Marinair 10368 Trannies (round/octal)

[muddy]

this is probably a completely dim bulb question, b-u-u-u-t..... can you wire 2 of these, in whatever number of parallel/series, & reversed configs, in order to match the 10468's spec's, so i can use 'em for a 1073-style mic input? or (using 1 reversed, ala 31267 as per jlm's solution), can the -3db gain be made up with a diff choice ic/opamp than the tl072cn that's currently in there? also, do you think mounting these externally/internally on ceramic sockets (if those are what you'd in fact use) is a good idea? and lastly, pin config aside, would one of these suffice as a replacement for the 2nd line input tranny? otherwise, maybe someone here has a 10468 they'd care to trade?


ml

[muddy]

geoff? please??...


ml

[Matt Syson]

Hi
If they have the same ratios then they can be directly substituted. They may not sound the same however, depends what each was designed to do, and the compensation components around it.
Other ratios will also work but may not have the best signal to noise ratio when you are done.
Are you really using a TLO72 in a 'wannabee Neve' mic amp?
Messing around linking 2 transformers together is a silly idea if you are after quality.
Swapping an op amp for any other type that fits in the holes will not change the gain as this is determined by the other components in the circuit.
Matt S

[muddy]

i'm not using the tl072, it's already there. i was looking to maybe replace it, if in fact it does make sense to in the 1st place. the trannies do not have the same ratios:




i already know that the 10368 wired in reverse will work, but at the expense of -3db. where my knowledge drops off (a STEEP cliff) is whether 2 of these can be wired together in whatever scenario to get them nearer to the 10468's spec's. OR... if the make-up gain can be reclaimed with the choice of another opamp. and i'm not stoopit enough to think i can simply "whack in" substitutes because of a shared pin config. i'n NOT designing a new pre, i'm looking to upgrade whatever components that will improve a neve/1073-inspired pre (the gap pre73, to be precise). i already have the carnhill replacement for the output tranny (+ a motorola 2n3055, & a much better cap & resistor). but i came into the 2 marinairs mentioned above for next to nothing, & i thought i'd see if they could be used for this pre. the 10368's were either buss return input trannies, or something similar (i forget what). i know the 31267's can be used in reverse as a mic input tranny, and i'm fairly certain these can be too, but at the expense of volume. the gap pre-73 actually has 2 input trannies, 1 mic, & 1 line, so even if i can use one to replace the 2nd line tranny, i'd be happy. & maybe trade or sell 1 to get a 10486, be it marinair or carnhill.

i'm not completely clueless. but it's the math/logarithmic end that's difficult for me to wrap my head around, especially when you have to factor in how these THEN affect the other components they directly (or indirectly) co-depend on, i.e., caps & resistors. having just been through over a year's worth of chemo doesn't help the cause, either. but i'm hoping to learn SOMETHING from doing this, at least enough to give me the confidence to maybe start tackling a few other projects that'll help make the recording process easier for me. after all, i'm just a lowly guitar player trying to get back to what he does best; playing (& recording) guitar. so ANY help would be MUCH appreeshkiated. i'm a fast learner...


ml

[Matt Syson]

Hi
You have 2 choices, either accept that your preamp will have 3dB less gain, simply turn up the gain on the following unit if need be, or recalculate the resistor values of the preamp section to give you 3dB more. This is only really an issue if you use low output mics and record in a way that needs the absolute maximum gain. The extra 'noise' issue will only be slight and thjis can easily be recouped by using quieter op amps than a TLO72.
Matt S