Dan (Drubin), the main reason for the cautions about not operating tube amps without a load is unrelated to magnetization. The concern is mainly the possibility of damage to the insulation of the windings in the transformer, and possibly also to the output tubes, that may result from what is called "inductive kickback," aka "inductive kick." That is the same effect by which the ignition coil used in cars produces the thousands of volts needed to fire the spark plugs. The voltage across an inductor (a coil) at any instant of time equals its inductance times the rate of change of the current flowing through it (i.e., the change of current per unit time). In the absence of a load on the secondary side of a transformer that would absorb the energy applied on the primary side, the primary acts like an inductor rather than as the primary of a transformer, and an abrupt change of current resulting from fluctuating signals can produce very large and potentially damaging voltage transients.
Obviously that will be a concern mainly if a signal is being processed through the unloaded amp. But IMO (which which some others will differ), although damage is presumably unlikely if no signal is present it would still not be good practice to operate an unloaded tube amp having output transformers even if no signal is present, because conceivably turn-on or turn-off transients could in effect put a brief "signal" into them.
As far as magnetization is concerned, as I indicated I haven't previously seen any reports of that being a problem with any audio amplifiers. But it does seem more likely that it would occur with a SET amp than with a push-pull amp, because with a SET amp the DC bias current, and in fact all of the current that is put through the primary of the transformer, is always flowing in one direction. It's magnitude fluctuates with the signal, but not it's direction. So the magnetic field generated by that current is always exerting effects on the magnetizable material in the core of the transformer in one direction, in contrast to a push-pull design where it alternates. That is a significant consideration that has to be taken into account in the design of transformers that are to be used in SETs.
As I said in my previous post, though, I'm not at all certain that operating a SET amp unloaded could cause or contribute to magnetization of the transformer. And in any event I would feel safe in assuming that Rebbi was knowledgeable enough to not do that. But I mentioned it as a possibility that from a technical standpoint seems conceivable to me, analogously to the mention that was made in the Bill Whitlock paper I referenced to how an input transformer used with a microphone that is "phantom powered" with DC could be magnetized if the mic were connected or disconnected while power is present.
Best regards,
-- Al
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Smctigue1,
The bass is good, just not as good as the Tekton. I'm in the middle of comparing the M-Lore against the DeCapo in my room, my ears. Overall the DeCapo is very nice with the Coincident Dynamo 8 watts across the board. I will go into detail at a short future date. I am going to, at some point also compare against my Lore. Going in I knew the bass should/would be better; but I'm interested to find out how they compare in all other parameter, i.e., tone, timbre,harmonics, naturalness, soundstage, etc. |
Smctigue1. I forgot to mention that I believe Rebbi will be in audio Heaven when he gets the AN-Kit back. I believe, as I listen, the Ref 3a and AN will perform superbly together, based on what I hear with the 8 watt Dynamo. The Tekton is also a great match. |
Rob,
I'm also looking forward to your impressions of the De Capo. I, too, am not surprised that the M Lore sounds more authoritative in the bass region. I am very interested to hear what you think of those other areas you mention.
When I mentioned to Eric Alexander of Tekton that I owned De Capo's, his first reaction was, "Excellent speaker." I was positively impressed that he didn't jump on the opportunity to trash someone else's product, something that I've heard other small speaker manufacturers (who shall go unnamed) do. Seems like a classy guy. |
03-24-15: Rebbi
When I mentioned to Eric Alexander of Tekton that I owned De Capo's, his first reaction was, "Excellent speaker." I was positively impressed that he didn't jump on the opportunity to trash someone else's product... Seems like a classy guy.
