Tube Preamp: How many tubes does it take to .................
My McIntosh Tube Tuner/Preamp has 17 tubes (some for tuner of course).
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This EAR 802 Tube Preamp has 14 tubes (and either MM or MC phono)
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Some have as few as 2 and no mention of Hybrid
Some call themselves Hybrid
What _____________________________?
McIntosh C220, with remote, with phono, total 4 tubes ’cool tube glow' out the top seems to be it’s claim to fame
http://www.berners.ch/McIntosh/Downloads/C220_own.pdf
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One major differentiator is if tubes are used for just the preamp or also for the power supply. Lots of preamps, used to only use them for the amplifier section. Over the last decades there has been a movement to use tubes for both. So my Audio research preamp and phono stage (very similar topology and function) use 8. Two for power supply regulation.
How many? Well, I guess the designer decides, and that I am sure depends on the sound quality he is going for. |
I'll throw in another possibility for 'extra' tubes in a preamp that can improve fidelity, cathode followers after again tube. They supply a nicer impedance match to the next gain stage. If every gain stage in a preamp used them you end up doubling the number of tubes. Another possibility is paralleling tubes to lower an amplification stage output impedance(like a cathode follower above). I haven't seen it used that much but I recall Conrad Johnson doing it on some of their top of the line products. |
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The amount of tubes means very little ,you truly only need2 somecj preampsonly 1 tube they split 1/2 of each side the transformers ,chokes and powersupplies make they most difference quality counts ,look atVacuum tube guru Radu Tarta all highendLundahltransformers or chokes ,or Yamamoto, or Monolith snd he don’t use coupling caps ,he believes in Highend transformer coupled its much more $$ but excellent signal isolation and purity . capacitor coupled too cap an be very good but high quality parts count look atLinear Tube Audio Micro Zoe very nice tube preamp with several tube choices . |
It also depends on when it was made. If it was in the 1950s or 60s them of course more tubes because that’s the technology of the day. My McIntosh Mx110z has 17 tubes but it’s a pre, phono and tuner and was made circa 1960. My more recent C2300 has 6, 2 for MM phono, 2 for MC phono and 2 for Aux. Same for amps where my MC30s have tube rectifiers instead of ss, They have one more tube per channel than my MC240. Technology. |
It also matters if one is looking to have opportunities to work with the sonic through Tube Rolling. I know a few individuals who have done this with their Pre-Amps and Pre-Stages on their Power Amp's. Less is more in this subject area as a Amp' using only a couple of Tubes, is much easier as a preparation task, to attain matched tubes from which era is selected for the tubes production. Transfer that same preparation to Multi Tube devices and options become diminished quite quickly, unless substantial sums are to be parted with for certain era's of production and follow up testing of supplied tubes is used to identify the measured accuracy of the matches. It is doable, I am sure I know one person who has 6 x 1960's Vintage ECC 83's in their Amps Pre-Stage. |
Your McIntosh Tube preamp in picture must be a maintenance nightmare. I had same bad experience with a AR sp-11 phono/line pre-amp 20 years ago. I bought the unit based on great audiophile commentator Mr. Chen's recommendation. I was impressed with the phono stage performance. Howerver, very soon, I ran into multiple tube bias issues and component(s) failures. I felt a pre-amp should not require to be baby sitting every 6 months to keep running at optimal state, so I gave it up. My current hand made line stage preamp are all single tube stage amplifier based on famous Western-Electric "Ultra path" circuit using best nickel signal transformers and Teflon coupling capacitors, and it out perform AR SP-11 by a big margin. Furthermore, tube type matters in line pre-amp. 26 direct heated triode sounds best in a cost no limit pre-amp design. |
In relation to matching tubes, it certainly is a Horses for Courses subject. Unfortunately the right horse is not found until tried in the race, pretty much the same for a Tube Roll experience. I have had a supply of Brand New Tubes, that when tested, the equipment owner made known immediately one Tube will produce sound, but is with a fault. It was an unknown how such a fault could impact on a circuit, which resulted in the suggestion not to use the tube. How many individuals are putting New Tubes into their equipment not knowing how it measures on receipt to them, and prior to be put into service. I have had tube equipment for more than two decades, I have developed my own disciplines, maybe a little cautious, but through careful practices, there is a plan for the usage, that has prevented the worst type of the associated stories occurring so far. |
