Speakeasy Vintage Music Suitcase "Vintage Tub" Preamp

[lukevintage]

I have just picked up a Speakeasy Vintage Music Suitcase "Vintage Tub" Preamp and I'm really happy. Does anyone know how the Dyno Filter works? All the way counter clockwise, the volume drops slightly and the EQ becomes active, in the sense that EQ at 0 means there's no volume. This means the EQ can bring out the glass or broaden the wooden timbre. As the Dyno filter is turned counter clockwise, it sounds (to my ears) that the mids are being raised and the preamp EQ is dropping.
Could someone tell me how I should be using the Dyno filter and preamp?

The suitcase vibrato is quite different from the tremolo in a Fender Twin. I had always assumed they were one and the same, the only difference being stereo on the suitcase. What Leo Fender had named Vibrato on his amps was actually Tremolo; vibrato has a pitch shift. To my ears, I hear a pitch shift when I turn on the 'suitcase' vibrato as the left and right come into phase. Is this true only to this unit or is it true on recording a true suitcase?

[lukevintage]

Has anyone tried swapping the valves? Sometimes I can't resist messing with equipment.

[Jenzz]

Hi :-)

The Dyno filter has a kind of two-way signal path. 'Normal' mixes the unaffected signal to the output.

The other path runs into a fixed mid-cut, then into a passive Fender-style Bass/Treble network. Because of this, the volume can got to 0 when kompletely turned CCW. Anonthe buffer takes the signal to the output mix.

The stereo tremolo might give some impression of pitch shift / vibrato, because the signal source 'moves' in the stereo field.

Jenzz

[lukevintage]

Hi :-)

The Dyno filter has a kind of two-way signal path. 'Normal' xixex the unaffected signal to the output.

The other path runs into a fixed mid-cut, then into a passive Fender-style Bass/Treble network. Because of this, the volume can got to 0 when kompletely turned CCW. Anonthe buffer takes the signal to the output mix.

The stereo tremolo might give some impression of pitch shift / vibrato, because the signal source 'moves' in the stereo field.

Jenzz

Hello Jenzz and thank you for your post,

So I imagine the passive tone stack of mid scoop is comparable to a fender twin amp (as opposed to a Baxandall one).
I suspected they're might be a blending of two signals, where CCW on the dyno, the treble and bass would add to the dry signal. As it hits 12 o'clock, the relation becomes more apparent and the volume may need to be lightly adjusted. Full CW, the volume needs to be boosted.
As with other tremolo fx, IME a perceived volume drop occurs the more the intensity is increased.
IIRC, reverb goes before tremolo in traditional fender amp circuits. I would assume this is true for echo or other modulation, with the possible exception of the Roland Jazz chorus amp. Could anyone confirm this?

[lukevintage]

I have tried swapping the valves. The originals are russian made au7A from electro-harmonix. I put in some old unbranded and the change was minimal. Not as bright. A little more smoother perhaps. Nothing extraordinary to write home about.

[lukevintage]

I am a little concerned with the hum apparent with the Normal volume below 80%. It sounds like a ground interference. The manual says 80% is the dry signal volume, so perhaps anything below acts like attenuation. No idea, but it does annoy me a little. Especially so since there's distortion with the lower register. I run the preamp into a headphone amp (https://www.behringer.com/product.html?modelCode=P0184). I thought it might be an unbalanced output from the preamp but it isn't really a noise issue, more a signal distortion.
I'll try it into a sound card when I get the chance and see if the issue persists.