[bmichels]

I did several time the tube biasing and found something strange.
 
I understand there are 2 steps (mesurements) in the process.  
 
- As described in the video, the first with the 2 metter's probs inserted in the headphone plug.

 
 
- The second step with the Plus prob in the headphone plug and the negative prob on the Ground of the BHSE's chassis.

 
 
 
1 ) how are called those 2 different mesurement ? is one the "bias adjustment" and the other the "DC offset balance" ? Which is which ? 
 
2 ) I found the first mesurement to be quite stable but the second mesurement quite UN-stable :  After I have set everything as close to 0 volt as possible, if I do another mesurement few hours/days later (always after 2 hours heat-up), the first mesurement remain very close to the 0 that I mesured the previous time while the second mesurement can again be between 10 and 20 volts and need re-adjustment again to go back to zero volts.    is it normal ? 
 
thanks in advance for your explanations
 
 
PS : now that my new Philips Metal base tube have passed 50 hours, I have a friend coming tomorrow to listen to my BHSE with the new metal base tubes, so please wait one more day before I can publish the listening results between the stock and the metal base tubes.

 

[NoPants]

these measurements drift with temperature, it's perfectly normal. 10-20v poses no danger to the headphones

 

[arnaud]

You'll get 30+V drift from cold start to fully warmed for the stator to ground so it makes no sense to adjust it until a couple of hours. Once adjusted, i haven't found the need to touch it, even switching nos tubes, they give similar results give and take a few volt.

Now bmichel, are those metal base making a difference?

Arnaud

 

[joseph69]

You'll get 30+V drift from cold start to fully warmed for the stator to ground so it makes no sense to adjust it until a couple of hours. Once adjusted, i haven't found the need to touch it, even switching nos tubes, they give similar results give and take a few volt.

Now bmichel, are those metal base making a difference?

Arnaud

I also found that after setting my initial adjustments to 0 and then checking 1hr later that the drift is in the high 20's very close to 30v as well.

 

[mulveling]

The BHSE takes a LONG time to fully warm up (like more than an hour), and once it does so it's extremely consistent & stable. A +/-30V offset is not ideal but it's not catastrophic either. And +/-10V offest shouldn't be any issue. I believe it's more important to get the balance adjustment to like a volt or less. You want to adjust when it's fully warmed up.
 
If I do the measurements 1.5+ hours after power on, I find that my THREE different quads of vintage British/Holland tubes -- 2 used, 1 NOS, and from different sources -- all end up being under 0.5V balance and a few volts offset with NO adjustments necessary. Maybe I got lucky, but then I think that this stuff was really well built and works very well if used with some sense.
 
Long live the BHSE!

 

[joseph69]

I was only adjusting after 1hr because I was following the instructions on the YouTube video Justin made.

 

[joseph69]

I was very curious as to what my bias/balance adjustment were being I adjusted them after only 1hr. I've had the amp on for the past 3hrs with my NOS Amperex "Bugle Boy: EL34's and I was surprised to see that the DC off set for both the L/R channels were at 0 and the balance adjustment for the L/channel was at 0 and the R/channel was -004 so I adjusted it to back to 0. Cant believe it stayed so damn consistent!

 

[TheAttorney]

Quote:

  1 ) how are called those 2 different measurement ? is one the "bias adjustment" and the other the "DC offset balance" ? Which is which ? 
 
2 ) I found the first measurement to be quite stable but the second measurement quite UN-stable :  After I have set everything as close to 0 volt as possible, if I do another measurement few hours/days later (always after 2 hours heat-up), the first measurement remain very close to the 0 that I measured the previous time while the second measurement can again be between 10 and 20 volts and need re-adjustment again to go back to zero volts.    is it normal ?

People here have used the term "bias" rather loosely to mean the balance and offset adjustments. But strictly speaking the bias is an internal adjustment set by Justin and which you can forget about unless (a) you really, really know what you are doing (i.e. a tube amp designer), or (b) you are recklessly stupid.
 
Of the external user adjustments, I don't think which is which has been formally stated, but I assume "balance" refers to the difference between + and -, and "offset" refers to + and ground. Both of these have the same "exponential curve" characteristic whereby they start off with a big difference at cold, initially quickly slide towards zero, the rate of progress reducing as zero approaches. Most of the slide has happened by 1 hour, but it continues sliding right up to 3 or 4 hours. As the Offset difference is an order or magnitude higher than Balance, its best to focus on that when measuring (the latter just needs an occasional check, but largely takes care of itself). The Offset adjustment is also more prone to a kind of hysteresis effect, i.e. nothing seems to happen as you turn the pot, then it suddenly overshoots. Even if you get it to zero now, it will probably drift a couple of volts tomorrow. This is all normal, but can keep OCD types amused for hours, or you can just not worry about a couple of volts..
 
The same applies to existing or new tubes. So there is no value in messing up Justin's original settings if you're putting in new tubes and adjusting after say 1 hour. All you need to do is use a voltmeter to check that the new tubes are following the same exponential curve. If at any time they are heading in the right direction, thenleave them alone. Wait until the rate of change becomes insignificant, by which time you will find that the new tubes are magically close to the old ones. so no adjustment is needed. If the new tubes do not broadly follow the same curve, then there may, or may not, be a problem that needs further investigation.

