mid 70s twin reverb as an all purpose amp

[Wasnex]

I'm pretty fortunate myself I picked it up for $26 from a yard sale over the weekend. I took the front cover off and noticed the speakers were blown so I put a fender speaker from a Princeton I had laying around and threw in one side of it and the amp seems to work fine although I don't know how to operate the vibrato nor do I know what it does this is all still relatively new to me

Nice bargain.

The output transformer should be 4 ohms. Best to show the amp the expected load.

The Reverb is normally on. You need a pedal to turn it off. The Vibrato is normally off. You need a pedal to turn it on. You can also use a shorting plug.

Vibrato is pretty much just a fluctuation in the volume, so the correct term is tremolo. It's a nice effect, but not something you hear very much anymore.

The Vibrato uses an optoisolator in the vibrato/tremolo circuit.

There are various names for this device but it is essentially a light dependent resistor (LDR).

An oscillator drives the light with a fluctuating voltage. The variation of light intensity changes the resistance of the cell. One side of the cell is connected to ground and the other is tapped to the signal path in the preamp. By varying the resistance it changes how much of the signal is shunted to ground, so you get a change in volume that corresponds to the frequency of the oscillator. The LDRs are fairly prone to failure.

 

[Auggieinks]

Wasnex ty

 

[thump54]

Totally ran a silver face 70’s twin through am Ampeg 2x15 back on the day as a stop gap til I could put together a conventional bass rig - plenty loud in a 4 piece rock band. Gigged it for 6 months or so 3-4 nights a week!

 

[Jeff Scott]

For solo practice at home or for recording at low to moderately low levels I think a Twin is overkill power output-wise. I used to have both an early '70s Princeton Reverb Amp (with a same era Celestion G12M-70 in it) and a 1962 Concert Amp. Both were fine for the above needs, and as others have mentioned, with a real bass cab, can sound superb.

 

[Rip Van Dan]

what’s your guyses thoughts on using a twin reverb, the master volume type from the mid 70s, but before they welt ultra-linear, as a practice amp and recording amp for bass? and a very very ‘bazooka to a gun fight’ recording/live guitar amp.

i think it was joe osbourne and carol kaye who recorded all/most their bass lines through open back fender amps, and more contemporary scoundrels like mac demarco recorded the bass on his second and third album through a twin reverb on his sofa.

all have incredible incredible sound, and the twin to me seems like the perfect beast. and if i really fell in love with it as a bass amp, and i wanna gig as a bassist, i can just hook it up to a bass cab.

An absolute GREAT Guitar Amp, but running a bass through it at anything above bedroom practice levels, you'll blow the speakers out. Long ago, in 1959 if I recall correctly, Fender learned the fallacy of using open back cabinets for their bass amps. They put out a 410 bassman amp with open back cabinet and replaced speakers like crazy until they changed the description to "410 guitar amp". It was still labelled "Bassman" because it had become a huge hit with guitarists under that name and they wanted to keep that 410 going.

Problem with open back cabs is that bass speakers move a lot to reproduce those low bass sounds and without an enclosed or a ported (tuned port) cab the speakers can easily exceed their excursion design limits. Long ago I remember seeing someone post a video where they played their bass through an open back cab and you could literally see the cones start tearing and then come apart. Just about anything can be used as a bass speaker at bedroom practice levels presuming you are not trying to let other folks in the house know you are practicing. But using it at higher levels such as gig levels will tear those speakers apart quickly.

Just don't do it. Using it for a guitar amp, it is stellar. I played bass back in 11967 and '68 with a guitarist who used a Stratocaster into a 1965 Fender Twin Reverb (blackface), and it was killer! He would get pissed if we bumped his amp while the spring reverb was on though - sounds like a thunder storm.

 

[Wasnex]

Problem with open back cabs is that bass speakers move a lot to reproduce those low bass sounds and without an enclosed or a ported (tuned port) cab the speakers can easily exceed their excursion design limits.

Possibly a bigger issue (IMHO): Even if the driver can survive, it cannot efficiently reproduce low frequencies, because at low frequencies the front and back pressure waves largely cancel out.

If the wavelength is large compared to the baffle, then the frequency response drops by 6dB/oct (compared to a monopole speaker) due to mutual cancellation of front and rear sound.​

Ref:
Open baffle speaker pitfalls | Audio Science Review (ASR) Forum
Electro-acoustic models (linkwitzlab.com)

Increasing the size of the front baffle and depth of the cab lowers the frequency where the 6dB per octave rolloff begins.

 

[Iristone]

The head is the same as a Dual Showman so it's more than great. But I'd just get a Showman head and sealed cabinet for bass.

 

[pfschim]

+1 on using a Twin with a bass cab. As others have said, for best results use a bass cab and it's kinda heavy for a steady gigging amp.
Back in the day (early 70's) I used 2 Showman heads driving 2 2x15 JBL D140 loaded cabs as my main rig for a time. I have a Rivera era Champ that I use from time to time for a low volume tube amp. I also have a Studio Bass head (standalone, in a head case, not in its original 1x15 combo form) ... which is basically the same as the Super Twin (with some modest tweaks to the EQ section).

