A 1948 Supro with some fuzz and speaker heat issues
I have a question for you. Recently, I was given an old Supro amp. As far as I can tell itās a 1948 model, all-original except for the power cord, which I replaced. There are no model numbers on the amp. Of course, itās an all-tube amp, with what appears to be a 10" speaker, two inputs, an on/off toggle switch and a 2-amp fuse. When I turn on the amp, it fires fine and sounds pretty good. After itās been on for about 10 minutes, it starts to lose a little volume, but the sound just gets better ā¦ sort of a nice fuzzy, bluesy sound. I noticed last night that the speaker frame was getting hot (after about an hour of playing). Is this normal for an old amp like this? Is it okay to use it without fear of it āblowing up?ā The amp is in excellent condition except for the handle. Any idea what the value of this amp might be? Also, I was thinking of replacing the transformer with one of the new ones on the market. Would it be worth doing? Thanks for your time, and I hope you have a great day. Love your articles in Premier Guitar.
Jim Edens
Hi Jim,
I donāt know that Iāve ever worked on that particular model amp, but from the research Iāve done it looks to be a very cool amp. It seems that there are quite a few different versions of the amp, but the common thread appears to be a bottom-mounted chassis with inputs and controls accessible from the lower rear. The speaker is mounted above the chassis and could have been either a Jensen or a Rola, the latter of which came in PM (permanent magnet) or field coil versions. Iād have to assume that the field coil version would have been the earliest version of the amp, as the field coil speaker predated the PM speaker. (Just FYI, in a field coil speaker, the magnetism needed for the operation of the speaker was generated by running the B+ (high voltage) of the amp through a coil on the rear of the speaker, essentially turning it into a large electromagnet.) The tube configuration in these amps seems to change as well. While all of the versions utilize a 5Y3 rectifier tube, the preamp section consisted of either a single 6SL7, or a 6SC7 along with a 6J7. Also, from the information Iāve seen itās possible that the amps were built using either a single 6V6 for the output stage, or two 6V6s in a parallel single-ended design. Thatās it for the history of the amps. Now letās get to your questions.
You mention that the amp loses some volume and starts to sound a bit fuzzy/bluesy after approximately 10 minutes of operation, and that the speaker frame was getting hot. Remember that the speaker is mounted directly above the entire chassis. On that chassis are the mains transformer and anywhere from three to five tubes, with an output stage running in Class A mode. This in and of itself is probably enough heat to warm the speaker frame, but excessive heat could be the tell-tale sign of a problem. The symptom of the amp dropping in power and becoming ādirtierā is a somewhat typical sign of an output tube thatās shorting internally once it gets nice and warm. This produces a substantial amount of extra heat that would add to the warmth of the speaker frame. There may be, however, an additional cause.
If the speaker is of the field coil variety, the excessive current that the malfunctioning tube is consuming is being pulled straight through the coil windings on the rear of the speaker. This may not only cause the coil to produce additional heat, but could be bad for the longevity of the coil as well. It can also cause the mains transformer to run warmer than it typically would. With that diagnosis in mind, I would suggest replacing the 6V6 output tube(s) and see if the performance of the amp is improved. If it continues to lose power and become buzzy, Iād have it looked at by a local tech to see if the filter caps need to be changed. The only reason I wouldnāt tell you to just have them replaced is that you mentioned the amp was almost 100 percent original. Since itās functioning rather well, replacing the caps may reduce the value of the amp on the vintage marketāshould you, of course, decide to sell it.
Which brings me to your question regarding the replacement of transformer(s). While there appears to be replacement transformers made for these amps, and installing one could improve the sound of the amp, the vintage value of the amp would be compromised. The decision should be based on tone vs. value. If you plan on keeping the amp and making it the best it can be, Iād say go ahead and try it. In my opinion, youād probably get a bigger bang for your buck by replacing the speakerā almost always the weak link in older amps. Just remember, if the speaker is the field coil type, youāll need to install a choke to take the place of the magnet winding, as itās an integral part of the power supply. I hope this will help you make your Supro amp super.
