Mellotronists

-----Original Message-----
>From: john barrick <astroboy@...>
>Sent: Jun 14, 2007 10:34 AM
>To: Mellotronists@yahoogroups.com
>Subject: [Mellotronists] Re: Strings Preference, Preamps, Heads too
>
>Martin (or Jerry, Frank, etc.),
>has anyone with an M400 swapped out their stock heads for High Z ones
>and impleted a tube/valve preamp?  I assume that the new preamp would
>take up more room and need to be placed elsewhere in the cabinet. 
>Would this be an exercise in futility, or should one, via this method,
>be able to get "the sound"?
>
>john


__________________________________________________________________________________________


Hi John,     Reverse-engineering a MK-II headblock into an M400 model , plus
adding tube preamp is an undertaking, to properly implement. 

The Pindertron for Frank S. in SD had hi-Z heads, mated to solid-state preamp
using impedance matching isolated line transformers (3 of 'em).  
And the MK-VI and MK-VII produced by Markus Resch uses tube preamp mated to
Low-Z headblock.  

Main reason for switch to Low-Z heads was the noise/interference  from Hi-Z units.
Was an often observed fact that SSCU pulses broke thru into the audio. 
Bringing one's hand near any of input cables would induce a terrible buzzing,
when orig. mated to tube/valve preamp. 

TIDBIT :  One individual tapehead from MK-II has same reading as ENTIRE M400 headblock
array. 

The valve preamp requires high-voltage DC (about 250-300 nominal) for B+ biasing , 
plus 6.3-7.0 VAC  (or rectified DC) for tube heater(s).  
SFX thru MK-V models only require filtered/clean  30VDC (18VDC w. low-noise mod). 

Hope this info is of help. Cheers,  -- Jerry Korb at the Mellotron Ranch