Blackstar Studio HT20 Head - My Take

[IM4Tone]

Re: Blackstar Studio HT20 Head - My Take

Correct me if I'm wrong, but 5751 should work well, because it's just lower output 12AX7. Given that resulting lower output doesn't clash with the amp design. 12AY7 might too, I'm not sure how they differ.

However 12AU7 and 12AT7 require different biasing for optimal operation. And as far as I know, preamp bias is not usually adjustable, so to make it work well you might need to mod the amp.

Actually they're all just variations for 12AX7 See THIS. No re-bias necessary, although I once read a post from someone who claimed it mattered (I wrote him off as fanatical...perhaps some miniscule element of fact IDK).

[Jacew]

Re: Blackstar Studio HT20 Head - My Take

Actually they're all just variations for 12AX7 See THIS. No re-bias necessary, although I once read a post from someone who claimed it mattered (I wrote him off as fanatical...perhaps some miniscule element of fact IDK).

I recalled the Premier Guitar article about preamp tubes and my earlier searches for 12AU7 as substitute of 12AX7.

Checking sheets for those tubes, it seems 12AU7 would probably work (cathode bias voltage 200v compared to 180v of 12AX7), but for 12AT7 it's only 90v.

From Premier Guitar:
"The 12AT7 also has less gain than the “AX,” but requires a slightly different bias voltage for optimal operation (it can be directly substituted in a pinch)."

I don't if 180v vs. 90v is "slight difference"...

[IM4Tone]

Re: Blackstar Studio HT20 Head - My Take

Actually they're all just variations for 12AX7 See THIS. No re-bias necessary, although I once read a post from someone who claimed it mattered (I wrote him off as fanatical...perhaps some miniscule element of fact IDK).

I recalled the Premier Guitar article about preamp tubes and my earlier searches for 12AU7 as substitute of 12AX7.

Checking sheets for those tubes, it seems 12AU7 would probably work (cathode bias voltage 200v compared to 180v of 12AX7), but for 12AT7 it's only 90v.

From Premier Guitar:
"The 12AT7 also has less gain than the “AX,” but requires a slightly different bias voltage for optimal operation (it can be directly substituted in a pinch)."

I don't if 180v vs. 90v is "slight difference"...

Voltage variation may be significant, but what is the impact on sound, due to less than optimal operation? Matters not to me, because 1) who in the world other than a fanatic/experimenter is going to mod an amp to vary preamp bias? 2) I was satisfied w/ the 5751 and certainly didn't care to lower volume of the amp(s).

Plug and play the various lower gain preamp tubes. If the result doesn't satisfy, the wrong amp was purchased....just my way of looking at it.

[Jacew]

Re: Blackstar Studio HT20 Head - My Take

Voltage variation may be significant, but what is the impact on sound, due to less than optimal operation? Matters not to me, because 1) who in the world other than a fanatic/experimenter is going to mod an amp to vary preamp bias? 2) I was satisfied w/ the 5751 and certainly didn't care to lower volume of the amp(s).

Plug and play the various lower gain preamp tubes. If the result doesn't satisfy, the wrong amp was purchased....just my way of looking at it.

I don't know. Haven't tried. Just thought it's good to take notice if/when you're going to swap tube types.

Tubes are not free, so it might be wise and more productive to start experimenting with ones that most likely yield results. (5751)

[IM4Tone]

Re: Blackstar Studio HT20 Head - My Take

.....Tubes are not free, so it might be wise and more productive to start experimenting with ones that most likely yield results. (5751)

My advice from the start...try a 5751. It's not a major investment.

[Jacew]

Re: Blackstar Studio HT20 Head - My Take

My advice from the start...try a 5751. It's not a major investment.

Exactly. I agreed right in my first reply

[Esseff]

Re: Blackstar Studio HT20 Head - My Take

Well there goes my thread.... off into the wide blue yonder.

I'm glad you are all in agreement, tho.

[Jacew]

Re: Blackstar Studio HT20 Head - My Take

Well there goes my thread.... off into the wide blue yonder.

I'm glad you are all in agreement, tho.

Sorry,it happens

How is the Blackstar working for you?

[IM4Tone]

Re: Blackstar Studio HT20 Head - My Take

Welcome to one of many internet forums where someone asks 'what time is it?' and a responder advises how to build a cuckoo clock!