No more than 2.4A then check heat sink if less than 50C with room temp of 25C up to 2.7 MAX
Colin Wonfor's SECA amp build
- Thread starter Marra
- Start date
No more than 2.4A then check heat sink if less than 50C with room temp of 25C up to 2.7 MAX
James Evans
Bedroom Bodger
Interesting re C4, any other changes to the circuit been suggested recently?
Yes James, Paul and I want to Master Slave about 10 Amp PCB's on one huge heatsink/ch and push the beast to 200W, but the heat sink comes at 1.6M H . 330mm W. with fins 150mm deep each. And power into each amp will be 600 - 750W nice.
I have also tried 47,000uF/25V on the amp board only, less ripple, that was fun but the cost are silly.
This set of PCB,s are DIY and thus variation on a theme is possible it for you to play learn and enjoy, and basically have fun like I am, now I was forced to retired/pushout from the cable company I started.
And I am designing a better cable soon to be on the market as I have sold the design and retailing at a lot lower price.
The One4 amp has been running for a couple of days now and is imho well worth building. the sound is punchy with a deep bass; open and detailed treble with a deep and wide soundstage.
My build is different than the norm as I used the p/s I already had which is common to both channels so no diodes or p/s caps on the pcb.
The small signal transistors were matched channel to channel on my dmm.Better matching would be achieved with an Atlas tester. All other components were as they fell out of the bag.
The bias trimmer should be set fully ccw before switch on and the offset trimmer set to centre position. Setting bias is straight forward the reading across R11 or R12 rising nicely. Output trimming is very sensitive and I wonder if a multi turn trimmer might be a better option in this position as it tends to overshoot with the slightest movement of the trimmer before settling back to a steady reading. Just take your time over this setting as readings very close to zero are achievable.
A couple of pics of the finished amp. The pcb is positioned to the back of the heatsink as this leaves me the option of installing the tracking power supply should I decide to go down that line.
.
My build is different than the norm as I used the p/s I already had which is common to both channels so no diodes or p/s caps on the pcb.
The small signal transistors were matched channel to channel on my dmm.Better matching would be achieved with an Atlas tester. All other components were as they fell out of the bag.
The bias trimmer should be set fully ccw before switch on and the offset trimmer set to centre position. Setting bias is straight forward the reading across R11 or R12 rising nicely. Output trimming is very sensitive and I wonder if a multi turn trimmer might be a better option in this position as it tends to overshoot with the slightest movement of the trimmer before settling back to a steady reading. Just take your time over this setting as readings very close to zero are achievable.
A couple of pics of the finished amp. The pcb is positioned to the back of the heatsink as this leaves me the option of installing the tracking power supply should I decide to go down that line.
.
Yank
Bulbous Also Tapered
So how does it stand up against the Aleph?
martin clark
pinko bodger
Nice work Marra.
Small suggestion if you need to play further at low cost - you have the existing PSU reservoir somewhat remote from the amp boards. But your loudspeaker 0v return appears still routed via the amp boards.
I think adding even relatively ' small' additional reservoir caps on the boards where you have the wire links could prove worthwhile in terms of sound quality. It will provide some bulk HF decoupling for the amp outputs by closing-up the output current loop: the PSU wiring from the main PSU then carries only LF current, not all the mid/HF decoupling also.
The extra four caps need not be anything as grand as the main reservoirs, but there is plenty of space and 4no. 1000-2200uF very easily fitted. Just a thought.
Small suggestion if you need to play further at low cost - you have the existing PSU reservoir somewhat remote from the amp boards. But your loudspeaker 0v return appears still routed via the amp boards.
I think adding even relatively ' small' additional reservoir caps on the boards where you have the wire links could prove worthwhile in terms of sound quality. It will provide some bulk HF decoupling for the amp outputs by closing-up the output current loop: the PSU wiring from the main PSU then carries only LF current, not all the mid/HF decoupling also.
The extra four caps need not be anything as grand as the main reservoirs, but there is plenty of space and 4no. 1000-2200uF very easily fitted. Just a thought.
Having tried that 10,000uf 50v worked very well indeed.
But link out the correct diodes, and get rid of that long bit of wire.
I'm with you Keith.
[/URL][/IMG]
Should make for an interesting winter project.
Why SECA
Well the Single Ended Class A published in HIFI world way back in the day was a design that interested me at the time but I never did get around to it. NK’s implementation was slightly different in that it used OP transformers.
Colin has come up with a nice simple design that’s been a little hard to resist and from the reports on sound that I've read should be worth the time, effort and expence needed to build one.
BTW the Voyagers are still sounding awesome but a change is as good as a rest IMHO.
And like Keith I like building amps
I have a spare U4 case and with my birthday and Xmas coming up now seems to be a good time for a winter warmer.
Another nice touch is that these boards can be had fully built and tested for those who find such things a little daunting.
I’ll be back with the stupid questions as they arise.
Should make for an interesting winter project.
Why SECA
Well the Single Ended Class A published in HIFI world way back in the day was a design that interested me at the time but I never did get around to it. NK’s implementation was slightly different in that it used OP transformers.
Colin has come up with a nice simple design that’s been a little hard to resist and from the reports on sound that I've read should be worth the time, effort and expence needed to build one.
BTW the Voyagers are still sounding awesome but a change is as good as a rest IMHO.
And like Keith I like building amps
I have a spare U4 case and with my birthday and Xmas coming up now seems to be a good time for a winter warmer.
Another nice touch is that these boards can be had fully built and tested for those who find such things a little daunting.
I’ll be back with the stupid questions as they arise.
Good to see that the boards have arrivedMy p/s and soft start pcb's are on order.
It didn't take you long to solder up the s/s board.
A friend built the Hi Fi World transformer coupled amp and I fine sounding amp it was too. He was I believe one of only a small number of people who successfully did so.
My p/s and soft start pcb's are on order.It didn't take you long to solder up the s/s board.
A friend built the Hi Fi World transformer coupled amp and I fine sounding amp it was too. He was I believe one of only a small number of people who successfully did so.
Yesterday I implemented a couple of changes to the One4 amp boards. As suggested by Martin and Colin I added power supply caps to the boards and at the same time removed the electrolytic input cap. This was replaced with a polypropylene cap mounted off board and connected directly between input socket and pcb and the 22k input resistor was soldered directly on the RCA socket. The p/s caps are 22,000uf as featured in one of Col's build shown over on Audiochews.
This amp is now beginning to sound really good and has lost the slight edge( to my ears) which it had initially. Down to the electrolytic??
This amp is now beginning to sound really good and has lost the slight edge( to my ears) which it had initially. Down to the electrolytic??
Good to see that the boards have arrived
It didn't take you long to solder up the s/s board.
A friend built the Hi Fi World transformer coupled amp and I fine sounding amp it was too. He was I believe one of only a small number of people who successfully did so.
Hi Keith
yes I remember the DIY Supplements well and used to look forward to them. The produced some superb Designs and had some great designers involved with their kits. The WAD kits worked really well (for the most part anyway) and I ended up building a few of them.
I realise that the HFW change where made for commercial reasons but I stopped reading it because everything in it was ready made.
And Id stopped doing that as much as possible by that stage.
I make one exception to that rule.
The soft start module is all Colins work.
That just leaves the amp and PSU which may take a little longer.
Dont forget Keith.
Xmas is the most wonderful time of the year Santa youve been warned
.You have 18V tranies if I remember correctly which is going to be just about perfect for the PSU upgrade but maybe running a little hotter than expected as you have things now.
Anyhow time to start the list.
