Great British Spring reverb problem

[onlymeeee]

Hi, I am having a problem with my GBS.

On some systems, the input is giving a very low distorted interference type sound.

When i feed a +4db signal straight from my cable tester into the input I get full signal out into my digi 002. 0db. Good sound.

However, when I connect it to an insert in Protools (in 7, out 7) I get barely any level, and it is distorted and sounds like loads of interference.

When I exchange the GBS for a compressor in the chain, everything is fine.

__

When I try feeding it off an old mixer, I get the same old distorted sound.

When I feed it from a compressor, everything is fine. (signal generator, to compressor, to GBS, to input of Protools)

When I fed it from a G series, everything fine.

__


Does anyone have any idea what is it about some setups that mean my GBS doesn't work?

On the setups that dont work, I have took the GBS out of the chain and connected the ends of the 2 XLRs together and I get signal through fine.

Thanks for any help,

David

 

[drpat]

...

 

[onlymeeee]

Hi,

I am running it balanced.

I believe the GBS is balanced. It is the black version, with DIN connectors and XLRs.

I don't have a schematic unfortunately.

 

[Bo Hansen]

David,

I was the GBS dealer here in Sweden under the 1980´s, so I have work with bothe the older in gray and newer in black plastic tube.
This black versions come in the end before Bandive that made GBS cloose down the business.

The version I sold meny hundreds of in Sweden was in a grey plastic tube, and have telejacks in un-balansed version and XLR in balanced version.

What I remember this black version have XLR´s even when it was un-balanced, and in this case, one of pin 2 or 3 are linked to ground.

When I´m in my workshop next time, I will check in my tech information if I guess right.

If the output on your mixer not have "cross coupled" electronic balanced output circuit, you can get this fault if you ground pin 2 or 3.
(some electronic balanced outputs have only a phase reversed amp from the "unbalanced output" to pin 3, so if you ground pin 2 or 3, you will drive the amp shorted to ground)

--Bo

 

[analogguru]

From the Operating Instruction 9/83:

Interfacing
The GBS has two, totally seperate, input and output driver circuits. This enables you to use the unit as two mono reverbs or by connecting the two inputs in parallel, as mono in, stereo out unit.

Connect the echo send or effects output of your mixer to the GBS female XLR input sockets. The UNBALANCED GBSoffers pin 3 signal, pins 2 & 1 common eart. For the BALANCED GBS, pin 3 is live signal (hot), pin 2 is neutral (cold), and pin 1 earth (ground). If the unit is being used in the mono in, stereo out mode, then parallel the input connections on either model.

The outputs of the unit are male XLR´s.

UNBALANCED GBS connections are pin 3 signal; pins 1 and 2, earth. BALANCED GBS connections are pin 3 signal, 2 neutral, pin 1 earth. These should be connected to the echo/auxiliary returns of your mixing desk or ideally to two spare input channels, thereb providing the facility for equalisation of the return signal path.

The unit will acept input signals from -10dbm to +0dbm. The output level is nominally 0dbm. Maximum output is +20dbm.

As far as I remember all black pipes came with XLR´s. The balancing was made wwith transformers. For this the output driver had different chips: 5534 instead of TL 071.

IMHO the unit was "junk" and a bit of rip-off. If you open the unit you will find a normal accutronics 3-spring and a cheap driver circuit inside. A Fostex 3180 was a much better spring-reverb with the same accutronics 3-spring inside.

But people believed that the spring inside is as long as the pipe.

I traced a unit 25 years ago and for this have a hand drawn schematic. I didn´t find it worth to draw it in the computer.

analogguru

 

[barclaycon]

Yes, I'm afraid I agree.
Great British spring - what was great about it ?
It didn't have a good sound.
If you want a great sounding 'spring' reverb i.e. reggae, King Tubby etc.
get yourself a Fisher Spacexpander. They crop up on eBay from time to time. Also worthy of note: Tapco, Grampian.
AKG made some very nice sounding springs - of their own design (not Accutronics).
They made a rack mount unit (was it the BX5 ?) and a larger one called the BX10. The biggest I think was the BX20 - which sounded very nice.

 

[Bo Hansen]

David,

I have check it up now, and my guess was right.

The un-balanced black version use pin 3 as hot, and have pin 2 linked to ground, so maybe if the GBS you have are un-balanced, and the mixer have unbalanced in or outputs connectors there pin 2 are hot, or if the mixer output have the type of balanced driving amp that not alove to be grounded, I think this can be your problem.

BTW, some of you don´t like the Great British Spring, but I must say, for the price and if you compare the sound with AKG BX-5, Orban 19" spring unit and some other brands in same style, GBS sounds better.
But it is very important that you use the GBS in mono in and stereo out configuration. (GBS was a real 2 channel unit with two "long decay" Accutronic spring tanks)

There was also other nice 19" spring units as Sound Workshop and some more, but the best unit was Mic Mix Master Room XLR-305, and of corse the bigger Master Room MR-3 (the high "gatepost")
Master Room made theirs own spring tanks, not Accutronics.

--Bo

 

[barclaycon]

Well, yes. I guess everyone has their own opinion....

