Greetings from sunny Lancashire (UK)!
After a bit of lurking I've finally joined up, initially for help on a project I need to build. This has also got me thinking that I would also like to learn more than just building a kit and would like to take it further.
My "pressing project" is a buffer preamp I need to build for my hifi system. I use a Streamer/DAC with variable output which goes into my modest power amplifier which has a lot more gain than I need. I have very efficient speakers (101dB @ 1 watt/meter) so currently have Rothwell 15db attenuators installed at the amp inputs. I've decided on the First Watt B1 design as it looks "quite" simple for a beginner project and would be ideal for my needs.
I'm primarily interested in solid state and would like to start by learning with simple mono, low power discrete circuits, which would hopefully build up some knowledge and experience before progressing to more ambitious projects.
Could anyone advise me of where to start, or point me in the direction of some good resources for a beginner (besides here of course!)?
I have a few bits and bobs to help me get me going:
Things I already have:
Fluke 77 MkII
basic hand tools
old Antex soldering iron
old USB DAC/ADC
Things I think I'll need to get first:
Decent temperature control soldering iron
Bench PSU
Prototype/breadboard
Small bookshelf speaker I woundn't be upset blowing up 😉
Is that a sensible list to get going or should I be looking at anything else from the start such as a function generator or scope?
Any advice gratefully received 🙂
Ian
After a bit of lurking I've finally joined up, initially for help on a project I need to build. This has also got me thinking that I would also like to learn more than just building a kit and would like to take it further.
My "pressing project" is a buffer preamp I need to build for my hifi system. I use a Streamer/DAC with variable output which goes into my modest power amplifier which has a lot more gain than I need. I have very efficient speakers (101dB @ 1 watt/meter) so currently have Rothwell 15db attenuators installed at the amp inputs. I've decided on the First Watt B1 design as it looks "quite" simple for a beginner project and would be ideal for my needs.
I'm primarily interested in solid state and would like to start by learning with simple mono, low power discrete circuits, which would hopefully build up some knowledge and experience before progressing to more ambitious projects.
Could anyone advise me of where to start, or point me in the direction of some good resources for a beginner (besides here of course!)?
I have a few bits and bobs to help me get me going:
Things I already have:
Fluke 77 MkII
basic hand tools
old Antex soldering iron
old USB DAC/ADC
Things I think I'll need to get first:
Decent temperature control soldering iron
Bench PSU
Prototype/breadboard
Small bookshelf speaker I woundn't be upset blowing up 😉
Is that a sensible list to get going or should I be looking at anything else from the start such as a function generator or scope?
Any advice gratefully received 🙂
Ian
Last edited:
Moved to 'Everything Else' as there are quite a few questions in there 🙂
A scope is probably the single most useful diagnostic tool you could have. Although newer digital scopes have become very affordable a good s/h analogue type might be more suitable.
For diy resources, kits, projects and lots more check out Elliot Sound Products:
https://sound-au.com/
A scope is probably the single most useful diagnostic tool you could have. Although newer digital scopes have become very affordable a good s/h analogue type might be more suitable.
For diy resources, kits, projects and lots more check out Elliot Sound Products:
https://sound-au.com/
Make that a two channel scope, along with a couple of x10 probes.
And an inexpensive function generator.
This gives you all of that for $165, when used with your computer.
https://www.amazon.com/Pico-PicoSco...ocphy=9018935&hvtargid=pla-404289765070&psc=1
And an inexpensive function generator.
This gives you all of that for $165, when used with your computer.
https://www.amazon.com/Pico-PicoSco...ocphy=9018935&hvtargid=pla-404289765070&psc=1
My brief look in to scopes both standalone and computer based looks like a bit of a minefield! Is an 8 bit digital scope adequate for measuring distortion? A lot more research for me there I think... 🤔
A test speaker (or pair) is always a good idea. But I might be inclined to build something a little tougher, with say an 8” that can take 60 RMS or more if you can spend more than $20 for it with a small inexpensive horn tweeter that needs to be padded down 15 dB to match it. With a test subject like that, when you have a smallish amp running on say 25 volts and something goes horribly wrong it won’t do any damage. To the speaker anyway. And you can test larger creations at higher volume that you might not want to risk good speakers with.
No scope is going to accurately measure or show distortion unless it is pretty bad but that in no way detracts from the usefulness of the scope. For example comparing two amplifiers, one a Class A with lets say 0.2% distortion and a high spec Class B with 0.002%. Both would look the same on a scope but that isn't the point of the scope.