 

[Jeff Scott]

Possibly a bigger issue (IMHO): Even if the driver can survive, it cannot efficiently reproduce low frequencies, because at low frequencies the front and back pressure waves largely cancel out.

If the wavelength is large compared to the baffle, then the frequency response drops by 6dB/oct (compared to a monopole speaker) due to mutual cancellation of front and rear sound.​

Ref:
Open baffle speaker pitfalls | Audio Science Review (ASR) Forum
Electro-acoustic models (linkwitzlab.com)

Increasing the size of the front baffle and depth of the cab lowers the frequency where the 6dB per octave rolloff begins.

That was one of the good things about my Maggies when I lived in apartments. Once we moved into our house I got a Definitive Technology SuperCube II to cover the bottom octave and a half.

 

[Old Ozzie Guy]

what’s your guyses thoughts on using a twin reverb, the master volume type from the mid 70s, but before they welt ultra-linear, as a practice amp and recording amp for bass? and a very very ‘bazooka to a gun fight’ recording/live guitar amp.

i think it was joe osbourne and carol kaye who recorded all/most their bass lines through open back fender amps, and more contemporary scoundrels like mac demarco recorded the bass on his second and third album through a twin reverb on his sofa.

all have incredible incredible sound, and the twin to me seems like the perfect beast. and if i really fell in love with it as a bass amp, and i wanna gig as a bassist, i can just hook it up to a bass cab.

There was a twin from around that time that had 1 x15" JBL (K130?), the 15" was "an extended range mid", I played guitar (6str) in a band, whose bass player used one. He had a separate JBL 15" K140 in a ported box under it . Massive sound, rich harmonics, plenty loud, and with both 15" , a decent frequency response..

 

[Old Ozzie Guy]

There was a twin from around that time that had 1 x15" JBL (K130?), the 15" was "an extended range mid", I played guitar (6str) in a band, whose bass player used one. He had a separate JBL 15" K140 in a ported box under it . Massive sound, rich harmonics, plenty loud, and with both 15" , a decent frequency response..

He often played a pedal steel through it, and I saw him afew yrs later using it for a Juno 60(early Roland synth) must have padded input somehow, when using the synth.. Anyway, I believe there isn't much that wouldn't sound good through a twin..(depending on what U aim at sounding like!)

 

[TheSpinDoctor]

Can't speak directly to the original question, but have played through a Showman head into bass cabinets and later an open back Fender amp with 4x10. The Showman head and the Twin Reverb are the same circuit design, though the Showman lacked a reverb unit. The sound was particularly good with a Jazz bass. The rig got loud enough for most venues that I played. Not loud enough to stand up to a Marshall 100W rig for one guitarist and a Twin Reverb for the second guitarist when playing outdoors. The Fender 4x10 amp was barely passable for playing at church services while deployed to Kyrgyzstan. The speakers would chuff if I played aggressively or tried to get more than just audible with the guitars, keyboard, and drums. Important to remain very focused on technique with using an open back cabinet for bass.

 

[2thAche]

You haven't actually used one yet? That's kind of the biggest question mark 'cause you better love something that old and heavy.

 

[primusfan1989]

for low volume it should work fine. Unplug the internal speakers and hook it up to 4ohm bass cab (or two 8ohm) and it would have enough juice to play with a drummer

 

[JimmyM]

I used to own a 70s Twin before it got stolen, and it’s fine for recording because you don’t need need to crank it hard for a recording. But those speakers are going to fart out and blow if you try to do anything at any decent volume. There’s a reason you never see open back bass cabs. You could plug it into a separate cab for bass, but that defeats the purpose of a combo.

 

[OldogNewTrick]

The amp section in your Twin Reverb is identical to a Fender Dual Showman Reverb, which makes for one gorgeous bass amp.

As others have said, a Twin Reverb Combo with 2x12 JBL's is one really heavy lump of gear plus you still need a decent bass box.
Even I will play out on my Dual Showman only on very special occasions.

 

[Lowbrow]

I believe that old Plush bass heads are very much like Fender guitar amps — if you can find one

 

[Redbrangus]

I believe that old Plush bass heads are very much like Fender guitar amps — if you can find one

Plush made tube amps?

 

[beans-on-toast]

I bought a twin in the 70’s and had it for over 20 years. Good amp overall. I still kick myself for letting it go.

At times I ran a Hammond organ into it which has pleanty of low end. It worked well but the speakers have to be able to handle higher volume levels if you push it hard. The amp does distort when cranked.

 

[Blues Bass 2]

In 1974 my SVT head needed a little work so I borrowed a buddys 69 twin to power my Peavey 18 folded horn cabinet . It sounded great to my surprise and did the gig fine , I liked it . It weighed the same as my SVT head so it wasn't a pain to move back then . I was in my 20's though .