Since my first BHK 300 thread got sort of hijacked, here's mine on evaluating tubes

First, pls understand that I am NOT a golden-eared audiofile…sometimes more of a tin-eared audiofool. I do hear some differences fairly quickly, but usually it takes me days or weeks to begin to be able to characterize differences. Hence, the tone of this note.

Friday, since the '300s have at least 500 hours on them and all seven sets of tubes have at least three to five days on them, I listened to each set, using the same short movement and using cold or at least cool tubes, twice around. My conclusions are that they all sound the same but for two sets which MIGHT sound SLIGHTLY harsher than the others. This ‘difference’ is possibly nonexistent so I’m not saying which tubes they are.

The seven tubes are, left to right, (A) original Genelexes, (1) and (2) both British 6DJ8/ECC88s–Amperex A-frames and Mullard ring-getters, (3) Tungsram PCC88 from Upscale, (4) Matsushita 6DJ8s labeled ‘National’ (note), (5) Vokshod 6H23ps (in the picture, these are in the amp and NOT on the carpet), (6) British Mullard (Mitchum) E 188 CCs (AKA 7308s) labeled RTC from
Meanwhile I’m off to spend an hour or two listening to them again. :thinking:

Note–these are from Vintage Tube Services and are also labeled ‘157 0125 00’, all in bright red ink.


I’m following a parallel path. I replaced the OEM Genelex tubes with the Tungsram PCC88’s from Parts Connexion and I was pleased with the sound. Smooth and detailed. I have a quartet of Amperex A Frame Orange Globes that I bought in anticipation of the amps and I’ll drop them in next week at some point. Let’s hope my old ears can discern some differences?

Well, watchdog, I hope your ears are better than mine :slight_smile:

I chose different music this time, still orchestral, and listened to the same 1-1/4 minutes twice per set of tubes. Initially, I excluded the two tubes I sort-of-thought sounded a tiny bit harsh, but after the second time around with the remaining five sets, I installed one set of ‘suspects’ immediately after the most-expensive set I have (type to be disclosed later) and confirmed that they did, indeed, sound slightly thin and slightly harsh. Then installed a different ‘expensive’ set, listened to confirm they did not sound thin or harsh, and then installed the second set of suspects. This process confirmed that this second set also sounds a little thin. I’ve segregated these two sets and will continue to evaluate the other five sets.

Oh ya…to make it even more ‘fun’, I’ve ordered a set of National Matsushita PCC88/7DJ8s from England, and I’m bidding on a set of Siemens Rohre PCC 88s (West German); these will be my first-ever Siemens tubes.

Is all this supposed to be fun? I’m beginning to wonder. But I also continue working at it and buying more tubes. One of these days…

Here is one reason why I keep rolling tubes. I don’t have to leave one of my wine storage units too far away! This is to the left of my seat.

Hi, I own the 300’s as well. Are you planning to post your thoughts on each tube?

Nice bro :ok_hand:

What, pray tell, is a ‘bro:ok_hand’?

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Yes, now. One of my golden-eared buddies spent over an hour listening to these tubes which survived the 1st cut, and later I was able to confirm his characterizations.

The tubes and comments:
Genelex originals. NOTHING wrong with these; if these were the only tubes I could buy for these amps, I’d still be thrilled with their sounds.

  1. 1960s-era Amperex 6DJ8/ECC88s made in great Britain. Nice tonal balance–VERY slightly warm–but a bit forward sounding. Those who like pop music probably will like this tube.
  2. 1960s-era Mullard 6DJ8/ECC88s made in great Britain. Very nice–slightly warmer than the Amperex and not forward sounding; perhaps a little lacking in detail/resolution.
  3. NOS Tungsram PCC88/7DJ8s. Did not pass my initial listenings–a bit (note 1) thin (note 2) sounding.
  4. National-labeled Matsushita 6DJ8 made in Japan. Warmer balanced than the Genelexes and maybe slightly lower in detail/resolution.
  5. Voskhod 6H23p. Inexpensive but did not pass my initial tests, being a bit thin and harsh sounding.
  6. 1970s-era RTC-labeled E188CC/7308 Mullards made in the Mitchum factory. Expensive, as in $100 - $150 each. 6922 / E88CC / 7308 / 6H23P / 6DJ8 / ECC88 Tube Types
    This my friend called ‘the bomb’. I asked ‘that means it’s the best of the bunch?’ Yes. Slightly more depth and warmth than any others while having great resolution, especially of the space around the orchestra in excellent recordings. My friend wrote ‘deep stage, very rich, sweet’. I’ve ordered another set.

All that said, I have a set of the 7-Volt versions of tube 4 coming from England for BP74…surely less than $150…and I’m bidding on a quad of Siemens/Rohre West-German '70s-era PCC88/7DJ8s. I hope they don’t turn into $500!

Meanwhile, I’m loving the sounds of Elgar’s first symphony tonite played by the Flemish Radio Orchestra conducted by Martyn Brabbins on a gorgeous-sounding Glossa-brand multichannel SACD, thru the RTC/Mullards. I’m VERY happy. :grinning::grin::yum::hugs::star_struck:
Note 1. When I write ‘a bit’ or ‘slightly’, I mean barely audible to me. That characteristic will be more audible to a golden-eared audiofile.
Note 2. ‘Thin’ means lacking in upper-bass/lower-MR energy, say from c. 100Hz thru maybe 400Hz. One of my GEA-buddies calls this the power region of the orchestra, and I think that’s an excellent description. Too much energy in this ‘warmth’ region turns into ‘thickness’ or muddiness, which is NOT good.


