Tube Rolling the Herron VTPH-2A Phono Preamp

You hear it over and over again, the Herron phono preamp does not respond favorably to tube rolling. In fact, when I called Keith Herron to place my order, less than 5 minutes into the conversation he mentioned he does not recommend tube rolling. Well, I’ve never been much of a follower, and when it comes to audio I need to learn things for myself. So of course I went about experimenting with some different 12AX7 (first gain stage) and 12AT7 (second gain stage and output stage) tubes in the unit. I feel like this exercise taught me a lot about this phono preamp.

First of all, I’ll start with a brief description of how the stock unit sounds to me. My unit shipped with 2 x Electro-Harmonix 12AX7 tubes (first gain stage), 2 x Electro-Harmonix 12AT7 tubes (second gain stage), and 1 x Ei 12AT7 tube (output stage). Right out of the box this phono preamp was very quiet, neutral, and snappy-sounding. I was immediately aware of the timing, how it handled rhythm. It is impossible for me to listen to records with this preamp and not be shaking my foot or tapping along with a stylus when I’m reading my iPad. There are lots of great things about the sound of this preamp, but to me, this way with timing is what ultimately makes it special.

After rolling some different tubes through this thing, I must say, I am not surprised that many people before me have not had a lot of luck. And this is primarily for two reasons:

1. the stock tubes that ship with the unit are amazingly quiet, balanced, and matched. NO microphonics that I can detect. I have no idea how many tubes Keith Herron starts out with or what kind of testing regimen he puts them through, but the tubes he provides are quieter than ANY NOS tubes I have been able to acquire even though I pay for the highest grade and all testing available for balancing, matching, and noise. So basically whatever you choose to roll into this unit is very likely to be noisier than the stock tubes, even if they are themselves very quiet. And this phono preamp will show off noisy tubes. With the stock, or very quiet NOS tubes, this preamp is very quiet. Even so, I have tried tube dampers for the first time in my life (I have used a lot of tube gear over the years, and my system now uses a DAC and an integrated amp using tubes). I was surprised how much they improved the tonal purity and color, without slowing anything down. I highly recommend them with this preamp.

2. It is really easy to lose the amazing snappiness with the wrong tubes. Even if the tubes are amazing in every other way, they may rob the preamp of its greatest strength: it’s timing. And once you hear how addictive that aspect of this preamp is, you can’t live with it any other way.

If you were to ask me if there are any areas where this (stock) preamp comes up short compared to the best tube gear I have heard (or tube gear with my favorite NOS tubes installed), I would say that it is not as 3-dimensional as is possible, and the tonal colors are not very saturated. These are likely design choices. These two areas are where I wanted to see if I could find some improvements for my personal taste. But WITHOUT losing the timing performance.

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The tubes:

Right off the bat I decided I wanted to use NOS Telefunken smooth plates in the first gain stage. They sound very linear and are slightly lean in the bass, like the stock tubes, but with a very sweet midrange and are the most 3-dimensional 12AX7 of which I am aware. I have a barely used, tightly matched pair that I bought for my integrated amp a few years back (I ended up preferring Mullard 10M’s in that spot). I tried them and they did exactly what I hoped for: increased dimensionality and a little more tonal sophistication. And no detrimental effect on the timing. The only problem was…they were not nearly as quiet as the stock tubes, particularly one of them that caused some noticeable noise in that channel. Unacceptable. BUMMER. I ordered a new pair with all available noise testing, tightly balanced and matched. These are in there now and sound amazing.

For 12AT7’s I have Mullard CV4024 (military grade/low noise), Brimar 6060 “Yellow-T”, RCA 12AT7 Black Plates, and one RCA 12AT7WA/6201 Black Plate (military grade/low noise).

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Combos:

· First Gain Stage: 2 x Telefunken 12AX7 smooth plates

· Second Gain Stage: 2 x Mullard CV4024

· Output Stage: 1 x Mullard CV4024

The warmest combo I tried. Nice tone, but the timing was all lost. I dismissed this combo pretty quickly based on how slow it sounded. It also did not have any sparkle in the highs.

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· First Gain Stage: 2 x Telefunken 12AX7 smooth plates

· Second Gain Stage: 2 x Mullard CV4024

· Output Stage: 1 x Brimar 6060 Yellow-T

This combo was impressive on some music. It was warmer than neutral and had really nice 3-dimensionality. The tones were nicely saturated and textured. An example that has stuck in my head: The Mofi reissue of Jerry Garcia and David Grisman’s “Shady Grove.” Jerry’s voice just hovered there in between and slightly in front of my speakers. It was gravelly and filled with nuance and texture. The acoustic instruments were also very well-served. The downfall for me was the timing was too compromised. I didn’t care with some music, but particularly with my jazz, I like that toe-tapping snappiness that just makes me feel the music. That wasn’t there with these tubes in these spots. The bass performance was enhanced, deeper. Another arrangement using the same tubes might be worth trying.

