DIY SECA Amplifier from Electronics World - by Colin Wonfor
I have just had the pleasure of putting one of Colin's Single Ended Class A amplifiers together, and I thought I'd write about the experience.
Colin published his SECA circuit for all to use in Electronics World, March 1999 (See here for link, EW1, EW2, EW3). There are 5 variants of differing outputs: 20w, 50w, 100w, 200w, & 300w. Colin actually built all these professionally, including the 300w SECA monoblocks, which is the largest SECA amplifier ever built. More recently he has developed his ideas further and refined his circuit, but his basic vision of a SECA circuit is all there in the magazine. This is the range he actually built:
I planned to make the 20w version. I have heard one of Colin's 20w SECA before and it is sublime (it's like the smaller one in the picture above). But monoblocks were planned because my speakers aren't that efficient and I had lots of lovely Kendeil capacitors from a previous project. So some MDF cases were knocked up, both a similar size to the 20w TOCA pictured except mine stand tall. They are painted gloss black and will be faced with Travertine stone.
The next step was getting the circuit sorted. About this time a friend of Colin's gave him some things called IGBTs. They are very large, they had been specified for large uninterruptible power supplies and have enormous current capability (and price, originally). This all goes far beyond my understanding, but Col was keen as mustard to use them, for two reasons: #1: It would be really simple to build (one or two output devices, as opposed to five or more), and #2: It had never been done in a SECA amplifier before, and in theory should be extremely good. The data sheet is here (400a IGBT), for those who are inclined!
I had expected to make the circuit up on Veroboard, but Col suggested getting the circuit drawn up on CAD & made as a PCB - which was a great idea. It allowed all the components to be labelled which was enormously helpful. It also gave me a beautiful quality item which was so easy to work with, and a few spares were ordered just in case.
The whole process culminated with a trip to see Colin at his lair, in order to benefit from some expert supervision. Also, the amplifiers would need setting up/calibrating and testing after construction, far beyond my abilities. As ever, Colin is patient and keen to impart understanding. Also, his enthusiasm was contagious - I started to understand that these amplifiers will be quite unique, it seems nothing quite like them has been built before. It was a real pleasure seeing the man at work.
I had a lot of fun with Colin, and it was great to get to know Kathy better. In between work, we all enjoyed each others company and a good meal out (I'm almost ready to eat again)!
Most remarkably, the amplifiers worked! And how they worked... I haven't stopped smiling since I heard them. They have all the SECA magic of the best of Colin's amps. Ridiculously, even with just one monoblock made, we had 3d depth of image from a single speaker, and real presence. Many on Chews will know SECA is special; well add IGBTs to it and something very wonderful happens. Even Colin was very pleased, and he has heard a lot. He even kindly offered to permanently look after them! I felt I couldn't burden him any further!
So, some figures for you. I hope Colin will join in this discussion as i am not qualified to answer questions, and I may have got some things wrong above/below. I am no electronics engineer or technician, but with good guidance I can put things together (rather like painting by numbers).
In the end, we made the amps 28 watts per side - the heatsinks allowed that (the IGBTs would have allowed much, much more).
The IGBTs see about 2.5 amps current, but can handle up to 400 amps each (!!!) - there are two on each monoblock, so will not get stressed.
The DC offset was 1.6 millivolts for one amp, and 0.2 millivolts for the other.
The damping factor is reckoned to br in excess of 4000.
The bass response is -3dB at 5hz, and the bandwidth is phenomenal (I can't remember Col!).
Some of those figures are pretty remarkable, but then Colin is in the habit of making remarkable amplifiers.
I cannot begin to tell how wonderful these amps sound, but I will try. Just give me some time to get used to what's going on, and for the amps to run in properly. Thus far, I haven't heard better.
I hope you enjoyed reading the ramblings of a confused but happy man.
Best,
A.
