Barcus-Berry Standard Preamp Model 1330 (OPAMP VERSION)

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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soulsonic
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Post by soulsonic »

Decided it would be best to start a new thread for this one, so as not to clutter up the thread for the earlier version of this preamp.
There is an unverified schematic of this already floating around the web. There are several differences from my trace, as well as missing values; let's assume that other one is wrong! :lol:
First, the schematic:
B-B 1330 Opamp Version
B-B 1330 Opamp Version
Now, some huge hi-res pics...
_DSC7351.JPG
_DSC7352.JPG
_DSC7353.JPG
_DSC7354.JPG
_DSC7356.JPG
Paint came right off. LOL
Paint came right off. LOL
This circuit uses an interesting opamp that I haven't really seen in a guitar circuit before. Here's the datasheet:
MC3476P1.pdf
Datasheet for the opamp. Not a typical choice...
(109.41 KiB) Downloaded 16 times
This was originally intended for use with the Barcus-Berry contact pickup. I haven't tried it with a contact pickup yet, but it works with usual magnetic guitar pickups as well. I suppose you could use it to drive an amp hard. It has a fairly high output. With a hot humbucker, it will distort easily if the Sensitivity is up, in a way that most people would not consider very "toneful". :lol:
Maybe useful as a retro recording preamp? Anyway, I'm keeping mine now that I've got it working. Well worth the $5 I paid for it. :lol:
"Analog electronics in music is dead. Analog effects pedal design is a dead art." - Fran

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Post by Manfred »

Hi Soulsonic,

Thanks, that's great.
Please tell me the size of the board, I want to make a PCB clone.

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Post by Ichabod_Crane »

Do somebody know with what we could replace that opamp, please?

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Post by Axldeziak »

I was looking into low pass filters and realized that calculation for 5h, 100k is the same as .5h, 10k. Both have a cut-off frequency of 3183Hz. The rise fall time is the same for both as well at 0.000115.

I guess it would be possible to sub the bass pot with a 10K and the inductors with .5h(???) I hope so because the ONLY 5H inductors I can find are $15 a pop before shipping, 2 1/2 pound Hammonds.

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Post by soulsonic »

Axldeziak wrote:I was looking into low pass filters and realized that calculation for 5h, 100k is the same as .5h, 10k. Both have a cut-off frequency of 3183Hz. The rise fall time is the same for both as well at 0.000115.

I guess it would be possible to sub the bass pot with a 10K and the inductors with .5h(???) I hope so because the ONLY 5H inductors I can find are $15 a pop before shipping, 2 1/2 pound Hammonds.
This could be a good solution. If someone wanted to get into mathy engineery stuff, they could redesign it using active gyrator circuits. I'm neither mathy nor engineery :lol:

What about those small Mouser transformers, like the "42TM018" and its siblings? Those have been used for a long time in the DIY community for compact inexpensive inductors. I think some of them measure up in the several Henries range. Anyone have a list of the different inductance values of that series?
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Post by soulsonic »

Manfred wrote:Hi Soulsonic,

Thanks, that's great.
Please tell me the size of the board, I want to make a PCB clone.
4" x 2,85"
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Post by soulsonic »

Ichabod_Crane wrote:Do somebody know with what we could replace that opamp, please?
http://www.freestompboxes.org/viewtopic.php?f=13&t=431 :secret:
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Post by Axldeziak »

soulsonic wrote:
What about those small Mouser transformers, like the "42TM018" and its siblings?
Smallbear has the Mouser 42TM013 for $2.25. It's listed as 500mh and it's footprint is 22mmx15mm.

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Post by Axldeziak »

Maybe this will work for someone.
If it's crap let me know.
Attachments
Barcus-Berry 1330-1 Standard Preamp Layout.png

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Post by soulsonic »

I found a reference for a transformer that may work. The 42TM019 is used as part of Craig Anderton's "Passive Tone Control" project from Electronic Projects for Musicians. He says the primary should be around 5H when used as an inductor.
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Post by soulsonic »

I just found a TM018 in a parts box. It measures about 4.7H across either the primary or secondary (the TM018 is a 1:1 transformer).
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Post by Manfred »

i am still at odds with the inductors in my opinion it is impossible to bring such a high inductance into such a small size.

If LCR45 cannot measure a safe value, a question mark appears immediately before the displayed value.
Does the LCR40 behave in the same way?

I have done some simulations of the circuit with unclear results, so I will look at it in theory.

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Post by soulsonic »

Manfred wrote:i am still at odds with the inductors in my opinion it is impossible to bring such a high inductance into such a small size.

If LCR45 cannot measure a safe value, a question mark appears immediately before the displayed value.
Does the LCR40 behave in the same way?

I have done some simulations of the circuit with unclear results, so I will look at it in theory.
My LCR40 gives a result of it guessing it to be a resistor. But using another meter, it will give a resistance value nearly the same as what the LCR gives (around 1,68K), but will also give a value of around 4,5H when I measure inductance, which is way too high for any resistor to read.
The fact that it reads a fairly high resistance (assuming it is a coil of wire), suggests that it is wound with quite fine wire, which would certainly be necessary to get an inductor of this value in a small size. The small TM018 transformer is honestly not very much larger than this, and it contains TWO coils of such inductance, so it seems very possible to me that these are inductors; they must have been expensive.
I can't see how a 1.68K resistor would possibly have this much inductance, no matter what its composition.
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Post by Manfred »

The fact that it reads a fairly high resistance (assuming it is a coil of wire), suggests that it is wound with quite fine wire, which would certainly be necessary to get an inductor of this value in a small size.
I understand, you are right, very fine winding wire with a large number of windings can realize such a high inductance.

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Post by Axldeziak »

The first layout I posted IS crap.
So I redrew it:
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Barcus-Berry 1330-1 Standard Preamp Layout v2.png

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Post by turbofeedus »

Axldeziak wrote:The first layout I posted IS crap.
So I redrew it:
Just a small thing, the model 1330 appears to be the opamp version, where 1330-1 is the discrete transistor version.

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Post by Axldeziak »

turbofeedus wrote:
Axldeziak wrote:The first layout I posted IS crap.
So I redrew it:
Just a small thing, the model 1330 appears to be the opamp version, where 1330-1 is the discrete transistor version.
Figures... if only this site let ya edit your posts.

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Post by roseblood11 »

Is there really no better solution than using transformers as inductors?
4700uH inductors are avaliable on ebay.

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Post by soulsonic »

roseblood11 wrote:Is there really no better solution than using transformers as inductors?
4700uH inductors are avaliable on ebay.
Very good point! I found several listed at a good price very quickly.

But I cannot help but notice: looking at the DC resistance of them, they are all specified as having a resistance of a few hundred ohms or less, with most being less than 100 ohm. This makes me think that perhaps inside that package is an inductor with a resistor wired in series with it. :hmmm:

This makes the circuit make more sense to me, because I was pondering how it would be functioning correctly in the opamp feedback loop.

I now also wonder if having the resistor in series with it would throw off the inductance reading.
:hmmm:
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