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Post by SoK66 on Jan 14, 2020 17:33:39 GMT -5
Anyone tried a 5751 in the V1 or V2 of a DR to exorcise the fizz & flub?
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pdf64
Wholenote
Posts: 556
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Post by pdf64 on Jan 14, 2020 19:16:18 GMT -5
It can’t hurt to try 😀
I seem to remember reading that different brands have different tonal balances, eg that the Philips are supposed to be a bit brighter, GE a bit darker.
I got both but can’t discern a noticeable difference. Whatever, the phase splitter V6 seems to work out best, as they overdrive a little nicer than 12AT7.
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Post by roly on Jan 14, 2020 21:51:53 GMT -5
I have tried them in both locations and they worked fine, but I didn't use them for the reasons you state.
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Post by ProzaKc on Jan 15, 2020 20:43:35 GMT -5
Never associated Fizz and Flub with a Deluxe Reverb.
Maybe get it checked out.
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Post by LTB on Jan 17, 2020 23:21:12 GMT -5
Anyone tried a 5751 in the V1 or V2 of a DR to exorcise the fizz & flub? 5751 is lower gain (70) verses 12AX7A (gain of 100) here is something to read: PREAMP TUBE GAIN |
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pdf64
Wholenote
Posts: 556
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Post by pdf64 on Jan 18, 2020 4:43:16 GMT -5
That’s a dodgy webpage, a 12AX7 / 5751 is generally not suitable for use as a regular BF / SF Fender reverb driver (eg V3 in 2 channel amps) where a 12AT7 is called for. The plate voltage / dissipation would be way over the limiting value.
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Post by LTB on Jan 19, 2020 2:07:00 GMT -5
That’s a dodgy webpage, a 12AX7 / 5751 is generally not suitable for use as a regular BF / SF Fender reverb driver (eg V3 in 2 channel amps) where a 12AT7 is called for. The plate voltage / dissipation would be way over the limiting value. Yes the 12AT7 is a current driver while the 12AX7/ 5751 typically a preamp gain stage tube operating on lower current/higher gain. Those tubes are not made to driver higher current circuits like Reverb and driving power tubes. I responded to the original posters need for a lower gain tonal concerns |
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pdf64
Wholenote
Posts: 556
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Post by pdf64 on Jan 19, 2020 6:47:30 GMT -5
That’s a dodgy webpage, a 12AX7 / 5751 is generally not suitable for use as a regular BF / SF Fender reverb driver (eg V3 in 2 channel amps) where a 12AT7 is called for. The plate voltage / dissipation would be way over the limiting value. Yes the 12AT7 is a current driver while the 12AX7/ 5751 typically a preamp gain stage tube operating on lower current/higher gain. Those tubes are not made to driver higher current circuits like Reverb and driving power tubes. I responded to the original posters need for a lower gain tonal concerns Yes, of course you were being helpful, it's just that if a webpage that apparently looks to be a technical reference has a error in the first few sentences, its value as a info source is blown for me; if that isn't pointed out it's kinda endorsed by default, and folks might reasonably expect to read it as gospel. I think that a 12AT7 is fine to use as a general purpose, RC coupled common cathode voltage amplifier stage; though initially designed for RF use, some manufacturer info suggests that application. FYI 'driving power tubes' in a tube guitar amp isn't a high current application; they operate in class A1 or AB1, ie no grid current. Their clipping point is defined by their bias voltage, signals whose peak positive voltage attempts to exceed the bias voltage (ie pull Vg1-k>0) will get clipped by the very low resistance of the control grid (to its cathode) when forward biased. No tube guitar amp has a stage feeding the power tube control grid that can overcome that, ie they can't achieve class A2 / AB2 operation. Yes, 12AT7 have a rather lower plate resistance, and can handle higher plate currents, than eg a 12AX7, so in a suitable circuit (eg transformer coupled) they could possibly be used to achieve grid current operation for power tubes; but no tube guitar amp uses such a circuit. I seem to remeber that Aspen Pittman RIP propogated that widespread misapprehension in his Tube Guitar Amp Book series. |
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Post by LTB on Jan 19, 2020 22:26:10 GMT -5
Yes the 12AT7 is a current driver while the 12AX7/ 5751 typically a preamp gain stage tube operating on lower current/higher gain. Those tubes are not made to driver higher current circuits like Reverb and driving power tubes. I responded to the original posters need for a lower gain tonal concerns Yes, of course you were being helpful, it's just that if a webpage that apparently looks to be a technical reference has a error in the first few sentences, its value as a info source is blown for me; if that isn't pointed out it's kinda endorsed by default, and folks might reasonably expect to read it as gospel. I think that a 12AT7 is fine to use as a general purpose, RC coupled common cathode voltage amplifier stage; though initially designed for RF use, some manufacturer info suggests that application. FYI 'driving power tubes' in a tube guitar amp isn't a high current application; they operate in class A1 or AB1, ie no grid current. Their clipping point is defined by their bias voltage, signals whose peak positive voltage attempts to exceed the bias voltage (ie pull Vg1-k>0) will get clipped by the very low resistance of the control grid (to its cathode) when forward biased. No tube guitar amp has a stage feeding the power tube control grid that can overcome that, ie they can't achieve class A2 / AB2 operation. Yes, 12AT7 have a rather lower plate resistance, and can handle higher plate currents, than eg a 12AX7, so in a suitable circuit (eg transformer coupled) they could possibly be used to achieve grid current operation for power tubes; but no tube guitar amp uses such a circuit. I seem to remeber that Aspen Pittman RIP propogated that widespread misapprehension in his Tube Guitar Amp Book series. Agreed on the same page now. Thanks  |
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Post by SoK66 on Feb 1, 2020 19:13:56 GMT -5
I grabbed a nice NOS RCA 5751 of Flea Bay and must say the results are impressive. Breakup is delayed about one nick on the volume spinner. I like it!
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Post by Seldom Seen on Feb 29, 2020 18:08:35 GMT -5
5751 works great in V1 or V2.
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