HT-40 Bias Information

[CrankUp]

They were both stamped gm 32. The mV bias reading changed from 51 to 54 when they were swapped. No change was required to biasing however I changed the bias to 60mV to warm them up a bit.

I'm about to order a new set of power tubes from thetubestore and was hoping to use the same perfect pair number as you so that I won't have to re-bias, but when I asked for a gm 32 pair, they said that they didn't use the term gm, but they did have a perfect pair number of 32. I just wanted to confirm if your Winged "C" (SED) EL34 tubes were the perfect pair number 32, and if gm was a mistake. Thanks.

I changed my tubes here too and the Winged C really sound amazing i adjusted the Bias to 59mV a bit warmer and the sound its with a nice body and presence. I changed my preamp tube too. I was using two 12AX7 Mullard Reissue before, and changed the V1 to 12AX7 TUNG-SOL. I loved, more open sound with nice mids! Better tha Mullard in V1. I have a JJ ECC83S here and i will try in V2 position to see what's happen. People claim that these valves are darker, well i will check it against the Mullard Reissue. An maybe after give it a try at V1 and put to V2 the TUNG-SOL.

Nice to know what people are doing with their Blackstars! I love Blues and Classic Rock. I think is nice to tell the kind of sound that you like because what sounds good for one kind of music maybe sound not so good for other sounds.

All the best!

[CrankUp]

I've tested the JJ83S at V2 and it cleaned the Clean channel. With the Mullard and TUNG-SOL even the Modern Clean (Fender) was getting distortion at high volume, and the Boutique voice (VOX like) was getting more overdrive oriented. I think for my propose, blues and classic rock it fits well JJ and TUNG-SOL. Mullard is warm but gets more distortion in my review. Well i will try different combinations between V1 JJ and V2 TUNG-SOL.
But if you want drive i think Mullard and TUNG-SOL is a good combination. In this case with the Winged-C- in the power amp.

I was thinking about the relationship os V1 and V2 with the Clean and Dirt channel. But after my tests i think both V1 and V2 influence in both channels. Am I right!?

Thanks guys!

[CrankUp]

Hi Guys,

I will stay with the V1 TUNG-SOL for a more birght clean and nice crunch with the Boutique voice. V2 with JJ for a less agressive drive, that is nice for my propose.

Some Mullards Reissue now getting some dust... I though they too smooth and with less headroom.

[shimmilou]

...I was thinking about the relationship os V1 and V2 with the Clean and Dirt channel. But after my tests i think both V1 and V2 influence in both channels. Am I right!?...

For the HT 20, the preamp tube closest to the rear of the amp is only for the clean channel (I call that one V2, but not sure how B* labels it), and the preamp tube closest to the front is for the dirt channel only (I call that one V1 as it is physically closest to the input). I found this by pulling each tube one at a time, and only had output on the corresponding channel. I put a 5751 in the clean channel for a bit more clean sound.

I don't see why B* calls the HT 20 "Cathode biased" when it is fixed bias, evident by the negative voltage applied to the control grid. There are Cathode resistors and caps, but they don't set the bias.

BTW, due to the Cathode resistors, I believe that you should measure the Plate voltage in reference to the Cathode and not in reference to the chassis. This is only about 12 VDC difference in the HT20, but still more accurate. I am assuming a higher voltage in the HT40?

[daniyalahmed97]

Just wanted to thank you guys for helping me bias my HT 50. I've got JJ power tubes and JJ pre amp tubes and they seem to have made the drive channel less aggressive which I enjoy. Thanks again!

[tienda]

Hi


If someone is going to change the power tubes in ht-40 please make a vid how to bias amp in a proper way

[CrankUp]

I did somes tests swapping the power tubes EL34 for the 6L6 checkout the post at the forum.

[tienda]

Got one question.
Should the BIAS trimpot turn continuously or does it have any mechanical stops that prevent further rotation?"

[tienda]

It looks like my PR2 BIAS trimpot is broken.
Have you any ideas where can I bay it. Should I looking for oryginal one?
Does any body knows its technical characteristics?
I ll be grateful for your help

[phreddybee]

just got a club 40, and found this thread on biasing-thank you! is this pretty much all I need to know?

I am just a bit confused about what test points to use, and if I just need to adjust bias, or if there is a way to adjust plate voltage too. I see 3 test points (10, 18, and 13), or at least that's what I think they are, and I just want to make sure I get this right.

I plan to get a matched quad set so I can have a spare pair ready. also, has anybody experimented with different pre-amp tubes? just want to see if there any other tonal options down the road.

thanks for the help-my 1st attempt doing this even though I have owned tube amps in the past.