- Jun 28, 2003
- Lille France
While reading Richard Kuehnel's site AmpBooks I was interested in his analysis of the Soldano SLO in the classic circuits section. As I had already exchanged with him , I tried to contact him again with the following remark and I would like to have your opinion two, you all bearded techs )
So, to sum up this is what I wrote to the [email protected] :
With the hope that my following question can reach Richard Kuehnel !
In your analysis of stage 3 of the Soldano Super Lead Overdrive on the AmpBooks website I encounter a difficulty in understanding your point here :
From the diagram we can see that even with 400 V plate-to-cathode voltage the maximum headroom peak-to-peak that you can reach with a 12AX7 is 5 V.
So how can we speak of a 4.2 V peak headroom considerably greater etc.... ?
In my humble opinion the maximum headroom ( for clean signals by definition) is 2.5 V peak.
What I understand , studying this stage, is that it is designed to unbalance the signal limiting it to the positive swing , the negative swing being truncated with the 0.3 V left to the cut-off limit. The effect, for me, is to restore a good part of the overtones with EVEN harmonics that the previous stages have considerably reduced. All the other preamp stages show a 1k8 cathode resistor which produces a symmetric amplification : with a gain pushed hard we get square waves whose symmetry considerably attenuates the EVEN harmonics , giving way to the (also desired) ODD harmonics. It is the subtle combination of those two types of harmonics that give this creamy overdrive and make the Soldano a really super amp .