Click pics to enlarge.
Review: BRZ A20B 6N2-6Π3C SE Amp, Part I
Letter from Shenzhen (23-13): Back to Normal
Letter from Shenzhen (23-13): Back to Normal
Part II detailed Tube Rolling and Summation
Part III is quite substantial and a must, as it covers Tube Rolling of 6S_7 types, Capacitor Mods and Preamp Matching!
Part IV introduces the WE 350B and a new development, Failed Volume Pot!!!!!
Note that basically Parts II and II combined gives an Overview of 6N2/6N1 Tube Rolling!
In my last post I related my recent sonic woes. I'm glad to report that, with time, things have become normal again. For no good reason, I happily resorted back to the Beydas LS3/5As. During this time, just because of the crazy low price, I bought something I never thought I'd and have been enjoying it since it arrived. I seize this chance to cover some of my fundamental beliefs.
Overview: SE Pentode (Tetrode) vs DHT I've had quite a bit of experience very early on, long before I started using the name Cheaptubeaudio on Yahoo Group. In fact, my first SE amp was not DHT - it was the Audion Sterling SE EL34. Its very reasonable price (at that time) and performance started me on the road to SE amps. 300B vs SE Pentode/Tetrode Things happened in rapid succession from that point on. I acquired my first SE DHT amp, the original UK Audio Note Kit 1. The 300B immediately overtook the EL34. Sometime later, I got an Audion Silver Night 300B. It was very good and different enough from the ANUK, but what was glaringly obvious was how much better sounding the same company's similarly built 300B is over the EL34. Yes, there are idiots out there who insist EL34 SE rivals or surpasses 300B, well, well...I went on to have numerous 300B amps , only some of which I have written on (AES SE-1, Softone/ICL, Advance, Sun Audio, Manley Neo-Classic [switchable PSE/PP], Verdier, Wavac etc, through the APPLause I use in Shenzhen now, and know many others well through friends, like Cary 300Bsei and many DIY ones, even the garbage Sophia.). But I did have one of the best SE Pentode/Tetrode amps - the built-like-a-tank old tube rectified Wai Lee 伟利 Amp (HK), whose trannies were said to be wound from WE material and which could use 2x 6J5 instead of one 6SN7). That was a versatile amp that took in every kind of tube, including esoteric ones, like 12E1. Suffice to say, DHT still reigned supreme. Later on, I never really dabbled much in SE pentode amps but did own one in the form of Elekit 8300 (a 300B amp that can also use pentodes, but again I always went back to 300B). More recently, I reviewed the Elekit 8800 (I urge you to read this article as it gives you my take on the various pentodes and tetrodes). Here, let me just say again that I still retain an interest in SE EL84 (as in my Almarro A205A) and SE 6V6 amps , as I think these tubes inherently sound better than the higher powered pentodes/tetrodes). Also, one can also make a compact and good sounding SE amp out of the triode-pentode 6BM8/ECL82 (I have San Ei and Elekit).
Point: take away the few losers or poorly built ones, In SE mode, DHT amps simply sound better than Pentode/Tetrode. Point: a good modern day 300B amp and good modern 300B tubes will sound superior to a good pentode/tetrode amp with even the most expensive NOS tubes. So, the 300B inherently (even in a modern incarnation) sounds good! But 300B is not the end-all.
And so I went on to explore other DHTs to great satisfaction. 2A3 (Sun Audio, Softone/ICL); 10/VT25 (Sun Audio); VT62 (Japanese San Ei) 45 (DIY and Yamamoto A-08S), 6C33 (Japanese Audio Professor, Almarro A318B), 845 (Unison Research Smart 845), 211 (Kondo Ongaku), FU-50 (BRZ). There are others that I'd try (like 205)!
And then, there is the very odd but miraculous DH (Pentode run as Triode) 2J27 (Nobsound/Douk E6 PREamp). Also, let's not forget that triode odd bird (but indirectly heated) 6SN7 (the amazing LTA MicroZOTL)!!!
SE Pentodes/Tetrodes Triode vs Ultralinear In deference to the low efficiency of most modern loudspeakers, many of the designs opt for the higher powered UL operation. A few allows switching between Triode and UL, and it's a very rare bird that uses pentode (like my Elekit 8150). It's a balance game, but I personally am not a UL fan and don't think it really sounds like Triode. But, given real world conditions, UL can work well and to each his own.
BRZ 6N2-6Π3C SE Amp Now, given my preferences, the only reason I bought this amp was because it's ridiculously cheap and I have all the upgrade tubes needed! Why not have another toy! But it turned out more than OK.
Design Solid State Rectification. Driver tube is the Chinese 6N2, and power tube is the Russian 6Π3 (=6H3C/6N3C) operated in UL. A rather simple circuit judging by the circuit board. FYI, this tube is a 6L6 type that likely is not even as robust as an old 6L6GC/5881 etc. I used to hate this tube, but here it was surprisingly OK.
Built Not to the level of the BRZ FU-50 amp (link above), but the looks is still crazy good for this price! Chassis is nice. The main circuit is on a smallish board. Immediately noticeable are the very small resistors, and one cannot help but wonder about their ratings (see pics below). The main coupling caps are blue nominal RIFAs, as is typical of this company. Unlike the FU-50 amp, the signal wire is generic Chinese, not even the very cheap (but good) Canare 2B2AT in the FU50 amp.
Bluetooth A Selector toggles between the Line In and BT. Note that the Input RCAs are soldered onto the BT board. So signal goes through both the switch and the tiny BT board before it goes to the volume pot. Sorry to say (see below) I never tested the BT before I did my mod.
First Impressions Right out of the box, the amp sounded quite decent. I was both surprised and pleased. It has a warmth and musicality that benefitted the music, and in some ways the mid and bass were better than the FU-50 (likely greater watts). The Russian 6Π3 sounds better than I remembered.
MODS As I have no need for BT on the amp, and looking at the signal path, I decided to remove the BT module and upgrade the signal cable with my trusted Canare 2B2AT (this is my go-to mod wire, see here; also see pics below). The stock cable was terminated on both ends with computer plugs. As the stock RCA sockets were soldered onto the BT board, I didn't bother removing them. Instead I installed a pair of my own. The sound improved in clarity.
Caveats There are a few. First, I asked BRZ whether I can roll in higher current tubes, like KT66 and KT88. The answer I got was equivocal, only 6H3C/6N3C or EL34 recommended. So! At your own risk.
Initial Conclusion This is a surprisingly good amp with the stock cheap tubes. I have plenty of old stock 6L6 and EL34 types, which I shall bring back from HK and test out. Also I have bought adaptors for use with the 6N2. The Tube Rolling would be in Part II.
There are 2 thru-holes for the L and R channel signal cables, but the shield is occupied by
the computer type connector, so I soldered the shield to the center pin.
Probably can do without the shield!
After removal of the BT board. The 6V current source are insulated.
The BT module. If you want to keep this module, you can easily solder
your preferred wire to the thru-holes next to the connector. This way
you can retain BT function and still upgrade the wire.
A small red hotspot on the plate of one of the 6H3C tubes. Common. Let's see.
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Able to provide the Power Transformer Specification?
ReplyDeleteUnfortunately not.
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