One question, though not tube related.
When I turn on the Preamp from the back power button, there is a red led that turns on the left side of preamp (closer to the left channel tube) and it never shuts off.
Is that normal ?
Yes, that’s a component that stays on while in standby mode, mine does same.
Ok but did you mean to say that it stays on only in standby mode ? mine is on irrespective of standby - as soon as I turn the back power button on, it turns up.
It should be on anytime the back switch is on.
Can anyone shred some light on how long the BHK pre and the Tungsram 7dj8 takes to break in ? Both my Pre and the Tungsram are new - I had briefly listened to the Pre with the stock tube for couple of hrs and liked it very much but I am finding that I don’t like the Tungsram as much - a bit more on the harsher side. Possibly attributing this to the burn in of the pre/tubes I guess.
I didn’t keep mine long enough to say but they were definitely lean sounding for the short time I had them. My Pre was broken in already so I was hearing the tubes. Just a guess but I suspect they are not as warm as the stocks.
I don’t think it’s fair to make any judgments with so little break-in. My BHK pre changed in obvious ways for the first 50-75 hours with more gradual refinement for much longer, maybe 200 hours. (Note that every piece of PSA gear I’ve owned has needed this kind of break-in: DS DAC, BHK 250, maybe a little less for the DMP.) I would put the stock tubes back in until the pre is well acclimated and you have a handle on its basic sound. Then try the Tungsrams. In my case they didn’t need as much break-in as the pre itself, but I would give them 75-100 hours before making a final decision.
The pre-amp is likely to take longer to burn-in than the tubes. In general I don’t think tubes take long at all to burn-in (maybe a few hours). My pre-amp was a year old before I switched to the Tungsrams. I did not find them harsh at all but one of the nice things about tubes is people can pick the ones they like best.
I realize every brand and type of tube will break in a little differently, I replaced a pair of 6H30s in my preamp, I went with the same tube that had come with the used preamp, th Eletro Harmonix gold pins. I bought the cyroed tubes from Cryoset.
Right in they sounded very good then went through some changes, I think around 50 hours they got a little harsh, then settled in at 100 hours.
Years ago I rolled a lot of 6CG7/6FQ7 and maybe it was the preamp not being as resolving, but they went through very subtle changes.
My point is that until you hit at least a 100 hours, you may not be hearing the true sound of the tubes.
Yes, I agree with everybody. I am not judging the sound of either the preamp or the tube - its too early to do that. I was merely asking what has been the experience with the break-in. very recently I also had a quad of cryo treated Tungsol 6SN7 for another preamp and it took around 100hrs (or even more) to settle down.
palerider saidAfter having matched Tungsram NOS 7DJ8 tubes from several vendors fail (pulsing, microphonic and outright died) I decided to move on to the 12AU7 family. First up is the CIFTE 12AU7. Round bottom with a much fuller mid range and a sparkling high on my system. I listen to a lot of live recorded music - these tubes added some dimensionality that was lacking. Next up - some CV4003 NOS. Tho it might be awhile before I pull the CIFTE tubes...
- I am also wondering why so little love for some of the very fine 12AU7 out there? I realize that in the high end market, 6922 has the reputation of being more desirable, but is it inherently so in this design? I have some nice 1960s Mullard NOS 12AU7 that I am going to have to try.
I have some of the CIFTE 12AU7 on order, along with Brimar, and Mullard. I already have some Mullard here at the house, but most of my 12 series are X or T.
Update: I have now around 150hrs on the preamp and around 120hrs on the Tungsram 7dj8. The harshness has settled down and mostly gone. soundstage is much expansive and becoming smooth everyday. Not sure if it was the tube or the preamp breaking in earlier but whatever it is, I am glad its going in the right direction.
Has anybody tried the Telefunken 12AU7 and has any impression to share ? What are the primary differences between the Tungsram ?
I am reading that the CIFTE has “wonderful 3D sense of space and nice top end sparkle”. Were are folks getting CIFTE 12AU7 from ?
For me, Upscale. Haven’t tried any Telefunken 12AU7.
I’ve tried Telefunken NOS 12AU7’s in my unit. I found my BHK sounded too lean in the midrange for my liking. Not as lean and strident as the stock Psvane’s (which are frankly unacceptable in my opinion), but no joy for the genre of music I listen to most, vocals and jazz. My personal experience leads me to conclude this design simply sounds better with 6 series tube types run at 5 mA bias. See my previous post on using NOS Siemens 7308s. The BHK is exceptional with these tubes. I’ve since tried NOS Siemens 6922s (A-frame getter, 1974 production). Same impression: vibrant knockout beautiful midrange and deep, powerful bass. I’d encourage others to at least consider adding Siemens to your list. Something special, so much so I’m buying Siemens 6922 backups to go with my 7308s.
