If you want to start with tube amps my recommendation is a nicely restored Dynaco ST70. A proven design (250,000 sold!) with adequate power (35wpc) for most speakers. If more power is desired adding a second one and paralleling the outputs on both will yield 70wpc. The ST70 has stood the test of time. Prices are reasonable, well under $1K. Output tubes are readily available (EL34's). I have two - one with a triode input board. The second one is a custom-build from a friend with the stock output transformers and a much larger power transformer.
Tube preamp topologies and music
I am searching for a tube power amplifier. I know very little (nothing) about what the pros and cons of tube topologies as they relate to certain types of music.
as an example, let’s take hard rock/heavy metal. It seems to be the consensus that say 300b single ended amps would be the wrong choice even if you had 100+db efficient speakers. Why is this?
Also, tube compliment. 211? EL84? 300B? I understand that they have power output differences, but what else?
I welcome everyone’s input.
42 responses Add your response
I do not recommend single-end (one output tube per channel) amps because they typically have low power and high distortion/noise with high output impedances. The last means that the amp will track the impedance curve of the speaker, meaning it will yield a non-flat response, acting like a tone control. Something to be avoided! |
A nice thing about the ST70 is the availability of various tube options for the input stage using different dual triodes to replace the stock pentode/triode. Mine uses three dual triode 6922's along with higher-quality capacitors. Plus you can try different brands of EL34's for different sonic "flavors". |
AudioXpress magazine had a good article on building a single-end 211 amp some years ago. The authors cautioned that such a project was not for the inexperienced! I suggest you track down this article! I no longer have my copy. Another valuable source of information on tube amp design are the issues of Sound Practices - recommended! Lastly, find issues of Glass Audio - more information on design and construction of tube amps. |
A OP - As to your specific question, single ended 300B amps tend not to be very well controlled in the bass - even with efficient speakers. A 300B valve is only good for a couple of watts before it starts to distort. A say eight to ten watt advertised SE 300B amp will not deliver that wattage at 1%THD. So they are not a good choice for rock music. The following link will give you a good overview of technical issues related to SE amps - a "high powered" one in this case.
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Tube amps are as subjective as anything in audio, which is extremely. The most important opinion is yours. IMHO it's more important to have an amp that works well with your speakers, and sounds good in your room than to try to match an amp to a music style. Every tube type and brand tend sound a bit different, and they also tend to vary from circuit to circuit, so absolutes are tough to come by. The preamp that you use will factor into the final sound as well. Either way, there's a lot to like about a good tube amp. Midrange clarity and depth galore. With that said, I agree that a Dyna 70 is a nice starting point. Legendary amp for the price. The VTA version from tubes4hifi.com takes things a step further, and is just a wonderful sounding amp....it has some good American iron, a great circuit, and sells new for as little as $995 in kit form, or $1650 complete.
