Two Stroke with Vibrato

[Handley]

Anyone ever add vibrato to your Two Stroke?

I really like the versatility of the Two Stroke but the addition of vibrato would add a big plus. I’m thinking something similar to the BF Vibrochamp but with the tweed tone.

I read somewhere that some of Clapton’s early recordings were done through a BF Vibrochamp with the tone stack bypassed giving it additional gain. I’m thinking I can add the vibrochamp’s vibrato section (adding a 12AX7 preamp tube) and get rid of the tone switch I can get by with the original build chassis and only do minimal drilling. I would also have to add an RCA plug for the foot switch.

Any thoughts?

[Robin]

I’ve shied away from any thing that adds length to the signal chain in the 2stroke but adding a tremolo or reverb circuit should be very do-able if you don’t mind sacrificing some dynamics. You could replace the tone pot with a 1meg pot w/ a push/pull switch for the tone control.

[Andy]

I love a great tremolo and reverb done right. There are a lot of variables and a great place to start is over at Merlin’s Valve Wizard site. The “cost” of doing it right is, in my estimation, a lot of tubes.

[Handley]

Here’s what I’m thinking of converting the Two Stroke to…

AA764 with Tweed Mod (bypassed tone section).
That means adding one 12AX7 to power the vibrato and getting rid of the input resistor/cap selector switch (which I don’t use). I would only need three pots on the front (vol, speed, intensity). Depending not the sound I may also mess with the Negative Feedback Loop i.e.. keep the Two Stroke values or make it switchable (on/off).

No power transformer changes and I would still get to keep the variable output (power tube swapping and speaker options) that I really make use of in the Two Stroke design.
Without the need to drive the tone pot of the amp I would add a touch of gain to the amp and I play through single coil or low output (TV Jones) pickups that would be nice.

Minimal chassis mods: add one tube socket and relocate the output jacks.
Still very similar to the tweed champ circuit.
Here’s the AA764 schematic showing removal of the tone section:
[attachment=105]vibrochamp-schematic.jpg[/attachment]

[Robin]

Please report how it works out.

[ArgStrat]

I have a similar plan that I have been working on. I started with the idea of converting a Tweed Vibrolux kit but that turned out to be too much unneeded parts so I am going to use the cabinet and chassis for the Vibrolux, the schematic for a Two-Stroke, and add the VibroChamp AA764 vibrato. After seeing the comments here I think I will add a switch to take it out of the circuit when I don’t want it so that I am in full Two-Stroke mode. I am also planning on adding additional switching to bypass the tone pot so that I can utilize it as a full blown Champ with the 8 inch speaker. I am a first time builder so I am looking forward to the challenge.

[Spooks]

ArgStrat

I will be building a 2 stroke amp when the gubbins arrives. Perhaps we can help each other as we go along.

[Robin]

Feel free to post questions, there are a number of experienced Two Stroke builders here that would be happy to help/ advise you. Good luck with your projects.

[Author]

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