NPN vs PNP Germanium

[Lord Tim of Wah]

Hi guys
I'm new here and I'm sure this has been asked many times.
If you modify a circuit to be negative ground by switching NPN for PNP, as Philip Bryant does with the Rangeblaster and Tychobrahe workalike, does this have any impact on the sonic qualities?
Thanks

[smoguzbenjamin]

Don't think so. Of course the tranny will be different so that might affect the sound....

[brett]

In theory you could get the same result, but in practice they're different.  For example, the AC127 complement to the AC128 sufferes from less leakage and is generally a higher gain device.  I actually prefer them for those reasons (and because I have access to a supply of them).  Sonically, the extra gain causes some subtle differences.  I couldn't really say whether they're better or worse.  Just a little bit different.

[phillip]

The sound of the Tyco certainly doesn't change since Silicon transistors are pretty consistent as long as you replace them with their gain matching counterparts.

As far as the RangeMaster goes, a good 70-90 gain Germanium transistor with low leakeage, whether it's NPN or PNP, will sound great if the circuit is tuned properly.  A lot of boutique RangeMaster clone builders will have you believe that the only way to get them to sound right is to use one of those "super rare" transistors that have been sprinkled with magic dust by the transistor fairy  With all the testing and tuning I've done with the RangeMaster, that just hasn't proven to be true.  I've used gain and leakage checked AC128 (PNP), AC188 (PNP) and 2N388A (NPN), and they all sounded the same.  the AC128 and AC188 were newer production ones too, not NOS.  Overall I'd have to say that I like the 2N388A better than any PNP...they seem to be much more consistent when it comes to leakage and gain.

Phillip

[bwanasonic]

A lot of boutique RangeMaster clone builders will have you believe that the only way to get them to sound right is to use one of those "super rare" transistors that have been sprinkled with magic dust by the transistor fairy  With all the testing and tuning I've done with the RangeMaster, that just hasn't proven to be true.  I've used gain and leakage checked AC128 (PNP), AC188 (PNP) and 2N388A (NPN), and they all sounded the same.  the AC128 and AC188 were newer production ones too, not NOS.  Overall I'd have to say that I like the 2N388A better than any PNP...they seem to be much more consistent when it comes to leakage and gain.

Phillip- Speaking of magic trannie dust, have you tried a bona fide OC44? I must say with my limited testing, no two trannies sounded the same in the RM.

Kerry M

[phillip]

I've tried the OC44 and the CV7003 (taking hints from Robert Keeley), and they are pretty nice sounding, but not 100% better than the AC128, AC188, 2N388A, etc.  What I ended up doing was building a RangeMaster testing "jig" using several trimpots (following the RangeMaster article at GEO) so that it can all be adjusted easily and the corrected resistor values can be chosen from the final settings of the trimpots.

Phillip

[saros141]

.
As far as the RangeMaster goes, a good 70-90 gain Germanium transistor with low leakeage, whether it's NPN or PNP, will sound great if the circuit is tuned properly.  
Phillip

I guess I'll find out soon enough myself (I'm putting together a RM with trimmers too), but why doesn't it sound good when the gain is above this range?  I can understand why the low-gain devices might not sound as good, they won't boost the signal as much and you'll be closer to the noise floor.  I have one Valvo OC44 with a true gain of 159 and low leakage (using RG Keen's test circuit).  To those who have "rolled" transistors in this circuit, how is it likely to sound different, assuming I get the biasing right?

[Lord Tim of Wah]

Thanks for all your replies guys

I seem to be able to get hold of AC127and AC128 quite easily in the UK so I'll go with one of those. I'll be following RGK's tuning advice for the transistor.

But I have another question:
I plan on using a Godlyke PowerAll power supply for a pedal board with a vintage wah, a home built RM, a Blackstone Mosfet 2 OD (magic pedal IMO) and possible a vibe of some kind or a Korg G4. Guitar is usually a Les Paul reissue, amp is either a 1965 AC30 TB or a Princeton BF Reverb (sometimes both). Now the Godlyke has reverse polarity leads that you can select. Is there any reason why I shouldn't be OK powering - ground and + ground devices together as long as the polarity is correct?

I also need to know how the Millenium bypass fits into the RM modified circuit but I'll ask that in a separate thread.
Cheers
Tim

[Samuel]

Yes, there is a problem. There can only be one ground reference per power supply. Otherwise you're grounding power supply on one effect to the ground on another. No workee. Got to have a seperate supply.

[petemoore]

Current production AC128's was it?/

[Lord Tim of Wah]

Samuel thanks for info
Pete my local electronics shop has quite few germanium transistors and diodes and yes I believe these are new production. But I did notice he had a load of old Mullard .22 tropical fish/liquorice allsort caps at 18p (30c) each so I bought the lot. :lol: