# Reverb installation

#### Deigh

Apr 26, 2011
171
Been out of circulation for a while but am now back and looking to complete a project start a while back. Want to sweat a reverb tank into an amplifier. I have mounted the tank and tried it out by just plugging it into the guitar input but no significant response, although banging the unit with my fist does send a small crash through the speakers. More experiments to follow.
Deigh

#### KrisBlueNZ

##### Sadly passed away in 2015
Nov 28, 2011
8,393
Post some photos too.

#### Deigh

Apr 26, 2011
171
Right, got a few days spare so it is time to try out reverb again.
Mounting problems have been solved. Pix are a rather lousy shot of amp itself, the workings of the reverb, one of the power units purchased to drive the amp and the circuit of the main amp.
Now, what I want to do is add the reverb to the input from the guitar. I will install a jack socket somewhere on the carcase and wire it up after instructions from someone on the forum.
To remind you of what has gone before......I am a long in tooth messeraboutwiththings person! I did a temporary wire up of guitar into reverb and reverb into jack input. It did not work, but if I tapped the reverb a crash did sound through the speakers.
The amp is about twenty years old and has served my well as a practice amp and now is needed to punch the output from 'Encore' into one jack input and allow me to plug the guitar into the other and use the rhythms I have recorded as backing for my busking setup.

Now I need some instruction and please remember that I am a doddering old man so make the advice simple please!!
Deigi

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#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
OK, so you need to connect the output of one of those small amplifiers to the input of the reverb unit and connect the input of the other one to the output of the reverb unit.

If you inject a signal into the first amplifier, you should hear something out of the second (headphones might be useful).

If you hear nothing, ensure that the signal is strongly audible from the output of the first amplifier (i.e. that something is going into the reverb unit).

This basic test will tell us if the amplifiers are sufficient for the task.

#### Deigh

Apr 26, 2011
171
Ok, will work on that....forgot to say that I dont want the reverb input to take over completely the normal input. Reason for this is that when playing rhythm guitar the reverb is not required. It is only when playing lead that the reverb sound is required. So rather that having to incorporate a switch it would be best if the reverb had its own seperate jacksocket

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
Yeah, I think in another thread there was a diagram showing how the output if the reverb should be mixed with the original signal so you can have between 100% normal and 100% reverb.

But let's check to make sure we can get a signal through the reverb unit first!

#### Deigh

Apr 26, 2011
171
LM386 is causing me some headaches. The pins are pretty close together and I need female plugs to fit them. Cant find them on the local market. Anyone know where they are availble in small quantities?

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
One way is to open up an old PC that's destined for the rubbish and salvage some from cables there. Take the whole cable, not just the plug because the wires are not easily replaced.

Alternatively, for a very small amount of money you can get a stack of cables with sockets for these attached to the end sent to you from China. See here.

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#### Deigh

Apr 26, 2011
171
In Auckland if there is something you dont want you put it on the sidewalk outside your house and usually someone takes it away. I have put an old tv (old, but still working!) on the driveway but no-one has taken it away yet. I dont like ripping things apart but I might have to cannibalize it!

Alternatively, for a very small amount of money you can get a stack of cables with sockets for these attached to the end sent to you from China. See here.[/QUOTE]

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
I've fixed that link. Something funny happens to me sometimes. I remember changing the H on here from upper to lower case after making the link. Maybe that was a bad thing.

In any case the full link is http://www.ebay.com.au/itm/331297041179 This is just one I pulled out almost at random. There are many of these leads available. You want ones with female ends on at least one end. These are held on by friction, so if you decide to use them permanently, it might be a good idea to place a bit of hot glue or similar on them to make sure they don't vibrate loose.

I'm not sure you'll find any of these connectors in a TV set.

Try placing a sign "$30 ONO" on the TV and I'm sure that people will see it's value and take it off your hands... possibly without making an offer #### Deigh Apr 26, 2011 171 Try placing a sign "$30 ONO" on the TV and I'm sure that people will see it's value and take it off your hands... possibly without making an offer

What a great idea, but I read it too late. Have just pulled it back in and taken it apart, extracting just the bits I required for joints. Pity, the set was in working order and for quite a while had it in the garage so I could watch 'The Breakfast Show' whilst doing my exercises. Fairly purile show, but just right for doing exercises to.

Regards
Deigh

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#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
Excellent that you found the connectors you require. The old TV provided some more value

#### Deigh

Apr 26, 2011
171
Excellent that you found the connectors you require. The old TV provided some more value
Yes, but now I have lost the information about the 386 unit itself, I need to know which pins do what? and should my input be a screened cable? The plugs I have obtained from the TV set have no coaxial connections and I plan to solder onto the wires already on the plugs rather than trying to remove and replace them.
Regards

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
For testing just use normal wire -- whatever is on them.

THe connections are shown on the board. The power goes to gnd and Vcc, the input signal to gnd and in, an the output comes from gnd and out.

Off the top of my head I'm not sure what the max voltage is, but google tells me that 9V to 12V should be OK (don't go higher unless the 386 is a -4 version!)

#### Deigh

Apr 26, 2011
171
thanks for that info, I remembered that the connections were shown on the board shortly after sending that E-mail!..OK about voltage which was specified as 12v. will run coax as close to contacts as I can. Looking forward to finishing job, Have had some good breakthroughs recently. Have dumped the old Macintosh computer and the three batteries needed to drive it and the midi interface. Have purchased up to date 'Encore' program to work on the PC and have got bluetooth working so there will be no need for umbilical cords. Amplifier is now a realistic weight and working OK with guitar punched through the 'instrument' socket. Getting the reverb working will give me a better sound and I can get back to some busking trips.
Regards
Deigh

#### Deigh

Apr 26, 2011
171
OK, did a bench wire-up and it worked. Only used one of the amps on the inlet side. NOW.......it is excellent, but a little too much reverb for my needs, how can I reduce the amount of reverb? There is an adjusting screw on the amp but it is purely volume control. Can I do it as simply as putting a variable resistance across the tank?

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
Yes there is a way. The best way is to adjust the gain from the reverb so that the level from it is the same as the incoming signal. Then you place a pot across them and take the signal from the wiper that way you can adjust from no reverb up to the max reverb available.

in some respects that is similar to placing a variable resistor across the reverb unit but done in a way that adjusting the reverb only affects that asked has no é effect on the volume.

#### Deigh

Apr 26, 2011
171
Thanks for that reply but it has confused me. Please accept that I have only a very limited knowledge of electronics and would like more details on how to do that exercise
Deigh

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
Yeah, I was hoping to get to a computer and draw you a diagram. I'll try to do that for you soon...

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
Sorry again for the delay.

Showing the input on the left and the output (which is the connection to your amp) on the right.

You almost certainly have all of this at present except for R1 and the associated wiring.

R1 allows the signal to come either direct from the input or through the reverb, or any combination of the two.

R1 should be a linear pot, probably around 10k should be OK.

This resistor will also introduce some feedback which may either accentuate the reverb effect or (in the worst case) cause fairly nasty feedback. This will be worst if the input is disconnected.

The idea is that as you turn R1 from one end to the other that there is no change in volume. This can be adjusted by changing the gain of the amplifier module.

This is simple, but if you have problems with feedback, you might need a slightly more complex version:

This is essentially the same, except the LM387 amp is adjusted to get a reasonable level to the output when R1 is adjusted for 100% reverb, then R2 is adjusted to give the same level when the reverb control is turned the other way.

R2 should be about 1k and should be a trimpot. Once it is adjusted you should not need to touch it again.

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