[jhellow]

Could someone that has done it describe how you bias for new tubes on the BHSE.  I am an early BHSE owner and have a NOS set of matched original KT77s.  I don't want to wreck these beauties.
 
Thanks,
 
JHellow

 

[verwandlung]

Quote:

Could someone that has done it describe how you bias for new tubes on the BHSE.  I am an early BHSE owner and have a NOS set of matched original KT77s.  I don't want to wreck these beauties.
 
Thanks,
 
JHellow

Oh, that is the kind of problem I would love to have... 

 

 

[Asr]

Quote:

Could someone that has done it describe how you bias for new tubes on the BHSE.  I am an early BHSE owner and have a NOS set of matched original KT77s.  I don't want to wreck these beauties.

You need a screwdriver with a really small flat-head (like a jeweler's screwdriver) to adjust the trimpots and a multimeter to follow the below instructions, which I originally copied down from instructions given by spritzer on another forum. The trimpots are located right by the tube base rings - there are 4 of them. Face down directly at the top of the amp and you can't miss them - they're gold in color and are slotted on the top. You may also need bright direct lighting to spot them.
 
Quote:

1: Let the amp warm up for at least two hours (maybe more since I'm not sure when it is running at full temp)
 
2: Place the probes of the multimeter between the + and - output for that channel (in the Stax socket seen here, red in the + [positive] output, black in the - [negative] output) and adjust the back trimpot for 0 VDC.
 
3: Now remove the black probe and connect it to the shell of a RCA socket on the back (aka ground) and adjust the front trimpot for 0 VDC.
 
4: Repeat for the other channel.

 
 
Stax Pro-bias socket diagram:
 

 
Also important: make sure to note which tube socket you use for each of the 4 tubes! If you accidentally change sockets on a tube, you may need to re-bias the amp.
 
Justin (HeadAmp) should have noted the tube sockets for the stock EL34s for example - in my case they were written on each tube's box.

 

[Golfnutz]

 
Quote:

You need a screwdriver with a really small flat-head (like a jeweler's screwdriver) to adjust the trimpots and a multimeter to follow the below instructions, which I originally copied down from instructions given by spritzer on another forum. The trimpots are located right by the tube base rings - there are 4 of them. Face down directly at the top of the amp and you can't miss them - they're gold in color and are slotted on the top. You may also need bright direct lighting to spot them.
 
 
 
Stax Pro-bias socket diagram:
 

 
Also important: make sure to note which tube socket you use for each of the 4 tubes! If you accidentally change sockets on a tube, you may need to re-bias the amp.
 
Justin (HeadAmp) should have noted the tube sockets for the stock EL34s for example - in my case they were written on each tube's box.

It would be nice if someone would volunteer to post a video on You Tube...
 

 

[spritzer]

Only one thing to add really, please use the adjustment tool supplied with the BHSE to make these adjustments since it was designed to do just that. 

 

[pachku]

 

I am an early BHSE owner and have a NOS set of matched original KT77s.  I don't want to wreck these beauties.

 
You're right, that's way too dangerous. I'll trade you a quad of reissue KT77 for them, so you can practice 

 

[googleli]

Can anyone recommend the most warm sounding NOS EL84s one can get for my upcoming BHSE which will be used with my 009? Many thanks.

 

[n3rdling]

Probably some with a lot of mileage.

 

[googleli]

Thanks, but I want NOS ones. I have good results with the Sylvannia EL84s and they compliment my MA speakers quite well. Did Sylvania make EL34 tubes? How about the XF3 brown based Philips tubes which someone recommended a few posts ago?

 

[David1961]

I'm planning on getting some extra tubes for the BHSE I've ordered, but this will mainly be for backup in case if or when something happens to the tubes that comes with the BHSE. The one thing I don't understand is why modern day tubes can't be made to sound as good if not better than tubes that were done in the 50's. Could anyone please explain why this is ?

 

[n3rdling]

NOS tubes are rarer -> more expensive -> better.  

 

[David1961]

Quote:

NOS tubes are rarer -> more expensive -> better.  

Hi n3rding,
I understand they're rarer, but I can't see why tubes today can't be made to sound better.
 
 

 

[googleli]

Not necessarily better or more expensive - I am just looking for warmer sounding ones. NOS just makes sure that lifetime of the tubes (if they are genuinely NOS) won't be compromised. Warm sounding is the key. So any suggestions?
 
Quote:

Hi n3rding,
I understand they're rarer, but I can't see why tubes today can't be made to sound better.
 
 

 

 

[n3rdling]

Quote:

Hi n3rding,
I understand they're rarer, but I can't see why tubes today can't be made to sound better.
 
 

My post was more of a joke than anything.  I have SED EL34s which sound perfectly good to me.

 

[googleli]

With O2 or 009?

 
Quote:

My post was more of a joke than anything.  I have SED EL34s which sound perfectly good to me.