Google search this thread.

They are great with acoustic material I find and generally very enjoyable all round. If you buy a good pair you should be very happy with yourself.

However, buy some tube dampers that will fit them, like Herbie's, as with all large tubes they tend to resonate more/are more subject to microphony. That said, it's an issue that affects tubes of any size and it's not to say some small signal tubes can't suffer from very high degrees of microphony. Because they can.

 

[marty]

If you want true high fidelity, look no further than the concert hall!

Absolutely true. But unfortunately, we must make concessions to reality.

To this day, the most dynamic sounding classical music albums I have in my 10,000+ collection at home are the 60 year old Mercury Living Presence series,

Overall quite excellent but many are a tad bright. Not true of the Lewis Layton RCA Living Stereos or the Ken Wilkinson Decca's.

 

[godofwealth]

The vinyl releases of Mercury Living Presence are far superior to the CD reissues, and much less bright on top. I snarfed a bunch of test pressings on ebay last year. They sound utterly fantastic. I also got the Classic reissues of many of Lewis Layton’ s great RCA recordings. As far as Ken Wilkinson, worth noting he did many of Lyrita‘s great recordings as well.

 

[godofwealth]

Definitely interested in the PX 25s.