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Tortuga TPB.V1 Tube Preamp Buffer Review

magicscreen

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1) Sixteen hundred and ninety five freaking dollars?!? You can get one for thirty-forty bucks with a weird Chinese/English name on it (albeit sans the balanced I/O).
I have the Fx-Audio Tube-03 preamp for only $30.
It vastly improves the sound of the Jds Labs Atom.
 

Kegemusha

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Maybe I am missing something: with no gain and no function knob, what is the purpose of this box? Impedance matching? Or rather distortion generator?

I wonder the same, and add the value of some $1600 and the question is even more valid.
 

Koeitje

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Consumer audio is part of the entertainment industry, so to each his own, I guess. But I HOPE something is just broken here.

I caution tube-o-holics all the time that we all hear tube sound every day, all day long since tube audio stages or tube emulators are very widely used in professional audio production and for good reason: people tend to like that wonderful, life-giving second-order harmonic distortion added to the signal. Hell, I love it, too! It’s another color in the palette. But I don’t second guess the audio production engineers, of which I am a retired one. So, pile-on more if you must, I guess. (But apparently you won’t find it done well in this box.)
If it was already added during the mastering and mixing process, why do we need to add it again through our playback system?
 

Grumpish

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Get a £30 FX-Audio pre-amp, keep the cheap Chinese valves, mod it for unity gain, and spend the rest on music. And I like tubes.
 

AudioSceptic

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This is a review and detailed measurements of the Tortuga TPB.V1 Balanced Tube Preamp Buffer with various set of tubes. It is on kind loan from a member and costs US $1,695 with "Matched Pair Electro-Harmonix 6H30Pi Gold triode tubes."

There is not a whole lot to look at here other than the two tubes sticking out the back:

View attachment 140633

There is an internal gain setting which I left alone meaning the unit runs as a buffer (gain of 1). Architecture is tube front-end but back-end is transistor based (I assume to keep impedance low). There is some kind of protection and monitoring circuit that blinks until the tubes have stabilized.

Like the balanced configuration which is rare in tube products:

View attachment 140634

The transformer bolt had come loose and I could feel it by shaking it. Tried to tighten it from outside but keeps turning. Likely need to hold the nut inside to keep it from turning.

There are no safety marks on the amplifier.

Tortuga TPB.V1 With Electro-Harmonix 6H30Pi Tubes Measurements
I installed the pair of tube supplied with the amplifier and fired up the dashboard:

View attachment 140635

I always think something is broken in my instrumentation until I realize this is a tube amp that is made to be a distortion generator (intentionally or not). These are stunningly high levels of distortion but we are driving it at full level. I will show lower levels in a bit. Note that the spectrum shows the dominant component is third harmonic, not second. So even if we assume the common myth that 2nd harmonic is good for you, this box won't deliver that.

Let's sweep the level and see how the distortion varies:

View attachment 140636

The tubes don't seem very "matched to me." That aside, at very low input/output levels, distortion+noise goes down to -60 to -70 dB. In my experience, typical audiophile can't perceive such levels of distortion so it is unlikely any effect you think you are hearing is due to this box.

SNR is better than I expected:

View attachment 140637

Frequency response is excellent:

View attachment 140638

As is crosstalk:
View attachment 140639

What is not so excellent is IMD distortion+noise:

View attachment 140640

Ditto for THD+N vs frequency which is off the chart almost:

View attachment 140641

Fortunately it is horrible at all frequencies so there is a silver lining there!

Tube Rolling Measurements
I was supplied with three other sets of tubes so let's look at how they do starting with Electro-Harmonix 6922:

View attachment 140642

Man, this makes the supplied tubes look hi-fi! It has so much distortion that you don't need to measure them: just look at how deformed the sine wave has become! People say "trust your ears." No, I say trust your eyes!!! This is horrid. Notice that gain has become negative as well. But maybe these tubes are broken, or the circuit is not optimized for them.

Another set that was supplied is from Russian Reflector factor, the 6H30P-DR:

View attachment 140644

We get the same performance as the supplied tubes which I guess is "good."

The wheels fall off again when we switch to Mullard CV2493 tubes:
View attachment 140647

The owner tells me these are highest spec'ed tubes of this kind. If they are, something is really, really wrong here.

Conclusions
I am sure everyone who bought these preamps had different ideas than what these measurements show. They thought they were getting second harmonic "tube sound" but instead are getting 3rd harmonic. And with half the tubes tested, the product is just outright broken with severe distortion. I don't care if you want to believe in tube products. Ask for measurements so that you know you are getting what you imagining.

No, I am not going to recommend the Tortuga TPB.V1 Balanced Tube Preamp Buffer. Don't screw up your system with stuff like this. Spend the money on good music, food and fun with the family instead.

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There's a certain fascination with reading reviews like this, a sort of guilty pleasure. Just how bad can things get?

I'm wondering, can the experts here tell me if this "performance" can be replicated for a few 10s of $, or even a few $, in solid state?
 

SIY

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There's a certain fascination with reading reviews like this, a sort of guilty pleasure. Just how bad can things get?