I had Klipschorns when I first spoke to Eric about purchasing the Katz Meow he had at the time. I told him that if the Katz didn't best the KHorns I would not hesitate to send them back. Eric simply said, "I'm familiar with Klipschorns. What's your address?" I still have the Katz. |
Pete should have the new transformers today or Monday. I'll report back when I know more about the ETA for the amp's return. |
Hi Rebbi,
I have enjoyed following your blog and this thread about the build, and am extremely pleased that they have sorted your problem. I just completed building a pair of the ANK 300B Interstage Monoblocks, and was on the phone with Pete last week about the voltage checks (everything tested perfectly), and he mentioned your issues and how he was determined to get them resolved the next day, and I am pleased that he did. He and Brian have been great through my build.
I am also building the Mentor Line Stage, that I hope to finish this weekend, and the Kit 4 Speakers.
I have thoroughly enjoyed the build process and, while happy that I will soon be listening to the full system, I am a little sad that the project will be over.
I'll have to find something else to keep my soldering iron going.
I look forward to you listening impressions with the properly functioning Kit 1. |
Raylinds, You are building quite a AN Kits system. The new Mentor preamp looks really great. I was hoping it might have a phono pre but I guess not. Your Kit 4 speakers have the Alnico drivers. Congrats! And congrats to Rebbi who will be hearing great music very soon. I've got some Audio Note output transformers coming soon. Were rockin! Jet |
Jet,
You have good transformers currently. Are you getting AN double C core output transformers? Copper or silver wired ? Let us know how they sound. I think you are in store for a real treat.
Charles, |
Charles, Yes the Sophia Electric 91-05 is a beautiful sounding output transformer and my amp is tweeked out WE91a with Black Gates in the tube bypasses and Duelund couplers and I recently optimized the power supply with some help from one of the guys on the Audio Ayslum site so at this time I dont want to upset the apple cart of sonic goodness so the plan is to build a second amp with the AN output trannies. They are double C Core Ultra HiB. These are the version just below silver. Take a look at AN prices for their silver transfomers in pounds and then convert to dollars, you'll gasp in horror. But before I build the second amp I'll uninstall the Sophias and put these bad boys into service on my present amp. These AN transformers have a 2.7k primary impedance which is specifically designed to work with Audio Note speakers. I havent posted anything in my system thread for a while so I'll update it with more info about my 2nd amp.
Grannyring we need to compare notes on our polypropylene capacitors. |
Jet
What output tubes will you be using in this second amplifier? Wow, you are in store for much fun and listening pleasure. I will follow your system page thread for sure. I know what you mean regarding the use of silver transformers, they are said to be the ultimate in sound but are very expensive. I am very curious to see how the Sophia Transformers compare to the Audio Note output transformers
Charles,. |
Charles I'll most likely be using EMLs in the second amp but it really depends on how EML300bXLS sound with Audio Note Transformers. Love the EML's they are so well balanced that I can use AC heat on the filaments with no hum pots. (The elimination of hum pots was a sonic revelation). EML also makes versions of their tubes with a 5th pin that connects directly to the center of the filament creating a "cathode" which should also make the tube completely hum free and making the biasing circuit even more simple than it is now. This means even less parts in the circuit. |
Jet, Raylinds, Charles,
Your knowledge astounds me; it certainly leaves me in the dust. I suppose I'll learn a lot more as my wife builds the AN-Kit 1. I will be with her step-by-step during the build process. I know I really enjoy Alnico speakers as well. Perhaps we should also build the AN Alnico speakers??? |
Rob,
We all learn from each other and the experiences posted here. For example I look forward to reading your impressions of the Tekton Lore and the De Capo with your amplifiers. Most of us posting on this thread are just music lovers who want natural sounding components to increase our listening enjoyment. I'm very eager to read Rebbi's impressions when he gets his properly functioning amplifier back.
Charles, |
"The problem, it turns out, was with the output transformers. Brian and Pete have NEVER seen this issue in all the years they've been shipping and assembling these kits, but somehow or other these transformers had become magnetized and as a result weren't putting out full power."
