Vetical versus horizontal reverb tank orientation

[Wally]

I finally got to hear the difference when a tank is installed in a situation that doesn't fit it's design. I got in a '72 Pro rEverb...little dirty and blowing fuses. A filter cap was shorted....all e-caps then replaced. The amp is original and cleaned up to near dead mint condition, so I didn't do any modifications to it. I even left the bias circuit as is. The new JJ's sat in there at 49.6% of max plate disspation...so that is good to go this owner.
When I got the chassis back in the cab and heard the reverb, I was disappointed. I pulled the tank and to my amusement there sat what looked to be an OEM tank....but it is the wrong model. It is a 4AB3C1C instead of the 4AB3C1B that should be in this FEnder, The difference is that the last 'C' in that model number indicates a tank that was built for a vertical mounting while the 4AB3C1"B" is built for horizontal mounting installations. The reverb was shallow and weak with a very quick decay. I oriented the tank in a vertical plane and Voila! there was that wet and warm Fender tube reverb that most of us love so much.
I had never before heard the difference even though I knew that tanks were built for specific applications. Now I know that indeed a vertical tank does not function well in a horizontal plane.

 

[blowtorch]

That is interesting, thanks for that.

 

[Wally]

This amp also had a factory error in the wiring at the pilot light. One end of the heater filament winding had a bad solder connection done at build time...and has been 'making and breaking' contact for all of these years. The amp is so clean, I am thinking that someone got frustrated with it and put it away..unused for a long time. The problem was a bit obscure...but a chopstick foudn it quickly. (;^)

 

[StephaninMelb]

Good tip!

To make matters even more complicated Accutronics have Vertical Wall spring reverb tanks made to mount in FOUR different orientations. Not only a vertical wall but is the tank aligned straight up-and-down or straight across the wall. Then also need to orient the connectors. The last I'd think is more a connector / lead routing issue.

Accutronics part Number: 4AB3C1C

7th character: Mounting plane
A = horizontal,open side up
B = horizontal, open side down
C = vertical wall,long axis horizontal, connectors up
D = vertical wall, long axis horizontal, connectors down
E = vertical wall, long axis vertical, input up
F = vertical wall, long axis vertical, output up

 

[StephaninMelb]

This chart might prove useful to people in working out Accutronics Spring Reverb part numbers:

 

[rolling56]

Thanks Wally and Stephan

 

[Glen W]

Good find! When I built my 6G15, I just used a 4AB3C1B pan and mounted it to the front panel. Sounds fine. I can't hear any difference whether it's vertical or horizontal. I guess those 4AB3C1C's are more sensitive to orientation.

 

[Wally]

Stephan, thanks for providing that data. I knew that there were at least two vertical types, but it has been awhile since I read that.....and until yesterday I never had much use for knowing that there are differences. I have never encountered a misoriented tank before this one.
GlenW, now I am going to have to orient soem 4AB3C1B's adn see what goes on withthose. OF course, there can be a lot of variation between tanks of the saem model, right? I find that loose inductors detract from the reverb effect greatly. A drop of some good modern glue, and things get better. IF inductors are loose in a tank, I would think that one orientation might be as bad as another.
What led me to discover this 'misplaced' tank is that I took resistance readings at the plugs at the back panel. The tank read close to 'normal' on one cable, but I read only 2 ohms on the other where I am used to seeing around 8 ohms. So, I went to the tank...and saw the 4AB3C1C model stamp.
With a proper tank, this is going to be one sweet and clean '73.

 

[BobbyZ]

When I bought that 62 Reverberocket I looked in the bottom of the cab and crap the reverb tanks gone. Was just about to talk the guy down some more when I saw it!
Good info thanks guys.

 

[stax]

Thanks for this, all new to me.

 

[jh45gun]

Interesting the reverb tank on my PA `100 is mounted vertical on the front baffle board.

 

[backline]

I think most of us have an idea of what the inside of a horizontal tank looks like.....
If we were to look inside a "vertical" tank, would it appear different.?
Thank You

 

[StephaninMelb]

Accutronics Reverb Tank Mounting

Magnetic Field Consideration

The Receive and Output (Send) transducers are shielded by the outer steel tank container. Even so the output transducer should be oriented away from transformer magnetic fields. The effectiveness of magnetic field shielding provided by the tank container varies depending how the tank is oriented relative to external magnetic fields.

 

[StephaninMelb]

Reverb Tank Connector Grounding & Insulation

To suit different guitar amplifier grounding schemes Accutronics tanks come in various combinations of Insulated and Non-insulated RCA jacks.

Non-insulated (Grounded) Jack

• Outer shell of RCA jack is grounded to the Accutronics reverb tank chassis

Requirement for Insulated Connector

If an amplifier connection to the Accutronics jack shell is not at ground potential a tank must be chosen with an “insulated connector” at the jack connection point.