Colin published his SECA circuit for all to use in Electronics World, March 1999 (See here for link, EW1, EW2, EW3). There are 5 variants of differing outputs: 20w, 50w, 100w, 200w, & 300w. Colin actually built all these professionally, including the 300w SECA monoblocks, which is the largest SECA amplifier ever built. More recently he has developed his ideas further and refined his circuit, but his basic vision of a SECA circuit is all there in the magazine. This is the range he actually built:
I planned to make the 20w version. I have heard one of Colin's 20w SECA before and it is sublime (it's like the smaller one in the picture above). But monoblocks were planned because my speakers aren't that efficient and I had lots of lovely Kendeil capacitors from a previous project. So some MDF cases were knocked up, both a similar size to the 20w TOCA pictured except mine stand tall. They are painted gloss black and will be faced with Travertine stone.
The next step was getting the circuit sorted. About this time a friend of Colin's gave him some things called IGBTs. They are very large, they had been specified for large uninterruptible power supplies and have enormous current capability (and price, originally). This all goes far beyond my understanding, but Col was keen as mustard to use them, for two reasons: #1: It would be really simple to build (one or two output devices, as opposed to five or more), and #2: It had never been done in a SECA amplifier before, and in theory should be extremely good. The data sheet is here (400a IGBT), for those who are inclined!
I had expected to make the circuit up on Veroboard, but Col suggested getting the circuit drawn up on CAD & made as a PCB - which was a great idea. It allowed all the components to be labelled which was enormously helpful. It also gave me a beautiful quality item which was so easy to work with, and a few spares were ordered just in case.
The whole process culminated with a trip to see Colin at his lair, in order to benefit from some expert supervision. Also, the amplifiers would need setting up/calibrating and testing after construction, far beyond my abilities. As ever, Colin is patient and keen to impart understanding. Also, his enthusiasm was contagious - I started to understand that these amplifiers will be quite unique, it seems nothing quite like them has been built before. It was a real pleasure seeing the man at work.
I had a lot of fun with Colin, and it was great to get to know Kathy better. In between work, we all enjoyed each others company and a good meal out (I'm almost ready to eat again)!
Most remarkably, the amplifiers worked! And how they worked... I haven't stopped smiling since I heard them. They have all the SECA magic of the best of Colin's amps. Ridiculously, even with just one monoblock made, we had 3d depth of image from a single speaker, and real presence. Many on Chews will know SECA is special; well add IGBTs to it and something very wonderful happens. Even Colin was very pleased, and he has heard a lot. He even kindly offered to permanently look after them! I felt I couldn't burden him any further!
So, some figures for you. I hope Colin will join in this discussion as i am not qualified to answer questions, and I may have got some things wrong above/below. I am no electronics engineer or technician, but with good guidance I can put things together (rather like painting by numbers).
In the end, we made the amps 28 watts per side - the heatsinks allowed that (the IGBTs would have allowed much, much more).
The IGBTs see about 2.5 amps current, but can handle up to 400 amps each (!!!) - there are two on each monoblock, so will not get stressed.
The DC offset was 1.6 millivolts for one amp, and 0.2 millivolts for the other.
The damping factor is reckoned to br in excess of 4000.
The bass response is -3dB at 5hz, and the bandwidth is phenomenal (I can't remember Col!).
Some of those figures are pretty remarkable, but then Colin is in the habit of making remarkable amplifiers.
I cannot begin to tell how wonderful these amps sound, but I will try. Just give me some time to get used to what's going on, and for the amps to run in properly. Thus far, I haven't heard better.
I hope you enjoyed reading the ramblings of a confused but happy man.
Best,
A.
Comments
You can't beat getting down and dirty with that soldering iron, and building your own kit, especially when its something as special as one of Cols A class designs.
We need pron...........this is the DIY section after all !
Happy listening.
Paul.
Do you have any pictures of the build? How difficult was it?
Quick edit to the main text above - I linked to the wrong output device. Should be right now (ESM3030DV).
Let's try again... Sorry Col!
