300b lovers

Which returned the Blackbird to the original Karna topology, with far superior power supplies, and the luxury of interstage transformers specifically designed for the Blackbird amplifier.

I give Don full credit for doggedly trying every possible form of coupling, optimizing each circuit with the most favorable operating point, and giving it a serious, I’d even say exhaustive, evaluation. While I sat back with original 20-year-old Karna circuit and criticized from afar. I’m sure I annoyed the hell out of Don more than once.

The selection of an IT for the output section is obvious. The driver, which has to swing a lot of volts at very low distortion, gets to transfer all of its power to the DHT grids. If the DHT grid swings into Class A2 and starts drawing current, no big deal. The power is there, and there are no caps to charge or discharge. Recovery time is instantaneous, unlike RC or LC coupling, and there no risk of DC-coupled failure propagating from driver to output, as there is in solid-state equipment. It really is ideal.

The input tube was another question. In principle, at the lower working voltages, there shouldn’t be much difference between any of the methods, with RC coupling as the obvious and cheapest method. Unfortunately, that’s exactly what it sounds like.

The more serious auditioning over the last year was between current-source + cap coupling, inductor loading + cap coupling (LC), and straight transformer coupling, with no coupling caps or grid resistors involved. And that sounded the best.

Also the simplest. Six parts ... two custom inductors, two good-sized and quite expensive caps, and two grid resistors ... are replaced by one reasonably compact, purpose-designed transformer. The folks who own the "shoebox" format amps, as demonstrated at the show, can be upgraded to the new circuit, which actually opens up space under the chassis. All new amps will have the new circuit, of course.

Charles1dad, thanks for the compliment ... much appreciated. Don and I put a lot of work into these seemingly simple amplifiers.

DHT’s had a rather short reign in audio (much longer in transmitting tubes). It was only from the early Twenties ... the dawn of radio ... to the late Thirties. Once the 6L6 and 6V6 came out (they were designed by the same team), that wiped out the 45, 50, 2A3, 300B, 211, and 845. Even Western Electric abandoned the 300B by 1940 when they designed their new generation of amplifiers around push-pull 6L6’s (WE350). Since the 300B first came out in 1935, it wasn’t in favor all that long.

300B’s have now been in production longer than they were in the Thirties and Forties, rather odd when you think about it. It was the vogue in Japan, Europe, and finally the USA in the Nineties that created the continuing demand for the type and DHT’s in general. It’s been thirty years now, so I think it’s safe to say they are here to stay, along with their pentode cousins.

Class D GaN amplifiers will continue to erode Class AB transistor amplifiers, but I think vacuum-tube amps have an enduring appeal that continues to grow. They now dominate high-end audio, which was not true thirty years ago. I remember going to some CES shows with hardly any tube amps at all, never mind DHT’s, and now they are everywhere.

Now you see quality record players, and tube amps, in movies as a marker of good taste. The movie viewer gets a little buzz when the tonearm descends into the groove, making that distinctive vinyl "click" sound, then you see a tube amp quietly glowing in the background, and wonderful music comes out. The camera pulls back, and you see the protagonist, looking contemplative, and out-of-focus city lights in the background. That alone sets a mood.

I’m really pleased about this. In an era of superb all-digital, all-solid-state 4K HDR video, tube amps continue to make new friends because they sound so good, on all types of music.

@lynn_olson

I’m really pleased about this. In an era of superb all-digital, all-solid-state 4K HDR video, tube amps continue to make new friends because they sound so good, on all types of music.

Agreed!!!

I believe that class D GaN amplifiers will definitely continue to grow market share and popularity. This seems undeniable. Yet I also believe that there will remain a certain number of music listeners who find that nothing satisfies their musical/listening desires as well as high quality tube products. The two will peacefully coexist.

Both can be excellent while simultaneously being distinctly different. I do not share the gloomy “demise of tubes “ forecast . Time will certainly tell.

Charles

First, loving the conversations here - delving into the correlated technical stuff. Everyone should have a Tektronix RTA for this hobby, lol. But the last time I used one they were over $50k. That's more than a good pair of interconnects🙄.

It's also intriguing reading that these amps will run Monolith output iron. Kind of curious which series they are based on, but maybe that's asking too much.

Tubes

Over the years I've used quite a few different tubes from NOS to current production - Shuguang, Psvane, JJ, Sophia, Linlai, KR (Kron), EML, Takatsuki, WE. Some brands aren't worth mentioning. In the past I preferred KR in amplifiers as they are wideband, dynamic, and have solid bass. But depending on the system, can come across as a little unrefined/aggressive. I liked them in what I had. (PX4, PX25, 242, and 5u4g)

But with 300b in what I've owned:

Art Audio - They make heat and conduct electricity. About the nicest thing I can say about them

Shuguang 98b - Meh. Pretty darn average across the board. Puts me to sleep.

Shuguang BT - Pretty good in a VAC Renaissance P/P amp. But other places are bright, lacking midbass weight, and little bass

Linlai 300b E - A good step up, decent bloom and detail, a little light in the midbass and down low

EML 300b XLS - Pretty good. Not as nuanced as the best. Depth and width OK, but not the best. Good low end drive. Much better than everything listed above.

Takatsuki - Excellent tube. Best bass drive. Good Detail. Depth and inner resolution good, but not the best.

WE 300b new production (2022) - Excellent detail, inner resolution, nuance. Holographic. Quiet. Appropriate bass weight and definition. Not as punchy as the Tak or the EML. That will depend on your system. 5 year warranty and projected long life. Love this tube in my SET amp. Well worth the money.

So I find a huge performance delta in the list. Spending the money will be rewarded, probably more in SET than P/P, but that's speculative.

Oh, regarding comments about DAC's made earlier, I concur with Don who has a Lampi Pacific 2 with DHT output, my Lampi Horizon dac is the most significant piece in my system. But there are no unimportant pieces.

Very curious to hear user comments once the production Blackbird and Raven hit the wild.

@tuckia08 

EML 300b XLS - Pretty good. Not as nuanced as the best. Depth and width OK, but not the best. Good low end drive. Much better than everything listed above.

Takatsuki - Excellent tube. Best bass drive. Good Detail. Depth and inner resolution good, but not the best

In my experience I’ve found that the preference for a particular upper echelon 300b is very dependent upon the specific amplifier in use. Some of these top quality tubes are simply better fits in certain amplifier/systems than our others. It’s very difficult to draw an all encompassing generalization.

Charles