erik2A3

FloridaBoy Thanks for posting the vintage hi fi link!

I'll quickly add that I just unexpectedly came across another Prima Luna reference in the July 2015 issue of Hi-Fi Choice. The Dialogue HP (four KT88s per side suggesting push-pull parallel operation) was being used in a simple, but high quality system, along with a Krell digital streamer and Martin Logan speakers. The Prima Luna again was highly praised. An above post mentioned how Prima Luna might pair with high efficiency horn loading. Check Art Dudley's Stereophile review above. Scroll down to associated equipment used in his review, and you will find Altec Valencias.

And to end my contribution to this thread, a recent review from Art Dudley, whom I have followed since his days at the helm of Listener magazine (he's of course now been with Stereophile for some time). http://www.stereophile.com/content/primaluna-dialogue-premium-power-amplifier#IpcU5QEWlh3KOitg.97

Some of you surely know of Ken Kessler http://www.hifi-notes.com/primalunaprologueone21-en.htm edit: Dennie: please continue to research Prima Luna. I own one of their preamps, and, as a builder myself for many years, was truly enormously impressed by the product on all levels.

thesloth I am surpised you are not more familiar with Prima Luna. I have read quite a bit about the company, and they are very well respected and build truly first rate vacuum tube audio electronics. The internal wiring of their products is quite esaily near the very top of other commercial products I have seen. They are designed in Holland, and built overseas to keep price down -- and that fact most certainly does NOT compromise quality. I have had, and continue to have considerable respect for what they do in a normally rather over-priced and highly competitive market.

As someone who has contributed here for many years (in those days using a different handle), it's interesting to observe the revisitng of topics that had been so frequently (and at times quite vigorously) "discussed." The SET vs PP and hollow state vs solid state in general was a path traveled over and over. one contributor referred to interstage coupling, which was yet another area visited. Better still, in my experience, direct-coupling (which helps do away with the dreaded coupling capacitor debate, or a combination of direct and interstage coupling -- about which I also contributed many posts. So, once again for fun! I have built both the 45 and 2a3 versions of Jack Eliano's DRD (Direct Reactance Drive) single ended 300B circuit that was published in Vacuum Tube Valley magazine in.............a long time ago. It is an unusual and extraordinary design, and there have been a host of variations done. I would point out, however, that while this particulalr implementation is fresh and new, important aspects of the circuit were known and used more than a half-century ago. I also built a version of this amplifier using parallel feed output topology. I have written at considerable length about Eliano's so-called "Ultrapath" connection in years past (again under a different avatar -- my name) and don't have nearly the energy I had back then to go over it all again. This circuit will be of interest to some of you. It is a truly fine sounding design (purely subjective of course). Why do SETs sound so good? I would answer that question by pointing out the fact that history on this forum would suggest that to some listeners, SETs not only don't sound good, they sound terrible. It is entirely and absolutely a personal taste sort of thing. The following is one SET topolgy that to me sounded very good indeed. Again, this is ground already very heavily traveled here. For those of you who may not be aware, Jack Eliano is the gentleman behind Electa-Print transformers. http://www.electra-print.com/300bdrd.php

Prima Luna typically gets extremely good reviews. In addition to preamps I have built myself, I also own a Prima Luna Prologue Three line stage preamplifier. One of the reasons invested in one was the fact they they are built to a very high standard, with extremely clean wiring, lead dress, layout, and of course circuit design. As I have said, they have been quite well-received, and I can say from experience that they are quiet and highly musical. I am very particular about quality workmanship, and while they are designed in Europe and built with under strict supervision and quality control in China, the latter fact helps bring cost down considerably. In my view, very highly recommended. PS: I also own the Decware Mini Torii 6V6 amplifier, and having studied both products wiring and overall construction, can say with certainty that Prima Luna is very much on par with the Mini Torii in terms of build quality.

Maynard: Just to give credit where deserved: the author of that audioasylum thread does in fact mention poor solder connections in the first example provided, but seemed to limit them to tube socket pins. By implication, I guess I still perceive that statement as referring to other connections, as well.

