New video : IT-11 Audio Supercharger Spring 70s

Eric Collet, from Mess Zero, is trying the new Supercharger Spring ’70s :

For more information, please see :

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Buffer samples !

Many  “true bypass” pedals, or long bad quality cables can create problems such as dull sound, loss of tone …

In this case, you can try a buffer, or even two buffers : one at the beginning of the chain of pedals, one at the end. Listen and decide what sounds best to your ears !

Please note that Fuzz effects and vintage-style treble booster may sound awful when placed after a buffer !

In this video, I use a “bad cable simulator” I built for show how a buffer can help to deal with long cables and/or many true bypass pedals :

For more information, see :

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Ray Dolby passes away at 80

Ray Dolby, the US engineer who founded Dolby Laboratories and pioneered noise reduction in audio recordings, has passed away today in his home city of San Francisco aged 80. Dolby was born in Portland  (Oregon) 1933, where he spent many years working on audio projects before earning his Bachelor degree from Stanford in 1957. He grew up in the San Francisco area.

He began his career in the Ampex Corporation, helping to develop early videotape recording systems while he was still a student.

Ray Dolby’s  work included noise reduction systems for tape recordings, something that went on to greatly improve the audio experience of cinema and more. Later on, Dolby Stereo was created with multi-channel playback, bringing to movies both surround sound and center tracks for those with the proper audio setup. And again, not too long later, another innovation was launched, this time being Dolby Surround.

Ray Dolby had suffered from Alzheimer’s disease for several years and was diagnosed with leukaemia this year.

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IT-11 Supercharger Spring ’70s

Hey, a new Supercharger ’70s, this time with a nice spring reverb !

50W, 2 x EL34 cathode bias (no need to rebias it while on tour !)

Tubes  : 1 x 12AU7, 3 x 12AX7, 1 x EF86, 1 x 12AT7 and 2 x EL34

Here, with its nice 2×12 cabinet (one WGS Veteran 30 and one amazing WGS BlackHawk Alnico) :

Video samples :

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Silverface Fender Bassman 100

A Bassman 100 on the bench.

Missing PT (burnt, I suppose …)


Thanks to for the layout, thanks to Chris A. for pointing out an error

This model of Bassman was made from 1972 to 1976. This one seems to be from 1975 (Schumacher date code 606-5 … on the OT) :

OK, once the new PT is in place (a Hammond 290FEX) and the four 6L6GC changed, time to rebias this thing. On this model, there is a balance bias pot and not a “real” pot to set the bias. Balance bias is easy : the minimum hum, the better !

Unfortunately, this does not allow to set the current bias, and on this Bassman, the current was as low as 18mA (for 440V to the plate). So I replace the 15k resistor by a 1k “security” resistor and a variable resistor (a 50k I had, but a 20k should be even better) :

Before :

After :

Hence, I can set balance AND bias !

I replaced the 40 years old Mallory caps (I keep them, maybe someday I will try to reform them ?)

I noticed a wire going … nowhere ! Soldered at one end, cut at the other end ! A previous mod ? A “factory” mistake ? Anyway, I removed it (and the amp works well after having serviced it)

New caps …

Another small issue : a very nice blue light in a 7025 tube :

Air inside (and the getter is half gone, btw) : little break in the envelope … and one of the triode does not work (bass channel does not make any sound) :

Didn’t have any 7025 left, so I used a JJ 12AX7 “V1″ (low noise)

Anyway, the baby can sing again !

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IT-11 ActivABY Box

A new product from IT-11 (see : active ABY Box.

My client ordered this to send his signal to 2 amps. Each output has its own JFET buffer to prevent loss of definition of the signal / sound (high impedance presented to the pedal board, low impedance output to amp : very usefull when long cables are used on stage).

And you know what ? Playing with 2 amps makes definitely pretty cool sounds !

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New ! The Highwayman Route 88

Same as the Highwayman, but with more meat !

Please go to the Highwayman Route 88 page

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Simple buffer !

Two very simple buffers prototype : one based on a 2N5457 J-FET transistor, the other with a Burr Brown OPA 134. No really differences between the two pedal, maybe the one with IC is lightly brighter … hard to say.

Switches :

  • switch on the right is simply Buffer On / Buffer Off (to test with or without ;-))
  • switch on the left insert a 6.8k resistor to “emulate” a guitar pick-up. Not a very accurate simulation, but it helps when buffer is in front of a fuzz face, for instance !
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Maxon treble booster … “untrebled” !

I had this ’70s Maxon Treble Booster somewhere in a drawer … While I like very much Range masters TB, I don’t like this one, it sounds terrible to my ears.

I redrawn the (very simple) schematic :

With 2.2nF coupling caps and 47 / 50k resistors, the roll off point is about 1500Hz … verified with PSPICE simulation :

Inside the box :

So replacing the 2.2nF coupling caps by 470nF (or 1uF) will flatten the bandwidth :

Here it is ! Just perfect with my ’66 Mustang !

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12″ guitar cabinet – vented

It’s a cab equipped with a great WGS Reaper 55Hz speaker !

  • 600mm x 408mm x 290mm
  • Vented (70Hz)
  • Speaker : WGS Reaper 55Hz – 30W
  • Wood : 18mm / 12mm

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