[Designsfx]

All-
After much reading and efforts to discern the curves provided on tube data sheets I’m realizing that referring to published data may be futile when it comes to determining how a tube will perform when used in a TRP dac.
It seems the required (yet missing) data are the specifics where voltage limits are concerned between power tubes within the circuit. I believe these to be self biasing to a degree but think it would be helpful to know how far each tube is capable of performing so that published data can be “marked up” to be relevant to the dac being used.
Does anyone know if such information exists and is available for use?

 

[Polygonhell]

I believe the way the lampizator circuit works is the “pre tube“ acts as an active load for the primary tube, it’s also a cathode follower.
That configuration is often referred to as an SRPP, or a mu follower.
That will be a massive active load on the primary similar to a CCS.
So on a datasheet you would draw a horizontal line, probably at much less anode current than you would expect.
But your not really going to get much from it IMO.

But I’m guessing based on some old posts on the old lampizator poland site.

 

[Designsfx]

Thx Polygon-
I read through some of the old docs on the site showing scope curves and waveforms and it alluded to some of what you mention. I guess I could try lifting a tube and putting a meter to it under power but the clearances around the other tubes makes that iffy at best.
I’m trying to determine a method of quantifying data based on tube data sheets, what the dac is outputting and what I hear in hopes of being able to correlate a “best guess” on what I could expect from a new tube (as opposed to buying and returning, rinse and repeat. But of course factoring used NOS or grab bag into the mix and that goes out the window anyway.
So far I’ve had 6 quads of tubes through this Dac- each time I ordered another set I went off the data sheet comparing it to a known new set and in two cases got results that were the exact opposite of what I expected. I guess that’s were the “fun” of rolling tubes comes in.

 

[Polygonhell]

So far I’ve had 6 quads of tubes through this Dac- each time I ordered another set I went off the data sheet comparing it to a known new set and in two cases got results that were the exact opposite of what I expected. I guess that’s were the “fun” of rolling tubes comes in.

There are a number of problems doing this.
The first is that most likely changing the tube will change the current flow over the cathode resistor, so you can't easily even draw the right line.
The second is that the datasheets are gross approximations at best.

You might be able to get a measure of linearity, if you can determine the bias point.
But that isn't very relevant for a balanced amp, since it's largely 2nd Harmonic content and that all gets cancelled in a balanced circuit.

You'd likely need to reverse engineer the actual circuit, but I can tell you I've modelled similar circuits in Spice and there is surprisingly little difference between very different tubes even looking at FFT's, so I think trying to predict performance from tube datasheets is going to be at best challenging.

 

[Designsfx]

You'd likely need to reverse engineer the actual circuit, but I can tell you I've modelled similar circuits in Spice and there is surprisingly little difference between very different tubes even looking at FFT's, so I think trying to predict performance from tube datasheets is going to be at best challenging.

I’m obviously not as skilled as you are when it comes to understanding circuit designs and the response given but I have been wondering if using smaller pentodes (9 pin) might provide a wider variety of results. It seems that the dac isn’t really exploiting the tube’s potential- maybe something that reaches full potential with a lower power state might allow me to experience more of a difference?
There is definitely a difference in character when changing tubes (KT88 vs 6L6, 6L6 vs 6BQ6 and so on) but it also seems that some just don’t play well or at least align with my taste (KT88 and KT150). I don’t know if this falls back onto how they work within the dac itself or if it falls back into the interaction with the entire system.

 

[Polygonhell]

There is definitely a difference in character when changing tubes

Yes I'm not saying there isn't, the differences are quite apparent when listening, What I'm saying is it's hard to correlate the heard differences to the simulated results which all look very similar.

I'm using a DHT lampizator, and I haven't played a lot with the input tubes.
The mu/gain will make a difference, the higher the more linear, because it will result in a stiffer load (more horizontal load line), but swapping it will also move the anode voltage on the power tube, which will in turn move the load line. Secondarily depending on if the Lampizator pulls it's output from the top of the power tube or the bottom of the "pre" tube, it will have more or less direct influence acting as a cathode follower.
So it will make a difference, but predicting what to me would be complete guess work.

