The Fisher Space Expander Tube Spring Reverb - Racked
Greetings.
From the depths of Don One Sound in Brooklyn NY, iFixAnalog is proud to present one of the coolest spring verbs out there. Made famous by King Tubby, this IS the sound of classic dub.
I built this unit with everything I would personally want as a mix engineer. No corners cut. All parts selected are of high quality and sourced from reputable distribution here In the USA. The main issue with these units is the input/output impedance. Originally this preamp was meant to be driven by a tube stage and its output sent to another tube stage, basically to/from the "fx loop" or "tape loop" on a home stereo receiver. These units, in their original state, can be problematic interfacing with modern gear causing gain or frequency response issues. The Jensen input and Edcore output transformers I installed solves this problem fully, providing a balanced/unbal input at 13K Ohms and a floating 600 ohm balanced output.
By adjusting the ratio between the input and feedback resistors, I was able to achieve a fixed 12 db boost in input gain with no increase to the noise floor (this is the infamous King Tubby "boost" mod). This thing is screaming loud. 1 volt @ 1K = 4.6v of pure spring reverb output. The power supply rebuild and full re-capping brought the noise floor down to below factory specs. This unit is very usable and sounding great!
Two of the tubes are the original tubes made by Telefunken and labeled for Fisher. The third tube is an NOS RCA tube. This was the best combo for noise and tone. I have the third original Fisher/Tele tube which will be included in the sale. The RCA simply sounds better to me.
I struggled with where/how or if I should mount the tank. Mounting it inside the chassis would require an abnormally deep chassis, which I did not like the idea of. The front panel mounting is the best solution. The tank is easily accessible for the classic "crash" sounds and is also easily removable (4 screws), if desired. Rubber feed thru grommets were employed to isolate the tank from the chassis mechanically and electrically.
This unit should provide decades of trouble-free use. If you are wondering why I am selling it...... I built two........
The service manual and schematics are all readily available online. Power cord included.
Upgrades & Modifications:
1. 3U powder-coated rack mount chassis (grounded for safety)
2. XLR input/output
3. Audio ground lift switch
4. IEC power entry module with EMI filter
5. 500mA fuse
6. Power switch
7. 120VAC indicator LED
8. New Hammond power transformer, filter caps and rectifier
9. All electrolytic caps replaced
10. Fixed 12 db input gain boost mod with input trim potentiometer
11. HPF cutoff frequency adjusted
12. Jensen input transformer (13K ohms)
13. Edcore output transformer (600 ohms)
14. Front panel mounted tank. Removable
15. Canare Star-Quad for all audio signals
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Listed | 5 months ago |
Condition | Excellent (Used) Excellent items are almost entirely free from blemishes and other visual defects and have been played or used with the utmost care.Learn more |
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