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BA312 replacement

B

bubhardy

AK Subscriber
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I have a 9090 that has a dead BA312 on the tone board. In the right channel, the test signal is fine at the input, missing at the output. The left channel is fine.
I want to replace both BA312s with an NE5532. I have some, and it is a fine audio opamp for this purpose, which seems to be to add gain.
I have read some ideas on this, but I was wondering if anyone here on the Sansui forum has any practical info on implementing this-or, why I shouldn’t pursue this idea.
Yes, I’m being a bit lazy, but after all, these forums are all about sharing knowledge.
Thanks for reading!
 
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I can’t see any reason why I should spend that amount on Sparko’s module, when I have the NE5532s and support components already.
I’m familiar with building prototypes on perf board, so I felt that I could put something together myself to do it.
I know that it’s doable.
I was really looking for a schematic that had the right values for the input/gain resistors. I can handle the power supply requirements and decoupling caps. From what I’ve read (and measured), the BA312s take the line level signal and amplify it to the level required by the power amp.
 
My understanding of the BA312 is that it is a 'Transistor Array' not an 'OP Amp' as such, I am thinking an OP Amp will not be a good match for the original BA312 for this substitution.

I agree though good, the Sparkos BA-312 modules do seem expensive, but in the absence of anything else, you don't have much choice?
 
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Hyperion said:
My understanding of the BA312 is that it is a 'Transistor Array' not an 'OP Amp' as such, I am thinking an OP Amp will not be a good match for the original BA312 for this substitution.

I agree though good, the Sparkos BA-312 modules do seem expensive, but in the absence of anything else, you don't have much choice?
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Right, the BA312 is a transistor array, but from what I’ve seen, it IS being used as a gain stage, a job that a good op amp can easily accomplish. At the time of the 9090, there were no high fidelity audio op amps. Now, an NE5532, for example, should be able to do this job very well.
I was just hoping that someone had a “canned” solution, rather than having to do this by the cut-and-try method. The boards in these old Sansuis are fragile enough, without having to do excessive soldering/unsoldering.
Maybe, I will install SIP sockets at the two BA312 positions in my 9090 tone board, so that my attempts won’t risk this?
I’ve looked at the SparkOS modules, and they look very good. I understand that development takes time and effort, as I’ve done a lot of it, in my working career. I just can’t really justify paying premium price for what is billed as “high end”, for a piece of gear that, while very good, doesn’t fit today’s high end category. Especially when a much less costly, high fi solution like the NE5532 exists.
 
bubhardy said:
I just can’t really justify paying premium price for what is billed as “high end”, for a piece of gear that, while very good, doesn’t fit today’s high end category.
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I was looking for some notes I remember that the replacement was discussed in diyaudio.


BA312.png OG_BA312.jpg

I guess you could use an adapter and make a discrete "BA312" board with the circuit, just in case the NE5532 adaptation, do not work
 
Hipocrates said:
I guess you could use an adapter and make a discrete "BA312" board with the circuit, just in case the NE5532 adaptation, do not work
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I'd only ever seen a 'representation' of what was inside a BA312, not a full circuit diagram with component values. :bowdown:

Armed with that, a great idea to create one yourself with discrete components. :banana:

Well done Hipocrates!
 
bubhardy said:
I have a 9090 that has a dead BA312 on the tone board. In the right channel, the test signal is fine at the input, missing at the output. The left channel is fine.
I want to replace both BA312s with an NE5532. I have some, and it is a fine audio opamp for this purpose, which seems to be to add gain.
I have read some ideas on this, but I was wondering if anyone here on the Sansui forum has any practical info on implementing this-or, why I shouldn’t pursue this idea.
Yes, I’m being a bit lazy, but after all, these forums are all about sharing knowledge.
Thanks for reading!
Click to expand...
Perhaps someone will send you a good used BA312. :D
 
Hyperion said:
Well done Hipocrates!
Click to expand...
To be fair, this is not my work... that's information from a guy on diyaudio. I don't know where I put the link.
bubhardy said:
Now, an NE5532, for example, should be able to do this job very well.
I was just hoping that someone had a “canned” solution, rather than having to do this by the cut-and-try method. The boards in these old Sansuis are fragile enough, without having to do excessive soldering/unsoldering.
Click to expand...
How about NE5534?
Regarding a ''canned solution" well, we have to grind a little, that's how it works and maybe in forums we'll find someone willing to help between the bunch of ''why not to do something". Not a big deal usually.

That said it would be fun to adapt a modern IC, with some work, simulations, prototypes and mods I think It can be done, but that would be more expensive (time wise) than a batch of sparkos replacements.

I forgot to add, on the other hand, making a little PCB with SMD resistors and the circuit could work and it would be way less time consuming.
 
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I would be very, very in for an alternative to SparkOs replacements.
They are great, but again very expensive. I’ve used them and the noise floor disappears.
I’m worried however based on the block diagram and the current alternatives that an op amp with some surrounding components isn’t quite an option.
 
I would think that a small piece of fine pitch 'perf-board' with the circuit laid out just as it is in the posted schematic will be fine. Using non-SMT components, you could stand the resistors up to reduce the size of board needed. I would be surprised if such an easily made thing didn't work very well. ;)
 
Thank you all for your ideas and suggestions!
I was thinking of using NE5532, because I could replace both BA312s on the tone board with it. It’s stable at unity gain without compensation. The hole patterns on the F-2544 board don’t line up nice, so a carrier board to adapt to the F-2544 would be needed, but I can handle that.
But the discrete component replacement is interesting, too. I was thinking KSC1845s might very used for it. It’s all voltage and little current. What do you guys think?
 
bubhardy said:
I was thinking of using NE5532, because I could replace both BA312s on the tone board with it. It’s stable at unity gain without compensation
Click to expand...
Seems like you have something there keep going.:naughty:
bubhardy said:
I was thinking KSC1845s might very used for it. It’s all voltage and little current. What do you guys think?
Click to expand...
I like it.
A board like this one I think can work to keep it neat, meanwhile a proper PCB is been produced ;)
https://www.proto-advantage.com/store/product_info.php?products_id=2500020
 
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