[zardon]

  Just curious, did you have to reset the bias voltage back to 0 when you put the XF1's in?

You should always BIAS tube amps when putting in new tubes. I BIAS them every couple of months regardless as they will change (first time I would bias them 5 minutes after start up, then 1 hour in as the amp settles). But its critical when putting in new tubes. With the BHSE, its only a 2 minute job. If you need help Justin has a video on youtube, you only need a cheap AC DC Voltmeter set to 1000V from somewhere like Amazon (£20 or so) and the pin layout is pretty straightforward but you probably already know this.
 
I was quite surprised Justin didn't supply the standard tubes with LF (left front) RF (right front)  LB (left back) RB (right back) markings etc, as even bog standard matched quad EL34s from Russia have a little variance. Then again if they are slightly out its not a massive issue - I just have a bit of an OCD with BIASing as it can really wear down the tubes faster if they are configured badly.

 

[Crashem]

Just curious, did you have to reset the bias voltage back to 0 when you put the XF1's in?

Yeah. I rebiased when I put in new tubes.

 

[zardon]

Just wanted to share with you guys my list of "have to" try EL34's based on my research and various recommendations from all sorts of sites.  They range from semi reasonable to really expensive.  I do know sources for a lot of them but they tend to be expensive (if you dont mind expense, PM me and I'll recommend some tube dealers).

Here is site with good info on european EL34:
http://www.tube-classics.de/TC/Tubes/SieTel%20EL34/EL34.htm

Current List of Aspirational EL34 (with notes):
1) Dutch EL34 Metal: Can be marked Philips/Amperex or others.
2) Dutch EL34: Usually marked XF3/4/5.  Make sure not to mix up with British made XF3/4.
3) Mullard EL34 Metal: Unclear if there is actually such a tube that was made in Britian or are they all just relabelled Dutch EL34 tubes
4) Mullard EL34 XF1: Need to see if different sound than XF2
5) Mullard EL34 XF2: OO getter preferred.  Single O may sound the same
6) Mullard EL34 XF3: Single O.  Same say no difference between XF2 and XF3 single getter
7) Telefunken EL34 Metal: Very rare.  Most say not as good as Dutch EL34
8) Telefunken EL34 OO Getter: A lot of germans like it
9) Telsa EL34: Complicated here.  You want the ones from late 60's and early/mid 70's.  Two factories you want 33 or 37.  The newer ones are fine, but not the ones people say they love.  Some say 33 is the only ones to get.  Some say only 33 and OO getter.  In any case, get the date range right
10) Sylvania EL34 "Fat Boy": Branded under different manufacturers.  Supposedly this guy puts out a ton of BASS
11) Matshu****a Japanese EL34: Looking for cheaper mullard?  These guys bought Mullard factory and equipment and made them in japan. 

Sylvania 6CA7 fat boys triple getter are an interesting tube to try in an el34 amp, i was never a huge fan of the 6ca7 but those are one of my few exceptions. havent tried them in the bhse but they produce a little more bass/sub bass than the el34's in other amps i have. Its also a slightly different overall sound signature.

That said, the specific design of the bhse means that tube rolling often doesnt change the sound dramatically like other amps.

 

[joseph69]

  You should always BIAS tube amps when putting in new tubes. I BIAS them every couple of months regardless as they will change (first time I would bias them 5 minutes after start up, then 1 hour in as the amp settles). But its critical when putting in new tubes. With the BHSE, its only a 2 minute job. If you need help Justin has a video on youtube, you only need a cheap AC DC Voltmeter set to 1000V from somewhere like Amazon (£20 or so) and the pin layout is pretty straightforward but you probably already know this.
 
I was quite surprised Justin didn't supply the standard tubes with LF (left front) RF (right front)  LB (left back) RB (right back) markings etc, as even bog standard matched quad EL34s from Russia have a little variance. Then again if they are slightly out its not a massive issue - I just have a bit of an OCD with BIASing as it can really wear down the tubes faster if they are configured badly.

Thanks, I have a DMM and it is a simple procedure to bias the tube voltage.
I will be in the same boat as you it comes to biasing my tubes as well! 
 

Yeah. I rebiased when I put in new tubes.

Thanks.

 

[Crashem]

Question about Biasing:
 
Can you bias while a headphone is plugged in using the other port?  Or should you have no headphone attached?

 

[Golfnutz]

  Question about Biasing:
 
Can you bias while a headphone is plugged in using the other port?  Or should you have no headphone attached?

http://www.head-fi.org/t/439657/headamp-blue-hawaii-special-edition/4860#post_10411774

 

[TheAttorney]

  ...I would bias them 5 minutes after start up, then 1 hour in as the amp settles). But its critical when putting in new tubes.