How easy was it? Well, Colin kept insisting it was simple, and in the end I guess it was - a lot is down to confidence. That comes with experience and I know a lot of you have made stuff before.
I do know that Colin would be delighted if more people made their own DIY kit, and his SECA design is perfect for home building. I can't see why it couldn't be made for building from kits.
I will take a few snaps soon, at the moment only their mother could love them! I haven't put the stone on yet, as it needs to be drilled & switches fitted.
Col - that was a meal and half (maybe two and a half), but it was a perfect setting after a days work. Looking back, I had no idea I was so tired, I'm amazed I didn't fall asleep in my dinner! Would definitely like to meet you & Kathy there with my whole tribe sometime, then we'll tear the joint up! The kid's will be riding the Harley round the restaurant, our wives moaning about how obsessed their men are with music, and we will be designing your next world first on a napkin!
I just got more into the world of DIY HIFI and built the dddac that Brumjam has. I am loving the DIY approach but I'm frustrated by my lack of knowledge, but I guess that takes time to develop and this is where help from Colin is invaluable.
I too would be very interested in trying this build.
Col did warn me to sit with a sound meter because I would have no idea how loud these play... I just had peaks of 95dB in a semi on a Saturday afternoon!! Good old count Basie... had to turn it down a bit though. There is just no stress to the sound (or my ears) even at loud levels.
The imaging is just superb, forward & back, with huge energy right from the centre of the image. This in no way diminishes at low volumes (my speakers are 83dB @1W/1M).
Don't know what else to write at the moment, it's all a bit of a blur...sensory overload or something.
They are speakerer-eaterers for sure. Respec' due, Col does not pussy foot around...
Having just paid the best part of 100 quid each for some 300 x 200 x 83 sinks for some 20w mono's, I dread to think what anything bigger would cost
Paul.
Hehe........A Brownium Motion Amp.
Next door is due to be vacant from the end of next week.
Room i have.
Deaf wife... Hmmmm.
Give me a few days.
Components mostly came from maplin, a few from RS/Farnell, whatever. Also the bridge rectifier.
My capacitors were massive overkill, but there are loads of suitable high spec items around. Mine are 63v 22000 uF.
The circuit board was drawn up by a friend on easyPC. I have AutoCAD experience, but not on 'lectrics, so a friend who understood the diagram in Electronics World drew it for me. If you want to know who made my PCBs, email me.
The IGBTs were through a friend who used to work with them. No one needs to spend £400 a pop though, there are more modern ones which are properly cheap, and faster than mine (therefore better). The thing is, my project was based on a beer-money budget, so I used what I could get.
I just want to thank Colin for his encouragement to go through with this project. Many designers wouldn't venture out from behind their company desks to support enthusiasts and end users like us, Col deserves a lot of praise for this. Only Nelson Pass does similar, and he is better known for it (loved, in fact) which doesn't seem fair. It's also a great credit to TQ that they care about the people listening to music through their equipment, and want to encourage more understanding. I find that refreshing, most companys would just view us as cash-cows, so well done.
But mostly thanks to Colin, da boss, for sharing his basic SECA circuit 15 years ago.
Outlay - I'm not sure really. If you had to buy every part in my amp & paid for proper cases, you'd be looking at a lot of money. I reckon something similar could be done for well under a grand if you're careful.
Can you bi-wire the RR3 Alan ?
You could bi-amp with the 10w SECA for treble.
As Dave says the Wonfor Class A sound is something special. I love my Quickie revamped ID25. Best amp I've owned.
Bass and smoothness to die for.
Can someone clarify for a numpty what exactly consititutes a "single ended" class A amp...?
I will be doing this soon....need to split crossover on speakers
Given equal gain, would it be better to bi amp with 'Beasts from the east' and 'baby blob',
Or double the heatsinking on the beasts and try for a hole in one with 40 - 50 watts?
This is just for fun, in no way do I feel I'm missing out here. In fact I have goose bumps right now (my sweet Carolina, Ryan Adams).
