Thanks B! Appreciate the help and the insight on CCS/cathode in regards to the differential circuit… Really hope the regulator can handle the increased load because the 6N6P sounds really good, just don’t want to leave it in without knowing long term effect… when looking around I did have on a short list the 12bh7, 6cg7/6fq7, 6gu7, etc… to try,… all of which can be bought cheap… comparatively speaking of course, and have suitable load lines…
Best,
Well, I took my preamp out to my lab and set up to check the heater regulator’s input and output voltage for the stock 12AU7 load vs. putting in a pair of tubes that would draw more current and still be pin for pin compatible. The tubes were 12BH7 which draw 600 mA each for a total of 1.2A. The input to the regulator with the stock 12AU7 tubes was about 11-11.5V for 120 V AC line voltage. However with the 12BH7s, it dropped down to about 8-9V and the regulator was just dropping out for 120 V line voltage and the output was showing ripple break through. NOT!! So some of the tubes of interest like 6H30, 5687, and others which would work for loadline considerations just won’t work for heater current limits. What might work is a 6CG7 which is very similar to a 6SN7 and would draw about 900 mA which might just work and would worth a try. Someone had asked about a Western Electric 2C51. That one is OK for heater current but is not for loadline considerations. If I learn more or look into some more tubes, I will update this post.
I appreciate you looking into it! So you think that heater current (~700ma.) for a 6V tube would be ok and not overtax the regulator? The 6n6p I have been referring to are 6V w/700ma heater current (essentially the 6V version of a 12bh7)…
For what it’s worth,… I have had the 6n6p’s in and running without a problem,… and they sound GREAT!,. I just don’t want to continue to do it if I am running the risk of frying the regulator due to insufficient heatsink, etc,… Thanks again!
For what it’s worth,… I have had the 6n6p’s in and running without a problem,… and they sound GREAT!,. I just don’t want to continue to do it if I am running the risk of frying the regulator due to insufficient heatsink, etc,… Thanks again!
You may have overlooked what I said about the 12BH7. Twice the rated 600 mA PER TUBE is 1.2 A of total current and that is what made the regulator start to drop out. The 1.5A heater current of two 6n6p tubes would be even worse than with the 12BH7s with the actual heater voltage being less than the regulated value of 6.3V and then would be AC line voltage dependent
One major thing that is not commonly known about the heater 6/12 V selection in the preamp. The heater supply is 6.3 V ONLY! The jumper, when in the 6 V position connects to pins 5 & 6 of the tube socket with pin 9 of the socket always being heater supply grounded. For a 6 V tube, all is well connection wise as they don’t have a connection to pin 9. Many 12 V tubes have the 6 V heaters in series internally with the mid point going to pin 9. So when the 12 V heater selection is made in the preamp, it ties pins 4 & 5 together and that feeds the 6 V with the two heater parts in parallel for double the 12 V rated heater current.
I failed to think about the regulator being current specific regardless of output voltage, and also was thinking that the jumper in 12V position was actually throwing 12V,… and at 6 would possibly handle the higher current… Do understand now, thanks for the clarification,…
Its was odd to me that it sounded as well as it did though (since the heater V should be dropping out at that current),. so I measured the heater V to see what I was getting,… a solid 6.2V for both tubes, and after being on for a little bit too… seems to be holding steady… I guess that would explain why the 6n6p’s sounded good. For the moment the regulators are handling the load and the tubes heaters are running in spec @6.2v. I imagine that with enough time the excessive and unaccounted for load/heat will work towards premature failure though.
It’s certainly not worth the risk of frying the reg’s due to the higher than allowed current draw so I won’t use the tubes anymore.
Curiously, are the vertically mounted boards directly behind the tubes the heater regulators for each tube?
Thanks again for your help and insight. It is much appreciated!
Although I have two sets of the Upscale Audio BHK Select Tungsram PCC88/7DJ8 in my hands, I have not yet tried them. I am hoping I will not get the oscillation that some have experienced. I am now at about 250 hours on the BHK pre with the original tubes. Because my Bob Carver mono block tube amps use 12AX7 and 12AT7 tubes, I have assembled a wide selection of vintage/NOS European and American tubes of these types, but my 12AU7 collection is thin - one pair of NOS GEs. However, I own a beautiful 1965 Ampex Fine Line tape recorder that I know only has a few hundred hours of use, so I took a look at the tube complement. Nice little treasure trove: Five smooth plate Telefunken 12AX7s (a popular tube, but one I am not fond of), a couple RCA 12AT7s and three RCA “clear-top”, side getter 12AU7s. They all tested like new. I put a pair of the clear-tops into the unit and Immediately I was impressed with the sound. My impression is similar to what I have experienced with RCA 12AX7s and 12AT7s; a really nice balance of the sparkle and high end detail and extension rivaling tube such as the Telefunken smooth plates, or Amprex Bugle Boys, but with a rich, liquid, full mid range similar to Mullards. Has anyone tried any RCA black plates in the BHK Pre?
