hunting for a 5e3 in a DR

[uneumann]

I've built a DR-clone amp many years ago. It has a preamp channel with a switchable scoop tone stack and after many years I've found that using the lower scoop frequency can make the DR sound a lot like a 5e3. Of course I could just build a 5e3 tone stack and switch it in/out, but this approach also allows the range of tones that lie between the two tone stacks.

This "discovery" didn't come about from playing the amp. The setting combination was too unlikely - I never thought to try it. It came from a deliberate hunt for 5e3 tone using SPICE sims, so here are some plots that show the idea. The first is the 5e3 tone stack (with variable tone settings) and the second shows the switched DR stack with varied bass and treble settings. You can see similar rising slopes all through the mid freq range which are the defining character of the 5e3. After figuring out the needed settings on the DR based on the spice sims, I just dialed in the 5e3 tone on the amp I never even realized had it. More range in tone stacks seems desirable. I get the user interface problem in a long row of dials or sliders. Is a better way?

BTW - I've posted more about this at https://sites.google.com/site/string...xe-plus/drp-v2

[pdf64]

I suspect it may be even more useful to simulate the system as wholly as feasible, rather than just a section; surely there's the affect of DR's bright and peaking caps, and perhaps most significantly, the open loop power amp of the 5E3 will lead to significant shaping of the frequency response when loaded with a typical speaker (with this effect being greatly attenuated in the DR due to the global feedback)?

[uneumann]

I suspect it may be even more useful to simulate the system as wholly as feasible, rather than just a section; surely there's the affect of DR's bright and peaking caps, and perhaps most significantly, the open loop power amp of the 5E3 will lead to significant shaping of the frequency response when loaded with a typical speaker (with this effect being greatly attenuated in the DR due to the global feedback)?

No doubt... it all adds up - including the speaker/cab. The DRP has a NFB control and switching it on/off does make a difference - as many have described. (It's a bigger difference than fix/cathode bias - IMO) It's there, but it's 10% (IMO). Brite caps also matter, but in the DRP, they are minimal and easily swamped by tone settings. I have whole system Spice sims for both amps, and they also show the tone stack has the biggest impact. The presence or absence of that BF dip around 800-900 Hz is the key difference IMO. That's right in the ear's critical mid-range. Change the PI, change the output stage bias, even change the OT... they all matter some, but they get swamped by the TS difference. In hindsight it should have been clear - but at the time it wasn't. That's also why I did the post. The experiment put things in perspective. If I really want to change an amp tone - or emulate an amp - I'd start with the tone stack next time.