Pictures of your diy Pass amplifier

"Penultimate" Zen V4

This is still a work in progress. There are challenges to using these particular PCBs, which are not well documented. I really wish there were good boards available from the store.
Transformers are from some of the old Hafler amplifiers that I've collected over the years. Unloaded secondary voltage is 48V, and they exhibit some sag when under ~ 2A quiescent current load. Internal regulated rail voltage ends up being 47.7V, with a zener diode stack totaling 51.8V. Using IRFP150 in the regulator and current source positions, FQH44N10 in the signal amplifier position.
 

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Between Covid-19 and winter weather that won't go away, I've had time to finish projects I started awhile ago.
First up, was the stereo ACA v1.6 using premium parts, I used the schematic and parts list from TungstenAudio. Using an old Hafler DH-200 amp, I gutted and cleaned the enclosure and used it for the ACA. Without the massive transformer inside the enclosure, it was far to light weight, along with holes in the bottom from all the Hafler parts installed. So I used sound deadening material from 3M, peel and stick about 4mm thick, I cut two pieces for each side of the lower panel, added heft and quieted the inside of the enclosure.
I'm using a Meanwell power supply (24v 6.5A) from Parts Express, with a voltage adjustment I dialed in 24 vdc.
I kept one of the "speaker" fuse holder for the 115 vac line. The on-off switch is illuminated red when on, instead I'm using the amber "overheat" lamp for an indicator. (I've owned these amps since 1979 and only once did I ever see the ambler light go on.) The other fuse holder position I used for the mono-stereo bridge switch.
Of course, each PCB has a blue LED which are visible from the top and bottom through the vent holes.
The amp is about 8 hours old now and playing music for the next couple of days to break it in.
Photos show the ACA version on top of an original Hafler DH-200.
 

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That's a good looking ACA build. I love the clean lines of the old DH-200 chassis. I have one or two of those lurking around as well. Looks like you found a good way to mount the boards. The amp is definitely lighter with the SMPS inside instead of the big iron transformer. :)

There is a variation of a capacitance multiplier which can be used as a soft start to allow a large bulk capacitor to be used after the SMPS on the power rail. Look for the Mr Evil / PMI cap multiplier in the power supply forum. Jason Kuetemann has a slightly simplified version as well. Since this uses a P-channel Mosfet, it may be adjusted for a low dropout of ~1 Volt or a little less. The MeanWell SMPS can be adjusted to compensate for the dropout to keep your amp's rail voltage the same.
 
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F2J

I’ve never posted in this thread before. I figured now that I’ve finally reproduced one of Papa’s original First Watt amp designs why not?

I viewed the F2J as a natural progression in the baby steps I’ve taken since I joined DIYAudio back in 2008? I work slow ;)

My first amp was one of Peter Daniels gainclone kits. My second amp(s) was a pair of ACA monoblocks. In between I built a DCB1, some phono amps and various other projects and modifications.

I wanted something that focused on the simplicity of the fullrange drivers that first attracted me to this hobby and made me believe I could actually build my own great sounding audio system.

These amps were built to try and bring the best out of 8” fullrange drivers in my Oris 200 front horns. I’m currently using Lowther DX3s in them.

I started building the cases back in July of 2019. They’ve been playing for several days now.

Here’s some pics from along the journey.
 

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Thanks for all the kind words. I have really been enjoying listening to the new amps in my system this past week.

I try not to get too worked up about comparing or describing changes to my system with fancy words.

I will say that I have read comments by others about equipment “opening up” after a certain amount of play time. I would just as easily say that perhaps the person simply became accustomed to the change they were experiencing.

However, there was a feeling that the sound of these amps felt distant or congested when I first listened to them. I feel that a lot of that sense is gone now. Did I get used to them? Who knows.

I will say that I put on a very interesting album the other day Ry Cooder & V.M. Bhatt-A Meeting by the River and experienced a beautifully defined sound stage and remarkable detail that I had not experienced previously listening to the album.

@thompson I’m lucky to have a very tolerant wife who realizes this hobby is very much an important creative outlet for me. TV doesn’t get used much anyway. I am trying to get a sunroom rebuilt on the back of the house to repurpose for my system.

@Andersonix I built the DCB1 back in 2016 or so. I did go back into it some time this past spring to change out some Noble pots that I originally put in and turned out to have a linear taper as opposed to log (according to the seller). I also added some gain by installing Jensen transformers at the output with the help of ZM and his “What’s wrong with the KISS” thread. Did some rewiring and added a safety ground. I attached a few pics.
 

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