Here is the article on the head amp.
Mine uses a single pcb with ground plane on top, also mine uses bd139/140 instead of the old MPSU56 MPSU06,
LED on/off indicator directly driven from transformer secondary (AC). When power is turned off, LED extinguishes immediately -- no waiting for the DC filter capacitors to slooooooowly discharge.
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Thank you for article ! But bias pot wiper connection directly to generator transistor base are not good pratice.I will try to sim this amplifier in spice.
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I did a quick simulation (works fine with different transistors, 100mA bias, 10pf parallel to feedback resistor to remove small peak at 400Khz ) Bias generator changed to BD type TO126 for easier mounting on heat-sink. If someone interested - i can attach LTspice asc file. hope not copyrighted ...maybe one day I'll build it - a version of a reduced power amplifier😎
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Wish a knew how to use sim.
Well I'm very happy with the amp, so I'm sure it's worth building.
Ps. The article is from the start 80s, and the magazine that published it is long gone, so no copyright problems
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I would just point out one last time that there is a headphone amp reverse engineering threat for the Pass Labs HPA-1 headphone amp which sells for $3,500 and is described as superb by Stereophile: Pass Labs HPA-1 headphone amplifier | Stereophile.com ...someone laid out a PCB and built one and then compared it to some other headphone amps. Said it was in another league above the others.
No idea why there seems to be so little interest, but its at: Pass HPA-1, what do we know?
No idea why there seems to be so little interest, but its at: Pass HPA-1, what do we know?
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I will be very interested if a source of the PCB and a BOM is available. I have only seen the schematic.
What Jeff Young did is amazing. I do not have the resources to do what Jeff did.
Understood. If you would be satisfied with the great sound without the fancy case, then you could make a very nice HPA (world class says Stereophile). You might try a PM to Jeff to see if he will share Gerbers, don't know if he will or not.
I think I posted the Gerbers in the "What Do We Know" thread. Let me check....
Nope; evidently I did not. Here's the final schematic, Kicad board file, and Gerbers. (If anyone wants the other Kicad files just holler.)
Nope; evidently I did not. Here's the final schematic, Kicad board file, and Gerbers. (If anyone wants the other Kicad files just holler.)
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Well, it is NOT the fancy case. I want a well made PCB for the project. For larger PCB like the Pass HPA-1, it is difficult if not impossible to make high quality PCB on a hobbyist itching tray at home. The HPA is just a mini power amplifier, no mystery about it and design coming from Nelson Pass' shop should be exceptional good. I also believe that selection and matching of components are critical to the superb sound quality. If I build the HPA-1, I will need help in that department too.
THE WHAMMY CLASS-A HEADPHONE AMPLIFIER by Wayne Colburn will be easier for hobbyist to build and a kit (less case) is available at the DIY shop on this forum.
I am in the process of updating my E19 HPA. Up the supply rails to +/-18volt and replacing the output MOSFET using matched pair RENESAS 2SK1058 2SJ162 from jackinnj.
The most important matching is the JFETs in the front-end, and you can buy those matched.
Next is the current mirrors, but my experience with the KSA992s is that if you get them on cut tape, they'll all match.
I didn't match anything beyond that.
Cheers,
Jeff.
Thank you for sharing your experience and encouragement. I am using the E19 HPA with a Sennheiser HD600. I am happy with the sound stage and tonal neutrality of the combo for now. I am very, very tempted to build the Pass HPA if all the stars line up for me later this year. 😉
What do you think of THE WHAMMY CLASS-A HEADPHONE AMPLIFIER by Wayne Colburn? Cost wise, the kit is about the same as getting all parts for HPA-1.
My current project is the Wayne Palmer designed phono stage and E19 upgrade on the side.
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