CurvyMama is a special preamp that will give flesh, curves and grit to harps and guitars…
It can also give nice thighs to skinny guitars !
In that aim, it features an original tone control and a germanium preamp.


CurvyMama by GuitarPoppa ; preamp/overdrive for harmonicaCurvyMama, 2022 model.

Main features

Gain control to get clean sound or overdrive with any mike.
Original tone circuit, improving the nuances
in the low medium and at the medium-treble junction.
  Optional medium notch filter for ceramic mikes

  Germanium NOS transistors in the output stage
to bring a mild and organic overdrive.
  Phase invert switch to minimize feedback issues.
  High level low impedance output.

Listen to samples

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 To order

1. Choose your filter option
2. Specify the shipping zone.
3. Click <Add to cart>.
4. Click ‘Cart’ on main menu, or keep on visiting.

Unchanged price
169 €

Preamp for harp, as described on this page.
• 5 basic controls :
drive, bottom, biting, contour, volume.
Phase invert switch.
• MidNotch
switch (free option).

The [S]cream

Shipping costs (by the french Post) :
France: 8 € — CE + Switzerland: 14 € — Other countries: 24 €

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Technical details

Universal input

• 500kΩ high impedance, friendly connectible on every source.
• Admissible level: 10mV to 500mV, adjustable by the Gain / Drive potentiometer.

Piezo or ceramic bullet pickups
(antiques: JT30, Green Bullet… neo-antiques: Superlux D112C)
• Nominal output level: 200 to 500mV, high impedance.
• Standard setting: gain between the minimum and 9h00;
• MidNotch filter on.
• NB: With the D112, the gain can be set higher because its output level is moderate.

Old or neo-vintage dynamic microphones
(Shure Control Magnetic, Shure 515, 588 switched to HiZ, … Bottle O Blues, Silverfish …)
• Nominal output level: 100 to 500 mV, medium or high impedance.
• MidNotch filter not usefull.
• Standard gain adjustment : between minimum and 10:00 am, depending on the mike.

Modern dynamic microphones
(Shure 55SH “skull”, 565D, SM57, SM58, Audix Fireball V …)
• Nominal output level: 10 to 30mV, low impedance.
• MidNotch filter not usefull.
• Standard gain setting: around 12h00…

Output level

Output volume potentiometer
Standard setting : around 13.00.

With these standard settings, the output levels in bypass mode and effect mode will be balanced.
Nominal output level : -15dBm (150mV).

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Tone controls

• Bandwidth and tone settings have been designed specifically for the harmonica.
• 3 controls : Bottom, Biting, Contour…

Bottom : the belly of the harp sound, at the junction of bass and low medium.
Biting : The global roundness or sharpness of the sound, according to the played styles.
Contour  : Carves symmetrically mediums and presence …

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CurvyMama by GuitarPoppa, NOS germanium transistors

New Old Stock transistors of the output preamplifier, with their bias trimmer/em

Output/Overdrive stage


• The output preamp uses two NOS germanium transistors.
• Germanium rounds out the sound, and brings a dynamic rendering.
• The grain and the volume are modulated in real time by the instrumental playing.


• The standard settings shown above set the preamp at the clean/overdrive junction.
• You can sweep with the Gain knob from a totally clean sound to a fuzzy grain.
• Overdrive depends a lot on the tone controls that operate upstream:

Guitar Poppa applies the principle that made the sound of vintage amps: the last stages saturate before the firsts, depending on the tone settings.

The overdrive adds its grain to a sound material already sculpted by the bottom / bite / contour settings.
The sound texture is thus more complex and diversified, with a less uniform or washed-out coloring.

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Auxiliary controls

Invert Phase switch : phase inversion in order to minimize the risks of Larsen and improve listening comfort on stage.

MidNotch switch (free option): This switchable filter, which can be ordered free of charge, attenuates the midrange around 1.5kHz, and softens the tone of old bullet microphones.

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Power supply

CurvyMama is powered by a 9V battery or an external 7 to 12V supply.
• Sound is typical with 9V, more dynamic with 12V, dirty and compressed with 7V.
• An internal electronic filtering eliminates common supply noises:
Hiss of switching power supplies, hum from transformer power supplies.
• Typical consumption with 9V: 8mA.

Like all germanium circuits, Curvymama gives its best sound after 5 to 10 minutes under power, when its internal temperatures have stabilized.

CurvyMama by GuitarPoppa, electronic card

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To know more…

Technical links

Technical sheet (downloadable pdf )

Contact Guitar Poppa

Audio links

Listen to samples


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