Connection at Ground Potential

If an amplifier connection to the Accutronics tank RCA jack shell is at ground potential:

• Either insulated or grounded Accutronics connector may be used

Accutronics Recommendation

Accutronics specifications recommend insulating Input and Output connectors and providing separate tank grounding.

Note: Check whether the amplifier Reverb RCA jacks carry through ground potential to the jack shell. If they do then a ground will be made via the RCA cable to the reverb tank.

 

[StephaninMelb]

Reverb Tank "Best Mounting Methods"

Amp designers need to attempt to mount the spring reverb tank in a vertical orientation with the connectors up if at all possible. The two other alternatives are a compromise and will not produce as high quality reverb. There are more player operating issue encountered with reverb tanks mounted in the two other orientations.

Issues that Need to be Considered

• Spring weight
• Displacement of transducer magnets along the air gap (tank orientation)
• Isolation from vibrating mounting surface
• Mechanical feedback from too tight cable connections between the reverb tank & amplifier

Illustrations from Top to Bottom

(1) Most Desirable Mounting Method
(2) Next Most Desirable Mounting Method
(3) Least Desirable Mounting Method

 

[StephaninMelb]

Tank Mounting Transducer Orientation and Centering of Magnet

The Reverb tank installed vertically with the connectors up provides an ideal orientation for the magnets. The weight of the transmission springs in this orientation keeps the magnets naturally centered in the air gap and also keeps the magnets away from the transducer lamination.

A reverb tank mounted vertically turned to a horizontal orientation is also less susceptible to floor vibration.

 

[Wally]

Stephan, I was musing about the effect of the speaker magnets on this tank. I am going to pull the tank and use some extension cables to get it away from the amp/speakers. When I put that tank in the vertical orientation, I had it just outside of the cab. I am going to see what the effects are of the magnetic field of the speakers and/or the orientation of the tank.
Backline, I'll take some pictures of the tank whiel I have it out. I don't think we are going to see much of a difference to the eye.

 

[StephaninMelb]

Originally Said by backline

I think most of us have an idea of what the inside of a horizontal tank looks like.....
If we were to look inside a "vertical" tank, would it appear different.?
Thank You

Hi backline: To the naked eye it is impossible to tell the difference between the three reverb tank versions:

• Vertical Mount with Horizontal Alignment Plane (Transducer Connectors Up)
• Vertical Mount with Vertical Alignment Plane (Transducer Connectors Sideways)
• Horizontal Mount (Flat Mount)

What can't be seen is that Accutronics have made adjustments to the transducer section to account for mounting alignment (gravitational orientation) for each tank type. These are delicate alignments and mounting a tank in the wrong orientation will impact reverb performance.

For this reason it is important to identify the tank via the Accutronics part number. Always install tanks in the orientation for which they were designed.

 

[StephaninMelb]

Multiple Spring Reverb Units in One Amplifier

If there is enough space within an amplifier it is possible to have multiple spring reverb tanks.

Parameters You Could Adjust using Multiple Tanks

Type 4 (2 Springs)

You could select between Short and Long Delay

• Short 33 ms
• Long 41 ms

You could select from long, medium and short decay

• Long (2.75 to 4.0s)
• Medium (1.75 to 3.0s)
• Short (1.2 to 2.0s)

You would use an RCA Switch Box with Manual Switches or Remote Control to switch between the spring-reverb tanks. The Switch box would perform the signal routing between the tanks and amplifier drive / retrieve pre-amp sections.

 

[StephaninMelb]

Installation of Spring Reverb Tank for Best Quality Reverb

Where to mount the thing and ultimate spring reverb

Skip Horizontal Mount

1. Horizontally Mounted Reverb Tanks are the Worst Performing
2. Horizontal mount is out unless last resort

Reverb Tanks Work Best Mounted Vertically on Amp Enclosure Wall

• The tank mounting point has to be on one of the three amp enclosure walls
• Tanks function work best in a vertical mount with horizontal orientation
• The two side walls can't be used because the tank transducers will point right at the speaker magnetic field (act as antenna)
• That leaves the back baffle
• In a typical guitar amp combo the amp chassis and transformers are directly above at the top of the amp
• If the tank is vertically mounted in a horizontal orientation on the back the tank transducers will point away from the transformer fields and away from the speaker magnet fields

It can be seen that the prime real estate for a spring reverb tank placement would be mounted on a rear baffle board just above the junction of the baffle and enclosure bottom.

If an amp lacks a partial baffle across the back a short baffle section should be constructed.

Reverb Tank Vibration Isolation / Magnetic Field Protection Container

Ideally the baffle incorporates a reverb tank container that is fully padded with high-density foam like a transport case. Foam should be selected that has maximum vibration isolation properties. Reverb container walls should be painted with copper paint or have copper tape shielding applied. The tank would slip from the top into the reverb container. The box would have a top cover and exit slots for the cable leads.