Just finished building/testing and now amp has been playing on and off for about 6 hours or so trying various types of music.
My first impression after connecting all input/output cables and switching on was one of disappointment as i couldn't hear a thing from either speaker, (even with volume turned high), literally dead silence, and thinking major trouble shooting ahead, having been accustomed in the past after building numerous tube amps with varying degrees of normally very low but audible hum, however after turning volume control back down and pressing play button, then slowly increasing again only music came from the speakers from a background of black silence, i was gob smacked!
It’s this silent background that seems to make the actual music stand out with such great resolution, this is a superb amp so thumbs up to Mr Pass for making it available to us Jo Public amateur builders.👍👍👍
I have made a few notes and attachments which might be of interest to other builders:
I used EasyEDA software for drawing the schematic and designing the PCB layouts, the gerber files can be exported and you can order the PCBs directly through the Easy EDA programme.
https://easyeda.com/
The minimum quantity is 5 boards for each design (good to have extra in case of soldering mistakes), they are cheap and good quality, just make sure to get the design you want before committing to order, check and re-check all component spacing, dimensions and hole diameters.
This was the first time I used this programme but after a little while it is easy to work with and good fun.
The below schematic is the one i used after re-drawing it in EasyEDA, the only change would be to leave out R7 fixed resistor and just have the R7 trim pot because with the R7 fixed resistor in place there is insufficient adjustment to reduce the offset.
![IMG_5445[1].JPG](https://www.diyaudio.com/community/attachments/img_5445-1-jpg.1053847/ "IMG_5445[1].JPG")
The same goes for the PSU board, you can design it any way you want to suit your own needs/budget, the attached PSU schematic is for one channel.
The chassis was ordered from Aliexpress, China and although it took a while to arrive it came well packed and of excellent quality, it can be completely disassembled so drilling and tapping etc is easily done and board/component installation also very easy, no complaints at all:
Brzhifi Bz4315a Double Radiator Aluminum Case For Power Amplifier - Home Theater Amplifiers - AliExpress
The MOSFETS/JFETS came from DIYaudio, the rest of the components mainly Mouser, there are plenty of lists/advice on forum on what to use.
The build was straight forward once I was confident with the PCB design, the only problem I had was adjusting the offset due to the addition of the fixed R7 which I mentioned earlier (this was my error due to the interpretation of original schematic I used), as soon as I removed it the offset was easily adjustable to zero and the bias likewise to 400mV.
Not much more to say really, like i said I've built quite a few tube amps in the past including a pair of 300B monoblocks which i thought up till now would never be beat, but this is right up there., thanks again Mr Pass.
My first impression after connecting all input/output cables and switching on was one of disappointment as i couldn't hear a thing from either speaker, (even with volume turned high), literally dead silence, and thinking major trouble shooting ahead, having been accustomed in the past after building numerous tube amps with varying degrees of normally very low but audible hum, however after turning volume control back down and pressing play button, then slowly increasing again only music came from the speakers from a background of black silence, i was gob smacked!
It’s this silent background that seems to make the actual music stand out with such great resolution, this is a superb amp so thumbs up to Mr Pass for making it available to us Jo Public amateur builders.👍👍👍
I have made a few notes and attachments which might be of interest to other builders:
I used EasyEDA software for drawing the schematic and designing the PCB layouts, the gerber files can be exported and you can order the PCBs directly through the Easy EDA programme.
https://easyeda.com/
The minimum quantity is 5 boards for each design (good to have extra in case of soldering mistakes), they are cheap and good quality, just make sure to get the design you want before committing to order, check and re-check all component spacing, dimensions and hole diameters.
This was the first time I used this programme but after a little while it is easy to work with and good fun.
The below schematic is the one i used after re-drawing it in EasyEDA, the only change would be to leave out R7 fixed resistor and just have the R7 trim pot because with the R7 fixed resistor in place there is insufficient adjustment to reduce the offset.
The same goes for the PSU board, you can design it any way you want to suit your own needs/budget, the attached PSU schematic is for one channel.
The chassis was ordered from Aliexpress, China and although it took a while to arrive it came well packed and of excellent quality, it can be completely disassembled so drilling and tapping etc is easily done and board/component installation also very easy, no complaints at all:
Brzhifi Bz4315a Double Radiator Aluminum Case For Power Amplifier - Home Theater Amplifiers - AliExpress
The MOSFETS/JFETS came from DIYaudio, the rest of the components mainly Mouser, there are plenty of lists/advice on forum on what to use.
