Jan made individual articles available for sale. https://www.linearaudio.net/
For a +/-15VDC supply search DK for a DC-DC converter, 2 outputs, 7 watts, Murata or Meanwell. The converter, if necessary, can outboard LM317/337 to remove a lot of switching transients. Make sure to put a choke on the input to the DC-DC converter. Marsh HPA will run well on +/- 12VDC
That is no longer the case.
The paper copies at Amazon are also printed to order, as far as I know.
The entire volume is available in a USB stick.
https://diyaudiostore.com/collections/books/products/the-complete-linear-audio-library
Over the years, he made a loss at the end, after all the effort.
Only doing this for love. My deepest respect.
Patrick
Here are some PCBs that Prasi designed for me to use Toshiba 1571/1930 TO-220 type BJTs. Provision is also included for original footprints so lots of choices to use.
They sound excellent, I had a pair of these running non stop for two weeks. Very addictive sound. I will now build up a second pair to fit as a balanced amp. All running at 26V from a Gilmore Golden reference PSU.
A few boards and matched toshibas left at cost if anyone wants to try them. A truly excellent head amp indeed.
They sound excellent, I had a pair of these running non stop for two weeks. Very addictive sound. I will now build up a second pair to fit as a balanced amp. All running at 26V from a Gilmore Golden reference PSU.
A few boards and matched toshibas left at cost if anyone wants to try them. A truly excellent head amp indeed.
Attachments
Hey Chris, it's the Marsh all day for me. More better sound like... 
The Whammy is in fact excellent and the very best kit to try first time as everything is on the board, Brilliant for rolling the front end. you learn a lot. However, the Marsh goes a bit deeper, stretches a bit further in the sound stage. I use Focal Elears and they are stupid good phones. Perfect match for my Dynalo and marsh.
The Dynalo is my reference, the very best I have heard. A balanced Marsh might be very close to the Dynalo. I have a few Dynalo kits and boards if you ever want to try one but build the Marsh for sure, probably the best value for money amp around, the sound exceeds the sum of the parts.
The Whammy is in fact excellent and the very best kit to try first time as everything is on the board, Brilliant for rolling the front end. you learn a lot. However, the Marsh goes a bit deeper, stretches a bit further in the sound stage. I use Focal Elears and they are stupid good phones. Perfect match for my Dynalo and marsh.
The Dynalo is my reference, the very best I have heard. A balanced Marsh might be very close to the Dynalo. I have a few Dynalo kits and boards if you ever want to try one but build the Marsh for sure, probably the best value for money amp around, the sound exceeds the sum of the parts.
And to you Chris, all the best pal.
Finish the Marsh, it's a great reference amp. You will like it no doubt. Once you try balanced I guess there is no going back, should you find yourself in possession of a DAC with balanced out, then convert your headphone plug and have a go.
Meanwhile, this is how we roll in South Shropshire kid... I bloody love this stuff, the building aspect. Problem solving, being meticulous. I'm thriving with this new balanced Marsh build - pic below show setup for stacked boards on U channel extrusions, these are smashed onto the side panel, the Marsh amps do not get terribly hot, they are very well behaved so this assembly method should do. Power is wired to beneath the bottom boards, they are connected via stackable pin headers.
Waiting for one quad of fets at exactly 8.6ma to match the ones I originally had, these four boards are a super matched quad. All transistors are practically 1:1 matched. This amp will be a beast.
Found an excellent case for this project, very chunky and sturdy, the amp is built upside down into the lid, no screws visible from the outside - Enclosure
Finish the Marsh, it's a great reference amp. You will like it no doubt. Once you try balanced I guess there is no going back, should you find yourself in possession of a DAC with balanced out, then convert your headphone plug and have a go.
Meanwhile, this is how we roll in South Shropshire kid... I bloody love this stuff, the building aspect. Problem solving, being meticulous. I'm thriving with this new balanced Marsh build - pic below show setup for stacked boards on U channel extrusions, these are smashed onto the side panel, the Marsh amps do not get terribly hot, they are very well behaved so this assembly method should do. Power is wired to beneath the bottom boards, they are connected via stackable pin headers.
Waiting for one quad of fets at exactly 8.6ma to match the ones I originally had, these four boards are a super matched quad. All transistors are practically 1:1 matched. This amp will be a beast.
Found an excellent case for this project, very chunky and sturdy, the amp is built upside down into the lid, no screws visible from the outside - Enclosure
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Hello all, if anyone is interested I'm selling my Prasi designed Marsh HPA boards to fund the next stage in the evolution of the circuit layout. I have a plan to go mostly SMD and possibly a fully balanced amp in a single PCB with the Golden reference supply circuit built in. (also single ended boards maybe) Very likely to fit a specific chassis seen in my last post (excellent chassis)
I would like to have the input fets thermally tracked to each other or even use LSK489 / LSJ689 in SOIC or SOT packages, (not sure about matching these however)
Believe me Prasi will be doing doing the heavy lifting here but I will go to SketchUp or Blender to do a layout plan. It's quite a job bless him, he is a legend for sure. I recommend his work very much.
