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Post subject: Re: Fender Bassman hiss
Posted: Thu Feb 16, 2012 2:28 pm
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Jaykeyhunter wrote:
Heaven's sake, guys, go easy on me! And if a tube can't take a gentle tap with the business end of a 'driver, then it isn't going to last a 300 mile journey and a bunch of package-handlers at the courier depots like this one did!


Relax. No one is beating up on you. Just typical banter for this forum. :lol:

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Post subject: Re: Fender Bassman hiss
Posted: Sun Feb 19, 2012 3:26 am
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Ok, banter accepted and I'll take heed of the screwdriver faux pas.

Valve 2 was replaced with a new valve, lessening the hiss. Replacing valve 1 with another new valve does nothing. Now, however, I am noticing a faint 'rumble' when picking strings independently, especially on the b string. As the open note dies away the rumbling can be heard and dissipates over 2-3 seconds. 6 months old or not, I think I need to get this beast to an amp doctor. Still loving it, though!


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Post subject: Re: Fender Bassman hiss
Posted: Sun Feb 19, 2012 8:54 am
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Jaykeyhunter wrote:
Ok, banter accepted and I'll take heed of the screwdriver faux pas.

Valve 2 was replaced with a new valve, lessening the hiss. Replacing valve 1 with another new valve does nothing. Now, however, I am noticing a faint 'rumble' when picking strings independently, especially on the b string. As the open note dies away the rumbling can be heard and dissipates over 2-3 seconds. 6 months old or not, I think I need to get this beast to an amp doctor. Still loving it, though!


Just curious, but what brand tube did you buy to put into V2? V2 in the Bassman constitutes the voltage amplifier and cathode follower which are used to drive the tone stack. The cathode follower half of V2 has very little gain (it is used primarily to provide a low output impedance to drive the tone stack) but the voltage amp half has quite a bit of gain. It is important to use a good quality, low noise tube in the V2 position to keep hiss at bay. Also, what are your tone control and Presence control settings? All of these controls are highly interactive and can easily accentuate the inherent hiss of a tube amp.

Not sure what would cause a "rumble" while playing but I do know that the bass control of the Reissue Bassman keeps the low bass much flatter than the bass control of the original 5F6A circuit which rolled off the low bass fairly rapidly to prevent overload and "farting".

This is an "LTD" Reissue, correct? Did you check and adjust if necessary the bias setting of the power output tubes?

Still, probably a good idea to get the amp checked out.

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Post subject: Re: Fender Bassman hiss
Posted: Thu Feb 23, 2012 1:05 pm
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Sovtek 12AX7.

Tones roughly all midway, presence around 2.

No biasing. Why would I need to do that?

Please have a look at http://www.hotroxuk.com/matched-valves-links-page-12ax7-6l6-909-0/preamp-valves-12ax7-ecc82jj-groove-tube-12ax7m-1885-0.html; maybe you could recommend some valves for me. other than Groove Tubes?


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Post subject: Re: Fender Bassman hiss
Posted: Thu Feb 23, 2012 2:36 pm
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Jaykeyhunter wrote:
Sovtek 12AX7.

Tones roughly all midway, presence around 2.

No biasing. Why would I need to do that?

Please have a look at http://www.hotroxuk.com/matched-valves-links-page-12ax7-6l6-909-0/preamp-valves-12ax7-ecc82jj-groove-tube-12ax7m-1885-0.html; maybe you could recommend some valves for me. other than Groove Tubes?


I don't know anything about Sovtek tubes beyond the fact that Groove Tubes often uses them and rebrands them.

Tone settings are reasonable.

You bought the amp used. Tubes age and their electrical characteristics change. You do not know what kind of shape your power tubes are in. A simple bias check will show if they are operating in their optimum range. If you decide to change power tubes, it is extremely important that bias be checked and adjusted if necessary. There is no such thing, in my opinion, as a perfectly matched tube.

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Post subject: Re: Fender Bassman hiss
Posted: Thu Feb 23, 2012 3:50 pm
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I understand power tubes and need for biasing; I just wondered what the connection was with the hiss. The amp is defo just over six months old and is immaculate.

TBH, what I've been reading about on that valve site has me scratching my head. It would cost a good bit to experiment with various valves and since I don't understand all of what the valve chain does, it's a bit of a minefield.


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Post subject: Re: Fender Bassman hiss
Posted: Thu Feb 23, 2012 4:34 pm
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Jaykeyhunter wrote:
I understand power tubes and need for biasing; I just wondered what the connection was with the hiss. The amp is defo just over six months old and is immaculate.

TBH, what I've been reading about on that valve site has me scratching my head. It would cost a good bit to experiment with various valves and since I don't understand all of what the valve chain does, it's a bit of a minefield.


You don't know that your tubes are biased properly. It may or may not have anything to do with the hiss. It is just something worth checking to make sure the amp is operating properly.

You understand power tubes and biasing but you don't undertand what the valve chain does?

I use JJ tubes exclusively except for a few NOS tubes that I use in V1 of my amps.

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Post subject: Re: Fender Bassman hiss
Posted: Tue Mar 13, 2012 2:54 pm
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what I meant was I know what power valves do and that they need to be biased; and no, I don't truly understand the valve chain cos I'm a bassist who has used tranny gear all his days and is just branching into valvesville so there's no need to be sarcastic, ok?

Like I said, the amp is heading for a service, anyway. Thanks to all for their input.


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Post subject: Re: Fender Bassman hiss
Posted: Tue Mar 13, 2012 6:00 pm
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Hi Jay I also have a 59 Bassman however not the LTD and mine is from 1990 so is alittle older than yours. I have no hiss at all. Im just interested to know are you playing Bass through it. If so your the first Ive heard of to do so even though it is a Bass amp. I love mine but play guitar through it. Good luck hope it gets worked out. :mrgreen:


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Post subject: Re: Fender Bassman hiss
Posted: Wed Mar 14, 2012 3:49 pm
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Jaykeyhunter wrote:
so there's no need to be sarcastic, ok?


No sarcasm intended. It was a simple question.

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