Jeff Bober
Jeff Bober, Godfather of the low wattage amp revolution, co-founded and was the principal designer for Budda Amplification. He can be reached at pgampman@gmail.com.
An amp-in-the-box pedal designed to deliver tones reminiscent of 1950s Fender Tweed amps.
Designed as an all-in-one DI amp-in-a-box solution, the ZAMP eliminates the need to lug around a traditional amplifier. Youāll get the sounds of rock legends ā everything from sweet cleans to exploding overdrive ā for the same cost as a set of tubes.
The ZAMPās versatility makes it an ideal tool for a variety of usesā¦
- As your main amp: Plug directly into a PA or DAW for full-bodied sound with Jensen speaker emulation.
- In front of your existing amp: Use it as an overdrive/distortion pedal to impart tweed grit and grind.
- Straight into your recording setup: Achieve studio-quality sound with easeāno need to mic an amp.
- 12dB clean boost: Enhance your tone with a powerful clean boost.
- Versatile instrument compatibility: Works beautifully with harmonica, violin, mandolin, keyboards, and even vocals.
- Tube preamp for recording: Use it as an insert or on your bus for added warmth.
- Clean DI box functionality: Can be used as a reliable direct input box for live or recording applications.
See the ZAMP demo video here: https://www.youtube.com/watch?v=xJp0jE6zzS8
Key ZAMP features include:
- True analog circuitry: Faithfully emulates two 12AX7 preamp tubes, one 12AX7 driver tube, and two 6V6 output tubes.
- Simple gain and output controls make it easy to dial in the perfect tone.
- At home, on stage, or in the studio, the ZAMP delivers cranked tube amp tones at any volume.
- No need to mic your cab: Just plug in and play into a PA or your DAW.
- Operates on a standard external 9-volt power supply or up to 40 hours with a single 9-volt battery.
The ZAMP pedal is available for a street price of $199 USD and can be purchased at zashabuti.com.
You may know the Gibson EB-6, but what you may not know is that its first iteration looked nothing like its latest.
When many guitarists first encounter Gibsonās EB-6, a rare, vintage 6-string bass, they assume it must be a response to the Fender Bass VI. And manyEB-6 basses sport an SG-style body shape, so they do look exceedingly modern. (Itās easy to imagine a stoner-rock or doom-metal band keeping one amid an arsenal of Dunables and EGCs.) But the earliest EB-6 basses didnāt look anything like SGs, and they arrived a full year before the more famous Fender.
The Gibson EB-6 was announced in 1959 and came into the world in 1960, not with a dual-horn body but with that of an elegant ES-335. They looked stately, with a thin, semi-hollow body, f-holes, and a sunburst finish. Our pick for this Vintage Vault column is one such first-year model, in about as original condition as youāre able to find today. āWhy?ā you may be asking. Well, read on....
When the EB-6 was introduced, the Bass VI was still a glimmer in Leo Fenderās eye. The real competition were the Danelectro 6-string basses that seemed to have popped up out of nowhere and were suddenly being used on lots of hit records by the likes of Elvis, Patsy Cline, and other household names. Danos like the UB-2 (introduced in ā56), the Longhorn 4623 (ā58), and the Shorthorn 3612 (ā58) were the earliest attempts any company made at a 6-string bass in this style: not quite a standard electric bass, not quite a guitar, nor, for that matter, quite like a baritone guitar.
The only change this vintage EB-6 features is a replacement set of Kluson tuners.
Photo by Ken Lapworth
Gibson, Fender, and others during this era would in fact call these basses ābaritone guitars,ā to add to our confusion today. But these vintage ābaritonesā were all tuned one octave below a standard guitar, with scale lengths around 30", while most modern baritones are tuned B-to-B or A-to-A and have scale lengths between 26" and 30".)