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After recommending some time ago (months) to Kevin Jackson in Customer Service and Duncan Taylor in Sales that a pictorial or video aide would be helpful for me to see the location and shift direction for the voltage and current “jumpers,” (to enable use of the Tungsram NOS 7DJ8 tubes in the BHK preamp) and recently reminding Duncan, he sent me a video where he (barehanded) pulled out the stock 12AU7 tubes and showed location and moving the voltage jumper “behind” each tube socket. When I again reminded that I had asked for similar regarding the current jumper location and shift, his response was:
"Well apologies for excluding the current jumper adjustment, but really no adjustment is needed there. In retrospect we think we could have been fine excluding the current jumper information from the manual. To date hardly any customers have been interested in tubes where the current adjustment might help.
Really the only adjustment to consider for the great majority of tubes capable of running in the BHK is the voltage jumper which I change in the video.
This includes the Tungsram 7DJ8 you want to use. Just switch the voltage jumpers like I showed you and you will be ready to listen using your new tubes."
This seemed a little uninformed or even possibly negative, so my next response included:
“I have followed the discussion thread in the PS Audio forum on the “BHK preamp tube rolling” and it is the reported consensus there that with this 7DJ8 tube (and actually any of the 6 and 7 volt tubes) the BHK preamplifier sounds better with the bias jumper(s) shifted to the 5 milliamps position(s) from the jumper position(s) for 4 milliamps.”
Duncan’s next e-mail included:
"As much as we try to keep abreast of the discussions in the forums, a large amount of it happens on a daily basis that we miss. That the tubes sound better on the higher current is news to me and the engineers! Well I’ve created a new video for you that shows where the bias jumpers are. They are in front of the tubes instead of behind them as you face the front of the unit.
I didn’t mean to imply that we’re too busy to help! Truly none of us here had heard the Tungsram tubes sound better with slightly higher bias current."
So he made a video of the bias current jumper location (and actually wore the white gloves which were showing in the background of the voltage jumper video), but this hampered moving the bias current jumpers with the tweezers.
At any rate I finally got the information requested and “closed the loop” by sending Duncan and Kevin (and Paul for his ready reference) selected posts from earlier in this thread, particularly the one from Bascom H. King (the BHK preamplifier designer!) explaining that the bias current jumper was essentially in the circuit design to allow optimum use of the 6922 family of tubes.
I removed stock PSVane 12AU7 tubes (wearing the white gloves), took off the gloves and moved the voltage and bias current jumpers for 6/7 volts and 5 milliamps settings, put the white gloves on again and installed the Tungsram NOS 7DJ8 tubes in the BHK preamp and “enjoyed the music” over the rest of the weekend: Seeming soundstage increase in each of 3 dimensions; more “air” around instruments/voices; greater timbral accuracy; fuller midrange, with excellent bass and highs.
The tube dampers and upgrade fuse for BHK preamp should come in later this week…
I will change the BHK Stereo 250 power amp tubes to the 7DJ8s and fuses soon.
Enjoying the music as the preamp tubes gain more hours…
BHK signing in here - I am surprised that the Engineers didn’t know that the 6/7 volt tubes are SUPPOSED to be run at the 5 mA setting and the 12AU7s are supposed to be run at 4 mA. This from the designer who defined these operating currents!
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Thanks Roger and welcome to the forum!
+1. I can understand that the PSA tech guys don’t monitor every forum post. However, listening to the designer is usually a good idea.
Hello.
My new BHK Pre is arriving next week and I have purchased a few pairs NOS Tungsram PCC 88 from PartsConnexion, I think UpScale reserves for their customers.
Are any hints to be offered setting up before listening.
Thank you in advance
Not sure what you mean by hints exactly.
Follow the instructions regarding appropriate voltage and bias settings described earlier in the post for the aftermarket tubes. Let the preamp burn in for a good 200 hours or more before doing any serious evaluation then enjoy!
The preamp stays powered on all the time unless you turn off the switch on the back panel. The logo switch will power down the tubes only for when you aren’t going to listen for a time and want to extend their life potentially. Give the top of the unit plenty of ventilation for heat dissipation.