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First of all, I disagree with some of the comments above. A well-contructed single-ended amp can rock pretty hard with the right speakers. But the key thing for you is, what kind of speakers do you have? That's going to determine the amount of power you need, and that in turn will go a long way toward dictating the tube choices. |
@gochurchgo I hope I do not upset anyone, as this is very personal for each of us. Every amp has characteristics that could be positive, and/or negative. Speakers, room size/acoustics, listening distance between listener and speakers, music selection and taste, optimum and enjoyable volume levels and of course, other characteristics the individual is wanting. For cheap, I would buy a used Nuforce STA200. At a higher price, maybe a used Pass XA25. Both fantastic, and with horns. There are many more to choose from. I would not go tubes at this point with technology (power amp specifically). BTW, if you appreciate tautness, control, speed, fast transients, rhythmic momentum and less "color", particularly with the lower octaves, these are not the forte of tubes. I am not knocking tubes, as I understand why the love. I left tubes (again power amplifiers specifically) a very long time ago, and the virtues of music and sound reproduction I look for and appreciate, are with great solid state. Please pardon me. My best, MrD. |
@gochurchgo , in a discussion about the definition of the term "musical" I once made the comment that a SET amp would be the wrong amp for a head banger. At least two (possibly more) members informed me that I was dead wring, and also that 4 wpc of SET power with the right speakers could bring the house down. |
All valid points above.Eventually it comes down to the characteristics you value and finding and matching equipment to get you there. Speakers and room size are key. Unfortunately or fortunately this requires research and trial with your ears. If you value slam and dynamics, single ended tube amps are at a detriment compared to solid state amps. If you want set and forget, go with solid state. If you like modifying, rolling tubes, then... If you value soundstage depth, solid state is at a disadvantage. It comes down to the end result you want to hear and how you want to get there. |
@jasonbourne71, spot on. OP I would look at Quicksilver Audio see here. Mike |
thinking about it, I am pretty sure I was using the term "metal-head" in that discussion I alluded to in which I was corrected, not "head banger." I better correct my misquote that I made in case there is an important distinction between the two. Regardless, I was told (in no uncertain terms) that 4 wpc of SET can make the right speakers scream. I have no experience whatsoever with ANY watts of SET, so on that subject I can only relate what I was told. |
@dogearedaudio thanks. I run a pair of subs off the speaker taps which I assume I could still do. I’m a fan of high efficiency speakers and would like some La Scalas at some point. I am trying to wrap my head around tubes to see where I may land. I have only run solid state so far with zero complaints. In fact I was looking to upgrade to the Coda S5.5 until again researching tubes. |
@jasonbourne71 -- You have provided some very good information. I would like to pick your brain a bit. A couple of years ago, I acquired a beautiful Dennis Had Inspire 45 amp and a Dennis Had LP 3.1 preamp. The seller included a set of brand new, in the box, 45 tubes from Emission Labs. My plans are to use the Had gear with a pair of Klipsch Forte II's that I've had for years. Do you think this will be an amp that can handle driving the Forte's without any issues? The Had gear could not drive a set of Monitor Audio Bronze speakers or a set of Polk Audio Model 10 speakers -- not enough power. I hope the higher efficiency Forte's won't have the same problems. What speakers would you pair with the Had amp and preamp if you owned them? Thanks.
Some details: I mainly listen to 1968 -- 2024 Progressive Rock, Prog Metal, Classic Rock, Shoegaze, Math Rock, and good old Heavy Metal. No Country, Rap, Hip Hop, Opera, or Classical. If I'm really jamming, I listen not at ear splitting levels, but loud enough that you can't easily carry on a conversation with someone at a normal speaking level. After all, I'm there to listen to music, not catch up on gossip. The Forte's are in my Man Cave, which also includes my home theater system, but the 2 Channel system is separate from the HT. Thanks. |
@allenf1963 , here is the thread I alluded to a few posts ago. This thread turned into an argument about what the definition of the term "musical" is, but near the end of page 5 I made the comment that a SET amp might not be "musical" to a metal-head because it wouldn't play loud enough. @atmasphere (and @newfzx7 on page 6) weighed in, and basically told me that SET would work with the right speakers, based on their experience. If you start reading on page 5, you may or may not find some of it helpful.
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@immatthewj -- Thanks for the info. I was able to wade through the posts and glean some insight.
