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Topic: SMS Spectrum Tube Preamplifier |
Brad Sarno
From:
St. Louis, MO USA
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Posted 17 Sep 2023 5:46 am |
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To celebrate our 20th anniversary since we launched the Steel Guitar Black Box tube buffer here on this forum, I wanted to do something I've always wanted to do, to make a no-holds-barred, hand-wired tube preamp with real spring reverb. We finally got the new Spectrum going this year.
The Spectrum is a culmination of all my years tweaking the old classic tube preamp circuit. I learned a lot in the early years of our Revelation Preamp, tweaking the voicing of the EQ, capacitor choices, etc. with the wonderful help and ears of Randy Beavers, Buddy Emmons, John Hughey and others. Much of that related to the shaping and range of control of the midrange, the midrange dip, the frequency range. Also influenced by a bit of inspiration from Dan Healy of the Grateful Dead, his mods and tweaks to Buddy Cage's steel amp and Jerry Garcia's guitar preamp, and his shared thoughts on a variety of aspects. All these inspirations and influences mixed with a bunch of my own basically amount to subtle tweaks and mojo and capacitor choices, resistor choices, etc that all add up to something new and unique. And this great forum was no shortage of brilliant minds and great ears and invaluably helpful insights too that helped feed my design work.
For the Spectrum Tube Preamp, these are some of the aspects I included:
- Hand assembled turret board
- USA stranded/tinned cloth (vintage style) hand-wired throughout.
- 100% tube (12AX7, 12AT7 reverb driver, 12AX7)
- Add a "Dwell" (reverb send level) control to the spring reverb to control the range from smooth to surfy
- Tubes accessible on the back, no need to open or remove the preamp from the rack
- 2 RU chassis, heavy steel faceplate, aluminum chassis
- Real Spring Reverb tank, external, connected by a cord (like a Fender Amp does it)
- VERY high voltages for the most depth and dimension you can milk from a 12AX7
- Extremely well filtered power supply, very clean DC, very 3D dimensional sounding
- Every single cap and resistor thoughtfully and consciously chosen for its character
- Simple controls: Gain, Bright switch, Treble, Mid, Bass, Dwell, Reverb mix, Master out
- BIG central ground bus bar across the circuit for great noise control
- Ships with a modern Accutronics 3-spring, medium decay tank
- Tweaked and refined reverb send and recovery circuit to expand the depth and richness of the reverb effect itself.
The Spectrum really stunned me. I knew what to expect, I thought. But the synergy and culmination of all the factors, the layout, the components, the voltage, it just does the classic tube preamp thing better than I could have dreamed. It's lush, sweet, responsive. I hand build each one myself here in my little garage/shop/factory with a lot of love and a LOT of hours.
And here's a very incomplete list of more great minds that have inspired and influenced me in this work.
Obeid Khan
Keith Hilton
Ken Fox
Derrell Stephens
Jim Evans
Jim Webb
Tim Marcus
TC Furlong
Randy Beavers
Mike Scaggs
Pat Quilter
Hartley Peavey
Craig Baker
Goodrich
Dave Beaty
Kenneth Cain
Last edited by Brad Sarno on 9 Oct 2023 1:37 pm; edited 1 time in total |
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Brad Sarno
From:
St. Louis, MO USA
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Bob Hoffnar
From:
Austin, Tx
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Posted 17 Sep 2023 6:24 am
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I got one to check out for my little studio and I’m blown away so far. The tonal shaping is amazing. But the unexpected feature to me is the ability to shape the tonal response to touch. Those mastering grade components the hands of a builder who understands them is on another level. There is a dimensional quality that is very elusive that the Spectrum absolutely has.
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Bob |
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Mitchell Smithey
From:
Dallas, USA
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Posted 20 Sep 2023 8:34 pm
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| Great to see a new product from Brad, I use his stuff every day. |
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Larry Dering
From:
Missouri, USA
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Posted 21 Sep 2023 6:40 am
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| Nice job Brad. Looks like a serious product. Should be very popular. |
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Bill Cunningham
From:
Atlanta, Ga. USA
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Posted 21 Sep 2023 5:49 pm
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If this tops the original SMS it will be great. The SMS was a my choice for a long time. Then, like most folks, I decided to try a new different direction. But lately I’ve been thinking I should dust off my SMS.
And very nice to see you pay homage to your peers/competitors. This is such a cool community. Once at a steel show, I listened to three famous steel builders talk shop until 3:00 AM!
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Bill Cunningham
Atlanta, GA |
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Justin Shaw
From:
Ontario, Canada
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Posted 22 Sep 2023 5:13 pm
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| This looks great! It's not for sale yet on your website I guess? I see the SMS without the dwell knob but not the spectrum up there. |
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Brad Sarno
From:
St. Louis, MO USA
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Posted 9 Oct 2023 1:46 pm
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Updated title. Oops. This is a PREAMP, not an AMP.
B |
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Brad Sarno
From:
St. Louis, MO USA
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Posted 9 Oct 2023 1:50 pm
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| Justin Shaw wrote: |
| This looks great! It's not for sale yet on your website I guess? I see the SMS without the dwell knob but not the spectrum up there. |
The Dwell is on the Spectrum mostly because the Dwell (aka reverb send level) affects the quality, smoothness, character of the reverb response. It doesn't affect duration, decay-time (dwell) as much as the name suggests. But it dramatically affects the smoothness. Low dwell is very smooth, plate-like. High dwell is fluttery, surfy.
It's not on the site because it's such a labor intensive build. I have a wait list of a dozen or so people, and I'm happy to add anyone to the wait list, no deposit, no commitment. Turnaround is currently about 8-9 weeks.
Also, they're intro priced at $1450 + shipping.
Brad |
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Brad Sarno
From:
St. Louis, MO USA
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Posted 9 Oct 2023 1:54 pm
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Don Mogle
From:
Round Rock, TX, USA
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Posted 9 Oct 2023 3:53 pm Spectrum
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Hey Brad,
That chassis looks fantastic! Exceptionally clean and tidy. Nicest lead dress I've ever seen!
Don |
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