All American Model 5

We've discussed this many times in the past. A step further in this thread: Of course it's essential to discharge PSU capacitors in circuits that don't have bleeders across the output of the power supply. HOWEVER: More importantly, if you are unfamiliar with audio electronics or have minimal experience in electronics in general or are uncertain about what you are doing (such as what leads or tube socket (plate) pins may present high voltage storage charges, or how to interpret positive and negative connections on filter capacitors, or understand the nature of the design of the power supply of the particular component in question - do not proceed with the installation of power resistors to bleed dangerously high voltages to ground. I have learned from experience that it is not something about which one should be casual or take lightly. Keeping one hand in one's pocket is the generations-old practice to prevent electrocution between one's hands and through one's heart, but you should have a very clear understanding of what you are doing before that. Since I joined this forum about twelve years ago, there have been times members posted about how they, on other forum member's dare, decided to solder and make connections in a chassis that was plugged into the house mains and fully energized -- and how they subsequently unknowingly touched something that was carrying high AC or DC current and instantly received an extremely hard and painful shock. Trust me when I say that it's not only unpleasant (as some contributors here will know) but potentially truly lethal. I have had amplifiers sent to me that had been unplugged and out of service for several days, yet still had hundreds of volts in reservoir capacitors. Discharging caps and obviously unplugging a component to be serviced is certainly smart. Be comfortable and familiar with working on high voltage electronics first.

Maynard: Tubes and Klipsch is always a great topic, yet we have always discussed the two often on this forum, which has fulfilled the task just fine IMO. I first ventured here in 2002, and was up to many thousands of posts before I took a break to work on projects. The topic is always of interest to me, but the 2-channel forum has been just fine, actually.

Very interesting! I really liked the Wright 2a3 amps when I had a couple of pair here several (maybe 10?) years ago. George was such a really great guy, and shared some information with me about his circuits when we spoke on a couple of occasions. He was a close friend of the gentleman who introduced me to Lowther horns about 20 years ago. Those amps use low impedance coupling between the voltage gain and output stages, and subsequently have somewhat better noise rejection than a number of other single-ended topologies with a similar compliment of tubes. Regarding the frequency response of this two-way application with which you're experimenting: you are the one doing the listening and know what you are hearing. Just in terms of integrating a multi-driver system, where different drivers are being used for LF, bandpass, and HF (in a 3-way system), I would opt for a two-way if, based on your listening thus far, you think a tweeter unnecessary -- which is what appears to be the case. Have fun, enjoy, and stay cool (whew!)

I have been building my own amps and preamps for some time. For those possibly inclined to immediately point out flaws, such as small output transformers, solid state rather than valve rectification for B+ voltages, a pine board instead of a fully-enclosed metal chassis, please consider the fact that we are talking about a budget of $200. One sometimes has to know where to look. The following kit was designed by a very knowledgeable individual, and is being sold by a company that specializes in vintage tube audio electronics (both radio and hi fi - as well as musical instrument). I have purchased parts from them for a long time, and received excellent customer support in all cases. Also available in monoblock form. Granted one needs to know how to solder, which is simply not a big deal with a little practice. I learned to solder when I was five years old -- it can be easily mastered with just a bit of practice. From an electrical engineer and noted OTL (output transformer-less) tube amplifier designer http://www.transcendentsound.com/Transcendent/Amplifier_Output_Impedance.html Have a look just for fun! https://www.tubesandmore.com/products/K-502

Sloth, we have discussed parallel or shunt-feed output topologies at some length in the past. I first joined the forum in 2002, and single-ended parallel-feed was one topic we visited often back then. I've also brought it up more recently. Good plate chokes, as Maynard pointed out, can be expensive, although in my experience the benefits in terms of sound quality over conventional single-ended designs offset the cost of parts required. I also once experimented with a combined interstage/direct coupled front end with parallel-feed output with grid chokes on the outout triodes instead of more common grid-leak resistors. I do recall one response to the parafeed discussions of the past where another forum member frowned on the approach because, according to him, the output transformers were too small to be any good.......

Hi, Steve I can see how that would be a very nice setup! I have built several SEOTL amps (original version) as well as six T16s (and own examples of both of those), but I am completely unfamiliar with the sound of Bruce's current generation of OTLs. However, I have been following his work since the very early 90s, and find him to be an extremely original thinker and designer. I would think that the output impedance and damping characteristics of the SOB (acronym for Son Of Beast -- for those unfamiliar) would be particularly good with the RF7II. Should be done with the MP in a few days -- I'm working on a few different amp projects at the same time. I will be using it with our La Scalas and Grado and Senheiser headphones.

