6C33-B vs everything else.

Hi KT-88,

I had Almarro A318A & A318B integrated SET amps for about 4 months recently. Both use 6SL7 and 6SN7 input and driver tubes to drive the 6C33C-B output tube. The rated output is 18 wpc.

For comparison, I also have an Art Audio PX-25 SET amp(6 wpc), Welborne Labs DRD 300B SET monoblocks (7wpc), and an Audion Sterling ETSE EL-34 SET integrated.

My primary speakers are 95-97dB Cain & Cain I-Ben double-horns with the optional Fostex T-900A supertweeter. The FR is rated 40-36kHz. Along with those I have a pair of passive C&C Bailey subwoofers drivin by a IcePower 500ASP module amplifier. Check the rest of my system listed under my moniker. Secondary speakers were Jean Marie Reynaud Twins mkII monitors (90dB, 8ohm).

Anyway, on to the important stuff. I can't give a definitive description of the 6C33C-B's attributes because I have only heard it in this SET amp and never in any push-pull design.

But, my opinion is that the output tube via Almarro's design is extremely neutral and powerful with a crystal clear view on the musical material. Very balanced across the frequency range without highlighting any particular region.

Oddly, I found the A318B slightly hard sounding(not edgey) on the more efficient Cain & Cains. Not bad, simply more "up front" with a slight glare. The combination was never totally satisfying, although midbass and bass was great.

But, once hooked up to the 90dB Reynaud's, all objections disappeared. The A318B was really able to strut it's stuff. The tonality was rich and full with great dynamics and punch. This was match made in heaven. Midrange and midbass were spectacular. Bass was good (as far as I can tell with monitors). Highs shimmered and decayed without any hint of glare or edge.

As with all SET amps, midrange was where the magic happens. Vocals like Ella Fitzgerald, Nat King Cole, Sinatra, KD Lang, etc. had a full sense of body and tone. It was almost eery at times. Likewise, cellos and double bass had a great sense of wood and resonance. Even better was that the strings of those instruments were rendered with excellent detail and attack.

In comparison to my other amps, the 6C33C seems to lean more towards the neutral/accurate side of the fence than others. This isn't to say that the 300B, PX-25, and EL-34 are "colored" in comparison, just each has specific area where they clearly reveal "more" of a recording than the 6C33C-B:

The DRD 300B is a marvel of transparency and neutrality. It sheds all the typical lushness of other 300B amps(re: Cary) for a purer view. The amps have fantastic bass resolution and highs, but the real magic is their "spatial" rendering. There's a spooky sense of space created in a live recording venue or between peformers/instruments.

By comparison, the A318B w/ Reynauds provided an equal, if not greater, sense of depth at times. But, the soundstage wasn't as wide. The 6C33C obviously had more power and drive than the 300B's which tend to have a slightly softer more mellow approach to music. I prefer the 300B's on the C&C's and it is very close call on the Reynauds, partly because of the power difference.

The Audion EL-34 has a certain "tonal density" that is almost the exact opposit of the A318B. There seems to be more sound from within the recording, sometimes too much to the point of clutter. Part of this, I think, is due to a more diffuse focus than the A318B which tended to have better fine definition. I bounced back and forth between the two preferring one then the other. The A318B provided the more straight-forward, literal, presentation while the Audion leaned heavily towards the more lush.

Now, the PX-25, and this is an unfair comparsion because of it's 3-4x gigher price alone, features this amazing "lit from within quality" to instruments and tones. I've never heard anything like it before. Musical colors are much more vibrant and distinct. Across the board this amp outperforms all the others, as would be expected.

The A318B seems much more "dry" in comparison. Not bleached , just not as vibrant. Still rich, just not as much as the other amps. Although, it does impart a good sense of that SET magic.

I think is part of the reason why the A318B was not as great a combination with the I-Bens as these other amps. The Fostex drivers can be ruthlessly revealing in some situations and the A318B's slightly dry character ended up being accentuated, wereas with the Reynaud's (known for their warmth/richness) the A318B brought the performance a step back in the right direction. Adding greater focus and detail while retaining just the right amount of richness.

