Can i replace reverb tank in Prince Boogie Copy with an Accutronics tank?

[Paolo]

Hi

I have a Prince Piggy-2 PS200R amp that has the most pitiful reverb ever. It sounds like someone throwing a metal pipe down the stairwell of a block of flats! I was wondering if replacing the reverb tank with an Accutronics would improve this situation? I realise the tank is not the only factor, but it's the main one.  I will also point out that i would be putting the new tank in the base of the amp cabinet.
As you can see from the picture below, the tank it'self is a ridiculous (one spring) 2" square emarrassment to audio electronics! 

I'm familiar with the concept of matching input and output impedances from other similar discussions on other boards, but how close do they have to be?

The measurement for the input is 208 ohms and the output resistance seems to fluctuate between 214 and 330 ohms depending on whether the amp is switched on or off while measuring. I am measuring where the wires from the PCB are soldered to the lugs on the input and output, as this reverb tank does not have those RCA type connections, it's all soldered.

I have looked on the accutronics website, and while i could get a match for input resistance, the output resistance is quite a difference on any of the models.  Failing that, could the pcb component values be altered to accept the different impedence from the accutronics tank?

Any advice or comments greatly appreciated! More detailed photos on request.

Paolo

[J M Fahey]

1) unsolder at least one end of the tank coils and remeasure
2) that tank is certainly larger than "2" square" .
Looks at least 6 inches long.
3) take aìcturte of the inside of the tank, showing the spring, and the end transducers.
Maybe it's rubbing against something and can be reoaired.
4) just now I notice an "A 440" knob.
Is it some kind of tuner?

[Paolo]

Hi JM

I mean't it's 2" square around the thickness, probably less at the sides.  It is about 6" long. I can't recall if it has one or two springs, but i think it's working correctly. It's a consistent sound, just not a good sound. Have you ever heard a Danelectro Corned Beef 'reverb' pedal? It sounds similar to that, but worse.  I probably exagerated the description to get attention with the post. Maybe more like a bee trapped in a aluminium tube in a shower room! At full tilt it can just about do a kind of Dick Dale surf thing (badly) but there's no sublety to it at all compared to a Fender reverb, though the reverb knob itself works fine.

Do you mean desolder the wires from the pcb where they join to the lugs of the tank, or wires somewhere inside the tank?

You've just noticed that knob!? Yes, the A 440 knob is a tuner. It's like a click-on volume knob/ tone generator. It's tuned to 'A'. There is also a screw/ dial thing on the back to tune the tuner to  'A' more finely. There is also a trim pot on the pcb at the opposite end to the gain knob, which also adjusts it.  I don't use it, though it works perfectly.  I always wish that knob was for tremolo, so the whole amp would be more like a Fender Princeton.

I'll try and take a picture of the inside of the tank when i do the other photos of the gain input/ circuit.

Thanks for your comment

Paolo

[Roly]

{As JM says, plus...}

The resistance at the drive end is generally more important than the resistance at the pickup end.

Generally with spring reverbs, the longer the spring, the better; the more springs, the better.  Many console organs are being junked these days that have both long and complex spring reverb tanks, and also rotary speakers which can make guitar sound way cool.

[Paolo]

Hi Roly

I have a couple of accutronics reverb tanks already from old amps. One is a full length 6 spring from a big combo (which is obviously too big for this amp), and the other is a short 2 or 3 spring, which is ideal, but i think i already tested that a few years ago and it didn't work, although i just clipped leads to it but the amps onw tank was still attached.  I think i'll desolder out the Prince tank when i take pictures of it and try it again.

My favourite reverb of all time is the accutronics in my USA 1990's Fender Princeton Chorus, which has the best clean sound (i know i said that about the Prince, but it's similar to the Prince, but in stereo and with reverb!).

[phatt]

Hi again Paolo,
                  Well Your chances of success are close to nil as the circuit that drives the tank well be the issue not the tank.

By all means try it if you wish as you will learn stuff along the way.
Oh and do yourself a favor turn off all power and disconnect the tank from amp before you measure the DC resistance. That is why you can't get a proper reading.

A bit of spring rev trivia while I'm here;

As Roly mentioned *Generally* the longer the spring the better the sound.

Don't be fooled by having many rows of springs as it's only the *First spring* closest to the transducer that delivers and picks up most of the energy.
This can easy be shown in multi row tanks by gently holding (thereby muting) each spring.
When you mute the spring closest to the transducer you will loose 80% of the rev sound.

2 rows does add a bit but Past 2 rows is just market hype.

As you have spare tanks why not build a stand alone unit? :tu:
I find most on-board rev circuits leave me wanting something better so I built my own setup.
Phil.

