Wednesday, June 20, 2018
A 9V electron tube guitar preamplifier with the 13CW4 Nuvistor
The 13CW4 Nuvistor electron tube, vacuum tube or electronic valve should make a space age electric guitar preamplifier operating with just a 9V battery.
An anode follower circuit can be used. So just a load resistor at the anode. A coupling capacitor to the control grid. An output coupling capacitor from anode. A Pleiades bias resistor from anode (plate) to grid so that electrons are free and operation can be possible at just typically 6V at the anode or Vb=9V.
The heaters can be underheated at such low anode voltage. 9V would be great. So everything can be lowered by just a 9V battery.
Battery drain should be about 70mA.
Reduced cathode temperature has beneficial results to sound and low noise. See previous euroelectron posts and of course the Neumann U47 schematic with the underheated VF14 Telefunken electron tube.
Everything can be put inside an MXR type die cast aluminum box. A Hammond manufacturing color die cast box should be great.
If an XLR to 1/4in input transformer and a 1/4in to XLR output transformer are used we have a space age electron tube microphone booster amplifier of exceptional quality and ultra low noise.
These circuits are in class A meaning electrons are flowing all the time. Distortion tending to 0 as the input signal tends to 0. Distortion gradually increasing as the output signal approaches the power supply rails.
So far from Nuvistor types the 7586 electron type has been tried with amazing results on the Pleiades V6 circuit.
So an 7586 can definitely be used as a guitar preamplifier too with a li-ion 3.8V battery.
A fuse should always be used in series with the battery holder for safety.
Great battery holders are by Bulgin.
Below is the full balanced in balanced out schematic for using a microphone, ribbon, moving coil, condenser etc. An electric guitar or bass or synth would not need an input or output transformer. So the schematic is simplified to Pleiades V4.
For a great 1 transistor power amplifier see the previous euroelectron post.
Pleiades circuits and concepts are open source.
References:
Neumann U47 schematic
Pleiades V6 schematic
On preserving transconductance of electron tubes at an anode potential as low as 3 volts - euroelectron
Operating features of the Audion - E. H. Armstrong
A one transistor amplifier should make a great guitar or bass amplifier
The Pleiades 2N3053 has been tried with a 12 in vintage Philips full range speaker.
Excellent dynamic and liquid sound.
A preamplifier was needed.
The Pleiadss V5 electron tube operating with 2 li-ion batteries was used with excellent sound.
One transistor amplifier from record player cartridge to loudspeaker?
At your own risk.
By taking inspiration from the books at the reference and the fabulous Dansette Bermuda vintage record player which uses one UL84 electron tube from crystal cartridge to loudspeaker...It sounds so alive. It was used by Mike Oldfield when he was a kid [BBC]. He must have learned a lot from such an immediate reproduction to just one point source loudspeaker.
It may be possible to use a good quality crystal or ceramic cartridge driving a small JFET. At the drain is connected an 800Ω loudspeaker such as Philips AD5046N. The other terminal of the voice coil is connected to battery + through a few milliampere fuse. Or using a step down impotence transformer. See also the Pleiades 2N3053. The 2N3053 is very suitable for a line out output of low impedance and it works very well if we include a series variable resistor to base which can be used as a volume control. The Pleiadss 2N3053 with the Philips AD5046N even with just 8mA quiescent current can sound amazing and fill a room and even much more area with a so natural sound. For a crystal cartridge we need a JFET for its high input impedance property. It might be possible to connect a bipolar transistor such as RCA 2N3053 by using a high impedance series input circuit. More experiments needed.
Piezoelectric cartridges are constant displacement ttansucers for constant voltage output like condenser mocroohine capsules. Moving coil ttansucers are constant velocity for constant voltage output. Therefore most of the RIAA EQ is there.
So just a Pleiades amplifier possibly a few resistors and a battery. Using a fuse in series with the battery is very important for safety.
References:
Mike Oldfield Tubular Bells documentary - BBC - YouTube
Transistor audio amplifier manual - Clive Sinclair - page 6 - Bernard's radio manuals (full of transistor amplifiers where the load is the voice coil itself)
Audio Amolifiers - J. R. Davies - page 41 - Data Publications (it contains the brilliant K. Jones circuit where the voice coil itself is the collector load).
Semiconductors Handbook Volume 2 - page 100 - Piblishers De Muiderkring NV Bussum Netherlands (many class A one transistor circuits including at keystone with the voice coil the collector load itself and bias from collector to base)
When there is choice between money or fame...
The choice is very easy and simple.
No money, no fame.
Usually these things seem to come free. But there is a price to pay.
No money, no fame.
And then the world is yours.
It has always been.
Bibliography:
Enchiridion - Epictetous
Subscribe to:
Posts (Atom)