What a luxury to have time away from teaching for audio construction projects! With a strong preference for scratch building, kits, particularly those that do NOT use circuit boards, are always enjoyable. I have built many Transcendent Sound products over the last twenty years, including designs published in Glass Audio magazine (before TS Kits were even available.). The latest from that company for me is one for which I have very high expectations. The "Masterpiece" as it's called, is a combination high output current preamp and headphone amplifier. I have built a number of line stages using the more common dual triodes in various output configurations -- cathode followers, SRPP, unity gain impedance buffers, etc. -- and while many sounded quite good (and a couple not so good), none comprehensively addressed an issue many of us encounter: the deleterious effects of pairing higher output impedance preamps with amplifiers that are connected via long runs of cable. Cable inductance, capacitance, and resistance are electrical characteristics which some cable companies don't address (at least overtly), and what the end user is often left with are flattering descriptions of speaker and line-level cables that are named after various species of snake or, perhaps, the names of famous composers or tall mountains -- all of which to me are essentially meaningless in terms of determining suitability with one's specific components. The "Masterpiece" was designed to take advantage of the perceived sonic attributes of the 300B (which for me has become a favorite) and develop a linestage/headphone amp that can drive long ICs with ease, and/or be used as an extraordinarily high quality headphone amplifier that's compatible with large number of headphones. I am not the designer of this circuit, so it would not be appropriate for me to share specifics of the circuit. Transcendent Sound is well known for its OTL amps (which as an owner I can tell you are (subjectively, of course) stunning with Klipsch Heritage horns, but this preamp is one product I think is going to be exemplary. The chassis is completely pre-punched and machined (good for me since my Greenlees are getting old and dull), but the entire circuit is wired point-to-point. Those of you who know what you're looking at will be able to quickly determine that it does not use tube rectification for B+. http://www.transcendentsound.com/Transcendent/Masterpiece.html Hardware has been installed and basic power supply connections complete: I use my own wire of choice and in some cases make changes in terms of overall parts layout. One of the advantages of PTP wiring, in my view. I would not recommend this project for a first build. The Grounded Grid preamp would be a better choice.

For those of you that remember, this topic came up once or twice a dozen or so years ago...

Maynard Excellent - A truly well-written explanation. Thanks! I think you are one who can appreciate this: speaking of tubes with metal envelopes, my dad (building vacuum radios since about age 10), was recently making his own metal envelope tubes out of copper tubing. Fascinating process! They were for VLF receivers he used to detect and record, as they are sometimes called, "whistlers," which are potentially musical-sounding by products of lightening. And absolutely right on PSU bleeder! Single-ended 6v6 can be incredible! Job well-done!

And Maynard: I appreciate your willingness to share. Since I joined this forum (initially in 2002), that kind of generosity has most certainly not been the norm. Thank you

Maynard If your preference for filaments, in my view there is enough space both above and within the chassis for a separate filament transformer, full-wave bridge and small filter section (10,000uf or so) to smooth DC. As you know, the first filter cap often has the subsequent effect of boosting output voltage, which is desirable on plates, but not with filaments. So, an additional dropping resistor and then another cap in the range of the first would do the trick. Those valves use indirectly heated cathodes, though, which IMO makes the need for DC heaters much less mandatory, particularly in the output stage. Were you designing the circuit around filamentary cathode tubes (eg 2a3, 300b, etc) the use of a hum null potentiometer (in the case of preferred AC) is pretty much required. I have built amps around triodes like the above many times, and have experimented with both AC and DC (including regulated DC) and always seem to prefer what I perceive to be a somewhat more sort of organic quality with AC. Definitely something that is builder/user/listener dependent. No right or wrong way of doing it providing current and voltage demands are met. Didn't have time before to check the schematic, but it's nicely done. Always good to see a bleeder circuit on the output of the power supply. I agree that 1watt would be very much a minimum power rating. Just for kicks (if you felt so inclined), you could experiment with the use of a lower value (47uf or so) poly film cap as the bypass for the output stage cathode resistor. If you are needing such a high value electrolytic based on measured drop off of low end response, then of course 47uf is not going to do it. I have even used motor run caps in that position with extremely good results, but those obviously take up quite a bit of space. Observation: The small cap across the volume control: the schematic indicates it's connected between input to the pot and ground. I am assuming your inclusion of that cap is for the same reason I use them on virtually every integrated amp I own, after having found the same neat and simple trick done on many guitar amps. Just more accustomed to seeing the connection made between input and wiper vs input and ground as shown. In any event, are you using a silver mica cap there? Again very neat little amp! I always like your neatly parallel-perpendicular wiring and placement of parts. Makes for a tidy interior.

