Barcus-Berry Standard Pre-Amp Model 1330-1 [schematic]
- turbofeedus
- Breadboard Brother
Hey all, picked up this preamp last week. Came to me with a pretty bad crackle/hiss. Haven't sorted that out yet, but I did up a schematic.
I verified the transistor pinouts and gain with a DCA55.
Diodes are 1N7xx, forward voltage is 0.78V.
Enjoy and feel free to ask questions.
More pics here.
I verified the transistor pinouts and gain with a DCA55.
Diodes are 1N7xx, forward voltage is 0.78V.
Enjoy and feel free to ask questions.
More pics here.
- turbofeedus
- Breadboard Brother
Unfortunately not, and as far as I know, measuring for inductance is complicated.Axldeziak wrote:Are there any visible markings on the Bass pot inductor? (Is it painted over?) Measurement, perhaps?
I'd probably just start with a 500mH like this, and go from there.
Updated schematic with a couple corrections.
- Manfred
- Tube Twister
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Not realy using a LCR-meter.Unfortunately not, and as far as I know, measuring for inductance is complicated.
- Axldeziak
- Breadboard Brother
I may have found a few clues as to what the ITS30326 is. Seems the style of JFet, round, white on the sides with a black top was produced by Siliconix in the mid 70's and was known as the E series.
From there I was able to find mention of E230 Siliconix fets being used in early Barcus Berry amps. The model number was later changed to J230. Looking in a copy of the 1986 Siliconix FET Databook the J230 is listed alongside the J231, and J232 as being N-Channel "Audio and Sub-Audio Amplifiers."
From there I was able to find mention of E230 Siliconix fets being used in early Barcus Berry amps. The model number was later changed to J230. Looking in a copy of the 1986 Siliconix FET Databook the J230 is listed alongside the J231, and J232 as being N-Channel "Audio and Sub-Audio Amplifiers."
- turbofeedus
- Breadboard Brother
Don't have one of those unfortunately.Manfred wrote:Not realy using a LCR-meter.Unfortunately not, and as far as I know, measuring for inductance is complicated.
Nice, ultimately it doesn't matter much in this context. It's just being used as a buffer, so any modern NJFET should work ok; J113, 2N5484, etc.Axldeziak wrote:I may have found a few clues as to what the ITS30326 is. Seems the style of JFet, round, white on the sides with a black top was produced by Siliconix in the mid 70's and was known as the E series.
From there I was able to find mention of E230 Siliconix fets being used in early Barcus Berry amps. The model number was later changed to J230. Looking in a copy of the 1986 Siliconix FET Databook the J230 is listed alongside the J231, and J232 as being N-Channel "Audio and Sub-Audio Amplifiers."
- Manfred
- Tube Twister
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I see, perhaps there is repair shop in your area you can aks for measurement.Don't have one of those unfortunately.
- Manfred
- Tube Twister
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The treble and bass controls are in the feedback loop of the gain circuit.
I ran a simulation of the bass control where I have inserted the control circuit into the feedback loop of an inverting OP-Amp amplifier.
I have found the following center frequencies depending on the inductance of the coil. I made a PCB-Copy for retracing the schematic.
The coil on the very right of the layout is not marked Ready to print PDF-files: Sprint-Layout 6.0 - file:
I ran a simulation of the bass control where I have inserted the control circuit into the feedback loop of an inverting OP-Amp amplifier.
I have found the following center frequencies depending on the inductance of the coil. I made a PCB-Copy for retracing the schematic.
The coil on the very right of the layout is not marked Ready to print PDF-files: Sprint-Layout 6.0 - file:
- turbofeedus
- Breadboard Brother
Awesome work Manfred! I did call around and no-one had an LCR meter. I'd loe to get my hand on one of these:Manfred wrote:The treble and bass controls are in the feedback loop of the gain circuit.
I ran a simulation of the bass control where I have inserted the control circuit into the feedback loop of an inverting OP-Amp amplifier.
