I recently came across an article by Marshall Leach " Construct a Wide Bandwidth Preamplifier" The article mentions Daniel Meyer as a reference and the schematic is similar if memory is correct to the phono preamp that Meyer put out as a kit in the mid 75-77 era with the exception that Leach used Fets in the front end of his phono preamp instead of discrete transistors. Meyer actually had two versions of the phono preamp board with the later sounding better. Sorry, all my Southwest Tech info was lost in a recent move so I cannot mention specific board numbers or model numbers. I can only remember the phono board sounded very good if my memory is still intact.
To make a long story short I have the article in hand which includes the circuit board foil pattern for the RIAA input board along with the output board. I don't know how to make a board so I am either seeking information on a company that would make a board or a newer circuit that will sound good, have discrete transistors instead of OPAMPS and the ability to purchase a blank circuit board.
Any help or ideas would be welcome. I would like to keep this as a project since I am retired and bored out of my mind needing something to put together. I would like to mention I am a Tube Freak and currently have a tube phono preamp but would like to give this a try.
To make a long story short I have the article in hand which includes the circuit board foil pattern for the RIAA input board along with the output board. I don't know how to make a board so I am either seeking information on a company that would make a board or a newer circuit that will sound good, have discrete transistors instead of OPAMPS and the ability to purchase a blank circuit board.
Any help or ideas would be welcome. I would like to keep this as a project since I am retired and bored out of my mind needing something to put together. I would like to mention I am a Tube Freak and currently have a tube phono preamp but would like to give this a try.
The pearl 2 boards are available from PassDIY, it is very highly thought of and 6l6 has a build guide for it. Check the pass labs forum.
The Leach circuit is simple enough to build on a proto board. Alternatively, what can be a better excuse to learn a schematic capture/pcb package?
I made this preamp from the original Audio magazine article before Leach published his FET revision. As I recall I made the boards photographically from the actual magazine pages. Slow to finish, I added the stepped attenuator and IC regulated power supply and though I obtained the upgrade designs from Dr. Leach in correspondence, I never tried the FET circuit. The original has been my only preamp ever since. I like it.
That said, the preamp (and my DH-200 amp) are currently out of service and on the operating table for re-capping (about time!) and I've been thinking about new projects too.
I have given some thought to a version of the FET (Leach called it "Universal") phono circuit. If I can figure out how to lay out circuit boards on the computer (in my day...) I will do it and a Current Mirror pre-preamp and maybe a Marsh Pooge-3 line stage and...
Here are a couple of links:
Dr. Leach's Amplifier and Speaker Projects
Moving Coil Cartridge Head Amps
On the other hand Wayne's Pearl II is worth very serious consideration. The boards and transistors are available from Pass.
PassDiy
That said, the preamp (and my DH-200 amp) are currently out of service and on the operating table for re-capping (about time!) and I've been thinking about new projects too.
I have given some thought to a version of the FET (Leach called it "Universal") phono circuit. If I can figure out how to lay out circuit boards on the computer (in my day...) I will do it and a Current Mirror pre-preamp and maybe a Marsh Pooge-3 line stage and...
Here are a couple of links:
Dr. Leach's Amplifier and Speaker Projects
Moving Coil Cartridge Head Amps
On the other hand Wayne's Pearl II is worth very serious consideration. The boards and transistors are available from Pass.
PassDiy
I think I'm going to pass on the pearl. I had a Dunlap Clarke model 10 Fet years ago and I didn't like the sound of the Fets. Not a Fet fan. I prefer simple bipolar transistors.
You're condemning fets based on a +40 year old design that maybe wasn't very good to begin with.😕
jeff
jeff
Google "Toner Transfer".
You make a heavy laserjet print on a Playboy or similar glossy paper. Clean copper PCB really well. Tape the transfer. Hold a hot iron on it a while so the toner (powdered plastic) melts to the copper. Soak the paper off, dunk in etchant.
1999-2018 this was THE way to make one or two boards.
I have made boards that complicated with Carbon Paper (is that still a thing?). Trace the pattern onto scrubbed copper, go over twice with a fresh Sharpie, etch.
There was tape with lines and dots. Also rub-on transfers with various useful curves. Any stock still in stores is liable to be too stale to stick.
And as said: perfboard and a foot of bare wire (peeled CAT3) can do that job.
I loved handcrafting PCB layouts with tape and stick-on pads. But as you say those materials (from the '80s!) are all "stale" as my original artworks are now fragile.
Still, there's an attraction to photo processes. Photo-etch boards are still available. Layouts can be done at 2x size and reduced to "full" size on a copier. You can do fairly precise work in this manner. The line work should wind up denser too.
One good reason to use printed circuit boards is to accommodate particular components in a compact neat form. Using someone else's boards can be too restrictive unless you choose the same components (capacitors are especially problematic).
CAD programs coupled with the manufacturing services can be the best of both worlds. And when I find one I can figure out I'll use it. Not sure that I'd use the translation from schematic feature.
For a simple layout drawing directly on the copper with a Sharpie seems attractive.
