BOSS CE1 PROJECT: MN3002 or TDA1022P: DOC UPLOADED

[Ricotjuh]

Does anyone have the schematic for this project? The link in the first post does not work anymore. I am mainly curious about the powersupply part

[RDL68]

Does anyone have the schematic for this project? The link in the first post does not work anymore. I am mainly curious about the powersupply part

Here's the schematic.
I had trouble posting it but Brian said the file was too big, so he resized the file & emailed it back.
I'm now just re-posting the smaller file size version for anyone else that needs it.
I was surprised by that because I downloaded the original from this thread months ago & tried posting the original at first to no avail. Not to worry. Computers, you know what they're like...

[Ricotjuh]

Thanks a lot for the schematic. You helped me a lot with this.

[luchin542]

Hi everyone, for the TDA1022 version i have to change another components on the circuit or tweaking some voltages? or just make an adapter pin to pin? Reading the datasheets this is the equivalent pin configuration:


TDA1022 Pin -----> MN3002 Pin
1                             2                CLK1 
4                             12              CLK2
5                             3                Input
8                             13              Out1
9                             4                -15V
12                           14              Out2
13                           11              -14V
16                           7                GND

Thanks!
     

[RDL68]

@luchin542

It was drog_trog that got the 2 different (but almost identical) CE1 PCB layouts done for MN3002 & TDA1022P chips.
He hasn't been registered on the forum for a while now, so I'm not sure he or anyone else will answer your question.
He also said interest in it wasn't as much as he expected, so I'm not sure doing another CE1 layout now would be a good investment of time, if that's what you're doing. Maybe the power supply section could be improved, but apart from that it's a CE1 circuit part for part.

It's still a good question because there will be more genuine CE1's needing repair in the future & the MN3002's are too difficult to source now. The ability to replace a dead MN3002 with an IC socket & a small riser-board with a TDA1022P would be knowledge worth having.

I'll just add, having soldered up both versions for MN3002 & TDA1022P myself, the BOM & part count was identical for both versions.  One had a 14pin BBD the other had a 16pin BBD & the only other difference was a few parts reorganized (slightly moved out of the way on the PCB) to accommodate the longer 16pin IC.

[luchin542]

Thank you RDL68!!!
I have a noisy CE-1 original unit. I read the problem is the MN3002 and change to TDA1022 will fix the problem. So i make the swap between the chips with an adapter that i made, and sockets to replace easily with the proper pin to pin configuration. Finally the unit works nice with the TDA chip, without noise but to my ears there is (slightly) less headroom on the chorus/vibrato effect, but is just a little difference.
Thanks for your help.

[RDL68]

@luchin542

Well done repairing your original CE1 with a TDA1022P.
As for the headroom, assuming all your capacitors are new & not still the old ones from the 70's, maybe you could try replacing the 2 opamps with something modern (not the LM1458 chip because that is the clock).

I was just looking at the schematics (original & clone) & noticed there are some changes between the original CE1 & drog_trogs PCB.
He was clear his CE1 was a part for part replica of the Retrosonic Chorus (CE1 clone). I always assumed the Retrosonic was an exact Boss CE1 replica, but I assumed wrong.
Most, if not all, of the transistors are different.
The original CE1 used 2 x ta7135p opamps (I think they're the old Toshiba single row parts). The clones are using the more common TL072 opamps instead. So you could try Burr Browns or whatever else to see if the headroom improves. Obviously it would get fiddly & time consuming, but it's up to you. Maybe socket some ribbon cable to a riser-board.
Unless you get lucky & find another MN3002, I can't see much else you can try.
Maybe try replacing the 50k level pot with 500k for better impedance if you're using guitars.

[Scruffie]

None of those things will affect headroom, only noise levels.

The problem with the CE-1 is it uses a fixed bias for the BBD and the reason they normally have a bias trimmer is because they're not consistent in their optimal bias point, if the headroom is low, adjust the bias or try another BBD that might bias up better with the fixed bias point.

The TDA1022 is actually a little superior to the MN3002 from a cursory glance of the datasheet, S/N is slightly improved, it claims an extra 0.5V P-P headroom @ 1% THD and the insertion loss is lower, which might mean the mixing resistors need adjusting to get a proper wet/dry mix but the datasheet doesn't have enough info on that and it'd need measuring.

Another thing I notice is the TDA1022 states adjusting the bias for 5V while the MN3002 says 3.3-4.9V so even with a fixed bias (I haven't looked at what the CE-1 has) the TDA1022 has slightly different requirements.

[RDL68]

My misinterpretation, Scruffie, I was indeed thinking noise & clarity. To use dirt boxes as a comparison, to get it away from the compressed muddy sound of an Ibanez Sonic Dist & closer to the clarity & better dynamics of a Boss Blues Driver.