[Paolo]

Thanks for your input Phil. Yeah it might well be the circuit, but i've got to at least try a different tank in there.

I bought a Boss FRV-1 '63 Fender reverb pedal a few months back, but i find it only really useful for the full on surf tone reverb. It's not very subtle. I wish i'd bought the Digitech Hardwire RV-7 now as it has more options, and is popular as a back up to the real stand-alone tank among the surf band community.  Mostly though, i only use reverb sparingly and prefer a kind or room reverb for general playing, but occasionally need more for atmosphere, or surf tone.

That's interesting about the amount of springs, i'll have to try that out. By the way, the accutronics with 6 springs had 3 rows with 2 springs per row (or maybe it's 2 rows of 2 springs.  It's a few years since i looked at them).
I suppose long springs in a long tank like that needs some kind of support in the middle. It didn't sound no where near as good as the shorter tank in my Princeton though, far too distant and dark.

I'd love to build my own reverb unit, and have thought about it for a few years, but haven't had much luck finding any info on how to do it. How hard is it to build your own tank then Phil? Do you have a schematic for future reference?

This site is great i'm learning all the time from you guys!

Paolo

[phatt]

Well Paolo,
              Easiest way,, go here; http://sound.westhost.com/project34.htm

Build the circuit at the bottom with the booster on the end. :dbtu:

also here; http://sound.westhost.com/articles/reverb.htm  (good pics)

I spent years trying to perfect a good,,, (no make that Stunning) Reverb setup and although I'm no q'ed enough in maths to explain a lot of the hidden details I'm qualified via
experience. 8|

Most of the Rev circuits you will find on the net don't work that well.
I know that because I tested quite a few of them.
I spent years messing with stuff, even the circuits on Accutronics site are just pathetic.
Then I tried Rod's circuits. Worked as stated first time.
I highly recommend it above all others. :dbtu:

Rod's circuit is aimed at the later SS driven tanks.
So his circuit won't work with Very low Z driver transducers (i.e. 8 Ohm) as they are for
Valve driven circuits mainly.

You need the Driver end to read around 40~60 Ohms DCR.
The PU end can be 100 Ohm, even 200 Ohm DCR and it will work with ESP circuits.
(You will likely need to tweak the *SOT* resistor up and down in value to better match the transducer you have)

The Accutronics tanks have a number on the case so go to the website and look up the number which will give you all the relevant data on that tank. (They at least got that part right )

If you want to understand the complexity of these little things and you like maths.
go here:
http://roymal.tripod.com/reverb.htm

Roy Mallory obviously has a very good grasp of the maths involved and He focuses on the
current drive trick which may look clever but sadly those circuits could not deliver the big
Reverb I was chasing.
Not to mention they where unstable (in my hands at least) and broke into oscillation if the pu side became detached.

ESP circuit impressed me from the start but I still was not completely happy as it still did
not have enough drive to make the tank slap like the old valve circuits did.

After several Emails to Rod he finally conceded that even with LM386 chip as driver it would not be able to do really big Reverb.

I have a hunch that I'm partly the reason for the added booster circuit down the bottom. 

Although the transducer looks quite small and puny the novice might think they would not
require much to move them. Big mistake
Thanks to the maths that Mr Mallory page goes into you realize they need a fair voltage to get excited so I opted for a brute force circuit and my booster circuit runs from 35-0-35VDC. <3)

Note; Roy Mallory Obviously understands the maths far better than I ever will and maybe I missed something but I did spend many months Years testing and retesting and found His circuit ideas have a flatter response than mine due to the drive setup but I find these things rather dull and boring in real live use,, which Might work well for some.
His pages are *well worth the read* if you are looking for a more in-depth study of the maths involved.
(He explains the voltage swing @ frequency issue which Helped me understand some of my problem)

Sadly opamps only have about 30 volts to work with and although you can do tricks to improve the drive NONE of the opamp powered driver circuit I prototyped ever got the tank to slap.

They work ok but don't expect it to ever sound like a big Valve driven reverb.
You really need s lot of energy to drive those things.
My own circuit was a mix and match of an old TS100 Traynor Reverb circuit and ESP's mixer circuit.

Those old Reverb circuit where unique simply because the EQ curve ripped massive bass BEFORE the driver. Most modern opamp powered units (YES Even in most Fenders) Are nowhere near the same sound and you can't get the drive needed unless you wipe the bass FIRST.

Drive transducers where never designed to handle massive bass and if you don't wipe the bass you can't drive then hard because bass and Reverb sound horrible.

Also an A/B comparison of Digi Rev verses mine it won't take long to realise the EQ is a very different.
EQ and bandwidth is a big part of the sound of Spring Rev.

Digi allows a lot more bandwidth to be reverberated and even though you have the advantage of some beauitful long reverbs it still won't sound like the old ones.

