On my design chassis I have two totally independent preamps that I would like to experiment using together at the same time. One has two gain stages and the other four so they are in phase. What’s the consensus out there on paralleling the inputs together? I know a lot of players of say two channel Fender amps just run a cable between the two to run them in parallel. Is there a better way that keeps the input impedance still up there and doesn’t affect tone? And what about the summing. Any thoughts.
(I do have un-used pre-amp tube holes so adding extra triodes is no big deal)
Paralleling inputs
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Kagliostro
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Re: Paralleling inputs
See Hiwatt schematics (at M. Huss site)
there is one model that has a paralleled input jack connection
Kagliostro
there is one model that has a paralleled input jack connection
Be sure you have enough current or your PT can Blow(I do have un-used pre-amp tube holes so adding extra triodes is no big deal)
Kagliostro
Re: Paralleling inputs
FWIW I went to a parallel input to the V1 stages in my 5F6A (surfin' amp) variant. I mixed the stages aft of the separate coupling caps and this enables quite a bit of variation in gain (and I suspect that if I changed the RC cathode arrangement on one of those V1 stages, I could get more tonal variation).
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Re: Paralleling inputs
Thanks Kagliostro and tubeswell for the additional info.
I've included the 2 schematics off of the HiWatt site. In version 1 the Linked input feeds each of the 68k input resistors which each have their individual 1meg grounding resistors. Normal Y configuration. In version two, 2meg grounding resistors are used on each channel which each have paralleled 2meg resistors when the individual channel inputs are used (1meg total input resistance) AND when the Linked input jack is used each input is at 2meg input resistance but now the two 2meg additional resistors now bridge across the two inputs. What is this 4meg bridge doing?
I've included the 2 schematics off of the HiWatt site. In version 1 the Linked input feeds each of the 68k input resistors which each have their individual 1meg grounding resistors. Normal Y configuration. In version two, 2meg grounding resistors are used on each channel which each have paralleled 2meg resistors when the individual channel inputs are used (1meg total input resistance) AND when the Linked input jack is used each input is at 2meg input resistance but now the two 2meg additional resistors now bridge across the two inputs. What is this 4meg bridge doing?
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Re: Paralleling inputs
Never mind ...... I see it now. The 4meg tied across the inputs is a really a non-path as the two inputs are directly connected to each other thru the linked jack. I see now that V.1 ends up being 500k input resistance when linked input is used; and in V.2 the 1meg input resistance is maintained using ANY input jack. Nice.