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· First Gain Stage: 2 x Telefunken 12AX7 smooth plates

· Second Gain Stage: 2 x RCA 12AT7 black plates

· Output Stage: 1 x RCA 12AT7WA

This combo is very nice. I could definitely live long-term with this. I would say that this combo is the most similar in character to the stock tube configuration. The timing is uncompromised in any way versus the stock tubes. It is on full display. The Telefunkens are giving you some increased 3-dimensionality, and the RCAs are giving you some improvements in the tonal qualities. A little midrange magic. And the bass is deepened slightly. Overall a very nice way to go. This would be the choice for somebody who wants to preserve as much as possible Keith’s voicing but with some significant improvements.

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· First Gain Stage: 2 x Telefunken 12AX7 smooth plates

· Second Gain Stage: 2 x RCA 12AT7 black plates

· Output Stage: 1 x Brimar 6060 Yellow-T

The absolute best tonal performance. One of the albums I played with all these configurations was the Blue Note 80th Anniversary reissue of Pete LaRoca’s “Basra.” The tone on Joe Henderson’s saxophone with this combo was extraordinary. The texture and color and vividness just knocked me out. I am beginning to see a pattern here with the Brimar 6060 Yellow-T. Its tonal capabilities are through the roof! Unfortunately, the sacrifice to the speed and timing was just too much for me. Too slow. I was sad to have to move on.

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· First Gain Stage: 2 x Telefunken 12AX7 smooth plates

· Second Gain Stage: 2 x Mullard CV4024

· Output Stage: 1 x RCA 12AT7WA

This combo was the last one I tried. And I never changed it again. Incredible. This combo does change the character quite a bit versus the stock configuration. But all in good ways IMO. The tonal excavation is not quite where the Brimar combos were. But very beautiful in its own way. Perhaps a little more realistic. The bass is deeper and more detailed and articulate. The three-dimensionality is very nice. The whole presentation is different in the sense that there is body and bloom around instruments. The piano sounds far and away the best of all the combos I tried. You get the sense of the wooden chamber of the piano and the sound that reverberates. The upright bass you get a sense of the vibration of the strings that I didn’t get from any of the other combos. Tactility? Just the feeling of real people and their instruments and the interaction with the space around them. This is not something that the stock tube set excels at. And now it comes down to the timing, the rhythmic performance of these tubes. I really had to listen for quite a while to be sure of my conclusion. The timing is not quite as super-fast as the stock and the “all-RCA” combo. But it is only very slightly slower in comparison. In exchange for all that other magic. And I very much am still toe-tapping the entire time and with all genres with this combo. Timing is still a strength. This is a matter of personal taste of course, but this is what I was hoping for when I took the plunge on a far more expensive phono stage. Blows me away how great this sounds.

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Some notes:

The Brimar 6060s are pretty rare. I’m not talking so much about how expensive they are, but if you can even find them at all. I did manage to find a few NOS, but with no noise testing, and no balanced sections and no matched pairs. They were pretty far off from one another. So I didn’t even bother using them in the second gain stage. Tubes in that position need to be matched closely. I used my best-balanced one in the output stage only. Luckily it seems to be a very quiet tube.

The RCA 12AT7 black plates are a wonderful sounding tube. But in my experience they are more likely to be microphonic than the military builds. I had mine tested to the moon and back, and I could still hear some of that very high pitched ringing with my ear fairly close to the tweeter. The 12AT7WA, on the other hand, is quiet as a mouse. And sounds pretty much the same. If you go for the RCA approach, you may want to spring the extra dough for three 12AT7WAs. That’s what I would be doing if I were going to go with that combo.

When I was getting some microphonics from the RCA black plates, I decided to try some Herbie’s tube dampers to see how much effect they could have on noise. I bought 5 of their cheapest line (designed specifically for small signal tubes) and used them on all 5 tubes in the phono preamp. I think they diminished the microphonics I was getting a bit, but definitely not completely. However, I found the improvements I got to the overall sound to be impressive. I was not expecting that. A little deeper bass, more pure tonal qualities, a little more image specificity. I think it cost me about $80 with shipping, and IMO was well-worth the investment. YMMV.