I don't think this is good advice, and here's why:
 
At start-up, the + to earth voltage difference (front trims) is at its maximum, typically somewhere between -40v and -50v. It will then quickly start heading towards its end point, the rate of change reducing as time goes by. By 1 hour, the reading may typically be in the range -5v to -10v, but it will keep reducing  ever more slowly up to around 3 or 4 hours to it's ideal end point of 0v.
 
Therefore, it is counterproductive to change anything after 5 minutes - all you do is completely mess up the settings Justin originally made. Better to LEAVE IT ALONE and just periodically check the reading is heading in the right direction.
 
I've swapped in a variety of old and new tubes and in every case it has not been critical to change bias settings (more strictly these are balance/offset settings). i.e. every single one of them have been within a small number of volts of each other (admittedly they were all quad matched). But I would say that it is highly recommended to at least immediately measure any new tubes set, just in case of a duffer. Then only adjust if it's strictly necessary.
 
I'm also OCD so I like to adjust all measurements to 1v or less (easy for the back trims, less so to MAINTAIN that for front), even though the experts say a few volts either way is ok. It will drift from day to day, but I'm not so OCD that I will check any more frequently than every month or two.

 

[zardon]

  I don't think this is good advice, and here's why:
Therefore, it is counterproductive to change anything after 5 minutes - all you do is completely mess up the settings Justin originally made. Better to LEAVE IT ALONE and just periodically check the reading is heading in the right direction.

I was not referring to the tubes that Justin sent. I was refering to changing the Russian tubes to older NOS tubes such as the Mullard EL34 XF4's I use. The reason for the initial 5 minute change is that there will likely be massive BIAS adjustments needed between an XF4 and the modern Mullards, so running the amp for an hour with them 0.50+- out is not a good idea if you can avoid it. So generally I would bias them after the initial amp warm up, get them close. leave the amp on for another hour then BIAS them again (probably wouldn't even listen to music either for the first hour). If I was being honest, I would probably monitor the tubes for a few days after this to confirm stability.
 
Also as far as I know Justin makes a generalised BIAS before shipping, otherwise he would mark the tubes with positions on the amplifier, rather than letting the customer put them in any place he/she wishes. All tubes will have minor variances even those that Justin selects from a big order of Russian Mullards.

 

[TheAttorney]

My comments applied to any tube (based on the ones I've tried). So its still counterproductive to adjust anything after only 5 minutes.
 
I'm pretty sure the stock tubes were marked in pairs (going back a couple of years). It's possible that Justin has since found they all measured much the same (within the natural daily variance), so stopped bothering to mark them - just a guess 

 

[zardon]

  My comments applied to any tube (based on the ones I've tried). So its still counterproductive to adjust anything after only 5 minutes.
 
I'm pretty sure the stock tubes were marked in pairs (going back a couple of years). It's possible that Justin has since found they all measured much the same (within the natural daily variance), so stopped bothering to mark them - just a guess 

Its not counterproductive, I have been biasing amplifiers for 30 years. If you are moving between a modern Russian/Chinese tube to an older British GEC/Mullard (Or Americian Slyvania) tube, the construction of the tube is often substantially different. Modern tubes are not designed to the same structural integrity. If you are changing tubes on an amplifier which have been biased to one setting and are putting in an older set such as an XF4, or even a Sylvania 6CA7 triple getter Fat Boy,. the construction is massively different. This could lead to a 0.50+- variance which could get actually worse in the first hour, putting a lot of unnecessary strain on the structure and plates. The 5 minute BIAS adjustment is not meant to be a final adjustment, it is an initial 'ball park' figure to ensure that when the amplifier warms up for the first hour that it is working from a 0.00+- starting point, rather than 0.50+- or greater starting point.
 
I fail to comprehend your logic on this and you are focusing on the fact that I am telling people to adjust the AMP BIAS on the tubes that Justin sends. I am telling people that if they are moving from the stock, generic, modern Russian EL34 Mullards to a NOS British tube around 30+ years old that an initial BIAS adjustment after a starting warm up period is a wise idea to put less strain on the tubes and amplifier - until it can be adjusted properly later.

 

[TheAttorney]

@zardon, bow to your superior tube biasing experience, as I have only experience of the BHSE, but I think you are still missing my key points. One more (and final) attempt:
 
I have tried 7 different tube models in my BHSE, 4 new production and 3 vintage, with the metal base ones being around 60 years old. They ALL behaved broadly the same, which is to start at around -40v to -50v  from cold, gradually reducing to around zero volts after 3 to 4 hours. Therefore, if I was not the OCD type, I could have left Justin's original settings for ALL those different tube types and they would have ended up within a few volts of each other. Which is good enough to not get unduly concerned about, for short term listening comparisons for example. I personally would adjust down to near zero at the end, which is good to do, but not CRITICAL.
 
