BHK Signature 250 or 300 Tube Rolling

I tested a lot of tubes in my BHK Pre and 300 Monos. From my experience it is better to use 12au7 tubes in Pre as they are definietly lower noise than any E88CC family tubes.
The best results so far I got using 1954 Mullards CV491 Long plates D getter in my Preamp and Siemens & Halske E288CC tubes in my 300 Mono.
E288CC tubes are very underrated. They offer everything that CCa can give you for much lower price.
12au7 Philips Miniwatt 63 or 67 are also nice option for Pre and not so expensive like mentioned Mullards.

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The E288CCs are excellent tubes. Definitely not the magic or the Ccas, but close. The Siemens 7308s and Mazda 7308s are also great in the 300s (and Pre also).

I just ordered Matsu 7308/E188CC pinched waist for my BHK300.

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Hearing a bit of distortion in various music and with 6 years on the clock I want to roll the factory supplied tubes out of my 300s.

I had been planned to get some Matsushita 7DJ8 for the BHK300 but it seems those are not to be found these days. I’d love to find something comparable

What I’m finding is that there aren’t many NOS tubes available anymore without spending silly amounts of money. Most of what I find in the forum are either no longer available or have me priced out

Sound wise I’m looking toward enhancing vocals, soundstage, instrument wise my ear is more drawn to acoustic guitar and piano. My system handles bass well so not hunting stronger bass through tubes

One option is to just go with new Genalex 6922

For NOS I’m only finding these that might be options while remaining in a reasonable budget

60’s Amperex Holland made 6DJ8

60’s 6DJ8 Amperex “A” frame getter - “white Label”

70’s (early) 7DJ8 O-shape getter Valvo- Holland

70’s 6DJ8 Amperex Orange World

60’s 6DJ8 Siemens made in Germany “White Box” - Munich factory

Other tubes that show up avalible

Electro-Harmonix 6922

Tesla E88CC Mid 70’s NOS - Military Grade or Gray Support

GE 8771 industrial type 6DJ8 grey glass type

GE 6DJ8, 1960s vintage RF shielded

Any experiences with these or know of something else currently available that would be a step up from the Genalex?

Welcome!

Andy at VTS has Matsushita 6DJ8’s for $48 a piece. After years of owning far to many pieces of gear that used 6DJ8/7DJ8 tubes I have built up quite a stash of them including many that have never been used. If your interested I may can help you out as all of my current gear uses 6SN7 tubes and doubt I will own another piece that doesn’t. I have I know Matsushita 6DJ8’s but don’t know about the 7DJ8’s anymore. Let me know what price range you are looking in if you’d like.

I don’t think you can go wrong with current Genelec tubes in the 300’s. But, I am partial to 60’s Amperex (Holland) tubes in these amps. You can also give the Matsushita tubes a try, seems like a good deal and Andy at VTS is a reliable and affordable source.

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I dug through tubes I had for my pre and discovered a pair of Matsushita 7DJ8s . I suspected the right channel was my issue and tried swapping those. Sounds sooooo much better. But now I have Gold Lions for the left and Matsushita for the right. Not the best solution but did confirm my issue was failing tubes. Not sure how to connect with you directly to discuss the tubes you don’t need anymore.

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There’s some great tubes for sale here on the site.

https://forum.psaudio.com/t/misc-tubes-for-sale/36446?u=vkennedy61

Can someone shed some light on what measurements to look for when shopping for used tubes?

Came across these Amprex tubes with these measurements. Is GM the only number to look for, or are there other parameters that are meaningful to consider? Also what does GM pertain to?

Thanks

Tube1- 94/95% GM Tube 2- 95/96% GM

Did some research on what measurements to look for when purchasing used tubes and came across this:

"Vacuum tubes are an essential part of our tube amplifiers that bring hours of listening pleasure. I have a few ask me to look at a tube on ebay for a recommendation of purchase.

New old stock (NOS) tubes are a no brainer. NOS tubes usually meet specifications. And, NOS tubes lasts a long time. Preamp tubes may last as long as 50,000 hours providing good performance. Power tubes may last over 12,000 hours.

However, some new old stock tubes are thinning out. The vintage Mullard 12AX7 long plate is a good example of mostly depleted new stocks. Used tubes may be the only option. Paying even 30% or more of a NOS tube for used tubes is a gamble. And, many sellers want over 50% of a NOS tube. Be careful for ads stating ‘tests as NOS’. That test as on a B&K 667 that tests at 100 and drops to 60 at reduced filament voltage is far from ‘tests as NOS’. And, do not let a like new old stock tube box in pictures shown by some sellers enhance the value and some do not even mention it is a new or used tube anywhere.

Over time used tubes do not drop emissions on a linear curve. The tubes drop on a curve that looks more like going over a cliff. Thus, a used tube at 50% of new cost may have only 10 percent life left. Not a bargain in the least.

Many tube testers used for testing tubes listed on ebay do not test for transconductance. And, even so, the transconductance tube tester does not measure remaining tube life. Simple emissions testers mostly used for tubes listed on ebay are even worst at predicting remaining tube life.

Some tubes will give a better indication of health by testing at reduced filament voltage. However, some NOS tubes drop off emissions a lot with lower filament voltage and most others drop off little if any. Unfortunately many sellers carefully avoid this reduced filament test as it may deter sales if the truth is known.

If you can talk the used tube seller into performing this reduced filament test, most healthy used pentode and tetrode power tubes drop little from the standard 6.3 volts to 5 volts filament. Most NOS tubes drop zero.

Lets consider an emissions tube tester that tests new power tubes at 100-105 on the meter such as a B&K 667. A healthy used power tube on this emissions tester with a reading of 100 should not drop more than 5 points. If the tube drops 10-15 points, consider the tube possibly to have as little as 20% life left. A power tube that drops from say 80-85 to under 55 reading on the B&K 667 tester is likely to have only 10% life left. And, a lot of these 10% tubes are selling for 50% of NOS on ebay. On this tube tester, 12AX7s test about the same as power tubes. Many tubes test like this on reduced filament. However, some very healthy 6922 tubes may drop to a bad indication on the same tester. Plus the triode open filament type power tubes act the same as the 6922.

The transconductance tube tester is a better indication of tube condition. The 12AX7 is designed for 1600gm and unused usually test over 1600gm. Some brands test at 2000gm. I would still have interest in a used 12AX7 testing at 1600gm if NOS was not available. I would not purchase a 12AX7 reading at 1400gm.

So, I am surprised how many used 12AX7s for sale on ebay are listed at 900-1200gm, yet are asking 50% or more of NOS tubes. These tubes are worn out and worth zero IMO. And, in most circuits these worn out tubes would sound dull compared to NOS. Especially so in some phono sections.

The above info is only a rough guide I kept track of over the years, but better than no guide at all."

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