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Preamp and/or electrical specs (Pulsar 1, RCA I/O)
Posted: Mon Apr 21, 2008 10:48 am
by capacitor
Howdy,
I'm needing to bump up a low level guitar signal, going into the RCA inputs of a Pulsar.
I want to use a tube. My thoughts are with a single triode or pentode gain stage. I can also use a triode into a cathode follower - there are a couple of Mullard 12DW7s sitting here staring at me.
I think the Pulsar w/RCAs is looking for a -10db signal, to register 0db on a mixer channel coming directly from an analog input.
Any tube gearheads in here? I'm wondering if anyone has crossed this bridge already
Posted: Mon Apr 21, 2008 1:15 pm
by astroman
it may depend a bit on the pickup itself (of course), but the level most likely isn't a problem for a Pulsar - it will even (almost flawlessly) handle a vinyl record player signal in the 15mV range.
But the relatively low input impedance will load the guitar pickup and thus 'sucking the tone out of it'
All it needs is an impedance converter if you're not after a specific preamp sound via hardware - say real tube drive and crunch etc.
cheers, Tom
Posted: Mon Apr 21, 2008 3:08 pm
by capacitor
Thank you, Astroman.
I whupped up a cheap gain stage, using an existing preamp - just tapped off the signal after the first stage & sent it to the Pulsar. It let me reduce the gain on the incoming channel strip - from 18db to unity. Definitely reduced the noise floor.
I don't know if I'm overloading the Pulsar's input A/D stage - or if I'm only using (say) 16 bits out of the 24 available.
How can I tell if I'm close? (edit: a Modular solution would be great)
Posted: Mon Apr 21, 2008 4:02 pm
by capacitor
Found the manual, finally! Looks like the analog ins are 20 bit. Outs are 24.
So basically, I just want to know when I'm hitting that 20th bit
Posted: Mon Apr 21, 2008 4:31 pm
by garyb
yeah, not really an issue.
i would use a mic pre with a hiz input or a guitar pre with a line output to bring in the guitar signal, personally....
Posted: Mon Apr 21, 2008 4:38 pm
by capacitor
I was using a Digi Mbox in precisely that manner
That's gone to trade up to the Pulsar & Modular. The tube preamp I'm using does this as well, but I'm looking for a single stage of amplification to keep the parts count down.
I'll tell ya - straight in from guitar sounds great. Just not enough level. I do want to use a tube in front if I can, for voicing reasons.
I guess if I move the meters right at 0db gain & unity fader, I'm all set!
