Friday, October 11, 2013

Liquitone B15 Flipster Custom 001

This week I have been building a turret version of the ROG Flipster. It is an FET-circuit designed to emulate the Ampeg SB-12 Portaflex. These amps are still highly sought after for use in studio recordings and can be heard on a lot of classics, especially a lot of the old Motown recordings.
I was under the impression it was based on the B-15, hence my mistake in the name. The design is courtesy of

A befriended bass-player (yes, bass-players have friends too!) ordered a Flipster kit at
to build inside a 19inch-rack (should be 482.6mm-rack in Europe but that just doesn't sound quite right.) He got stuck in the building process and asked me to rebuild it using a turret-layout. It also needed a new front-panel.

Here it is with the new panel in place;

I went for the aluminium with amber jewel-light and creme Dakaware knobs because I really liked that colour-scheme on my Tweed Deluxe;

I really enjoy designing turret layouts of FET-circuits because them being based on tube amp schematics with the tubes swapped for FET's it is very easy to design an elegant turret layout.
I used a relay for bypass switching because it enabled me to keep the wiring reasonably short and also enabled using a external footswitch;

Because the customer wanted to use it with the effects-loop on his bass-amp the input and output
are located at the back;

I don't have a bass-guitar or bass-amp so I could only test it with guitar, but I really liked it on guitar.
It is a very subtle pre-amp/overdrive. It doesn't really do medium or high gain like the Wampler Plexi-Drive, with which it otherwise has a lot in common, sound and schematics-wise.
The best I could describe the Flipster is a vintage low gain growl with good mid-range and subtle compression like you would find on tube-rectifier equipped amp. Very reminiscent of that growly Fender Bassman sound, which makes sense since the Bassman was what the early Marshalls where based on, the latter having the tube-rectifier replaced with a solid state-rectifier, and this way comes to full circle with the less compressed Wampler Plex-Drive as these are designed to emulate those early Marshalls.

Here is a demo I made this afternoon. Equipment used are the usual suspects; Squier Classic Vibe '60 Stratocaster into the B15 Flipster into the Plexi-style, 1971 100W Fane DEA100MKIV.

Edit June 2014; This particular unit was plagued by the noise issues this circuit has been know to occasionally have, even though I knew about this and tried to avoid it by careful planning the layout and components in the power-lines. I have bought back the unit from the customer to research the issue
and once I can make noise-free Flipsters I can start building them for you under licence of Runofgroove (which I've managed to acquire). There will be a stompbox version along with the 19 inch rack version,
and perhaps a two-channel version.

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