 

[onlymeeee]

Ah, that would explain it. I thought it was balanced.

What do you reckon the best work around would be?



The thing with it is, I really like the sound of it. I often choose it over 480s, EMT 140s and BX20s. Horses for courses I guess.

I'm intrigued about the micmix and will be looking out for one perhaps.

 

[mikeyB]

I have a stereo unit with XLRs. The unit is unbalanced, now reworked for pin 2 hot use. The unit has two spring tanks made by O.C.Electronics. Both units have an ink stamped number on the casing. 583, i'm assuming this is the model number. There are 3 springs in each tank. input DC resistance is around 40ohm and output DC resistance is around 750ohm.
Looks like the unit has been stood vertical on the assumption that the end of the bottom tank is quite rusted and this happens to be the output end of channel B. The problem is that the output of tank B has a lumpy frequency response and lower output than the more consistent channel A. I mean lumpy as in amplitude when swept slowly/manually with a sine wave in the audio band. The actual spring/plate look good, it's just the outer case that is rusted. Is it likely that moisture has affected the pickup coil and if so, is there anything I can do to remedy this? I thought there was a dodgy solder joint that has now been re-soldered but that has no change??
Thanks In Advance

 

[RuudNL]

The problem was that the drive coil of one system was close to the pickup coil of the second system.
This introduced some cross-talk (due to the magnetic field coupling) of the direct signal, especially at higher frequencies.
(In my GBS I turned one of the spring units at the time, so now both drive coils were together. This solved the problem.)
Also I decoupled the pickup amplifiers (inside the spring units) with higher value capacitors. This reduced the amount of mains hum considerably.

 

[mikeyB]

Hi RuudNL,
Thank you for your reply, mmm - got the tanks out on the bench, tried distancing the pickup coil as suggested, but to no avail. The drive levels are consistent with each other, but the outputs of the 2 units coils vary in level very inconsistently to each other, is it time for new tanks or is there any way to remedy this??
Thanks in advance!!

 

[RuudNL]

I think the first thing to check if the problem is on the drive side, or the recovery side.
As far as I remember, the drive coil is connected between two OpAmp outputs, driven in opposite phase.
If one of the OpAmps would have failed, this would cause a 6 dB lower drive level.
I suppose you can get an idea of the recovery signal level, by carefully touching the springs. This should give a more or less identical level.

 

[mikeyB]

Hi Rudd, The drive is identical on both sides, monitored with dual scope and then use the scope directly on the output of the coils, both outputs do not track each other at all, the response of each coil is totally different!!?? This surely means the springs/coils are at fault?

 

[mikeyB]

When I get chance i'll try swapping things around to see if the fault follows with a particular part?

 

[mikeyB]

Hi Rudd,
Drive circuits - I have paralleled feed from sig gen. Outputs track each other pretty close.
Disconnected the output of the tanks and again parallel fed the makeup amps from sig gen and again constant tracking of both amps.
It's pointing to the tanks themselves - what would cause such wildly varying responses from 2 of the same tanks, they both give greatly varying outputs at different frequencies but do not track each other at all.
Is it a common thing for tanks to deteriorate like this over time? Could it be magnetised/saturated drive coils. DC resistance of both in and out coils are close on each tank. (Approx 40ohm DC in and 750ohm DC out)
BTW - would a pair of new tanks be expected to be fairly well tracked in response? I've no past experience of repair/building springline units.

Thanks in advance!!

 

[Electrobumps]

I have a stereo unit with XLRs. The unit is unbalanced, now reworked for pin 2 hot use. The unit has two spring tanks made by O.C.Electronics. Both units have an ink stamped number on the casing. 583, i'm assuming this is the model number. There are 3 springs in each tank. input DC resistance is around 40ohm and output DC resistance is around 750ohm.
Looks like the unit has been stood vertical on the assumption that the end of the bottom tank is quite rusted and this happens to be the output end of channel B. The problem is that the output of tank B has a lumpy frequency response and lower output than the more consistent channel A. I mean lumpy as in amplitude when swept slowly/manually with a sine wave in the audio band. The actual spring/plate look good, it's just the outer case that is rusted. Is it likely that moisture has affected the pickup coil and if so, is there anything I can do to remedy this? I thought there was a dodgy solder joint that has now been re-soldered but that has no change??
Thanks In Advance

Hi Just got my GBS out of storage wiring into the Studio. I have the black version XLR inputs. Inside PCB stamped GBS 3 issue 4. There is space for transformers but they are not installed.

I've always loved this unit and don't understand the people who say it sounds bad. It is not a work every time reverb like a 480L, but the 480L has many algorithms with many controllable parameters. In certain situations this reverb is fantastic. I hate the noisefloor on mine. I end up always having to use an expander on the return. How is yours for noise? I always run as much signal in as possible with out break up so I can keep the output low.

What did you do to rewire for Pin 2 hot? Did you just to this on an external XLR cable? or internally?

My tanks are Accutronics. I emailed Accutronics years ago and asked if they had a part number. They searched their archives and gave me the number 9EC2C1B. You can decode it here https://www.amplifiedparts.com/tech-articles/accutronics-products-and-specifications