K5synth

Hi,

thanks for the effort on this!

I am planning to perform this output modification on my K5, by replacing 
R33 through R40.
On the sequencer.de forum post I noticed you advise using 12kOhm 
resistors, while in the below message you mention 15kOhm.
What value would you advise?

Best regards,
Jeroen Oldenhof


Op 17-12-2015 om 7:09 schreef woerz.herbert@... [k5synth]:
>
> Hello
> (Please excuse my poor english.)
>
>
> The (since 2004) practiced output-modification prefer to the Kawai K5 
> (K5m) is not correct.
>
> Reasons:
>
>
> Point 1:
> The ORIGINAL upper-cutoff-frequency (at the modification area of the 
> circuit) is 28kHz.
> ((R26, R27, R28, R29): 56kOhm parallel to 100pF)
> But if you replace the original 56kOhm-Resistors by 150kOhm, the 
> resulting upper-cutoff-frequency is only 10kHz!!!
> (150kOhm parallel to 100pF)
> And so the sound of the modificated Synthesizer is muffled (not 
> brilliant), because the upper-cutoff-frequency is now much to low.
> Note:
> To keep the original upper-cutoff-frequency, you must replace C16, 
> C18, C29, C20 (100pF) by 33pF capacitors!
>
>
> Point 2:
> If you replace R19 (56kOhm) by 150kOhm, the gain of the Single-Mode 
> AND the gain of the Mix-Out is much to high.
> Reason:
> The Mix-Out bases on an ADDITIONAL OP-Amp (gainresistor: R19) and at 
> the input of this additional OP-Amp the four outs of the Output-
>
> Amplifiers (gainresistors: R26, R27, R28, R29) are
> summarized by (four) 100kOhm resistors.
> And:
> If the Synthesizer is in Single-Mode, the output of the additional 
> OP-Amp (=Mix-Out!!!) is switched (by the Relais RY3 and Ry5) DIRECTLY 
> TO ALL output-sockets (Mix, 1, 2, 3 and 4).
> And so it is NOT useful, to change R19 from 56kOhm to 150kOhm, because 
> in this case there are TWO amplifications SERIAL.
>
>
> Summarizing:
>
> The CORRECTED modification:
> Replace R26, R27, R28, R29 (56kOhm) by 150kOhm resistors.
> Replace C16, C18, C29, C20 (100pF) by 33pF capacitors.
> R19 must be 56kOhm (56kOhm is original)
>
>
> By the way:
> I have designed another (much easier and (prefer to noise-gain) 
> better) output-modification. You can see the details under following 
> link (german):
> http://www.sequencer.de/synthesizer/viewtopic.php?f=3&t=108837
>
>
> But here is the shortform for you:
>
>
> INSTEAD of the old modification:
> Solder eight 22kOhm-Resistors at THE UNDERSIDE of the print parallel 
> to the following (39kOhm) resistors:
> R33, R34, R35, R36, R37, R38, R39, R40.
>
> (Or: Replace R33, R34, R35, R36, R37, R38, R39, R40 by 15kOhm-resistors.)
>
>
> Best regards
> B�ckle Christian
>
> PS.: A special thank to Narfman96
>
>