HT5-R combo possible stress...

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lagedor
Posts: 24
Joined: Mon Apr 13, 2015 11:35 am

Sun Feb 26, 2017 12:36 pm

Hi , through this good forum I've got useful suggestions about the speaker swap . But I' like also reduce the exxagerated amount of gain ,not so easily manageable...so , conscious of the possible risks in terms of tone and sound , I'd like to try to replace the stock preamp tube with a less-gained 12AU7 ( eventually , since it doesn't requires biasing , I can give up...) . I just like to know if this change can really , sooner or later , stress the amp or/and the tubes or require more periodic biasing work . Thank you !

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thephantum
Posts: 1160
Joined: Wed Jan 29, 2014 7:42 pm
Location: Virginia, United States

Sun Feb 26, 2017 6:02 pm

There's no danger to the amp by replacing the 12AX7 with a 12AU7 and it will reduce the gain by a lot. On a scale of 1 to 10, if the 12AX7 has a gain factor of 10, the 12AU7 is about a 2. So you might want to look at something like a 5751 first, which would be around a 7 and makes the gain knob much more usable.

However, in the experiences I've had with my own HT5, replacing that tube with anything other than a 12AX7 caused the amp to lose all of it's edge. It sounded flat and lifeless...at least to my ears.

lagedor
Posts: 24
Joined: Mon Apr 13, 2015 11:35 am

Sun Feb 26, 2017 10:54 pm

I'm grateful to you ,thephantum, for your reply . But at this point ,I MUST someway understand the reason of that harsh and gritty tone ; so , since I've replaced the stock Blackbird and the preamp tube also with a better one (same type) , I guess all I can do is : 1- try a smoother and fatter cone as a Greenback ; 2- if it's not enough, risk with another preamp tube with less gain , and see the results...maybe it's 'better' some flattness than a pretty useless 'gain' that now I have ...for this reason , I'm going mad through pedals... 3 -try with a ever more less-gain preamp tube as 12AU7 ; sometimes it seems someone has fixed this kind of problem

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thephantum
Posts: 1160
Joined: Wed Jan 29, 2014 7:42 pm
Location: Virginia, United States

Sun Feb 26, 2017 11:01 pm

Like I said, I would not just jump all the way down to a 12AU7, as the amp will lose too much gain. I would try a 5751 first, then a 12AT7, then a 12AY7. If all of those still have too much gain for you (very doubtful), then try a 12AU7.

Just my $0.02

lagedor
Posts: 24
Joined: Mon Apr 13, 2015 11:35 am

Sun Feb 26, 2017 11:20 pm

Right , thank you very much ; I want to do these passages .

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