spring reverb, stereo connections

[benidubber]

hi!
do you think it might be possible to have a "stereo" effect listening 2 spring reverb tanks in a stereo channel, if they are sharing the same mono input?
I was thinking to use the same type of spring rev tanks for L & R, so i wonder if the little difference between one and the other would be enough for a stereo effect.
bye
sandro

 

[sahib]

I can not predict hundred percent but if both channels of the reverb are on the same phase I don't think so. In order to create a psuedo stereo out of a mono signal, one channel needs to be subtractive which creates the opposite phase response of the other channel. If I remember correctly Audi Handbook from National should have couple of reverb circuits like that. I should also have few psuedo stereo circuits using allpass somewhere. The problem is that I shut down part of my building and all of my books are boxed and stacked on the ground floor. So I don't think I can do that very soon.

 

[QUEEF BAG]

i haven't messed with springs, but my thoughts are - yeah probably.

EMT plates have one driver and two pickups for stereo,
they are not placed in a symetric fashion on the plate to catch different
reflections (i couldda put that better, but you probably know what i mean)

two springs with slightly different tension and possibly length may have a
similar affect. 

 

[abbey road d enfer]

No reverb springs are equal, ther's always some difference. I've done it a number of times, feeding two springs with the same signal gives a convincing width.

 

[inputoutput]

I did this to a Tapco 4400, with great success.

 

[benidubber]

happy to ear that!
great, thanks guys,
so I'll buy a second spring rev and enjoy fake stereo reverberations..
bye
sandro

 

[clintrubber]

Don't know if this D&R box reads both its springs in opposite polarity or not, but it sounds mighty fine (be it a bit on the noisy side).

http://www.d-r.nl/dnrsite/Service%20Parts/Reverb-Spring-Service.PDF

(Also note the way they drive the springs for higher bandwidth)

You could try a polarity-switch for one of the springs for increased possibilities. Or cascade both channels for increased ... or read one channel after one, the other channel after two sections.... or... and ... etc !

Enjoy

 

[PRR]

> springs in opposite polarity or not

Spring reverb does not have polarity. It is a significant delay (~~ a hundred mS), and no two springs will be identical. Mix 'em with each other, or with the dry signal, it comb-filters, but so densely that we don't hear "Wah-pedal" or "flanger". (Until you get to the too-too-short BBD chips which are more flange than reverb.)

> this D&R box

Very sexy reverb recovery stage. Differential parallel-device. Maybe because the power transformer is too close to the reverb tank?

 

[clintrubber]

> this D&R box

Very sexy reverb recovery stage. Differential parallel-device. Maybe because the power transformer is too close to the reverb tank?

My guess would be for noise. I don't exactly recall the internal layout, but it's a pretty deep box. So at least they could have kept the powTX & recovery stage well away from each other.
The unit can be a bit noisy though (depending on the settings of the subsequent internal semi-par EQ), so maybe they thought we need to do a hybrid recovery-stage & then simply went for their mic-preamp design.

Regards

 

[abbey road d enfer]

That's a quite surprising approach, because the Accutronics units are available in all sorts of impedances; in particular, the sensing element is availble in a nominal 2575 (sic) ohms version, which makes it ideal to mate with a basic 5534 with a very low noise factor. The D&R topology is optimised for lower impedance like a microphone, so they may have chosen the 600 ohms nominal sensor. But in fact the impedance at 7-10kHz is much higher (4-5 kohms), so the recovery amp noise factor is not that good (which seems to be ascertained by clintrubber). There is no low-pass filter in the output to tame that noise, and in fact there is not much usable signal above 8kHz from the tank.
I'be always found useful to load the sensor coil with a cap tuned to the highest useful frequency; that improves HF response AND noise performance.
When I see this schematic, I cannot help thinking: why make it simple when you can make it complicated?