I think that sound reproduction fidelity is inversely proportional to the number of gain devices. So do a lot of people. Accordingly, I don't think it's coincidence that the best sounding preamp that I've ever heard uses only one-half of a double triode tube per channel as the entirety of the gain structure. It's the Dodd Battery Powered Preamp. A simply extraordinary amplification device. No voltage rectification. Huge signal to noise ratio. Remarkably linear and remarkably transparent. There's a reason Danny Ritchie still uses one to demonstrate his speakers. To paraphrase Danny: "If I knew of something better I'd use it, but I don't." |
When it comes to transparency being perceived as a sonic trait from a Pre-Amp, I am very familiar with a model, that supplies this perception in a manner that is extremely impressive. The component responsible for this perception is the Korg Nutube The Korg Nutube assuming the the role of a Triode in the circuit is something to be experienced. I would suggest, if a line up of transparent Amp's were side by side compared, the model with a Korg Nutube as part of the circuit, will be a real contender for top place, as it has other very desirable sonic traits that work very well in conjunction with its transparency. A friend who is building Pre- Amp's using the Korg Nutube, has recently been at Hi End Munich 2023. There was, in their and an accompanying individuals opinion, not any Pre's witnessed during demo's attended, that delivered transparency in the manner the Pre-Amp produced with a Korg Nutube can. |
Tim de Paravicini's later (and still currently available) EAR-Yoshino pre-amps use far fewer tubes. The 868PL (phono and line) uses two tubes per stage, the 868L (line only) just a pair of 7DJ8's. The 912 uses the same two line stage tubes as the 868, with three tubes for phono gain. The ARC SP-9 mentioned above by @curiousjim is a tube/FET hybrid design, not a pure tube one. That's why it uses only a single tube for each stage. IMO ARC hybrid pre-amps sound more like FET's than tubes (I've owned two). |
My preamp uses one cathode-follower tube in the line stage but has 8 tubes (and 4 MOSFETs) in the power supply. My phono stage has 3 tubes for RIAA and 4 tubes in the power supply. The point is that tube preamps tend to use the most tubes regulating the power rather than amplifying the signal. And where there is a dearth of tubes, there is a reliance on solid stage regulation instead. |
There are many ways to design pre-amps. And many different designs can sound good based on execution and taste. The basic functions of a line stage pre-amp: If you prefer a KISS approach, a single ended pre-amp can get by with one triode gain stage per channel. This could be one dual triode tube, or two single triode tubes. Tubes by nature have a high input impedance. If chosen carefully, a simple single triode stage can meet most of the above criteria usually for a short cable and highish impedance (often tube) amplifier. There are many other approaches. A design like the classic Dynaco PAS uses feedback as so requires two high gain tubes stages (one tube) per channel. Some designs use a cathode follower which requires another one or two tubes. Other designs (like some Conrad Johnson) use many paralleled triodes per channel. If a pre-amp is fully balanced, then everything is doubled. As mentioned previously, some pre-amps use tube rectifiers (one shared or one for each channel) and some designs also use tube voltage regulators. As you add functions and features you can add even more triodes/tubes. A phono stage adds a minimum two triodes (one tube) per channel but can be more. Other features requiring more tubes can be a tape loop and phase inverter. So, depending on performance, features, and convenience requirements/preferences, old and current pre-amps can use few or many tubes. This variety makes our hobby fun, IMO. |
I have had many tube preamplifiers over the years. Ranging from only two tubes to many! The best that I have heard in my home, across multiple systems is the entry level Backert labs Rhumba 1.3. It uses only two tubes. It excels at detail, soundstage, clarity and more. I like the tonality. It is vivid and dynamic!. |
1965 MX-110Z is hardly a maintenance nightmare……. an excellent engineer w ears…. paid heed to SOE ( safe operating envelope ) of ALL the components in circuits, including line voltage variability = legendary tube life and reliability…. so Gow and company understand this w the RCA tube design manuals as stone tablettes ( yes that was intentional )… Of course further genius like Roger Modjeski….. used the envelope advantageously …..10 k hour tube life….in a power amp… |
