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Added Doepfer replacement section
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[http://www.muffwiggler.com/forum/viewtopic.php?t=17496 noisy A-199]
== Replacing the Doepfer A-199 spring tank ==▼
The Belton tank used as standard in the Doepfer A-199 is a BMN3BB2C1B, which breaks down as:
::BMN3 Belton, mini, new, short 3-spring<br />
▲== Replacing the Doepfer A-199 spring tank ==
::B - input impedance 190Ω<br />
::B - output impedance 2575Ω<br />
::2 - medium decay<br />
::C - input insulated, output ground<br />
::1 - no lock<br />
::B - horizontal mount, open down<br />
The two most important ones are the input and output impedances, and any replacement should try and match these two closely in order that the circuit functions as originally intended (different input impedances have different input drive level requirements, so if one of a different impedance is used, the tank may be either under- or overdriven, most likely resulting in poor performance, either a weedy signal and/or distortion of some type).
The 'connections' specifier, the 'C', is unlikely to be critical: in the Doepfer circuit the input is grounded in any case, so using a 'B' type (input grounded/output insulated) will not cause any problems; use of an 'A' (both grounded) or a 'D' (both insulated) will not cause any problems from an electrical standpoint, but may not be advisable from a noise point of view, i.e. leaving the case floating ('D'), may make it more susceptible to hum pick-up, and grounding both sides ('A'), may have implications for noise due to the very small signal levels at the output - without trying it, I wouldn't like to say!
As for the last two characters: the '1' = 'no lock', the only place you'll likely to see one with a lock (which simply holds the springs safely for transport) is in an ancient tank on one of the auction sites; the final letter, the mounting orientation, refers to the preferred mounting method to give optimal performance - I'm certain most people ignore this, and I've never seen an issue reported for which the root cause was not having the tank correctly orientated (apparently the 'bobbins' either end, with the spring-mounted magnets inside them, perform better some ways than others).
Thus an example suitable replacement would be an Accutronics '''9BB3C1B''', but any v'''BB'''wxyz, where v, w, x, y, z are any of the possible alternatives for that character position (with the proviso on the 'x' connection-specifier, the 'C', noted above), will be fine!
== Manufacturers ==
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