Marshall speaker reactance emulator

[mth5044]

Exactly. I don't know what the original circuit uses since I can't get to Dropbox, but if it was in a amp, there is a likely chance that is used +/- 15V. Perhaps it says it on the original circuit? Can you provide a link to the patent you reference?

[vmaxvmax]

Exactly. I don't know what the original circuit uses since I can't get to Dropbox, but if it was in a amp, there is a likely chance that is used +/- 15V. Perhaps it says it on the original circuit? Can you provide a link to the patent you reference?

Hi, thank you for your interest. The patent is here: http://www.google.co.uk/patents/US5467400

The circuit is one of the small images at the start of the document.

[vmaxvmax]

Hi Samhay and all who contributed to this project.

Just a short note to say I built it as you suggested using your circuit. It works fine! I tested it against some IR's and also against the resonance feature in my Eleven rack - it is very similar in operation and sound.

As I said before, this circuit only simulates the reactive relationship between a valve amp and a 4 x 12 speaker cabinet. It does not simulate the cabinet/speaker response. Hence it is ideal where a line out is taken from output transformer of a valve amp and fed to a SS amp then onto a guitar speaker cabinet as the line out does not convey any of the reactance.

Thank you again!

[samhay]

Good to hear that it seems to work and sorry - it seems I forgot to get back to you RE charge pumps.

I also forgot to mention at the time that  as the 56k resistor in the op-amp feedback loop (R7 in my schematic) sets the overall gain, if one wanted to make more of an effect of this design then you could replace this with e.g. an A100k pot. Fully ccw you get a flat response and unity gain, and as you dial the resistance up, you get more gain/filtering.

[garcho]

Sorry, wrong thread, using phone.