Barcus-Berry Standard Pre-Amp Model 1330-1  [schematic]

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Re: Barcus-Berry Standard Pre-Amp Model 1330-1

Postby soulsonic » 07 Jan 2020, 21:32

turbofeedus wrote:Just found another 1330-1 on ebay and bought it, hopefully this one has a working inductor that I can measure.
I'd also like to measure the trimpot, hopefully it hasn't been messed with :hmmm:

Maybe you could cut open the bad inductor and show what's inside...whether it's a coil of wire, or a coil with some other component in series. Or maybe even not a coil at all.

I've thought about getting another opamp 1330 to do this with to try and verify for my version schematic, they're so cheap! :lol: I'd have thought they had more mojo value what with being vintage and having a reputation for Jimmy Page having once plugged into one. :lol:
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Re: Barcus-Berry Standard Pre-Amp Model 1330-1

Postby turbofeedus » 08 Jan 2020, 03:09

soulsonic wrote:
turbofeedus wrote:Just found another 1330-1 on ebay and bought it, hopefully this one has a working inductor that I can measure.
I'd also like to measure the trimpot, hopefully it hasn't been messed with :hmmm:

Maybe you could cut open the bad inductor and show what's inside...whether it's a coil of wire, or a coil with some other component in series. Or maybe even not a coil at all.

I've thought about getting another opamp 1330 to do this with to try and verify for my version schematic, they're so cheap! :lol: I'd have thought they had more mojo value what with being vintage and having a reputation for Jimmy Page having once plugged into one. :lol:


All it takes is one JHS video apparently, not that I want to benefit off anything that asswipe does.
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Re: Barcus-Berry Standard Pre-Amp Model 1330-1

Postby turbofeedus » 11 Jan 2020, 21:37

Alright, second unit arrived today, with a working inductor.
Inductor: 963.9mH, 411.8Ω
So, basically one these at 1H.

Also got measurements on the transistors:
Q1 (E320):
- D: 6.124V
- S: 0.569V
- G: 0V

Q2 (2N2484):
- E: 4.701V
- B: 5.320V
- C: 9.40V

Q3 (2N4058):
- E: 8.87V
- B: 8.14V
- C: 5.311V

And the trimpot: 3.573KΩ

Updated schematic:
barcus-berry 1330-1.jpg


Pics of second unit:
unit#2-1.JPG

unit#2-2.JPG
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Intripped (11 Jan 2020, 23:51), Manfred (11 Jan 2020, 22:07), ppluis0 (11 Jan 2020, 22:59)
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Re: Barcus-Berry Standard Pre-Amp Model 1330-1

Postby ppluis0 » 11 Jan 2020, 22:58

turbofeedus wrote:Also got measurements on the transistors:
Q1 (E320):
- D: 6.124V
- S: 0.569V
- G: 0V


Using these voltage readings, can we figure a replacement for that jfet ?
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Re: Barcus-Berry Standard Pre-Amp Model 1330-1

Postby Manfred » 12 Jan 2020, 00:28

I recalculated the JFet stage and was surprised that I did not get the right values, so I took a closer look at the PCB picture.
The source resistance is not 6.2kOhms as shown in the schematic but 620Ohms, with this value the calculated values are correct now.
The measured values result in a forward transconductance of about 1.6 Milliamps/Volt @ 1Milliamp draincurrent for the JFET.
The 2N4560 would fit as replacement type.
BarcusSourceResistor.jpg
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Re: Barcus-Berry Standard Pre-Amp Model 1330-1

Postby deltafred » 12 Jan 2020, 00:38

ppluis0 wrote:Using these voltage readings, can we figure a replacement for that jfet ?

It's configured as a source follower (unity gain buffer) almost any N channel FET would work.
Try what you have in stock.
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Re: Barcus-Berry Standard Pre-Amp Model 1330-1

Postby Manfred » 12 Jan 2020, 00:42

Why the hell is the edit icon not always displayed? :x

The 2n5460 would fit as a replacement type with the electrical values but not from the pin out.
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Re: Barcus-Berry Standard Pre-Amp Model 1330-1

Postby Manfred » 12 Jan 2020, 00:51

It's configured as a source follower (unity gain buffer) almost any N channel FET would work.

Take a closer look, it is not a source follower but a source circuit of the trimming potentiometer is the drain resistor,
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Re: Barcus-Berry Standard Pre-Amp Model 1330-1

Postby turbofeedus » 12 Jan 2020, 02:47

Manfred wrote:I recalculated the JFet stage and was surprised that I did not get the right values, so I took a closer look at the PCB picture.
The source resistance is not 6.2kOhms as shown in the schematic but 620Ohms, with this value the calculated values are correct now.
The measured values result in a forward transconductance of about 1.6 Milliamps/Volt @ 1Milliamp draincurrent for the JFET.
The 2N4560 would fit as replacement type.
BarcusSourceResistor.jpg


Good catch Manfred. Updated schematic attached.

barcus-berry 1330-1.jpg
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Re: Barcus-Berry Standard Pre-Amp Model 1330-1

Postby Intripped » 12 Jan 2020, 03:27

The 6.8k res on the treb pot, isn't it a 680 Ohm instead?
Also the 220k res, in the last pic looks like a 120k
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Re: Barcus-Berry Standard Pre-Amp Model 1330-1

Postby ppluis0 » 12 Jan 2020, 03:37

Hi turbofeedus,

What taper of potentiometers are using this preamps ?
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Re: Barcus-Berry Standard Pre-Amp Model 1330-1

Postby turbofeedus » 12 Jan 2020, 03:51

ppluis0 wrote:Hi turbofeedus,

What taper of potentiometers are using this preamps ?


Great question, not sure why I didn't measure before, but I just opened it back up.

The 2Meg "sensitivity" pot is Audio(Log), the rest are linear.
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Re: Barcus-Berry Standard Pre-Amp Model 1330-1

Postby deltafred » 12 Jan 2020, 09:41

Manfred wrote:
It's configured as a source follower (unity gain buffer) almost any N channel FET would work.

Take a closer look, it is not a source follower but a source circuit of the trimming potentiometer is the drain resistor,

Doh, you're right. I shouldn't go posting after a few Scotches.
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Re: Barcus-Berry Standard Pre-Amp Model 1330-1

Postby turbofeedus » 13 Jan 2020, 21:27

deltafred wrote:
Manfred wrote:
It's configured as a source follower (unity gain buffer) almost any N channel FET would work.

Take a closer look, it is not a source follower but a source circuit of the trimming potentiometer is the drain resistor,

Doh, you're right. I shouldn't go posting after a few Scotches.


I'll take partial blame, I drew the schematic kinda weird.
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Re: Barcus-Berry Standard Pre-Amp Model 1330-1

Postby deltafred » 14 Jan 2020, 12:36

turbofeedus wrote:I'll take partial blame, I drew the schematic kinda weird.

Nah, I take full responsibility.

I should know better than to post (or bid on Ebay, but that's another story) when under the influence!
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Re: Barcus-Berry Standard Pre-Amp Model 1330-1

Postby turbofeedus » 21 Jan 2020, 01:28

Intripped wrote:The 6.8k res on the treb pot, isn't it a 680 Ohm instead?
Also the 220k res, in the last pic looks like a 120k


Sorry I missed your comment, it absolutely is 680 ohm, not 6.8K. Good catch.
The 220K is definitely 220K however.
Updated schematic attached.

barcus-berry 1330-1.jpg
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