 

[georgep]

  The BHSE takes a LONG time to fully warm up (like more than an hour), and once it does so it's extremely consistent & stable. A +/-30V offset is not ideal but it's not catastrophic either. And +/-10V offest shouldn't be any issue. I believe it's more important to get the balance adjustment to like a volt or less. You want to adjust when it's fully warmed up.
 
If I do the measurements 1.5+ hours after power on, I find that my THREE different quads of vintage British/Holland tubes -- 2 used, 1 NOS, and from different sources -- all end up being under 0.5V balance and a few volts offset with NO adjustments necessary. Maybe I got lucky, but then I think that this stuff was really well built and works very well if used with some sense.
 
Long live the BHSE!

 
I suspect that in most cases people shouldn't be doing any adjustments, and that the only time you might have out of whack measurements is when using out of whack tubes (usually new production or non true el34 tubes), which probably should mean you should look to other tubes. People shouldn't assume they need to make adjustments because they are changing the tubes. Instead, if they are inclined, or are not using tested used/new old stock tubes, then they may want to check only after a period of warm-up (at least one hour), instead of at the outset then finding that the measurements are all out of whack after it is warmed up.

 

[justin w.]

i test the amps at around 72F in winter and 74F in summer. unless your room temp -- with the amp running -- is greatly different, most of the time there is no need to make an adjustment, even when swapping tubes. If swapping tubes requires a very large adjustment then they are either not EL34 or may not be in spec which is possible with very old NOS

 

[bmichels]

Just purchased this tester to mesure/test my EL34.  I will let you know how it works when it arrives...
 

 
In the mean time, I shall report on yesterday testing of the Philips metal Base against the stock tubes.  In fact it was not so easy to compare tubes because the delay to swap the tubes and let the new tubes heat-up is too long to remember well the sound of the previous tubes.  So we have a meeting planed with another headFier who also has a BHSE : With 2 BHSE it will be much easier to compare A/B the tubes.
 
However, to make it short, the initial impression was that the main difference was that the bass where coming deeper and more textured with the Philips Metal base.  
 
I am sorry but we will need to wait for the A/B with the 2 BHSE to provide better listening impressions between the tubes.
 
In the mean time, I will try to forget about all those technical aspects and just enjoy my Music through the BHSE/SR009.   I must fight to avoid listening to my gears instead of listening to my music.  

 

 

[wrathofkhan]

Hi All,,, found this forum today.
 
Briefly, for many weeks now I have been trying to decide on what is the very best amp for the Stax 009. I finally settled in the BHSE.
 
Now I live in Australia, Perth actually and trying to find a dealer locally to listen is impossible so I have had to buy from the eastern states of Australia and take a chance. 
I was lucky it seems because to order now from USA there is a 3 month wait list but I have found a dealer that has an unopened BHSE with the alps AK 50 volume control and it is on its way to me and I should get it during this week. I must be very lucky to have found this still available.
 
It is serial # 222 so can I find out when that was built?.
 
I was reading through some of the OPs about voltage at 110v in this forum and I wonder, did justin make 220 -240v versions because I am buying it in Australia and we are that voltage,,,, I assume the dealer whom I cannot contact till Monday will confirm this as it would be not right to sell but just want to check now.
 
What is the best way of "Running In" my BHSE to get the best from it.
 
Many Thanks For all your help

 

[nepherte]

It is serial # 222 so can I find out when that was built?.

 
I own BHSE #233, which was shipped to me by Justin mid October. You definitely have a very recent one from the latest batch.
 

I was reading through some of the OPs about voltage at 110v in this forum and I wonder, did justin make 220 -240v versions because I am buying it in Australia and we are that voltage,,,, I assume the dealer whom I cannot contact till Monday will confirm this as it would be not right to sell but just want to check now.

 
The power supply of the BHSE is typically configured by Justin for the country it ships to (unless explicitly requested otherwise). If it was originally shipped by HeadAmp to Australia, it would be configured for the voltage used in Australia. So yes, there are multiple configurations out there, ranging from 100V up till 240V.

 

[joseph69]

  It is serial # 222 so can I find out when that was built?.
What is the best way of "Running In" my BHSE to get the best from it.

Congratulations…nice find!
My BHSE is serial #246 and is from batch #4 which is the last batch and I received mine early November. 
Justin burns them in before shipping, so just use it and enjoy! It is the best sounding amp out of the 3 I've heard with the 009…no complaints at all!

 

[icebear]

....  
In the mean time, I shall report on yesterday testing of the Philips metal Base against the stock tubes.  In fact it was not so easy to compare tubes because the delay to swap the tubes and let the new tubes heat-up [1] is too long to remember well the sound of the previous tubes.  ...
 
In the mean time, I will try to forget about all those technical aspects and just enjoy my Music through the BHSE/SR009.   I must fight to avoid listening to my gears instead of listening to my music[2].  

 

 
[1] How about you keep your kitchen oven cosy to have the tubes pre-warmed and they are at best operating temperature when you swap them in?

Just watch out that they don't overcook

 
[2] How much new music have you bought since you've got the BHSE and how many more tubes and acessories have you bought? I guess you've still a long way to go in this "fight" but at least you are aware of the issue, so there is hope...