I tried the above tubes in combinations with the stock tubes. The stock 12AX7s with the various NOS 12AT7s. The Telefunken 12AX7s with the stock 12AT7s. NOS for both, but with the stock Ei 12AT7 output tube. None of those combos worked for me. The cheap stock tubes seemed to rob the NOS tubes of their character, and the NOS tubes seemed to rob the stock tubes of their rhythmic performance.

I purchased the Brimars from Parts Connexion, the Mullards from Upscale Audio, and the Telefunkens and RCAs from Brent Jessee.

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I would love to hear from others what they have tried and liked (or didn’t like). For instance, I would be particularly interested to hear from anybody that has tried Amperex 12AX7s in the first gain stage. My experience tells me Mullards would probably not be a good match in that spot. But if you have tried them, I’d love to hear what you thought about that too. Or any other 12AT7 combos…

 

Nice write-up, very informative and well done. Curious, have you ever tried running it in the 4-12AX7 configuration?

 

Thanks! No, I have't tried it in the high-gain configuration. I am using a Soundsmith Zephyr mkIII, which is one of their high-output cartridges. So I have plenty of gain.

 

I'll be bookmarking this for reference. Thank you for sharing your observations.

 

Ditto. Herron owner here.

 

Some good info on your tube rolling results with the Herron.

I agree that the stock tubes are very quiet. I also agree with you and use tube dampers.

Like yours, my Herron came with Electro-Harmonix 12AX7 EH tubes in V1 and V3, Electro-Harmonix 12AT7 EH tubes in V2 and V4, and Ei 12AT7 tube in V5. However, mine developed a little tube rush when I max out the gain on my control preamp (though I never actually listen at that setting). So I went on the lookout for quieter tubes, especially for V1 and V3. One thing I recommend in order to ensure the quietest tubes is to get a tube tester (or know someone with one), especially if you use a lot of tubes in you setup. I've purchased some matched pairs, low noise/microphonics pairs, etc., only to test them myself and find otherwise. The ones that I actually measured for similar gain between triodes, good balance between triodes, and low noise/microphonics for each triode turned out to be in fact very very quiet. Others not so much, including NOS tubes.

To reduce noise, I am currently using the Electro-Harmonix 7025 in V1 and V3, as they are significantly quieter - measured and sound wise - than the Electro-Harmonix 12AX7 EH tubes (although one of the 7025 tubes from the batch I ordered had too much noise and was returned). They are also relatively cheap. I've tried a few other tubes in V1 and V3 but I sought to keep the Herron's voicing in tact (but see below).

I also replaced the Electro-Harmonix 12AT7 EH tubes in V2 and V4, and the Ei 12AT7 tube in V5 with a 1960s version of the Ei 12at7 tube for V2, V4, and also V5. But quiet ones from that era are very hard to come by. Very good bandwidth and bass response though. Given that the Ei tubes were made on Telefunken equipment, it would be interesting to try some Teles in these locations. I may at a later point.

As always, to me, the Herron is open, lively, and organic sounding. So I tried to keep it that way. However, to increase soundstage width/depth (perhaps what you refer to as 3-dimensional), texture (perhaps what you refer to as saturated tonal colors), dynamics, and musicality, I use an SUT. This bypasses the Herron's FET initial stage in the MC input and goes directly to the tubes in the MM input. It is an involving and seductive combination IMHO.

YMMV.

 

Right, if you aren't using the MM inputs, either with a high-output cartridge, or by using a SUT with a low-output cartridge, you are bypassing the tubes in the first two gain stages and the signal is only passing through the one output tube. I should have mentioned this in my post. The MC inputs on the Herron bypass the tube gain stages (it uses a solid state implementation) and then go through the output tube only. So if you are using the MC inputs, you only need to worry about rolling the lone output tube.

 

The best 12AX7 I ever used are Mullard 12AX7 long plates. Best 12AT7 I ever used are RCA 12AT7 long plate.

 

Let me know when you've heard them in a Herron phono preamp. I'd love to hear about it.

 

Actually, if you use the MC input, the signal first goes through the FET initial gain stage in the MC section and then through all of the tube stages (V1 through V5) in the MM section. So for the MC input, the FET section provides 22dB gain and the tube section provides the additional 43 or 48dB for a total of 64 or 69dB. So even with a MC cart, you can roll all tubes.

 

I completely agree with this. Everything is a compromise in a design. This unit does not sound particularly tubey and Keith clearly has a preference for running wide open (infinite loading). The result is a bit zippy and perhaps boosted in the midrange. But the design clearly was aimed at pleasing the widest portion of the bell curve of consumers. Even the FET-based MC gain stage was a pricing compromise in lieu of using more costly Lundahl's (for instance). My Herron always sounds best when running through my Zesto SUT when using MC carts - much smoother and quieter.

