|
|
Post by Charlie Hall on Jun 18, 2016 21:55:27 GMT
Hi Steve,
Interesting to see how they were trying to minimise distortion back then! Not what we want, of course.
Regards,
Charlie
|
|
|
|
Post by rogerbayliss on Jun 19, 2016 21:47:26 GMT
I have looked at two different amps with EF86 channels, one an AC15 circuit 3 clone, the other an early 60s Vox AC10 that has much the same preamp as the circuit 2 AC15 from 1959. The AC10 had 2 X 10" Elac speakers and it sounded wonderful for Apache. It had a bit more low end than the required sound for Wonderful Land which works better with the brilliance setting of the EF86 channel of a circuit 3 amp, or a top boost channel with the bass turned off, much as I had long suspected. The EF86 distorts much differently (very asymmetrical clipping ie, soft clips on one half of the signal much earlier than the other half) to the circuit 3 clone amp. I am close to replicating both sounds with solid state circuits. I have come to the firm conclusion that EQ, even multi band graphic EQ, is not anywhere near as effective as generating the correct harmonics and then fine tuning with relatively simple tone controls. EQ simply is not a substitute for having the right harmonics generated by the amp stage(s). So the final design(s) might not need such complicated EQ. I also might do a top boost channel emulation next. I am thinking it would be good to have all three channels in one unit. Such designs could be very useful for adding to an existing amp as a pedal in the chain, or as an additional device for recording purposes. Regards, Charlie That is interesting Charlie I would like to see that happen. I have the Wampler Thirty Something (which I had to send back for repair - now sorted) and the popular Caline AC30 pedal. The Thirty Something has a switch to select between the top boost type sound and the less toppy AC15 sound which over drives sooner than the Top Boost emulation. It has tone controls that seem to emulate the original Top Boost circuit tone behaviour as well. Brian Wampler has clearly worked at the dynamics of this pedal. The thing it probably does not quite crack is the Ef86 channel of the early AC15 / 30 amps. There is a gain control and also a Class A booster side to the pedal as well. I think you are right about the harmonic content and the bass cut in the brilliance circuit. The Wampler pedal does not cover the brilliance circuit behaviour as such as there is no bass cut other than turning the bass tone down. I think the overall EQ of the early Vox circuits without the brilliance circuit was a rather flat response, which is something you can approximate with a Top Boost by turning the bass and treble all the way down. The pedal does not come with speaker emulation by the way. It is designed to use with an amp. You can use it with a speaker cab emulator pedal though into PA etc. The Thirty Something pedal though is probably a good template for your thoughts on this and I hope you crack this one Charlie. It will be interesting ! |
|
|
|
Post by Charlie Hall on Jun 20, 2016 0:19:47 GMT
Hi Roger,
I didn't know Caline did an AC30 pedal. I only knew of the 10 band EQ. You are right that the EF86 is less toppy, but in comparison with the normal channel of the AC10 the EF86 positively had sparkle due entirely to the harmonics generated by it. I believe this is the missing ingredient of the Apache sound that is so hard to obtain.
I have heard a demo of the Wampler pedal on YouTube and liked what I heard as far as the transition from clean to overdriven was concerned.
The AC10 has a filter after the EF86 that is similar to the filter in my Cutting Edge pedal. This is because the EF86 on that amp has a tremolo effect. The brilliance switch on the later AC15 (circuit 3) removes a lot more bass, so much so that it is absolutely necessary to use the cut control to warm up the sound. The overall result is a mid heavy tone. This is why I think a complicated EQ won't be needed if it is done right.
The early Vox amps did have a flat response, except the brilliance channel that removes bass. The tremolo/vibrato channel removes bass too.
I think that turning the bass and treble all the way down approximates the brilliant channel ie. with bass removed.
I am wondering whether to include power amp emulation and speaker emulation. The whole thing will take a lot longer if I try to do that.
I have been doing some design work this evening. I use a computer simulation to design, which is what I did for the Hall & Collins preamp too. I think I am close to completing the design for the early EF86 (Apache) sound and just need to trim the gain a little, which is not easy as I don't want to affect the asymmetrical clipping that I have achieved. I'll do some more work on it later this week. I have already done the circuit 3 EF86 emulation, and will possibly fine tune it a little more when I finish the other.
Regards,
Charlie
|
|
|
|
Post by rogerbayliss on Jun 21, 2016 17:00:33 GMT
Sorry Charlie I meant Joyo AC Tone LOL
I mentioned this project to a friend of mine and he asked the question why does he not do an amp with these channels and designs. Maybe you are set on doing the pedal but have you considered maybe a boutique amp that covers these circuits ? Maybe a small practice sized amp?
You can get separate Cab sim pedals if need be if you do not already know that !
|
|
|
|
Post by Charlie Hall on Jun 21, 2016 17:08:42 GMT
Hi Roger,
I was thinking about just doing a 3 channel preamp but since the Vox cut control is in the power amp there would still have to be something that represents a power amp. Thanks for letting me know about the cab simulation pedals. I'll look into that.
I have made further progress with the "Apache" EF86 preamp.
Not sure I want to get into amp building again although I wouldn't have to do the building myself this time!
Regards,
Charlie
|
|