I'm wondering, can the experts here tell me if this "performance" can be replicated for a few 10s of $, or even a few $, in solid state?
FET diff amp with no source degeneration, run open loop.
 

mhardy6647

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I have the Fx-Audio Tube-03 preamp for only $30.
It vastly improves the sound of the Jds Labs Atom.
I was mammothly unimpressed with the one I've heard (actually the "TUBE-01J", ostensibly the same with the addition of a two position gain switch) -- FWIW. Definitely added an artificial "edge" to the sound of the system I tried it in (with some sort of 'recommended' European pentodes installed in it).
Glad you're enjoying yours! I have no idea what a Jds Labs Atom is, but if that little box improved it, that's good.
DSC_0642 (2).JPG


EDITT: That said, I was indeed specifically thinking of these little distortion boxes as a "value priced" alternative to the titular Tortuga gizmo!

I'll also add that I haven't worked up the gumption to try a beefy power supply with the little beastie.
 

Aperiodic

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Aren't tube enthusiasts just old peeps trying to recreate that 80s sound?
More like, that '50s experience.It's a fetish, like field-coil speakers.
It is possible to design tube circuits with acceptable performance (if not numerically competitive with the best SS) but that apparently didn't happen here. I have always disliked the 'peek-a-boo tubes' aesthetic anyway (windows on the front, sticking through holes in the top, etc.) anyway.
 

DSJR

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Back in the mid 90's lower end UK audio scene, 'What HiFi magazine' ruled sadly and customers would come in stating the system they wanted to buy, said systems full of '5 star' recommended components and usually awful. One CD player that had its year of fame was the Marantz CD63 in 'KI Signature' version, which took a gentle toned original and spiced it up to have an impressive 'edge' to it (Paul Miller said the transport was jitter prone but not sure how audible it would be). At this time, Musical Fidelity launched a dinky cylindrical range of X Series components and one of these was a valve buffer (X10-D), running on a 12VAC supply and ramping internal voltages with solid state I think. It cost around £120 which is around £230 today)

DSCF1349.JPG


The claim of said buffer was to offer a better impedance match to the amp connected to it and we sold the warm tones as that ('sounded' great with the aforementioned CD player). An upgrade came along with a larger mains transformer with outputs for four X series source components (valve? phono stage, valve line preamp and a nice dac for the times).

Anyway, many years later I bought one cheaply to try and was a bit miffed with the warm and slightly 'dirty' sound it offered. There's an update kit from Rock Grotto and I bought one (it's been further updated since) and did the component replacements as well as adding the better Russian sourced valves suggested

DSCF1350.JPG


Got to say I thought the sound rather better BUT, I then noticed it hardly made any difference in the circuit or not, so kind of defeating what it was supposed to be there for! Obviously no measurements at all. Rock grotto used to make a suggestion for a DIY 24VAC supply with a posh 30VA potted toroidal transformer from RS Components, the two secondary windings added together which I understand doubles the current capacity (again, forgive me if I'm incorrect here). I still have it here and run it from time to time to make sure it still works.

http://www.rock-grotto.co.uk/x-10dupgrade.html
 

tomchr

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levimax

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This post is very telling of the design ... uh ... philosophy? ... yeah! ... philosophy! behind the buffer.
https://www.audiocircle.com/index.php?topic=145836.msg1678520#msg1678520

It's a plate starved design that runs on +30 V. The performance and channel matching is exactly as you'd expect from such a design.

Tom
Hey Tom.... do you have one of your "300B" amps that you could send Amir for testing and listening. I would be interesting to see how a properly designed SET could do on the bench and subjective listening... not sure Amir has any speakers sensitive enough though.
 

tomchr

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Or to paraphrase: Do I 'happen' to have one of my 17.5 kg glass-and-metal, fragile as F... amps that I can 'happen' to spend an hour or two packing so I can ship to Amir at my risk and cost for no gain to me? Nope. I don't. Pardon my grumpiness, but this is a significant ask.

I sold both the amps I built and haven't looked back. I have no regrets. I had a lot of fun designing tube amps. I think it's utterly cool that I can tell the pinout of a tube by looking inside the bulb and tracing the wires. Try that with an IC! But in the end I prefer the clean sound of an ultra-low distortion setup. Tubes and ultra-low distortion (say < -120 dBc) just don't jibe.

You can find the design documentation for the DG300B here: https://neurochrome.com/pages/dg300b I'm pretty sure the Classic Tone transformer I used is now unobtainable. If you build this you'll have to have a transformer custom wound. Toroidy in Poland will be happy to help with that for a very fair price.
I no longer sell vacuum tube circuits as the support cost of those is astronomical. Each build requires hours of individualized support. That simply wasn't sustainable at my price point. And given that I only sold 10-12 board sets per year I doubt I could have charged more.

I've included the amplitude response and distortion sweeps of the DG300B here. Do keep in mind that the DG300B is a power amp and not a preamp. I would expect the distortion of a preamp to be much lower than that of a power amp. I also included a distortion sweep of a setup that runs both OPTs in series. Someone requested that at one point.

Tom
 

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  • DG300B_ Amplitude Response @ 1 W, 8 ohm (ref. 1 kHz).png
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  • DG300B_ THD+N vs Frequency, Output Power @ 8 ohm.png
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  • DG300B_ THD+N vs Output Power, Frequency @ 8 ohm.PNG
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  • DG300B_ OPT in Series - THD+N vs Output Power (2x8 ohm, 1 kHz, 20 kHz BW).PNG
    DG300B_ OPT in Series - THD+N vs Output Power (2x8 ohm, 1 kHz, 20 kHz BW).PNG
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