With a start point of say -50v, let's say that would drop to -40v after 5 minutes and would eventually drop to say 0v after say 4 hours. Then if at 5 minutes I adjusted to 0v, then that would mean the tubes are 40v higher than then should be at that point in time, which means they will end up at +40v at their end point in time. So much better to leave them alone at 5 minutes, but just periodically check that the voltage is going in the right direction in a reasonably uniform manner.       
 
Now, there may be a tube model that I haven't tried, which behaves very differently to the 7 ones that I have tried. And all my tubes were quad matched, which may or may not be significant for this purpose. Which is why I recommend everyone does measure these things. I just don't recommend blindly changing the settings after only 5 minutes, because at that point the readings SHOULD be far from zero in order to achieve zero at their end point in their warm up time. 

 

[zardon]

 
@zardon, bow to your superior tube biasing experience, as I have only experience of the BHSE, but I think you are still missing my key points. One more (and final) attempt:
 
I have tried 7 different tube models in my BHSE, 4 new production and 3 vintage, with the metal base ones being around 60 years old. They ALL behaved broadly the same, which is to start at around -40v to -50v  from cold, gradually reducing to around zero volts after 3 to 4 hours. Therefore, if I was not the OCD type, I could have left Justin's original settings for ALL those different tube types and they would have ended up within a few volts of each other. Which is good enough to not get unduly concerned about, for short term listening comparisons for example. I personally would adjust down to near zero at the end, which is good to do, but not CRITICAL.
 
With a start point of say -50v, let's say that would drop to -40v after 5 minutes and would eventually drop to say 0v after say 4 hours. Then if at 5 minutes I adjusted to 0v, then that would mean the tubes are 40v higher than then should be at that point in time, which means they will end up at +40v at their end point in time. So much better to leave them alone at 5 minutes, but just periodically check that the voltage is going in the right direction in a reasonably uniform manner.       
 
Now, there may be a tube model that I haven't tried, which behaves very differently to the 7 ones that I have tried. And all my tubes were quad matched, which may or may not be significant for this purpose. Which is why I recommend everyone does measure these things. I just don't recommend blindly changing the settings after only 5 minutes, because at that point the readings SHOULD be far from zero in order to achieve zero at their end point in their warm up time. 

Its fine, not really wanting an argument over it. you seem a nice guy on the forums, but I was only trying to explain how I would bias any tube amplifier. I have only tried a few different sets on the BHSE and they needed fairly minor/modest changes, unlike some of the other amplifiers which have needed large adjustments and can run very hot if you don't BIAS almost immediately as a 'starting point'.
 
The BHSE doesn't really dramatically change in overall sound signature between tube changes, its quite subtle, which I think is due to the Kevin Gimore approach of 'wire with gain'. Still I do have to stand by my ways of doing BIASing as it has always been the safest way. I am not letting anything run dramatically out of BIAS for any length of time. I speak with experience of my 845 tube amplifiers.
 
I think my routine is perhaps based on decades of tube changing and being as safe as possible when swapping out for new tubes. Running tubes badly biased for hours at a time puts unnecessary strain on both amp and tubes. I tend to BIAS fairly often, and always critically in the first hour when moving to a new set - multiple times. I appreciate you are saying that you are finding the tubes settle all closely to each other on the BHSE and honestly I can't argue with you on this as I have only tried three sets and they did only need minor adjustments from start to settling.
 
At the end of the day, whatever works for you I guess!

 

[astrostar59]

Thing is the BHSE is 4 gain stages, the first 3 are solid state, so the tubes only affect the last gain stage.
 
However, I have listened to the difference on David61's BHSE between the Mullard re-issues as supplied with the amp, new manufacture PSVanes and then Mullard 1960s (Genuine NOS XF4s).
 
The difference was quite a lot so I beg to differ here. The biggest change was the treble which warmed up and was more natural, less brittle especially on female vocals.
 
This difference is worth the cost IMO on anyone who has a BHSE, as that amp can go quite a bit further ahead with the right tubes (in a system of components that have synergy).

 

[Crashem]

On another topic.  I love the feel of the Alps RK50 and the flexibility.  That is one great potentiometer.  So smooth.  Highly recommend taking this option if you can afford it.  The DACT upgrade on the GSX is nice but this is at another level.

 

[zardon]

  I love the feel of the Alps RK50 and the flexibility.  That is one great potentiometer. 

Its one of the best in the world, costs a small fortune too - around £700 in the UK, the price of a modest headphone amplifier!