Stage 60 Speaker and Tube Changes: WOW

[HyFive578]

Swapping power tubes in the HT-60 without re-biasing isn't really a great idea. There can be big differences in current draw between brands of tubes, for instance. I swapped out the stock TAD's for SED Winged C's and the stock factory bias with the TADS was set to around 62 mV... Just plugging in the SED's, the bias jumped to 93 mV and the tubes were so hot, they were practically throbbing. Perhaps there is less difference with EH's, but I'm sure had I not immediately dropped the bias down to around 60 mV, something bad would have happened...

[gerrygt62]

duly noted, sounds like the SED run a little hotter--I might wanna stick wit hthe Mullards, since they gave me no problems whatsoever

[Jono82]

Thanks for sharing your experiences guys.

[Beejer]

I changed my HT60 tubes a little while ago for Electro Harmonics power tubes and JJ pre tubes. I did it without a re-bias and the amp sounded good.

Biasing is not always necessary if you are lucky. If not, you can damage the tubes or OT.
I'm not a tech or anything, but I have found humungous variations between tubes, never assume anything.

Changed my power tubes today to EL34 SED winged =C=, so far they added tightness and depth to the lows and generally sound pretty damn good.
They also run much hotter than the Ruby's they replaced, so it was a good thing I was near with the screwdriver.

I measured the plate voltage (?) at pin 3 (both tubes) and it came out to 496v.
Using the formula, assuming the EL34's are 25 watts: (25 * .7)/496= 35.3 mA
I biased it at around 36.
I hope this is right. It sure SOUNDS right. :>))

Really nice Amp, I must say.

[majikmojo]

my JJ's are biased about the same..roughly 70 total - i didnt do it a tech did but i remember
him saying "your gonna love this" and i have...almost a year now of steady use and sounds killer

[AscottAudio]

Biasing info is duly noted.

So far I haven't found a local tech that knows "blackstar" so I am a bit reluctant to go through the processes until I find someone that knows what they are doing.

I guess I took a chance not re-biasing. Also there have been quite a few conflicting post on weather or not it is necessary. ( I do believe it is much better/safer to do it)


I am still looking at putting some Celestion G12 Century Neodyme speakers in my HT60.

I have read good reviews and these suckers only weigh 1.66 Kilo which is VERY light..think I will bite the bullet and get some next week..let you know how they shape up.

[remov1]

I have to second those that say you need to bias. I read several posts on various forums that biasing wasn't really necessary. I replaced my HT60 stock power tubes with JJ EL34s without biasing and ran them for one gig and then started noticing I was getting intermittent distortion like I had a bad cable. I took a look at the tubes and they were glowing. Put the old tubes back in and it fixed everything. I'm definitely biasing in the future.

[AscottAudio]

I actual located a tech very near by that has worked on and knows the HT60..so i'll be taking it to him next week to check the bias.

Not having much luck with the celestion G12 Century speakers though. They are scarce over here and after a lot of searching and phone calls the best I could do was to find a pair of them in 8ohm ..I need 16ohm so I will have to wait..they seem to be readily availble in the USA and I would guess also in the UK..being at the other end of the globe we tend to get things later than the rest of the world..

[boxofspiders]

This is some info from Tube Depot...
"The Benefit of Burned in Power Tubes

New tubes have always sounded and performed better when burned in prior to final testing and installation. By running a tube at full operating voltages (and not just the 6.3 heater voltages) for 24 hours, the cathode is allowed to stabilize and any oxide contaminants on the metal surfaces evaporate and are collected by the getter. The burned in tube is "cleaner" inside and better able to reproduce sound.

For burned in power tubes, the initial matching is less likely to drift and rebiasing isn't needed. The stability is immediately apparent. And for preamp tubes, the improved tone is instantaneously accessible without having to wait for the tube to stabilize making "tube rolling" much easier. And the combined benefit, the burn-in process quickly weeds out weak and suspect tubes before they get into your equipment.

If you want the best for your equipment and your listening enjoyment, burned in tubes are the most effective methods to insure your satisfaction. You don't have to wait for the best."

I ordered a matched pair of JJs with this "burned in option" (the stock power tubes failed, big surprise) and it's been solid ever since. Sounds fantastic. I should mention this is on my HT-40, not an HT-60 which I realize is being discussed here. This is how I will do this whenever my next tube change rolls around and if I ever run into any problems I'll come straight here and post about it. I honestly don't think that's going to happen.

[Neriwan]

Hi everybody,

First of all, sorry for my english ( I'm french )

One month ago I bought a HT Stage 60, it's a great amp and I love him ! But I want to change the speakers and tubes.
I saw on the forum, people buy a pair of Celestion V30. More over, i saw on the internet, V30 and G12H is a great combination.
Do you think this combination is a good choice ? And what impedance must i choose ?

I will buy the tubes on Watford valves (I want to know if the amp must be biased ? (Sorry, i'm a newbie.)

Thanks for your responses !