Having a narrow bandwidth gives the reverb bite whereas a wide bandwidth tends to make the sound well *lost in space* so to speak and has no real definition.

Some may want the more spartial effect, Maybe for vocal studio work digi is brilliant but for guitar I find it sounds wrong.

Go forth and build stuff and be careful,, it is addictive.
Phil.

[Paolo]

Thanks for all the advice and lnks there Phil!

Alot of went over my head, and maths is definitely not my strongpoint!

The thing about schematics and me is that i can't relate a scematic to the real thing. Particularly if i haven't got the real thing or a photo of it.  For instance, with the reverb schematic, i can't tell if the finished thing is a stand-alone unit; or it goes inside the amp; or is it like a giant effects pedal that you plug your guitar into that way. Do the components go in a box beside the tank; do they go where the tank originally was in the amp; are they on a PCB, etc etc. I gather from reading between the lines, that it will go in the floor of the amp with seperate electronics box connected to the main circuit, but i couldn't tell this from looking at the schematic.
I like to use the analogy of a sheet of music, as i can't read music, but i can read guitar tabs because it looks like the 'real' thing, ie the gutar neck. 
Sometimes, when i see old valve amps that have all the components soldered side by side in a line (linear) fashion on a turret board, i think "I could probably build one of those" with some 'airfix' style instructions and a parts list.

Nevertheless i may give it a try at some point, as i don't know that the amps reverb will ever sound that good even with a new tank.

As you can see in the photos, the amps reverb tank only has one spring as i predicted.  It also looks to be undamaged. Though there is a hailine wire (see photo below) that comes from the end of the mount at one end and touches (but not soldered to) the base of the tank.  At the other end of the tank there is a similar wire, but this one is shorter and doesn't touch the base. Are these of any relevance? I tried connecting the short wire to the base so both now touching but no difference.  Also tried lifting longer wire but no difference.

The readings when disconnected are 215 ohms input and 210 ohms output.  In the photo's, there is also a polished metal plate behind where the reverb was, where some wires from the PCB are attched.  Any idea what this is?

The spare reverb tank i have is an Accutronics 4AB3C1B which is full size and has 6 springs. Straight off, this is too big to fit in the floor of the amp cabinet by about an inch. From your descriptions, it is also probably not suitable to be used in Rod's reverb circuit.  I'm also not sure that it is working correctly, as the readings are 1.2 ohms input and 40 ohms output, which is nothing like what it is supposed to be.  Anyway, i connected it to the amp to try it and there was a faint ethereal reverb and the springs 'boinged' when touched (along with the undercurrent of ghost overdrive i have previously mentioned).

The other reverb tank i had was from a 70's Carlsbro Stingray Combo.  I can't find it so i think i must have put it back in the amp (which currently doesn't work), but that was definitely full size and had either 4 or 6 springs.  I also remember that it sounder too mellow, dark and distant, but that's probably the amp circuit playing a large part. Anyway, again too large for the Prince amp. I have two other Carlsbro amps which i think have the shorter accutronics tanks.

As i've prevously mentioned, my favourite amp reverb is the Accutronics in my Fender Princeton Chorus.  This is a short tank with the code 8BB201B with 3 springs and medium decay.  If i had to buy a new one, this is the one i would get, as it sounds just right to me - bright, snappy and not too distant.  The Brian Wampler Faux Reverb pedal seems to nail this tone also.
(The Fender Princeton Chorus also has a minor problem with the bass, but i will do a future post about that!)

I generally only have a touch of reverb (or sometimes analogue echo, or mix of both) as i play rock'n'roll and blues based music and don't need epic cavenous decay. I also have the Boss Fender reverb pedal if i want 'excessive' wet reverb.

Anyway, i'm thinking that it's going to be impossible to get a tank that matches the input/output of the Prince amp(?), so i will either have to built one from the schematic at some point, or buy a pedal like the Wampler.

Let me know your thoughts.  Here's the photos.

Paolo

[J M Fahey]

CHEAP reverb indeed.
Nothing unexpected, of course.
The mistery single wire on each end is the suspension wire, stainless steel, and is connected to nothing, has only a mechanical job.
Think a .008" guitar string and you won't be far away.
As suggested above, peruse the Accutronics catalog for a short tank with input DC resistance between 150 and 200 ohms and use it.
As noted above, output resistance is less critical, but if able to choose, pick the highest.
Good luck.

[Paolo]

I was just looking on e-bay at reverb tanks and here is someone selling the exact tank from the Prince amp!  Has a few NOS units.  Apparently made by Tokai:

http://www.ebay.co.uk/itm/DIY-guitar-amp-reverb-tank-80s-NOS-Tokai-TA-35-made-in-Japan-limited-quantity-/250996691938?pt=UK_MusicalInstr_Amplifiers_RL&hash=item3a709193e2

Whatever you do, don't 'Buy it Now' (or ever)!!