I'd always recommend starting tube adventures with the Rectifier, find something you like there, then read opinions on power and pre tubes and try and find something to further tilt in the direction you want.

 

[Designsfx]

I'd always recommend starting tube adventures with the Rectifier, find something you like there, then read opinions on power and pre tubes and try and find something to further tilt in the direction you want.

This is a great suggestion. I‘ve noticed that changing rectifiers has provided the most change in presentation. So far I’ve liked the old Globe 80 tube the best- unfortunately it was very weak when I purchased it and it lasted no longer than a couple of weeks. I have another on the way now.
I also tried a Ken Rad VT 244 but same story- it died during the first run of music. The seller provided a split second refund though so no biggie. I also have another 5R4 type coming which is said to be NOS from the early 1940’s- hopefully it will produce a nice result. For now it’s the trusty Sophia 274B Aqua. I haven’t had the courage to order any of the higher dollar rectifiers yet as it seems a lot of them end are constantly being bought and sold.

 

[BlakeT]

Unfortunately for our wallets, the only way to know what tubes will work best for your system and preferences is to research, read all the feedback and attempt to find some consistency with comments, then come up with a list of potential candidates, buy, try, etc., etc. until you find your personal sonic nirvana.

Also, what works in Amber, Baltic, Atlantic may not hold true for B7, GG or Pacific, and vice versa.

 

[Designsfx]

@BlakeT
I get what you’re saying- and it is kind of unfortunate just due to the fact that with so many possibilities it could take a VERY long time to define what sounds best in one’s system.
As you seem to have much more experience than I with these dacs I would be interested in your opinion on something. As you’ve worked with your Lampizator how great of a “difference” have you found between the tubes you’ve tried? Along the lines of the previous comments with Polygonhell did you find the greatest tonal changes to be had across rectifier tubes or power tubes?

 

[BlakeT]

Hi @Designsfx. I will confess, I am very much a tube roller, I bought tons of tubes and tried lots of combos (I don't even want to think about the money I spent), so my views may differ from those that don't like to roll tubes. I actually understand not rolling tubes and just going with stock as the tube rolling possibilities are endless (particularly when you throw in adapters). That is one reason why I don't like having lots of headphones. I like just having one pair, so I am not always thinking "gee, I wonder what this song would sound like on my other headphones"? Having this thought in my head can detract from my personal music enjoyment (others probably disagree, this is just how my brain works). I can see the same line of thinking when it comes to tubes and sticking to stock. Plus, hand on heart, I've never heard any of the Lampizator DAC's I've owned (4) sound anything but very good, no matter what tubes are installed. But, I have had very noteworthy improvements (to me) with certain, specific tubes. Whereas with most tubes, the differences are definitely audible and worth pursuing, but comparatively more subtle.

What I have done, is to try as many tubes as possible, after whittling down the list of potential tubes. After I reach my sonic goals, I stop. No more tube rolling. That is where I am at now. I am 100% settled, so I won't even bother to try anything else in the future.

With my two current Lampi DAC's, what I found initially was that power tubes mattered the most, perhaps overall influence on sonics at 80% power, 20% rectifier (Golden Gate). There are some power/rectifier tubes that change that ratio. In my Golden Gate, I still think the power tubes are most important, but with the particular rectifier and power tubes I finally settled on, perhaps the ratio is now closer to 70% power tubes, 30% rectifer.

With my Pacific, and the particular tubes I finally settled on, honestly, I'd be inclined to split it at 33%, 33%, 33% (power, rectifer, anode circuit). That is definitely not the case with all tubes, however. With the vast majority of tubes I tried with my Pacific, I would put it 70% power, 20% rectifier, 10% anode. It is just with some very unique, particular tubes and high-end adapters where the ratio changed to roughly equal.

Of course, these are just my personal findings. I don't profess to have any special super powers, but I am very confident in what I am hearing. For many years, I wandered the audiophile desert, afflicted with FOMO and audiophile nervosa, but just within the last 6 months or so, I've found what I've been searching for and now, it is just the music .