That's a new one for me for sure. Glad they found the problem. Did they indicate the possible causes? I would want to know so as to know what to avoid in the future. |
Brownsfan,
With respect to your question above regarding the "Walking Bass" in comparing the DeCappo and Tekton M-Lore, here is my view with a little help from Wikipedia to sort out what I am trying to say, with the addition of my own personal take on the matter of the "quality and quantity" of the bass between the two speakers, I Quote (Wikipedia):
A walking bass is a style of bass accompaniment or line, common in baroque music and jazz, which creates a feeling of regular quarter note movement, akin to the regular alternation of feet while walking.Thus walking basslines generally consist of unsyncopated notes of equal value, usually quarter notes (known in jazz as a "four feel"). Walking basslines use a mixture of scale tones, arpeggios, chromatic runs, and passing tones to outline the chord progression of a song or tune, often with a melodic shape that alternately rises and falls in pitch over several bars. To add variety to a walking bassline, bassists periodically interpolate various fills, such as playing scale or arpeggio fragments in swung eighth notes, plucking muted percussive grace notes (either one grace note or a "raked" sequence of two or three grace notes), or holding notes for two, three, or four beats. Some songs lend themselves to another type of variation: the pedal point, in which the bassist holds or repeats a single note (often the tonic or the dominant) under the chord changes.
Walking basslines are usually performed on the double bass or the electric bass, but they can also be performed using the low register of a piano, Hammond organ, tuba or other instruments. They can also be sung. While walking bass lines are most commonly associated with jazz and blues, they are also used in rock, rockabilly, ska, R&B, gospel, latin, country, and many other genres.
A good example in classical would be the Walking Bass in the pedal part of baroque organ music (J.S. Bach's Nun komm, der Heiden Heiland, BWV 659, from the Great Eighteen Chorale Preludes):
In short the walking bass with the DeCappo is vague, lacking clarity, hiding in the shadows, missing in action, softer, as you stated above. With the M-Lore the walking bass is fully there, clear and present. More so with the Lore which reaches down to 30hz. On Jazz albums such as THE GREAT SUMMIT/Complete Sessions with Louis Armstrong and Duke Ellington, Deluxe Edition (Great Recording), Mort Herbert's double bass is so good with body, wood, buzzing, snapping, the M-lore gets it all. The DeCappo doesn't.
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Bass is where less efficient speakers will struggle more off just a few watts in some way. Its never good to work an amp too hard when it comes to detail, bass or otherwise. |
Mikirob you guys will learn alot about how an amp works and as I mentioned to Rebbie you'll learn that you can tweak a part or two in the amp to taylor the sound to your liking. I have no idea how Audio Note speakers sound with Alnico drivers. It is the highest level AN speaker kit.
Mapman, well said. One's amp should be relaxed and as comfortable as possible and the music will sound that way too. Makes me wonder about why there are so many different operating points that manufacturer's run their 300b amps at. Some really hot like 80-90 mA and some around 60mA or less. Arguments on both side make my head spin |
A few examples of jazz bassists who were known for "walking" the bass. Leroy Vinegar,Percy Health,Curtis Counts and Paul Chambers. |
Charles, I see you know Jazz and quality bassists. Did you know many bass players have difficulty with walking bass when they first take up the instrument? |
Charles,
Yes, have them all on various records or cd. I was listening to LeRoy yesterday with Chet Baker, then later with Ben Webster. I like it that he also did the Doors and Van Morrison on some numbers. |
Rob,thanks. The dynamo/decapo pair has much to like, but I think walking bass presents a challenge. When I get everything reunited in my new home I will reevaluate this with the decapos drive by the Frankensteins. |
Raylinds:
Thanks a lot for the kind comments and I'm so glad you have been enjoying the blog and this thread. I've learned a great deal from you guys as well. I can relate to your sense of impending letdown as you come to the End of your build. The process of watching the kit come together and the pleasure of handling the parts and understanding how things fit together is substantial. And wow, what a system you're building! I'm also planning on building another kit.
