Pass B1 Preamplifier with Korg Nutube Triode

Thermionics

Post Whore In Training
I missed that also. MarantzFan, it sounds like you have lots of build or diy experience. What Pass amps have you built? It sounds like you build an F5? I ask because I am wondering what Pass/First Watt you have heard/built that you enjoyed the most. Also, what speakers did you run your F5 clone with?

Thanks!
If you want to dip the proverbial toe, the Pass ACA build is not too expensive and is good for an honest 8WPC. I've use them successfully with a whole host of speakers with success (Klipsch Heresy III, Altec 604E, Linaeum LFX, Vandersteen Model 2, holey-basket Corals in a ported box). Some of them obviously play a bit louder than others due to the speaker load and sensitivity, but they certainly did not embarrass themselves. My current office machine (which I haven't seen since February when COVID hit Washington State) uses ACAs and Linaeum LFXs in a near-field arrangement and sound fabulous.

(sorry to barge in on your thread, Anthony)
 
I've built two FirstWatt/Pass class A amplifiers; the F5 and recently the Aleph J. Both are outstanding performers (especially for the meager investment). I used the F5 with Altec Model 19's and right now I have the Aleph J hooked up to my Altec 608-8G speakers. So, my only experience with these has been on very sensitive speakers.

They sound similar to a single ended tube amplifier but to me they lack a little of the "flesh and blood" feeling you get with SET's. Both the F5 and Aleph J are outstanding and unfortunately I didn't own them at the same time to compare.

If you're contemplating a build, I would recommend you do it. With the way these have been put together on the DIY Audio Store and the build threads on that site they are a very easy first time build.


thanks for the notes! I suspected they were great. Nelson speaks straight to the heart of a certain segment of us enthusiasts. I have the M2 and love it. I would like to do a build of one of his older amps. Probably one with a little wider bandwidth or more drive. I don't need more drive, but it would be fun for the a/b experiment an of course to just have two different flavors on hand.

thanks again for your thoughts.
 
OK, circling back on this one. I ordered the DIY Audio Korg B1 kit back in April and after a series of delays received it on Christmas Eve. (This is par for the course on DIY Audio pre-orders and no big deal, at least not to me.) Anyway, after a series of my own delays I finally got the thing put together this weekend. So what I can say at this point is a) it works, and b) I like it. To my ears, with my equipment, it sounds really good. I'd even go so far as to call it a bargain at $300. End of high-quality audio review. Carry on, folks.
 
I built one of these and I freakin love it. I had a shootout between a a Mac MX110, a Slagle elmaformer, a Benchmark DAC1 pre, a diy Pass B1, and a B1 Korg running into my restored Fisher 55a’s. Of the 5, I preferred the B1 Korg followed closely by the Slagle Elmaformer. A bargain at $300 is an understatement IMO.
 

marantzfan

Administrator
Staff member
I built one of these and I freakin love it. I had a shootout between a a Mac MX110, a Slagle elmaformer, a Benchmark DAC1 pre, a diy Pass B1, and a B1 Korg running into my restored Fisher 55a’s. Of the 5, I preferred the B1 Korg followed closely by the Slagle Elmaformer. A bargain at $300 is an understatement IMO.
Interesting parallels. I also have an MX110 and an Slagle elmaformer preamp here to compare it with. Also a Bottlehead BeePre which is my current favorite.
 

marantzfan

Administrator
Staff member
I would be surprised if anything mentioned in the last couple of threads didn't curb stomp a 110 with impunity.

You know, I’ve never listened to it apart from the MC240 to hear it on its own merits. I will say that the Mac’s aren’t the last word in detail and resolution, but man do they look nice on the shelf together. ;)
 

paulbottlehead

Active Member
Yes, they do look nice. I think with the 110, Mac either ran out of space or power transformer capacity to really finish the job. The output impedance is higher than any preamp I've ever seen, and I would expect a 110 and a Mac tube power amp to be no better than -3dB at 20kHz from the interaction of the 110 and the Miller capacitance of the power amp.
 

marantzfan

Administrator
Staff member
It appears as though I never did put a bow on this thread.

I did finish the B1 Korg and listened to it with my Aleph J on the Altec 604-8G system, up until just a few weeks ago actually. I never intended to leave them in rotation for that long I just lacked the desire to swap them out. That's a good thing, especially considering the company around here. Remember that what preceded them was the Bottlehead BeePre and my JE Labs Simple 2A3 amplifier.

It did take a day or two for things to settle in but once they did I can tell you that this combination is really quite satisfying. Not quite the same as the DHT SET goodness and lifelike tone, but a lot closer than one should be able to get for the meager price tag on this set (just over a kilobuck). With those (slight) trade offs mentioned, I will say that the Pass stack really shined on the extreme ends of the frequency spectrum as well as their ability to remain composed with complex musical passages. Ultimately, I still prefer SET amplification, but could easily live with these.

If you didn't hear this the first time, this is crazy good value for just over $1,000 for the pair (parts cost from DIY Audio Store, $300 for the B1 Korg and about $700 for the Aleph J).

I think my next experiment will be to swap this combo in for the McIntosh MX-110 and MC240 which are currently driving the big Onkens.
 
I for one would not touch that "tube" with a ten foot pole. Nor a six foot lithuanian.
Edit: de gustibus non est disputandum
 
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I for one would not touch that "tube" with a ten foot pole. Nor a six foot lithuanian.
I've been touching one here since January, also in a Korg B1 preamp, with not a pole or lithuanian in sight. And my take on this preamp is pretty much dead on with Anthony's. For $300 this is a shockingly good preamp. Throw in a DIY Pass amp and you've got a pairing that's really hard to find much fault with, especially for the money, or at all, really.
 

paulbottlehead

Active Member
The problem with the Nutube is that you need an active device sitting before it to drive it and another active device sitting after it to drive any kind of load. Thus you end up with a FET at the input and a FET at the output just to make it work.

I hope they make a bigger one!
 
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