So, is third time lucky, or not yet?
Well it’s a tough thing right? The pre is able to accept a pretty wide range of tubes given that the user switches the jumper. If the pre starts measuring poorly and is acting up while there are NOS tubes that could be poorly matched, I don’t know how fair it is to blame the pre. Specially when you put the stock tubes back inside and all is fine.
Hundreds if not thousands of people have installed something like the 7DJ8s in their BHK pre without problems at all. For years. I think this is another scenario of only hearing when people have problems. Why would folks come on here mentioning “yep, just another day with the 7DJ8s inside and it’s sounding great!”
There is not enough evidence that our techs, Darren, nor Bob have been able to gather that says different tubes are causing faults. However, like I stated in the tube rolling thread, I wouldn’t put tubes inside that are pulling double the current of the stock tubes.
These are the types of things we open ourselves up to when rolling tubes. Sadly the nature of it. I’m sure some of the long in the tooth audiophiles will be oh too familiar with this. I’m relieved it’s not a tubed phono pre because rolling tubes in one is a whole other beast!
Well, in all my years of using tube devices, I have never had a poor measuring tube cause a failure in a tube device. If a tube that doesn’t measure right can damage the pre-amp, there is something wrong with the design of the pre-amp.
Where did I say that a poor measuring/un-matched tube is causing harm to the preamp?
Putting an engine in a car twice as powerful as the original without changing anything else up or down stream from it probably isn’t the best idea.
I get it, this analogy isn’t perfect. Doubling the current doesn’t have anything to do with doubling the power of the engine, but you get the idea.
I go that from the people that reported that boards on the pre-amp are failing when using 6922 tubes.
Do 6922 tubes pull double the current of stock tubes?
copied from Brent Jesse:
This is one of two premium versions of the 6DJ8 tube. First of all, it is the same tube as the 6DJ8, and will work wherever a 6DJ8 is needed. It has premium features such as low noise, low microphonics, and usually a longer lifespan. Sylvania made a version that is JAN military spec without gold pins. Amperex made all of theirs with gold plated pins and most have the PQ shield logo, standing for Premium Quality. See note below about Amperex 6922 and Bugle Boy tubes. Some of the later gold pin Amperex have the orange world logo. I have seen both orange and white PQ logos. Some of the early versions also have a number etched into the glass, like the 7308 tubes. These were also made for other manufacturers, and will have that makers name labelled in white, but these are the same gold pin tubes. Amperex opened a factory in New York to make these for the US military (since the government contract specified only USA constructed products) and cranked these and 7308 tubes out. A “made in U.S.A.” Amperex tube is not a fake! In fact, these tubes are really excellent. A few were made in Holland for non-military industrial use, but these are rare. Also rare are the “pinched waist” versions of this tube. This is actually a molding flaw which made the glass bottom slightly fatter around the outside than the rest of the tube, and the center of the tube actually dips inward and touches the metal elements inside. Clients report these are incredible sounding tubes, and the upward spiral of prices for the rare pinch waist types seem to bear this out. Finally, Philips (the parent company of Amperex) owned a number of tube brands, and many were never seen outside of Europe. Most were actually made in the same Heerlen, Holland factory that turned out the Bugleboy 6DJ8 and PQ 6922 Amperex. Watch for tubes labeled E88CC with brands like Valvo, R/T, RTC, Miniwatt, Dario, Philips, and Adzam. These tubes are identical to the Amperex PQ and Philips SQ (Special Quality) types more often found in America, and are perfect if the Amperex is not available. Also rare in America are these same brands made at the Philips-owned Mazda factory (La Radiotechnique) in Suresnes, France. These usually have a capital “F” in the second line of the date code. They are sweet like the Holland tubes, with a bit better detail and punch at the top end, and still have nice balanced warmth. We are one of the very few worldwide tube dealers to offer these rare NOS French Philips tubes.
They can pull up to double but it’s because they’re half the voltage that of the 12AU7 stock. This is fine as it’s within the heater current spec. It’s the 6SN7 you want to avoid because they pull 2x that of the 6922.
Thanks for the clarification on the 6v. tubes Jamesh!
In my case, FedEx damaged three P20s before I suggested PSA to freight it over. Problem solved.
One was so badly damaged – the transformer broke from it’s mounting bolt and was rolling around in the unit.
You have to give PSA kudos for their packaging system even though it can be abused. My latest P20 was delivered by FedEx. When it came the driver rolled it out of the truck like a tire. He asked what it was and I told him it was expensive stereo gear. He said “oh, sign here” and left. I was surprised it was in perfect shape when unboxed even though the box looked like it rolled down a hill. It’s easy to see how this stuff can arrive DOA.
That’s a rather unsettling way to receive new gear…
The drop tests we put the gear through are pretty nuts and I’m glad I don’t have to watch. I wouldn’t be thrilled watching a BHK amp or P20 being dropped from 7 ft.
No. I wasn’t too impressed when he rolled it like a square tire either. You guys have obviously done a lot of research along with trial and error to get the packaging to be as good as it is. Unfortunately you cant fix stupid.
My P20 box had a forklift hole through the bottom. Unscathed inside. Fed ex delivered it a skinny and incredibly strong 160 lb asian guy brought it hand carry in a bear hug no hand truck to my door on a Sunday afternoon.