VOX AC30 guitar combo amplifier emulation

[Emil]

Hi all! Finally I think I have finished my work. I bring to your attention an emulation of the VOX AC30 Tone Booster guitar combo amplifier, made in the FS v3.0.9b2 environment. The amplifier consists of 2 channels: Normal and Tone Booster. The difference from the original circuit is that I added another tube stage to each of the channels in order to increase the degree of distortion, because It seemed to me that the original scheme did not have enough of it, at least for me. The front panel is a pre-amplifier. When you click on the logo, you go to the Power Amplifier panel and select cabinets. The Damp control is a dynamic attenuator at a frequency of about 3 kHz, depending on both the signal level and the position of the SAG knob also. SAG regulates both the degree of compression and the dynamic level of distortion. The power amplifier has 3 positions: class A, AB and Grid. It would be possible to do this without Grid in relation to this amplifier. However, Grid was conceived by me as an addition to the Hi Gain amplifier and I decided to leave it, despite the fact that it is still unfinished. However, this is not a Hi Gain amplifier. I didn't use impulses in the cabs. I formed them using filters. It was more convenient for me this way. Please leave comments, including unflattering ones. This will help me in future work. And also, I would ask you to help me translate my work into the VST3 plugin, because... I don't have a very good idea how to do this. Happy holidays to everyone and wish you peace, happiness and prosperity!

[martinvicanek]

Wow!
Congradulations, Emil! That is quite a remarkable amp sim. I owned an AC30 in the 80s, so I had to check this out.
I like the sound a lot, although I cannot really judge on how faithful it represents the AC30, because I no longer have my old Les Paul, and my ears are not what they used to be. Perhaps ask Brian May?

I have noticed that three of the cabs don't work (Green 25, Basket, and Recto), and I apologize because it is my fault. There is a bug in the coefficient calculation for the high cut filters (and in Recto, also for the highpass filter):

bug.png (25.89 KiB) Viewed 1961 times

Please remove the offending line

Code: Select all

float a1,a2,b0,b1,b2;

Apparently FS3 was more permissive than FS4 is. I still develop much in FS3, but I have made it a habit to always check with FS4.

[Emil]

Thank you Martin!
I followed your recommendations and removed the extra lines in the filter coefficients. Now everything is in its place. But I won’t publish it yet, because I want to understand the Preset Manager module in detail and write several presets for ease plugin use. As for the authenticity, I can say that since 1960, when the first AC30 appeared, there have been many modifications to the circuits that were significantly different, and I cannot speak of complete compliance. The main thing that remains is the 2 channels Normal and Top Boost and important the original Tone Stack, to the extent that I was able to do so. As for Brian May, his combo only had one "Volume" knob, which I think implies a modified circuit. These combos were produced in a limited edition, I think about 500 pieces. It's obvious to me that this combo has SAG due to the use of GZ34 in the power supply. Therefore, I decided to introduce the SAG knob, and to reduce the “sand” I introduced the Damp control. Depth and Voicing are taken from modern amplifier circuits. The SAG knob is also available in some VST plugins, such as S-Gear (Scuffhan). I decided to make it more “noticeable”, saturated in sound. In general, what got is what I got. In addition, BM used a 6 pence coin instead of guitar pick. This also radically changes the sound.