The only trimmer in the CE1 is across pins 13 & 14 of the MN3002, they're the 2 output pins, so useless in this case. Therefore, it's just a matter of determining which resistor(s) to replace with a trimmer to fine tune the bias.
1 volt may not seem like much, in fact it could be as much as 1.7 volts out of focus, but it's enough to cause the problem for him. Once established (I'd be surprised if it isn't already), that info would become a mod everyone that builds these (or owns the originals) would probably use.

[lars]

I have a noisy CE-1 original unit. I read the problem is the MN3002 and change to TDA1022 will fix the problem.

As for the headroom, assuming all your capacitors are new & not still the old ones from the 70's, maybe you could try replacing the 2 opamps with something modern (not the LM1458 chip because that is the clock).

Where is the head banging desk emoji?

[RDL68]

Fair go, Lars, we don't all have the knowledge of scruffie with BBD's. He was very diligent to spot an oversight from drog_trog with the slight variance in BBD voltage. Most of us are just hobbyists or guitarists that assume things like that are already sorted before buying the PCB's.

Personally I've heard the term "headroom" applied to many pedals, run the Wrecktifier at 18v instead of 9v for better headroom, run the Zirconia compressor at 15v instead of 9v for better headroom, do Monty Allums Boss GE-7 EQ mod for better headroom & so on, but never heard it in relation to tuning in a BBD, nor did I expect it in relation to a circuit that has it preset without a trimmer.

With the capacitors in the old original CE1's, it's not such a crazy idea to replace them. That Dod Flanger 640 from the same era that I restored last year had one ceramic disintegrate in my fingers from age. When replacing the polyester caps, several measured way beyond their original tolerance which could've caused any number of problems. Most were still OK, but I concluded it was best to replace the lot. In Madbeans Collosalus, the capacitor that determines the clock frequency has to be accurate, so you wouldn't want some 40 or 50 year old part no longer functioning at the intended value in similar circuits. 

[Ricotjuh]

Hello, I have a question about the wiring of the stereo output. If I understand correctly from of the schematic and the manual, it should be something like this.
However, the "Dry" signal from the stereo jack will not be adjustable with the Level button. So only the signal from the mono output is adjustable.
Can somebody verify whether this is correct?
Or does anyone know how this is done in the Retro Sonic?

[marcinzera]

Hello,

it's possible to buy somewhere PCB's?

[RDL68]

Hello,

it's possible to buy somewhere PCB's?

He's on ebay selling the PCB's :

https://www.ebay.co.uk/itm/CE1-CLONE-PCB-KING-OF-CHORUS-USES-THE-TDA1022-512-BBD/254107550399?hash=item3b29fd82bf:g:8pQAAOSwm-FcKVxP:rk:11:pf:0

[RDL68]

As a few people have emailed me about power supplies for this circuit over the last few months, I'll just do a quick post about it for anyone else building one of these.

I usually test whatever build I do with a 9v battery with a short battery clip to DC plug. This is not a circuit where an internal battery clip can be used because there is simply not enough current in a 9v battery to power it. The circuit itself runs off dual rail charge-pumped power, so that's +14v, -14v & ground (a big ask for a 9v battery). When I tested it with a battery it did manage to run the vibrato mode, but not the chorus mode.

So moving on to power adapters. The majority of 9v power adapters available, including those sold in music stores touted as being designed for effects, are all switch-mode power supplies. Sure they can run a daisy chain of common Ibanez/Boss pedals off the one 9v adapter, but not this particular circuit. It simply doesn't like switch-mode power supplies & creates a very loud hum which makes the effect unusable.

And so starts the quest for the ideal "isolated" power supply.
I ended up buying a "Caline P1" power supply. 
It provides 5 x 9v outputs at 500ma, along with options for 12v, 15v & 18v at 1000ma.
I've attached a photo so anyone interested can have a look at the size of it next to a common Boss pedal.

As I said to Ricotjuh recently, if I was looking for something to use in a pro touring rig, I'd be looking at a more reputable brand of isolated PSU for reliability, even if it cost $500 compared to $50 for the Caline P1, but I did find that it's adequate & works out of the box. Whether it lasts remains to be seen, as such I'm not recommending it, but for testing builds etc it's fine for myself. As far as the fussy power supply requirements of this CE1 are concerned, it works without hum off 9v povided by the Caline P1. With a few other builds for me to finish up later that require an isolated power supply, the Caline P1 will be handy for those as well, but I repeat, if I was going to tour with some of these demanding builds, I'd shop for something confirmed to be reliable...

I'll just add that the Caline P1 had an 18v power adapter in the box with a bundle of individual DC cables...