You have put way more effort than I did into tube rolling but the limited attempts I made always sounded worse so I always went back to the stock tubes. I even did try running the higher gain configuration with 4 12AX7's and it didn't change the sound at all other than adding a few more dB gain as expected.

 

Okay, I was mistaken in the above quoted post, and I want to correct what I wrote. Keith Herron was reading this thread, and he gave me a call to chat and to explain to me the path of the signal when using the MC inputs. The signal first goes through a series of FETs, which he described as sort of an "electronic" SUT, before being passed along to the full tube path (both gain stages and the output stage). So with either MC or MM inputs, you are running the signal through ALL of the tubes, not just the output tube. I just want to make that clear, and I apologize to Keith for my inaccuracy in describing the inner workings of his amazing phono stage.

 

True, and I think depends on how much tubeyness you want or don't want. I think Keith has it right. Plus, these days, there is trend to tube-based components being more neutral sounding than not. A generality perhaps but there were a lot more euphonic tube components back in the day.

Not my experience at all. Like I said, the Herron is lively and organic. But I would not call it boosted in the midrange based on my measurements and listening.

While I do prefer using an SUT (Hashimoto/Sansui HM7s), the FET section on the Herron is no slouch.

YMMV.

 

As a new Herron owner, this is the best thread ever. I’m currently so satisfied that I’m not looking to make changes but really appreciate the info in this thread for later. Well done OP and others. I’m also glad Keith chimed in as well, nice hearing from the horses mouth per say.

 

Who is Keith? Don't see posts from him in this thread.

 

Keith Herron. He did not post here. Look at post #12.

 

Sorry, my post was a bit misleading, he spoke to the OP and the OP clarified things, Keith did not post in the forum.

 

and of course edwyun set the facts straight before I could post my correction, so thank you!

 

Obviously this is a function of the carts being used as well as preference of the listener. I admittedly lean towards favoring the tubey side of sonics. Earlier this year I purchased a Luxman EQ-500 which absolutely nails the sound I'm looking for, admittedly at a higher price. I have moved the Herron into my second system where the synergies are actually better than my main system - a win/win.

 

Just ordered a Herron VTPH-2a from Keith directly. Asked him if he had any B-stock or demo units. He said he had a couple chassis laying around with a nick or two and he would put a new one together for me in one of those chassis at a very nice price. Never hurts to ask I guess. From reading this thread and others, many seem to believe that Keith spends a great deal of time making sure the stock tubes are as quiet as possible and work perfectly for his design. Has anyone ever asked Keith himself to deliver a unit with more expensive NOS tubes, i.e., where he himself voices the phono preamp with boutique tubes that actually increase the performance, albeit at a likely much higher price?

 

Now that I have officially signed up to drink the Keith Herron Kool-Aid, it seems that the only people who move on from a VTPH, move to significantly more expensive units like @Ontheone and @Josquin des Prez. I'm feeling pretty confident this piece will take my vinyl rig to the promised land. Fingers crossed, as this is my second most expensive audio purchase behind my speakers - an Audio Note Speaker-04 kit that cost more than my car - a 2002 Subaru Outback - is worth today!

 

Keith is very approachable. You should ask him if he's interested in doing something like that.

Before I sold mine he expressed some interest/willingness to change the voicing of mine to better match my Naim gear, but – and I cannot speak for him – I think he may have been doing that more as a gesture of our friendship and the fact he likes to experiment, but not because I asked him to. But I sold mine before that came to fruition. To the end I stuck with the tubes he spec'd. I tried some others (Genelex Gold Lion, NOS Mullard military) but they did not sound as good. I only moved on because I went with a Naim phonostage, a better match for my Naim preamp & I plan to take that to an even higher level (i.e. $13k phonostage) by adding a Naim SuperCap PSU to it.

 

I actually plan to run mine stock based on everyone's input. I guess my question was more theoretical about what the design could do with some of the super NOS tubes (at super expense). I'm super excited to plug this into my system, because I believe my current phono pre is the weak link in my system.

 

To answer your question then, I have never heard from any user of Keith doing this, either here or on Audiogon where there is also a group of users.

 

The finest tubes in the world won't make the FET-based MC gain stage work better. The VTPH2A is the best value phonostage at it's price point and it's designed to be the way. You will need to really ramp up costs with better isolation, costlier power supplies, and Lundahl SUTs to start exploiting the benefits of world class tubes. This is like asking an auto designer to supercharge a VW GTI and expect it to perform like a Ferrari.