I think you would be better off installing a set, listen for a couple of days, then do the same with each type. Cold or slightly cool tubes are not going to reveal the true nature of the tubes. It often takes 20 minutes to over a hour for a tube to reach optimum operating temperature.
Years ago I rolled many tubes through a preamp. Tubes aren’t easily A-B tested.
Just keep some notes, maybe list various things like warmth, detail, resolution, soundstage, etc and rate each pair. That will help when sharing conclusions. Actually one type will just make you forget about the tubes, and have you getting lost in the music. That will be the one. If availability is limited, sell off the others and buy a half dozen sets of “the” tube.


I’ve done that too with all these tubes.

I must have missed that, I just saw where you mentioned rolling a series of tubes through in a very short time.
Ok, never mind.
I think tube rolling is something every audiophile has to experience. I was lucky I just had a pair to try. After a lot of time spent I found 3 types that I liked.
My current preamp uses 6H30s, of which there are only 3 choices, and the NOS are too rich for me to try. Music always sounds better when I listen to it, and not the system.
Your expenditures and time will help a lot of future owners of the BHK 300. Maybe Elk can pin this topic, if the new forum allows that.
I think the Denmark guy was complimenting you.

I definitely agree that much-longer-term listening is key to hearing the differences among these tubes (or most-any system changes), and I did that while the amps and tubes were breaking-in. I didn’t make notes, but I definitely formed impressions.

I continue to be very pleased with the British-Mullard-made, RTC-labeled E188cc/7308s, so much so that I now have TWO more quads on the way, plus the 7-Volt versions of the National-labeled Matsushitas. Also, my bid on the PCC88 Siemens/Rohres is still high (but of course only God knows whether I’ll win those).

One of our local Dealers has Mullard E188CC / 7308 R.T.C. NOS. Yes they are true NOS in factory white boxes with the correct printing. They are expensive at $100 US a tube. I can also get Reflektor 6N23P-EV/6922 (6H23N-EB) for $30 each. Am I going to see a difference of $280 (for a quad) in terms of sound quality? Or is this a silly question from the guy that has 6 pairs of EML and KR 300B’s and too many pairs of Tung Sol Round Plates?

Watchdog, you, of course, know the correct answer to the $280 question–only YOU can make that judgement after carefully listening to both. I THINK my Mullard/RTCs are sounding better day by day, and they had about five days on them when my friend and I started the ‘quick-switch’ session.

In a week or so, I’ll have three quads of the Mullard/RTCs, and I’m still planning to win the Siemens/Rohre (West-German) PCC88s; I read somehere recently (but, of course, can’t find it now) that THEY are ‘da bomb’ 6DJ8s.

If those TSRPs are 6SN7s, pols e-mail me at jeffreybehr(at)cox(dot)net if you’d like to part with a few of those at not-outrageous prices. Where are you?

And there’s NO SUCH THING as having too many Tung-Sol roundplates. :grin:

I only have a pair of the 6SN7’s with round plates. I have three pairs of the 6F8G’s with round plates that I swear by. If you look at the second rack from the bottom. I have 6F8G’s in Woo Teflon and Silver Adapters.


Have you considered the Reflektor tubes? A Head-Fi review gave some a strong recommendation . I may order some from

No; I have too many 6DJ8-types already. I have a quad of Siemens/Rohre PCC88/7DJ8s coming; we’ll see how they sound.

Oh lord help me–I’m incorrigible. After culling the 7 quads of tubes to three–the original Genelexes, the Mullard/RTC E188CC/7308s, and the Matsushita/National 6DJ8s–I now have FOUR MORE sets on the way. They are:

  1. NOS PCC88/7DJ8 versions of the Matsushita/Mullards,
  2. NOS Siemens PCC88/7DJ8s,
  3. NOS Mullard E188CCs, and
  4. A second set of NOS Siemens PCC88/7DJ8s.

Jeez, it’ll take another four weeks* just to get these run-in! Oh well–no one ever said that tube-based hi-end audio was for the rational.

  • We’re now on Arizona Public Service’s 3PM - 8PM-peak-rate program, so I now don’t run my '300s between 3pm and 8pm, so I get only about 140 hours per week of break-in time. A week per set sounds to me like a good target.

We also changed to peak rates from 5pm-9pm but a $1 USD or so is worth it to me to break-in gear. Do the math, see what the percentage cost of power is compared to the equipment purchase price, it’s a small savings. Tripping over dollars to pick up pennies.

I appreciate you posting your findings of all these different tubes. I have the BHK pre with M700s. I’m still on the stock tubes, 150 hours, and will try the ‘BHK Select’ from Kevin soon.

You’re probably right on the peak-period cost, and I’ll restart the 24/7 break-in as soon as I have more new tubes in hand.

And you’re welcome; I hope my observations save someone some money. :slight_smile:

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