@dogearedaudio -- I plan on doing that, but I'm recovering from a Bone Fusion surgery on my left foot and surgery to remove plates and screws from my right foot, so my mobility is not very good right now. I don't have anyone to assist me with the gear, so when I saw all the info in Jason's posts, I thought I'd inquire on his knowledge of the Had gear. I wish I could easily snap my fingers and everything would be set up to test in listening sessions, but unfortunately I'm in rough shape right now. Oh well. |
Tube Amp's are not to be viewed through Rose Tinted Glasses. Prior to making a decision about adopting the Circuit Type as a Amplification, the individual who is to be using the Audio System is best to come to terms with how disciplined they are in relation to being present in the room when the Audio System is in use. A recent thread on a similar subject, where leaving a Tube Amp' Powered On, will introduce one to some of the realities that relate to using Valves in a Circuit and some of the disciplines that are best adopted if to become a Tube Amp' user. FTR, I am a very long term user of Tube Amps, as a Phonostage, Pre-Amp, and Power Amp. Most recently a Tube DAC is utilised as well, I treat all with the same respect that I began to cultivate in the earliest of days and have been vigilant in maintaining. FTR, the system when SS, was regularly used by Wife. When it went over to Valves, she was put off by the suggested attitudes to be vigilant that were made known to us, resulting in her only choosing to listen when I was present. The decision to change to Valves, has removed multiple hours of music encounters in the home, on the the home audio system from my wife's periods of R&R, she chose to settle for lesser quality methodologies to experience music. Enthusiasm for Audio Equipment can prove to be a cruel master, it would be so much kinder if the Music being Replayed and the listening was the major part of the interest. The endless obsession that can develop in a individual, towards the tools to create a music reply, is not really needing such time and energy put into it. As Music Replays as a form of being an entertainment are very easily enjoyed on the most basic equipment used to produce the end sound. With my Wife today, most of our in the home shared moments whilst listening to replays of recorded music are done with Alexa supplying the end sound. We are very very happy to have these moments of time together, calling up songs at the command from a voice. |
@tubes4good -- Thank you very much. Kind of you. |
So much commentary on single ended 300 B tubes and low wattage amplifiers. @jasonbourne71 has some outstanding commentary but requires great expertise to really understand things. My take away is that you risk higher distortion when you have low wattage amplifiers. I guess the speakers should be highly efficient but then this may lead to distortion when you want to turn the volume up in a bigger room. Maybe lower watt amplifiers are good for small rooms where higher wattage amplifiers Will have no problem filling a larger room. I didn’t follow the impedance curve tracking rationale where if it happens you’ll have increasing distortion. Impedance as a relates to lower wattage Single end tubes is not easy to understand for me at least but I’m open. I have 16 kt88s on my 300 watt tube monos and there doesn’t seem to be any distortion that I can here. |
Most single-ended tube amplifiers have relatively high output impedance a) because only one output device is being used and b) because they usually don’t use feedback, which also contributes to higher output impedance and poorer damping factor. Your amp uses multiple devices in parallel, and also most likely a good bit of feedback, both of which greatly reduce the output impedance and increase the damping factor.
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gochurchgo I can highly recommend the tube amplifiers and preamplifiers of Aric Audio, and I agree that a "Push Pull" configuration might best provide what you are looking for. Give Aric Kimball (owner of Aric Audio) a call, he builds 7 different amplifiers with several different topologies. He's great to have a conversation with and get some feedback; and he makes killer hand built tube gear, I've got several of his pieces including an EL34 "Push Pull" that is extraordinary. |
@gochurchgo There are now class D amps that have the same distortion character as the best tube amps (but lower overall). Distortion is why tube amps sound the way they do, just as distortion is why most solid state amps sound harsh and bright. Put another way, the sonic signature of any amplifier is caused by its distortion signature. So if you want an amplifier that is smooth, detailed and involving, you are not limited to tubes any more. Some (certainly not all) class D amps have a distortion signature that is identical to the best tube amps and so sound just like them too (although are more transparent owing to distortion being lower overall). |
@gochurchgo Wrote:
Yes. In my opinion, a push/pull class (A) tube amp would fare better, less distortion and more power than a single-ended class (A) design. Rogers High fidelity makes class (A) single-ended and class (A) push pull tube amps see here. 😎 Mike |
I owned a Rogers EHF 200 and while it had gobs of power (KT150 / 127wpc) it was nowhere near as sweet and detailed as the Raven Osprey (6L6GC / 35wpc) that it replaced at less than 1/3 the cost of the EHF (list price) and the Rogers is virtually impossible to resell with the “transferable lifetime warranty”.
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