Comments on: The Field-Coil Guitar Amplifier

By: mike ginter

mike ginter — Wed, 22 Jan 2020 14:22:53 +0000

In reply to koruptdj. yes lowering fc dc voltage allows for lower volume but retains the tone.

By: Steve Carey

Steve Carey — Sun, 21 Jan 2018 14:35:28 +0000

In reply to koruptdj. check the patent granted to FluxTone speakers

By: Carter's father

Carter's father — Mon, 18 Jul 2016 03:09:36 +0000

Just “Found out” about field coil speakers this month. When I was a wee lad, I used to knock the heck out of alnico speakers to extract the excellent magnet I would play with for months, hence I had a hidden bias against the Field Coil variety of speaker (a big disappointment, No magnet ! %$*!@#! Fast forward several years, and I starting to play guitar in rock bands, still within the prevailing Perma Magnet culture. Now Middle aged (to say the least), and bought a vintage Valco Supro…
What a Sound !!!! Still have my garden variety Marshall, but the Valco Supro with the field coil speaker brings some incredible tone that can’t be had by any ‘Modern’ amp, it’s like comparing an apple to an orange really.
My strong suspicion that the field coil speaker is responsible for the great tone and dynamic range is ‘Amplified’ ( hehe ) by this articles conclusions. Thanks for putting together that great amp, and the fantastic description of your build, and final test of the cool little amp ! I am going to actively seek out amps with field coil speakers from now on. Once again, Thanks!

By: chris

chris — Thu, 31 Jan 2013 04:05:01 +0000

In reply to Holt. no picks.

By: Holt

Holt — Thu, 31 Jan 2013 03:51:10 +0000

You play with a thumb and fingerpicks?

By: chris

chris — Thu, 31 Jan 2013 01:58:22 +0000

In reply to Craig.

hi craig. yes i think it’s always a good idea to run the screens at a slightly lower voltage. I honestly don’t know where I got that idea but I’ve certainly stuck to it.

regarding the demo: that’s just a single live gtr pass, no FX. I play lead and rhythm at the same time. usually in Drop D but this example is in standard tuning. c.

By: Craig

Craig — Wed, 30 Jan 2013 23:17:33 +0000

I’ve got a Gibson BR-6f field coil and have always dug the compression, and it really does sound SE – if not pushed. Also uses a 6SJ7 pentode preamp. With the low voltages in the driver & preamp & no cathode bypass on the power tubes, it would have to be harmonica heaven – they also use a local FB loob from the plates of the power tubes > 500k resistor to the plates of the paraphase inverter! I understand these were made for schools, and probably took forever to wear out tubes no mater how hard they pushed it – although the 6V6 are biased pretty hot with only a single 200 ohm & 300 V on the plates & screens, I lowered the screens to 285

GibsonBR-6fschematic on photobucket MOD01

Very cool riff in your bridge demo, are you thumpin the bass note AND picking the other lead riff at the same time? Man I hope for my sake the bass note is a loop, I don’t think I could do – even with many, many hours of dedicated practice

By: Supro Supreme Gtr Amp Overhaul | Preservation Sound

Supro Supreme Gtr Amp Overhaul | Preservation Sound — Mon, 30 Jul 2012 10:14:19 +0000

[…] that I scratch-built a few years back as part of my ‘Field Coil Guitar Amp’ article. Click here for that earlier piece, which contains links to the schematic as well as lots of information what makes these early Supros […]

By: chris

chris — Thu, 07 Apr 2011 00:38:54 +0000

In reply to koruptdj.

Absolutely. There was a dude in the UK a few years ago who was making a marketing guitar amps that used lower-voltage, higher-current fields, and the amps had a knob to adjust the field voltage. the result is basically that the speaker had infinitely variable efficiency – so you could truly get the ‘cranked’ sound of the amp at ANY volume. simple, efficient design. i cannot seem to find evidence of this guy any longer… maybe one of you readers can help?

By: koruptdj

koruptdj — Thu, 07 Apr 2011 00:23:02 +0000

Sounds great man. Just wondering if a modern implementation of FC speakers could yield an additional control for amp builders? Would it be useful say to adjust the DC FC voltage for a different response if so desired?