300b lovers

Lynn,

I have a burning question that you, Don, or Ralph might be able to answer.  So you start with a new design with caps and resistors and power supplies, etc. and then you put it on the bench to test it out and of course give it a good listen.  Conventional wisdom is that caps etc take a while to run in so do you have to run in the whole design for a a while to get the true sense of it and then tinker with the component parts thereafter.... and then wait for them to run in again before making an evaluation?  I would think this would be an even more difficult process with speaker drivers... which clearly  need to loosen up.   My Spatial Triode Masters sounded awful for the first 50-100 hours but gradually came to life.  At the risk of teeing up a disputatious topic, I often wonder if it is our ears that break in or the audio components.  Breaking in speaker wire just seems silly to me, something I have never honestly experienced. Any insights would be welcome on this tangential issue. which would give us a glimpse into the design process 

Fortunately, Don and I know where the "bad actors" are, and it’s no secret. Caps. Specifically, film caps. They’re the parts that need the 10 to 50 hour run-in. I do not like this ... it suggests the plastic film is undergoing a very slow chemical change while it is being charged, and a further change when the charge is modulated by an audio signal.

But direct-coupling is a whole another can of worms. The worst is that failures in one part of the amplifier cascade through the amplifier, and can even destroy loudspeakers. This is the typical failure mode of solid-state amplifiers ... a DC servo circuit, or voltage regulator, fails, and then destroys everything that is DC-connected to it. Cap-coupling or transformer coupling limits the failure to one part of the amplifier, and limits the scope of the failure to no more than a few parts.

Also, Don and I have prior experience and expectation to guide us when we try XYZ change. Is it audible at all? Is it better or worse, or just different? I don’t know about Don, but I can hear changes in ten seconds or less, and have a better, same, or worse reaction, or sort of a mixed feeling.

The mixed feeling is a danger sign and indicates that there’s something I don’t like but can’t describe or pin down. That’s pretty common at the serious design level, by the way. You often hear or feel things that just make you uneasy, which is a sign to turn it off immediately and take a good, hard look at the circuit and see what you missed. Maybe a wiring error. Look again. Stop, think, reflect, do something else. It happens to us all.

Yes, fresh film caps often sound dull, flat, and dynamically compressed. There are often subtler colorations I describe as "glossy" or softened, a kind of over-processed Photoshop impression. You hear it a few times, and you know it immediately.

But compared to an outright circuit error, that’s nothing. Those sound much worse, grainy, shrill, shouty, almost always something very very wrong, and almost always in the high frequencies. Does it sound "electronic"? Yeah, that’s bad. Find out what’s wrong. Look hard enough and you’ll find it.

@whitestix 

I make a change and live with it for at least a few days or a week before deciding.  Yes, the film caps have to run in.  With this amp project I built a stereo version first because I had a few of the Kootenay amp cherry cases laying about.  So I made it all fit.  There are different topologies to try.  The first was full "silicon assist" where the driver tubes each have a CCS on the plates.  I took this version to Spatial Audio a year ago and we all agreed it was the best amp any of us had heard.  But then I tried LC coupling and it was better to my ear.  So then I had Dave Geren of Cinemag design me a custom interstage transformer for just this circuit.  As Lynn said above, the 300b is a hard tube to drive.  Dave likes a challenge, and his interstage transformer sounds better than either previous version.  The IT version is more "musical" and "relaxed" sounding, yet has an insane level of detail.  Then we decided to go to mono blocks because we could improve the power supply considerably with more space to play with.  So my point is these things evolve over a year or more and I listen to each variation for quite a long time.   The mono 300b amps going to Seattle for the show are the result of a year of listening to different ways to build the circuit.  You have a pair of them and they are pretty special to my ear.  It took a lot of experimentation, guided by theory to get to this point.  That and patience of course....

Guys,

Just love reading about different type topologies that went into this 300b design and it’s quite amazing the time, effort and dedication it took to come into fruition...

I know this is going to be a special 300b as I am a current owner of Don’s Kootenay 120 ...😁

Wig 👍

Gents,

This was an excellent glimpse in to the design process, voicing the sound of the electronics, that has always mystified me.  Since getting Don's first preamp many years ago, he did improve upon the sound of the preamp with a few capacitor upgrades... not rushing right to the very pricey Dueland caps, but sleuthing out caps with similar SQ characteristic at affordable prices to the benefit of his customers' pocketbooks.  V-caps in the DS2 are very nice improvement.  As Lynn mentioned and I am sure Don agrees, there are go-to components for the gear.  I know from visiting with Don how much of a revelation it was to get the Cinemax transformers which is proof positive of his relentless search for excellence.

I always think that Don's prime aim was designing his gear for his own listening pleasure, and after 15 years of knowing him, I trust in his ears and know that others enjoy the fruits of his labors.  That you two collaborated on these 300b amps indicates to me that he is willing to stretch out with his designs, involving Lynn and working with Cinemax to get the properly designed components.   Often one doesn't see the whole picture and two heads are often better than one.

I have had your mono's running since dawn and I am inclined to wonder if my Spatial Audio Triode Masters have somehow been swapped for the excellent MBL speakers that I hear at every audio show... providing a holographic sound image, with amazing inner details and significant heft in the LF... and of course the HF is ethereal. I suppose I exaggerate to my peril, but the presentation of the music is just 3-D remarkable.   The sound is neither warm nor cool tonally, it is just true to the source.