Mapman,
Brian, his supplier and tranny designer are going to "autopsy" the transformers to try to ascertain what happened. Short of the package having been scanned in a very strong magnetic field during shipping, they don't know what would've caused it. (I reassured Brian that I don't have an MRI machine in the room where I built the kit!) :-) So, all that remains to be seen.
Rob,
I am not surprised that the Tekton on speaker has stronger presence and pitch definition in the bass region. The M Lore is rated down to 38 Hz, a full 4 Hz lower than the De Capo, and the full-size Lore digs all the way down to 30 Hz so that's a full 12 Hz lower.
To give you one example of where the De Capo comes up short at the bottom end, and I've used this example before in my online reviews, the Steely Dan album "2 against Nature," has a wonderful, jazz inflected tune called "Negative Girl." The opening bars feature a dancing, percolating electric bass line that goes very, VERY deep. I've never tried to figure out exactly what the notes are, but I mean, you rarely, if ever, hear that instrument played down that low on recorded music. On my old Merlin TSM-mmi's, those very deep notes were completely missing in action  I mean, they just weren't there at all, which is not surprising because that monitor is only rated down to 55 Hz. On the De Capo, the notes are what I would describe as "just barely" there. If you really concentrate, you can hear them, but the lowest of the low are very faint. I'm imagining this is an area where the Lore would smoke the De Capo! What I am really curious about, and guess I would never really know unless I had the chance to do a head-to-head comparison with my gear in my room, is whether, lower end aside, the rest of the Lore presentation has the resolution, delicacy and coherence of the De Capo. I mean, in a way, I can see where it might, since the design philosophies of the two speakers are really not all that different. You have a wide range driver coupled with a supertweeter, crossed over quite high. And I think that the crossover in both is pretty minimalistic, although the De Capo somewhat more so in that regard. |
Rebbi,
In my view and it goes without saying, YMMV, the Tekton M-Lore does match the resolution, delicacy, and coherence of the De Capo. If you aggregate all the reviews for example, all the reviewers say the same thing: neutral, transparent, huge well-layered soundstage, tone, timbre, harmonics right-on, well-balanced top to bottom, dynamic, no-fatique, and so forth. It really does tick off all the boxes. Maybe not the last nth of resolution, but it is very resolving, as reviewer Tim Smith said, you will here Miles chair creek. I heard it easily. IMHO, on balance, the Tekton M-Lore beats the De Capo. Tim Smith also liked the M-lore better than his Harbeth 7 overall. Both the De Capo and Harbeth are about for times the cost of the M-Lore. The Lore improves the bass even more. On both speakers the bass is very tuneful, solid, and just right to my ears.
I still like the De Capo a lot, they are wonderful speakers. I also like my brother's Harbeth SHL5. The Tekton can hang with either. Again, YMMV. Best. |
Mikirob
I am excited to hear that you and your wife will be building a Kit One. Great little amp, and I'm sure you'll love it. I look forward to reports on the process. |
Charles,
As you know, I was itching to upgrade the 300b's in my Kit One, but there were too many other financial priorities. I would love to have a set of the Takatsuki like you have, but that's out of reach now.
Sometime a week or so ago,another member mentioned that Parts Connexion had Black Treasure 300b z tubes on sale for $279.00 pr. I went for it as that is a good deal, and they are arriving tomorrow.
Obviously there are better ones, but they should be a nice upgrade from the tubes that came with the amp.
I will report when they have broken in a bit.
John |
John,
that is a very good bargain price for that caliber of tube. I got those tubes back in 2009 when they first hit the market and they were 600.00 a pair. They are very good 300b tubes and I used them(happily) for 2 1/2 years before I got the Takatsuki.
Charles, |
Charles,
If you liked them, then I know I will love them.
From a purely aesthetic point of view though, I think the Takatsuki 300b is a thing of beauty. |
Well, I spoke with Pete today. The new output transformers have been installed and the amp is working properly and sounds terrific. He's going to let it burn in for a couple of days and will ship it later this week. Pete's just terrific to deal with. I will check in again when I have the amp back in hand. |
"and sounds terrific"
Just what I expected, congratulations Rebbi.