The build was straight forward once I was confident with the PCB design, the only problem I had was adjusting the offset due to the addition of the fixed R7 which I mentioned earlier (this was my error due to the interpretation of original schematic I used), as soon as I removed it the offset was easily adjustable to zero and the bias likewise to 400mV.
Not much more to say really, like i said I've built quite a few tube amps in the past including a pair of 300B monoblocks which i thought up till now would never be beat, but this is right up there., thanks again Mr Pass.
Pass DIY Addict
Joined 2000
Paid Member
Congrats on a successful build! What gauge is the yellow wire between your rectifiers and power supply boards? Hard to tell, but maybe it looks a little thin?
Thanks, its 18 gauge, rated at 10A, its what i had lying around, normally max draw on this amp should be 2.5A, the fuse recommended is 2A for a 240V supply, actually i have a 3A slow in the live and 10A fast in the return, all that being said i might uprate it later
thanks for the feedback, but just for my understanding can you explain the need for separate fuses for the tx given that there is only one mains supply which splits to each tx after the main fuse, which will blow in the event of problem with either PSU
thanks
thanks
fuse value = Donut VA/Mains voltage
say that you have 2pcs of 250VA Donuts
for 230Vac that calls for, say, 1A5T Fuse per each Donut
if you want to fuse them together, you must use 3A16T Fuse
if just one goes in trouble (more likely scenario than both in same time), what level of secondary damage effect you expect , if each is separately fused vs. one big fuse for both of them?
same logic by which you have zillion smaller fuses in your home mains network, not just one (3) big
say that you have 2pcs of 250VA Donuts
for 230Vac that calls for, say, 1A5T Fuse per each Donut
if you want to fuse them together, you must use 3A16T Fuse
if just one goes in trouble (more likely scenario than both in same time), what level of secondary damage effect you expect , if each is separately fused vs. one big fuse for both of them?
same logic by which you have zillion smaller fuses in your home mains network, not just one (3) big
just remember - in case of anything gone wrong with channel, all what's preventing that your house go in flames - is exactly that one fuse
so, better to have it properly dimensioned, or you can just put a iron bar instead ...... and call it Audio Grade Fuse
seen those ...... in few cases I even denied any work on some poor equipment, abused by talented Audiophools
so, better to have it properly dimensioned, or you can just put a iron bar instead ...... and call it Audio Grade Fuse
seen those ...... in few cases I even denied any work on some poor equipment, abused by talented Audiophools
https://www.apexjr.com/wire.html#Teflon
For the rest of us who need at least two different color wires....
For the rest of us who need at least two different color wires....
Aleph J can dissipate a lot of heat. Having the heatsinks placed so close to those wooden side panels can't be good for cooling. I'd swap player and amp... Furthermore, the top and bottom plates have very little perforation, so letting that amp breathe freely seems like a sensible thing to do.
Or put some spacers under the amplifier feet to raise the amplifier 4 or 5 inches above the shelf to get some air flow and chimney effect.
Thanks for all the feedback, all fair comments.
Temperatures are fine, i have been monitoring with infrared thermo over some time max temp of mosfets is around 57 degC and sinks 53 degC directly behind the mosfet, obviously the rest of the sinks are all below that figure, anyway will continue to monitor.
I currently have a 3A slow blow fuse in the common AC live supply, will fit a 2A fuse in each of the tx supplies, and mount, (and mount a 20ltr fire extinguisher next to the amp
👍😉)
Temperatures are fine, i have been monitoring with infrared thermo over some time max temp of mosfets is around 57 degC and sinks 53 degC directly behind the mosfet, obviously the rest of the sinks are all below that figure, anyway will continue to monitor.
I currently have a 3A slow blow fuse in the common AC live supply, will fit a 2A fuse in each of the tx supplies, and mount, (and mount a 20ltr fire extinguisher next to the amp
👍😉)
AlephJ is reliable well designed amp. No need for fire extinguisher. Not to mention great sounding.
I would put fan on top. I always do, i do not like things too hot, unless they are tubes.
I would put fan on top. I always do, i do not like things too hot, unless they are tubes.