Maynard, Raising filaments can be effective. Also, since chassis space limits a fully wave bridge rectifier and ripple filter circuit, another way to do this (which could be useful if one's filament supply is not center-tapped) is to make a sort of pseudo center-tap by way of connecting each leg of the filament leads to one end of a resistor in the range of 100 ohms or so. I know you know where I'm heading with this! The opposite sides of the two resistors are grounded. If using a separate filament transformer with a center Tap, the classic way to do it would be to just ground the center tap. Very nice little amp!

It's been uncommon in my experience to learn of those who don't consider Jeff Beck to be among the most innovative and talented guitar players of recent decades. Absolutely refined, tasteful...astonishingly insightful and sophisticated musicianship. In my opinion. But there are those who have told me John Bonham was, without doubt, the best drummer of all time. My opinion is not in alignment with that sentiment, but I think he complimented the music of Led Zeppelin well enough. Certainly a case of each to his or her own.

Maynard: I agree on the dual mono pot approach. In fact I had done just that on more than one GG in the past, and in one case, used two linear taper pots for input level adjustment for each channel (for balancing gain in cases of mismatched tubes), both of which in turn were fed to a single audio or log taper stereo volume control for day-to-day volume adjustment. This put a total of four pots through the front panel, which takes careful machining so they all match. Obviously it can be done. Some people really don't like to hassle with two potentiometers, though, so whether or not two mono controls vs a single stereo can be considered an improvement would really depend on the person. That you and I both prefer that approach does not in my view make it something he should necessarily implement. In terms of performance this preamp is absolutely good enough to be used in any primary system. Glad you enjoy Carl, and Maynard did a nice job for you!

Justin: "GD is a well thought of topology." Not sure what you're referring to as GD. Without getting into the specifics of the circuit, "Grounded Grid" (also sometimes more quickly referred to as GG) designs have their origins, as indeed does essentially all vacuum tube audio, in high speed radio applications. The Grounded Grid preamplifier is the designer's (Bruce Rozenblit of Transcendent Sound) second linestage to made available to the public, the first being a dual output impedance (both high and low) preamp using somewhat more common approaches to circuit design. This first one was published in Glass Audio Magazine in the early 90s, and was when I first stumbled upon it and built it at that time from the published schematic. This was before Transcendent Sound made kit offerings. It's also included in his first book, along with those products more specifically associated with him -- the vacuum tube output transformerless amplifier, or OTL. The Grounded Grid preamp, of which I have built several, is both capable of quite wide bandwidth, and as Carl indicated, is extremely quiet. Much of that quality is due to the simple but effective technique of locating the power supply on one side of the chassis (in this case to the right in Carl's picture) and the signal circuitry on the other. Note the lack of shielded cable, which is just not needed. Transcendent Sound has yet another preamp/headphone amp designed for extraordinarily low output impedance and the ability to effectively drive long lengths of IC. It is based on the 300B triode, and is now in the first stages of construction on my workbench. My amazing wife bought it for me as an anniversary present -- with little time these days to work totally from scratch, which I prefer, the pre-punched chassis is a very welcome thing! This design is largely a point-to-point affair. See here -----> http://www.transcendentsound.com/Transcendent/Masterpiece.html Carl: the next time you take off the top panel of the GG, add a small dab of JB Weld epoxy to the sides of those nuts (keeping the epoxy off the threads of the machine screw). It will prevent headaches in the future. I have built many TS products for myself and others (absolutely zero connection with the company other than being someone who appreciates truly clever and innovative designs!) and have never had any of those come loose or fall off.

One of the only amps I have that I did not build or rebuild myself, is among the very best I have used with our Heresies (also very nice with La Scalas, I might add. A truly dual mono integrated single ended 6V6 (and others in the same family of tubes), with a voltage divider on the output that provides a strong line-level signal for use with a sub amp or biamping. My absolute angel of a wife gave it to me for Christmas a couple of years ago! http://www.decware.com/newsite/minitoriise.htm Edit: and yes, admittedly quite over budget. Apologies for that. It's just such an outstanding match for Heresies I had to mention it.