Sorry for the rambling...

 

[Designsfx]

@BlakeT
No worries- I don’t look upon it as rambling. So the Pacific takes things even further away from my experience not that a GG is the same as the TRP I’m using either. To be honest (and I’ve seen some of the great pictures you’ve posted at WBF) going through the history of threads regarding Lampi it seems the whole thing has been an experiment from the beginning BUT there are definitely some who seem to be going on and on without reaching the point you mention above- being 100% settled.

So the mission in my mind was to get to the bottom of who settled and what did they settle on for the ultimate expression in their system. What I found was that point never came (for most) as the chase of audio betterment led them to a dac upgrade and the wheel starts all over again. It sounds as if you’re trying to get off the wheel as well.

Back to tubes- I really hate the idea of blanket ordering boxes of various models, settling in with the dac and going Nope! Then getting the next pair and starting over hoping to get to a point where I enjoy what I‘m hearing and can get back to listening to music rather than wondering if a different tube set would be better. Then of course figuring out what to do with all the loser tubes that have accumulated- wow.

I guess that is what it boils down to though as it seems there is no formula for predetermining how a model/family of tubes will respond. So far I’ve found that I like the sound of the 6L6 family of power tubes and of the two quads I have there isn’t a large margin of difference (very nuanced with respect to output) even though one set is considerably older and the other brand new.

I currently have shopping carts loaded across a few different sites with various type’s waiting to be bought as I’m trying to weigh which has more impact- the rectifier or power tube. I new after the first day of receiving my dac I had no interest in sticking with the stock tubes- they just didn’t sound that good. I also think having too many choices could lead to time waisted as well. It sounds like what I’m hearing is that I’m going to be listening to many more sets of tubes!

How’s that for rambling!

 

[Designsfx]

All- I have a question about this tube, any help would be appreciated.
I came across a tube called a 6B4G. When I pull up the tube data it tells me it is a “triode power amplifier”. What’s different about this one is that it has an octal base, 6.3V/1A operating requirement which is very similar to a pentode. Data says it’s similar to a 2A3. Filaments are on pins 2 and 7 which means it will drop straight into my dac. Is there any reason why this tube couldn’t be used as a power tube (in a TRP dac)? I mean it’s requirements seem to be the same- am I missing something?

 

[BunnyNamedCraig]

Has anyone any experience in rolling a bendix 6X5 in an Amber 3? Curious about it…

 

[Polygonhell]

How’s that for rambling!

I personally hate tube rolling.
I have 3 sets of power tubes for my Pacific and Quads of good DHT's are expensive, lots of rectifiers from other devices.
My experience generally is find something you like and forget you about it.
The Power tubes I have are radically different (from a spec standpoint) and the Pacific still sounds like a Pacific with any of them in there, it's a trade off of stage size and mid range body vs dynamics.
I prioritized dynamics in my system so I run 242's, the T100's (which are basically a more powerful 300B) have a wider stage and more warmth, the PX25's are in the middle and to be honest it was a close call between those and the 242's. And I know people with Pacific's who've gone with PX4's, 300B's or PX25's.

One of the first tube devices I owned decades ago was a preamp, used 12AX7's, I was tied up in rolling tubes for it, had lots, every new tube seemed to be "better", one day I rolled back to one of my earlier tubes, and decided I liked that better too. Made me realize there is a fine line between different and better.

There are some rectifiers I'd like to try, I'd like to try C3G's in the pre tube location, but I don't feel a NEED to do any of that.

 

[Designsfx]

All of that makes it sound like I got off cheap going with the Atlantic TRP! I considered going single ended to reduce tube cost but when I tried it I just didn’t like it as much. I prefer staying balanced and it’s interesting that even something as small as changing pairs from the front sockets to the rear sockets influences the sound. Not drastically- but noticeably.
I would have loved to have bought a Pacific but am in deep with home remodeling projects- dacs and tubes pale in comparison to what contractors are charging these days!