One of the biggest difference between these and the smaller SECA (and any other amp for that matter) is the bass coming from these little speakers. It is truly room filling yet it retains delicacy and speed, and is oh so fast.
Another amazing trait is the super-imposing of another acoustic space into my own, including a spooky illusion of size. This lends itself very well to live recordings, which are frankly ludicrously fun!
Col's amplifiers all handle string especially well - in particular strumming and plucking. This is now so distinct that feel I could almost learn to play along, given the detail I'm hearing. This is equally evident on all woodwind instruments to basses and guitars (acoustic or electric).
Something these have managed to do far, far better than the smaller SECA is brass instruments, they have real 'in your face' presence,with all the raspy discordant overtones you get when you stand next to (or play) the real thing. I was listening to the tuba bassline on Hypnotic Brass' 'War' and the shape it threw into the room was extraordinary. Tubas really do sound (and feel) just like that when you're close! And the collective harmonics of a group of instruments playing together is scary good - it induces goose bumps just like being right there, which brings back so many memories of when I used to play.
Speaking of playing, what about my old instrument. I spent quite some time drumming a few years back and I truly thought hifi would never realistically reproduce drums. It's not just the dynamics, it's the speed of a snare strike, the deforming of a snare skin followed by the crack then tone of the drum as the heads reform and resonate. It's something I can visualise quite easily but never hear on recordings, along with the correct sound of a cymbal being struck (the shimmer seems to be easy enough for most decent kit). Well guess what? I can't get close in terms of dynamics - not surprising given the speakers - and neither would I want to. But this is without doubt a fully correct facsimile of the sounds I spent so much time making.
I could also talk about piano, the way it sits in the soundstage and energises the room, and human voice (especially choral), but it would just get too much. I shall have to desist, as I cant keep writing essays about what I'm hearing. I suspect it will take some time to get used to all I hear, as well as the amps slowly coming fully on song.
Much Hifi focuses on detail, pulling things apart & spotlighting. I quite like that, I am a detail freak, more details = more reality, as far as I'm concerned. The large SECA have managed to present more detail on individual instruments than I have ever experienced before, in terms of space, texture, impact, and what the musician wants to convey emotionally. But what they excel at is presenting multiples of this (for each instrument) within an ensemble that has so much fullness and so many layers that it is almost an multi dimensional layered analogue projection. It's so rich I could almost get lost within it. The whole is more impressive than the details.
Well, I know what I wanted to say there - I must say it made more sense in my mind!
One thing this shows, in my opinion, is that Colin & Tellurium Q are right to be addressing phase distortion in their work. This is really an unusual level of realism and energy as far as I'm concerned, and it must be the unique quality of Colin's ideas and designs as nothing else has come close. The Iridium amps and new Claymore show these qualities even more than my lash ups, and I fully expect people to sit up & notice when they hear what has become possible in hifi sound reproduction. In fact, I am eyeing up the longer interconnects I now have to use between the pre & power amps, and wondering how to finance a TQ replacement. Because I am extremely confident it will bring real benefits.
I'm sensing relief in that last sentence. :-)
I often find myself seeking and taking huge satisfaction from psychological contact with others. When with creative individuals who have created things for me, the contact infuses their creation. If it's a hifi component it doesn't make it sound any better, but rather adds an extra dimension of appreciation to the creation.
I often find myself seeking and taking huge satisfaction from psychological contact with others. When with creative individuals who have created things for me, the contact infuses their creation. If it's a hifi component it doesn't make it sound any better, but rather adds an extra dimension of appreciation to the creation.
I'd like to hold the first naked hifi bake-off...x
Each core contains 25 individual insulated strands, as opposed to 5 for blob. There is also a lot of screening and a suitable earth, although the amps are double insulated. The cables will be hard wired to the amps, and I have yet to find a suitable mains plug choice.
It's taken 3 hours to construct these so far, and they weigh a flipping ton! I wonder if I'll hear any difference?