To all that have the thumping / pulsing sound from the right channel. I had the same issue. I didn’t have the problem when using the stock PSVANE but when I switched to the Tungsram 7DJ8 the pulsing static sound was quite loud. The cause of the sound was the WiFi from my router. As soon as switched the router off the noise stopped. I moved my router was originally about 1.5 feet behind my preamp. I moved it to about 2 feet away from the preamp and it worked.
When I had a REF 1 pre I had the same intermittent noise issues.
The first cause was a pair of antenna leads connected to an A/B switch for my tuner, which was on a shelf directly below the Ref 1.
The second cause was a cell phone ( long ago ancient technology ) that would cause noise if too close to the pre.
Re-routing the antenna leads and keeping the cell phone away solved the noise problems.
The top and bottom covers of the Ref 1 were entirely perforated .
So there was little shielding to block any stray RFI.
I have no doubt that the stray RF causes more noise and interference than we know or are willing to accept.
Having read the good reviews of the Amperex 7316 and also having the right channel noise issues with the Tungsrams, I purchased a pair of 7316’s. My first impressions aren’t that spectacular. The bass has no definition, almost muddy. Top end and midrange detail is maybe on par with the Tungsrams but not better. Soundstage size is smaller. Attack speed/impact - especially drums - is night and day worse. The Tungsrams have a vibrancy that is hard to describe.
My questions to all that have tried these are; Did you notice a change that might rectify these issues after 15 hours or so - I’m at 10+. What bias setting did you use?
I would let them break in for around 100 hours before giving a critical listen. They will change during that time. Bias setting are the same as the stock 12au7s. I assume you also picked them up from a reputable/trusted dealer.
I’ve generally had tubes give me a good idea of what to expect after the first 6-9 hours - improving of course as they go. These just seem to be so far off at this point. May just be the nature of this tube to need more break-in (?)
I am assuming that they are not brand new unused tubes. With that said,they should already be broken in. By chance, are they from the the orange globe era? Do you know the getter style and delta date codes also? They say the earlier date coded ones sound better than the latter[orange globe] ones.
My feelings is that the “super awesome” Tungsrams will give a bit more liveliness but only a smidge more and the stock Psvanes or whatever they’re called are pretty damn good sounding tubes.
Also, when switching to the Tungsrams, the first pair caused a significant pop each time I increased or decreased the volume; the second pair did not.
Finally, when I first took the lid off the preamp, I noticed that one jumper was set to 4ma, the other to 5. I switched it to 4. Apparently Blanche the PS Audio jumper lady must have spent too much time on the Pearl St mall that day.
After multiple issues with various Tungsram tubes in my BHK Preamp and only slightly better success with them in my BHK 250 the BHK 300s amps, I’m sticking with stock Psvane and Gold Lion tubes respectively. In retrospect the Tungsrams had a much higher noise floor which makes me doubt they actually sound better. The various clicking noises they make are not good for speakers or electronics either.
At the end of the day, what is being solving for and what are the odds you will best factory selected audiophile inspired new tubes with 40+ year NOS tubes? Lastly, unless you are comparing each set of replacement NOS tubes to the factory originals, are you certain you bested them?
Funnily enough, I have used the Tunsgram in my Preamp with zero issues. Might just be lucky! I just bought some off Ebay - not cryo ones and they sound great - no noises (except the ones you expect when changing volume). I can see why BHK thought these were the pick of the tubes that he tried when he was prototyping the preamp. They’ve certainly been the best tubes I’ve rolled so far!
I just put in my first pair of Tungsram - ‘BHK Select’ as Upscale is calling them, no noise and super nice goodness coming out of them. They sounded great cold, got a bit harsh between 10-30 hours but have since smoothed nicely at 50 hours. They are nice upgrade from the PSVANES but I still like them too.
Whilst noodling around on this thread, I found this statement from BHK and so with about 200 hours on the Tungsrams, I changed the bias to 5mA and the difference on the top end is significant! Far airier and more open.