At the time, those Danelectros were instrumental to what was called the ātic-tacā bass sound of Nashville records produced by Chet Atkins, or the āclick-bassā tones made out west by producer Lee Hazlewood. Gibson wanted something for this market, and the EB-6 was born.
āWhen the EB-6 was introduced, the Bass VI was still a glimmer in Leo Fenderās eye.ā
The 30.5" scale 1960 EB-6 has a single humbucking pickup, a volume knob, a tone knob, and a small, push-button āTone Selector Switchā that engages a treble circuit for an instant tic-tac sound. (Without engaging that switch, you get a bass-heavy tone so deep that cowboy chords will sound like a muddy mess.)
The EB-6, for better or for worse, did not unseat the Danelectros, and a November 1959 price list from Gibson hints at why: The EB-6 retailed for $340, compared to Dano price tags that ranged from $85 to $150. Only a few dozen EB-6 basses were shipped in 1960, and only 67 total are known to have been built before Gibson changed the shape to the SG style in 1962.
Most players who come across an EB-6 today think it was a response to the Fender Bass VI, but the former actually beat the latter to the market by a full year.
Photo by Ken Lapworth
Itās sad that so few were built. Sure, it was a high-end model made to achieve the novelty tic-tac sound of cheaper instruments, but in its full-voiced glory, the EB-6 has a huge potential of tones. It would sound great in our contemporary guitar era where more players are exploring baritone ranges, and where so many people got back into the Bass VI after seeing the Beatles play one in the 2021 documentary, Get Back.
Itās sadder, still, how many original-era EB-6s have been parted out in the decades since. Remember earlier when I wrote that our Vintage Vaultpick was about as original as you could find? Thatās because the modelās single humbucker is a PAF, its Kluson tuners are double-line, and its knobs are identical to those on Les Paul āBursts. So as people repaired broken āBursts, converted other LPs to āBursts, or otherwise sought to give other Gibsons a āGolden Eraā sound and look ... they often stripped these forgotten EB-6 basses for parts.
This original EB-6 is up for sale now from Reverb seller Emerald City Guitars for a $16,950 asking price at the time of writing. The only thing that isnāt original about it is a replacement set of Kluson tuners, not because its originals were stolen but just to help preserve them. (They will be included in the case.)
With so few surviving 335-style EB-6 basses, Reverb doesnāt have a ton of sales data to compare prices to. Ten years ago, a lucky buyer found a nearly original 1960 EB-6 for about $7,000. But Emerald Cityās $16,950 asking price is closer to more recent examples and asking prices.
Sources: Prices on Gibson Instruments, November 1, 1959, Tony Baconās āDanelectroās UB-2 and the Early Days of 6-String Bassesā Reverb News article, Gruhnās Guide to Vintage Guitars, Tom Wheelerās American Guitars: An Illustrated History, Reverb listings and Price Guide sales data.
Some of us love drum machines and synths, and others donāt, but we all love Billy.
Billy Gibbons is an undisputable guitar force whose feel, tone, and all-around vibe make him the highest level of hero. But thatās not to say he hasnāt made some odd choices in his career, like when ZZ Top re-recorded parts of their classic albums for CD release. And fans will argue which era of the bandās career is best. Some of us love drum machines and synths and others donāt, but we all love Billy.
This episode is sponsored by Magnatone
An '80s-era cult favorite is back.
Originally released in the 1980s, the Victory has long been a cult favorite among guitarists for its distinctive double cutaway design and excellent upper-fret access. These new models feature flexible electronics, enhanced body contours, improved weight and balance, and an Explorer headstock shape.
A Cult Classic Made Modern
The new Victory features refined body contours, improved weight and balance, and an updated headstock shape based on the popular Gibson Explorer.
Effortless Playing
With a fast-playing SlimTaper neck profile and ebony fretboard with a compound radius, the Victory delivers low action without fret buzz everywhere on the fretboard.
Flexible Electronics
The two 80s Tribute humbucker pickups are wired to push/pull master volume and tone controls for coil splitting and inner/outer coil selection when the coils are split.
For more information, please visit gibson.com.