Most popular digital scopes are 8 bit and personally I don't feel it is sufficient. An analogue scope winkles out detail to the n'TH degree while with the digital it is just lost in quantisation noise.
If you to use speakers for testing amps and are afraid of damaging them, particularly with DC faults then make up a small inline series capacitor feed using two back to back electrolytics (to create a bipolar cap). Two 1000uF 100v caps with 10k 1 watt equalising resistors across each would be suitable. The speaker is safe from DC faults with those.
PC sound cards can be used for audio testing; many have good enough resolution to measure the quality of op-amps. Look into what Rightmark Audio Analyzer can do (RMAA).
Function generators don't have low enough distortion for serious testing, but they're fine if you want a constant tone for measuring. Or if you are hunting for a mechanical resonance in speakers or headphones or listening room, slowly sweeping a sine wave is the only way. There are kits based on XR2206 or 8038 function generator chips on ebay etc; the chips are clones, so performance may be worse, but they're cheap. And some day you might stumble across a real 2206 or 8038.
Ham radio swap meets can be good sources of old test equipment, if those ever happen again post-COVID. Also of electronic components of all kinds. Prices are low as, "you touched it, you own it" because vendors don't want to bring anything home. If you arrive late, check the nearby garbage containers, because lots of unsold stuff gets dumped.
For soldering, I went with a clone version of the Hakko T12, reasoning that if the generic tips weren't any good, I could buy real Hakko ones and have all the magic, since the T12 has heater/thermocouple/tip all in one unit. More expensive, but probably more accurate temperature control. There are assembled versions from various "brands", or kits with everything but case and power supply, using a variety of controllers from analog to LED display to OLED or LCD. I settled on an LED version since it was cheap, and while the calibration turns out to be wrong, the number doesn't matter as long as it stays where I set it. There are also T12 irons with a controller in the handle, from analog, to LED to OLED. I picked up an LED version because at the time it was ridiculously cheap, and more convenient for soldering outdoors.
So far the generic tips seem just fine.
Function generators don't have low enough distortion for serious testing, but they're fine if you want a constant tone for measuring. Or if you are hunting for a mechanical resonance in speakers or headphones or listening room, slowly sweeping a sine wave is the only way. There are kits based on XR2206 or 8038 function generator chips on ebay etc; the chips are clones, so performance may be worse, but they're cheap. And some day you might stumble across a real 2206 or 8038.
Ham radio swap meets can be good sources of old test equipment, if those ever happen again post-COVID. Also of electronic components of all kinds. Prices are low as, "you touched it, you own it" because vendors don't want to bring anything home. If you arrive late, check the nearby garbage containers, because lots of unsold stuff gets dumped.
For soldering, I went with a clone version of the Hakko T12, reasoning that if the generic tips weren't any good, I could buy real Hakko ones and have all the magic, since the T12 has heater/thermocouple/tip all in one unit. More expensive, but probably more accurate temperature control. There are assembled versions from various "brands", or kits with everything but case and power supply, using a variety of controllers from analog to LED display to OLED or LCD. I settled on an LED version since it was cheap, and while the calibration turns out to be wrong, the number doesn't matter as long as it stays where I set it. There are also T12 irons with a controller in the handle, from analog, to LED to OLED. I picked up an LED version because at the time it was ridiculously cheap, and more convenient for soldering outdoors.
So far the generic tips seem just fine.
After reading advice and doing some more research I aquired a nice linear power supply and a basic Picoscope. Over the weekend I put together a very simple amplifier on a breadboard (I know it's not ideal). The circuit I borrowed was this:
I think it's probably a bit limited in ability to provide current into 8 ohms (I've swapped the resistor on the LM317 to get 0.32A @16V). It doesn't sound too bad even though my measurements show it's a bit suspect when it comes to distortion 😉
All in all a very enjoyable first build and learnt a bit including biasing the MOSFET.
I think it's probably a bit limited in ability to provide current into 8 ohms (I've swapped the resistor on the LM317 to get 0.32A @16V). It doesn't sound too bad even though my measurements show it's a bit suspect when it comes to distortion 😉
All in all a very enjoyable first build and learnt a bit including biasing the MOSFET.
well done. I've spent many hundreds of hours with breadboards arranged like that.