So, two sets of boards, a pair each set along with Gilmore Golden Reference PSU PCBs and a few parts to help build the PSU boards. The parts kits vary slightly as I scraped them together with bits I have spare, but both kits are same price. Bear in mind each matched quad of K170/J74 cost nearly £50. All active devices are essentially super matched 1:1, very tight groups. DC is zero. You will not find better.
In the attached picture, the right hand kit (kit #1) is more complete, the HPA boards are entirely built and ready to play, Mounted as a stack on U channel block. the PSU filter caps are Vishay MAL high end caps, Toshiba 2SA1930/2SC1571 BJTs for Cap Multi section, LEDs and connector blocks.
Left hand kit (#2) Have the output transistors removed as I tried some Toshiba 2SA1360 & 2SC3423 TO126 BJTs, the original 1930/1571 BJTs are included along with two T-section mounting plates. PSU kit contains KSP42/ 92 small signal transistors, Nichicon filter caps, LEDs and Toshiba BJTs.
Both kits are £65 plus shipping and worth every penny. Brilliant sounding amps, the Toshiba BJTs are a definite upgrade, The boards however can accommodate several types of transistors, certainly worth experimenting. I have a few pairs of blank PCBs left if someone wanted to try different combinations. I cannot recommend this amp enough, a classic by Mr Marsh.
Get in touch, questions welcome, I put these here first before the swap meet.
Much love, build on..
I would like to have the input fets thermally tracked to each other or even use LSK489 / LSJ689 in SOIC or SOT packages, (not sure about matching these however)
Believe me Prasi will be doing doing the heavy lifting here but I will go to SketchUp or Blender to do a layout plan. It's quite a job bless him, he is a legend for sure. I recommend his work very much.
So, two sets of boards, a pair each set along with Gilmore Golden Reference PSU PCBs and a few parts to help build the PSU boards. The parts kits vary slightly as I scraped them together with bits I have spare, but both kits are same price. Bear in mind each matched quad of K170/J74 cost nearly £50. All active devices are essentially super matched 1:1, very tight groups. DC is zero. You will not find better.
In the attached picture, the right hand kit (kit #1) is more complete, the HPA boards are entirely built and ready to play, Mounted as a stack on U channel block. the PSU filter caps are Vishay MAL high end caps, Toshiba 2SA1930/2SC1571 BJTs for Cap Multi section, LEDs and connector blocks.
Left hand kit (#2) Have the output transistors removed as I tried some Toshiba 2SA1360 & 2SC3423 TO126 BJTs, the original 1930/1571 BJTs are included along with two T-section mounting plates. PSU kit contains KSP42/ 92 small signal transistors, Nichicon filter caps, LEDs and Toshiba BJTs.
Both kits are £65 plus shipping and worth every penny. Brilliant sounding amps, the Toshiba BJTs are a definite upgrade, The boards however can accommodate several types of transistors, certainly worth experimenting. I have a few pairs of blank PCBs left if someone wanted to try different combinations. I cannot recommend this amp enough, a classic by Mr Marsh.
Get in touch, questions welcome, I put these here first before the swap meet.
Much love, build on..
Attachments
So I wanted to my own PCB layout of the Marsh amplifier based on the article which I bought from Jan (very easy BTW). Now, being a bit lazy I started from a previous layout of the Alpha20/JISBOS diamond buffer by AMB whch is a very similar circuit (https://www.amb.org/audio/alpha20/).
Now, the question is of course: Will I go to hell if I just leave the Vbe-multiplier that AMB added to the Alpha20 instead of replacing it with the diodes that the Marsh-amp is using? To be honest I quite like the idea of being able to adjust the bias a bit
Now, the question is of course: Will I go to hell if I just leave the Vbe-multiplier that AMB added to the Alpha20 instead of replacing it with the diodes that the Marsh-amp is using? To be honest I quite like the idea of being able to adjust the bias a bit
Fair point Mark. However, what I really wanted to know was if there was any (obvious) downsides to keeping the Vbe-multiplier? Obviously three diodes is a bit simpler and may do the job, but if the Vbe-multiplier is already there then what?
I did actually do a revision of the board with the original Marsh biasing arrangement (took all of 5 mins to change the board) and I may well order them both, but still would be nice to know where to start testing (and where to deploy my remaining SK170/SJ74s)
I did actually do a revision of the board with the original Marsh biasing arrangement (took all of 5 mins to change the board) and I may well order them both, but still would be nice to know where to start testing (and where to deploy my remaining SK170/SJ74s)
@Nisbeth if you want a pair of my revised layout Marsh boards I will send them for free for you to play with, maybe you can bug-build the VBE across the diode section to get a sense of performance initially.
Interesting idea for sure, as you say the Alpha 20 is very similar, stick a Sziklai pair on the output and it's almost a Marsh. One thing I wished I had thought of was having the input fets connected to thermally track each other. Not sure this would revolutionise the performance, but wouldn't hurt.
Interesting idea for sure, as you say the Alpha 20 is very similar, stick a Sziklai pair on the output and it's almost a Marsh. One thing I wished I had thought of was having the input fets connected to thermally track each other. Not sure this would revolutionise the performance, but wouldn't hurt.