[Roly]

In the photo's, there is also a polished metal plate behind where the reverb was, where some wires from the PCB are attched.  Any idea what this is?

In your pix 0844 the shiny plate behind the reverb position is the heatsink for the output stage; the two black blobs screwed to this are the two output transistors, the white goo under them is a thermal compound to better thermally couple the transistor cases to the heatsink, and the white blocks look like sockets that the transistors plug in to.  Note that the tabs on these transistors are connected to part of the circuit and are insulated from the heatsink by plastic washers on the screw and small wafers of mica or similar underneath.

Avoid touching the white goo because it sticks to everything like thick paint or ink, and also may be somewhat toxic to ingest.

Ideally heatsinks should be matte black, not bright and shiny, but at least this one looks of a reasonable size, which is more than can be said for a lot of small amps.

Yep, that's a pretty basic reverb "tank" (or "spingline"), but I have actually see ones out of ghetto-blasters that are much smaller and more downmarket than this one - at least it's metal.   

[phatt]

Hello paolo,
                Sorry if I dived in too deep 4 U? 

No matter,,, you just suck up what makes sense and then over time you slowly learn. :tu:

Well that is how my brain works and I've still got a long way to go compared to some of the brilliant minds that grace these pages. 

Rev tanks are very hard to grasp as many parameters need to be understood. The tank itself can make changes to the way they sound.
i.e. meaning the springs natural resonance, the transducer and the way it is mounted, the magnet quality, and, and, and, the list goes on.

Understand the basic principal,
You are converting electrical energy into Acoustic energy and then back into Electrical energy again and as such there is loss.

My guess is that you are too young to remember audio from turntables and vinyl records which had some sonic quirks that most younger kids today would not even be aware of. 8|

So my advantage here is that I'm old enough to remember the problems encountered when limited to mechanical pickup of Audio sound.

Sadly there is no easy way to make stunning spring reverb. xP

If after a quick fix try the *Belton Reverb circuits* as they seen to have nailed a fairly good approximation of guitar reverbs.
Digital will be far easier to make happen.
Phil.

[Paolo]

Hi

The thing with living in the UK, is when it comes to certain musical instruments or related products, the postage is often more than the actual item. This is the case with Accutronics reverb tanks shipped from USA. New Accutronics reverb tanks are seemingly only available from one dealer here in the UK, but the price only seems slightly higher than the USA price, and of course postage is minimal. Ss that is a viable option.  I was thinking the 8BB2C1B?

Phil - I'm assuming you mean the Belton Digi-log/ 'The Brick'?  I've come across this box in my recent research into reverb tanks. Also now available in some sort of pedal i believe.
This option would be far cheaper as they can be bought for about £10.  I think you have to have some kind of supporting circuitry and power supply though?  (Incidentally, i have an old K Kustom amp that has a small open 2 spring reverb tank made by Belton, and that does sound very good.... very Fender. I've thought about trying that but reverb tanks made for modern  non fender amps seem to have specific input ohms tailored to the circuitry of that amp.

Also, while looking into the reverb problem, i've come accross someone who changed the RCA reverb jacks to 1/4" jacks in a silverface fender and used an Alesis nanovervb as the reverb tank. Probably, a stupid question, but would this work or not work with a reverb pedal?

Everyone has been very helpful with detailed opinions and possible solutions. The thing is, that before i attempt to build ciruits and/or spend over £50 on an Accutronics tank, i need things explaining in a non technical language that i can understand, so i can get my head round it. I need to know i can do it before i slpash out on all the parts and tank.  I also need to know more of the fine details like i mentioned in an earlier post.
The main reason i need to know all this is because this is one of my favourite amps so i don't want to fry the electrics by guessing or not understanding! If you look at it from my point of view -  for example, suggesting i get a Belton Digi-log.  Say i get one and all i have is just a mystery box with no input or out put jacks. What do I with it?  I need to know how easy or difficult it is to connect it to the amp, and what else is needed.

Phil - Yes i am old enough to remember Vinyl records!! I have an extensive collection.  I also currently collect old soul and R&B 45's form the 50's and 60's, so i'm an active turntable user and have good gear. I understand sound, just not so much electronics and it's language.

Roly - I've seen those plates in amps before now you mention they are usually black. They sometimes look like a 3d comb.

[J M Fahey]

I'm sure the Digital Belton is well made (although haven't tested them yet) *but* big problem is, we don't have the Prince Schematic !!!!!!!!!!!!!!
While a similar impedance tank replacement, will work, because it's already doing so.