On the other hand... so does perfboard.
@PRR -- what boards do you use? I've never been able to figure out the logic of the ones with copper patterns.
Still, there's an attraction to photo processes. Photo-etch boards are still available. Layouts can be done at 2x size and reduced to "full" size on a copier. You can do fairly precise work in this manner. The line work should wind up denser too.
One good reason to use printed circuit boards is to accommodate particular components in a compact neat form. Using someone else's boards can be too restrictive unless you choose the same components (capacitors are especially problematic).
CAD programs coupled with the manufacturing services can be the best of both worlds. And when I find one I can figure out I'll use it. Not sure that I'd use the translation from schematic feature.
For a simple layout drawing directly on the copper with a Sharpie seems attractive.
On the other hand... so does perfboard.
@PRR -- what boards do you use? I've never been able to figure out the logic of the ones with copper patterns.
Some here can tell differences in capacitors and resistors as well as other components. I can hear the differences between a Fet front end and a bipolar transistor. I'm sure the Pass design is a very good one. I don't particularly want to gamble $200 for a board and a supply of matched Fets so I can try a design I've never heard before. I'm retired and yes funds are tight considering I have other hobbies in which I have to split my allowance. So, yes I'm condemning Fets based on what I've heard in the past as well as other audio pieces that I've heard that are newer in design. Also, I don't know Fets so its fear of the unknown that and the fact I have a lifetime supply of 2N5087's and 2N5210's. I like the past so I prefer what I'm used to playing with.
Concerning the toner transfer method... I've watched youtube video's on making PC boards and it looks fairly simple. I have a Dell Laser printer in my computer room and I'm assuming that I could hand feed a sheet of glossy paper (no Playboy's here) so that much I believe I grasp. The article I posted has a copy of the PC board traces so my question is do I scan that into the computer and make a print onto the glossy paper? It says "Circuit board foil pattern for the RIAA input board.) Also has a PC foil pattern for the output board. So do I scan these into the computer and then print to a glossy paper? Also, how do I print the other side that contains symbols?
I've looked for software and found some but for some reason my computer won't unzip them. I thought maybe I could do the schematic capture thing and send the file to a board house to be made.
I've looked for software and found some but for some reason my computer won't unzip them. I thought maybe I could do the schematic capture thing and send the file to a board house to be made.
Hi
If you are using this method, don't scan a paper copy, use the PDF in the link I provided and just print.
The diagrams of the component side aren't a "silk screen" but just a stuffing guide.
A question: doesn't this method create a mirror image of the circuit and does that matter?
If you are using this method, don't scan a paper copy, use the PDF in the link I provided and just print.
The diagrams of the component side aren't a "silk screen" but just a stuffing guide.
A question: doesn't this method create a mirror image of the circuit and does that matter?
I expect so but why bother? You have the circuit layout and the stuffing guide both well documented.
Silk screens are really only helpful when you have no knowledge of either. For instance, if you managed to send the article to a board manufacturer who created new PCB layout (different from Leach's) where it wasn't immediately obvious where components belonged then a silkscreen would be helpful, maybe even necessary. Otherwise it's just decoration.
Silk screens are really only helpful when you have no knowledge of either. For instance, if you managed to send the article to a board manufacturer who created new PCB layout (different from Leach's) where it wasn't immediately obvious where components belonged then a silkscreen would be helpful, maybe even necessary. Otherwise it's just decoration.
I just thought it would be nice for when I forget where my documentation was for this particular project. I'll just glue it to the bottom of the enclosures cover plate. Your right why make something more difficult. Now to find some ferric chloride.
Now you're talking.
One more thing... you could always take a (fine) Sharpie and make helpful "notes" on the copper side "+", "-" for power polarity etc. Just don't accidentally "connect" parts of the circuit together!
One more thing... you could always take a (fine) Sharpie and make helpful "notes" on the copper side "+", "-" for power polarity etc. Just don't accidentally "connect" parts of the circuit together!
pcb fab memories from yesteryear
I get all my pcbs from jlcpcb these days
The leach is a nice discrete design, reminds me of high end kenwood designs BUT
if you can live with a std opamp supply V, try a OPA1656 or even a NE5534 first and get back to me if all the effort in a discrete design is worth it.
Self writes about it in his early works.
In my setups I use a passive attenuator between the sources (CD, tuner) and amp. Unless you are into vinyl, do you need all that gain. I do not even use tone controls.
Oh well have fun building what you come up with, it is fun none the less, hope it works out for you.
I get all my pcbs from jlcpcb these days
The leach is a nice discrete design, reminds me of high end kenwood designs BUT
if you can live with a std opamp supply V, try a OPA1656 or even a NE5534 first and get back to me if all the effort in a discrete design is worth it.
Self writes about it in his early works.
In my setups I use a passive attenuator between the sources (CD, tuner) and amp. Unless you are into vinyl, do you need all that gain. I do not even use tone controls.
Oh well have fun building what you come up with, it is fun none the less, hope it works out for you.