I have found the following center frequencies depending on the inductance of the coil. I made a PCB-Copy for retracing the schematic.
The coil on the very right of the layout is not marked Ready to print PDF-files: Sprint-Layout 6.0 - file:
- ppluis0
- Diode Debunker
Hi turbofeedus,
You (and all of us...)can build an inexpensive inductance meter presented in this link: http://electronics-diy.com/inductance-meter.php
Cheers,
Jose
You (and all of us...)can build an inexpensive inductance meter presented in this link: http://electronics-diy.com/inductance-meter.php
Cheers,
Jose
- Manfred
- Tube Twister
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Hi turbofeedus,
I own the LCR45 and am very satisfied with it.
it also measures the impedance and shows real part, imaginary part, absolute value and phase angle. If you are familiar with these expressions of electrical engineering then I can recommend the device, if not then I would consider an LCR meter device with a lower price to be sufficient.
I own the LCR45 and am very satisfied with it.
it also measures the impedance and shows real part, imaginary part, absolute value and phase angle. If you are familiar with these expressions of electrical engineering then I can recommend the device, if not then I would consider an LCR meter device with a lower price to be sufficient.
- turbofeedus
- Breadboard Brother
I'll check that out, thanks.ppluis0 wrote:Hi turbofeedus,
You (and all of us...)can build an inexpensive inductance meter presented in this link: http://electronics-diy.com/inductance-meter.php
Cheers,
Jose
They sound vaguely familiar I have the DCA55 and really like it, so I'm familiar with using Peak products.Manfred wrote:Hi turbofeedus,
I own the LCR45 and am very satisfied with it.
it also measures the impedance and shows real part, imaginary part, absolute value and phase angle. If you are familiar with these expressions of electrical engineering then I can recommend the device, if not then I would consider an LCR meter device with a lower price to be sufficient.
- Manfred
- Tube Twister
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Then the LCR45 is a good choiceThey sound vaguely familiar I have the DCA55 and really like it, so I'm familiar with using Peak products.
- turbofeedus
- Breadboard Brother
Couldn't swing the ~$120, so I ordered a cheap but well reviewed LCR meter off Amazon. Should be here tomorrow. Allegedly measures down to 200uH, so we'll see what happens.Manfred wrote:Then the LCR45 is a good choiceThey sound vaguely familiar I have the DCA55 and really like it, so I'm familiar with using Peak products.
- turbofeedus
- Breadboard Brother
Wasn't able to get a good reading with the LCR meter.
Important to remember, this unit started with problems, perhaps the inductor is part of those issues.
Regardless, either the inductor is more than 20H, seems unlikely, or something else is wrong.
Important to remember, this unit started with problems, perhaps the inductor is part of those issues.
Regardless, either the inductor is more than 20H, seems unlikely, or something else is wrong.
- Manfred
- Tube Twister
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Such a large inductance is not possible in this size.
Can you measure the DC resistance maybe you did not have good contact to the coil terminals?
Can you measure the DC resistance maybe you did not have good contact to the coil terminals?
- turbofeedus
- Breadboard Brother
Duh, don't know why I didn't think to test that. Yep, it's open.Manfred wrote:Such a large inductance is not possible in this size.
Can you measure the DC resistance maybe you did not have good contact to the coil terminals?
Only thing valuable about this now is the dimensions which are ~13mm long and ~7mm diameter.
- plush
- Cap Cooler
They are present in case input voltage swing exceeds supply voltage (i.e. input overvoltage protection).VivMeLol wrote:What do those back to back diodes at input do?
- ppluis0
- Diode Debunker
Perhaps it's time to make several speculations to guess what is the correct value of this inductor.turbofeedus wrote:Duh, don't know why I didn't think to test that. Yep, it's open.
Only thing valuable about this now is the dimensions which are ~13mm long and ~7mm diameter.
I'm not have luck using software simulators, so my best guess is that that coil must have a value of 1 to 2 mili henries.
Cheers,
Jose