Charles, |
Rebbi,
Congrats, can't wait to hear your impression. |
Cool! Glad there is finally resolution! |
Charles and Rob,
Thank you! I'll be thrilled to have it back. I've missed playing music! |
Reb,
Great news. I'm happy for you, and anxious to see how you enjoy it when it comes back. Pete is a really great gent isn't he? |
It is great news the issue is finally resolved.
Reb, my only other advice is to make sure to not place the amp near anything that might be generating a strong magnetic field as a precaution.
If teh transformers had become magnetized, one explanation would be that they were in close proximity to a magnetic field of some sort at some point in their life, possible well before you ever met them. |
Got the tracking numbers from Pete! Amp ships tomorrow! Yay. |
Congrats very happy for you. Post right away when you get it back. |
Jwm,
The two packages (I take it one of them contains the tubes) are due in Austin on Monday. Can't wait! |
Everyone,
I am happy to report that the amplifier arrived yesterday, safe and sound. Pete did a superb job packing the unit. It came in two boxes, one for the amp itself and one for the tubes. The amp was lovingly packed and double boxed. Nothing UPS could do was going to do any damage. :-)
I took the bottom cover off the case before putting the amplifier back in my rig because I wanted to see what Pete had done under the hood. I will post pictures on my blog in the coming days, but he did a beautiful job cleaning up some of my less than pretty wiring and resoldering where he thought the joints needed some TLC. Pete is really quite an artisan.
I am delighted to report that my beloved Kit 1 is working great. I wouldn't say that it is an entirely different beast, because that wonderful purity of tone is still there. But it feels like a much more powerful unit. Clearly the amplifier was not putting out full power before because I had to crank the volume knob up to around 11 o'clock or 12 o'clock to get any real volume out of it. Now, I find myself playing the amplifier at around 9 o'clock  quite a difference.
The distortion with music with lots of deep bass in it has vanished! Clearly, the amplifier is not running out of juice anymore.
By the time I get everything hooked up last night I only had about 25 minutes to listen to music, but I will post more impressions here and in the blog.
Very happy camper here!
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Glad to hear its working as it should now. Time to just enjoy now hopefully. |
Rebbi,
Terrific news, I look forward to reading your impressions of this properly functioning amplifier. You are not running out of steam anymore with heavy bass music driving your speakers, that tells me those are high quality output transformers and a very good power supply.
Charles, |
Rebbi,
Congrats, look forward to your impressions. |
Rebbi, if there is a Nobel prize for patience, you are a slam dunk. I am so happy this finally got resolved. We will all be wanting to hear how the burn in goes, and also if you find the amp to be up to driving the deCapos. |
Very happy for you Rebbi! |
Thanks everybody! More to come. Off for some listening now... |
Rebbi, I'm sure you're in for some good times after all of this long process, Enjoy! |
Amp sounds amazing! Orchestral music is especially intoxicating. Soundstage is huge!
Rob: Just for fun, spoke with Eric Alexander today. He recommends the Lore 2.0 in my room with my amp. Thinking about it. As great as my rig now sounds, IÂm curious about what the Kit 1 could do with a really efficient speaker that reached down significantly lower than the De Capo. Hmmmm... |
"Amp sounds amazing"
Rebbi that says it all! Glad that Taking the step into SET worked out so successfully for you.
Charles, |
Tekton will be a better match on paper from a pure performance perspective. That should mean it sounds better as well, but of course that is a more subjective call so you can never know for sure until you try. |
My view is that if one truly cares about getting the best possible sound, you have to use components designed to work best together. Otherwise, things may still sound good, maybe even good enough for all practical purposes, but you will likely be missing the best performance possible until everything is more optimized together.
Anyone looking for a nice well cared for pair of Decapos keep your eyes open...
:^) |