Hope this helps and sorry for the longwindedness.

The 6C33C-B performed flawlessly in my A318B over the 4 months or so. Bias was rock steady without any hiccups. I had 3 Sets of tues and none gave me any problems.

The early prototype A318A was another story altogether, though.

Hi KT_88,

You've never stated whether you are interested in a SET or PP amp and the type of speakers you have. Unfortunately, there is such a big difference in power output between the 300B & 6C33C-B (both SET & PP) that under 94dB and a fairly steady impedence your speakers will be a larger determining factor in the resulting sound than the amp. By that, I mean bass performance primarily.

300B's and 90dB speakers was good for most jazz trio, acoustic, chamber, and quartet types of music. Even most low key rock at moderate levels. But, if you still have the Quicksilver V4's and Meadowlarks, I think you'll find stepping down to 300B SET, or even PP, might be underwhelming. 120 wpc driving 89dB speakers gives pretty good control.

celebrer_le_temps,

I actually sold the Almarro a month or so ago along with the Reynaud monitors so I could focus on just one system. To clarify my comments a little more, I don't think the A318B needs anything, it is excellent as it is. It just happened to be a little less than perfect with a very unique speaker - the I-Bens. That's just the way it is with single drivers, sometimes it works, sometimes it doesn't. 95% of other efficient enough speakers are going to sound awesome.

I actually have spent a bit of time listening to Meadowlark Kestrel HotRods being driven by a 300B Cary 300SEI integrated SET amp about 5 years ago. The sound was very warm, smooth, and engaging. A bit soft on the top and bottom ends, but I later realized that had more to do with the Cary than the HR's when I had a 300SEI at my house for a few weeks.

So, I don't doubt that you can get great performance from Meadowlarks and 300B's.

It's not clear whether you are hoping to find a 300B PP amp putting out 20-40 watts per channel or 20-40 watts total(10-20 per channel). 20-40wpc is nearly impossible with a standard 300B being kept within it's most linear range of operation. Most amp designers like to keep the 300B somewhere between 6-8wpc single-ended, 10 wpc is really pushing that tube to it's max cleanly. PP results are simply twice that amount. So, a really good PP amp that is staying in the sweet spot distortion-wise, will most likely yield 12-20 wpc at most. I know Cary and some other manufaturers like to claim 15-20 wpc single-ended, but that kind out output is highly suspect. It's possible, but you probably won't find them quoting distortion specs anywhere near their max.

Manley Laboratories makes the Neo-Classic SE/PP 300B amp that puts out 11wpp SET and 24 wpc PP. Their amps are extremely well made and sound fantastic. Not cheap, though.

The other options are amps running the monster 300B variants like KR Audio's 300BXLS tube. These puppys need a lot more current to run, but will legitimately put out 15-25 wpc SET. Although, if you simply drop these tubes into a standard 300B amp without current modification, you'll only get the normal 8 wpc.

Art Audio and KR Audio, itself, make 15-25 wpc SET's using the 300BXLS tube. They're awesome, but pretty expensive. I don't think I know of anyone making PP amps with them.

Don't write off 845 SET amps, they kick ass and I like them just as much as 300B's. You get 16-25 wpc of meaty, luscious, power with serious low frequency punch.

I think it will easier to find a great 845 SET than it will be to find a great 300B PP amp. Price-wise, neither will be cheap.

Hi KT-88,

I'm nowhere near an expert(or even novice) on power amp output, but 24 wpc 300B PP is really pushing the envelope for the standard type tubes. Although, great companies like Canary and Manly Labs(as I linked to) probably pull it off with flying colors. But, lesser or lower-end manufacturers claims in that range should be held suspect.

Go for one of those used Canarys, I bet they will kick ass with your Meadowlarks. But, don't leave the 845 too far off your radar, it's a monster.