For my work, "close scrutiny" = observed casually and in gloomy conditions at a distance of 10m or less by a partially sighted mole. My work doesn't stand up to close scrutiny.
Sounds like my kind of close scrutiny too. I find it impossible to saw anything in a straight line or even drill a hole perpendicular to the surface. I need screws that bend! The main thing putting me off getting the PSU boards finished is the thought of more metalwork!!
undarra I would love to see your build but I'm in hospital at the mo and I can't seem to see your pictures. Maybe it would help if you put up a photobucket (or what ever you use) link up for me. Cheers
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100mR or 0.1R 3W
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The smaller resistors.
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The resistors mounted.
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Capacitor mounted. C5
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The current control preset near the AD820 op-amp.
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Fuse holder and 18-0, 0-18V power input for the transformer.
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Bending and mounting the 6Amp diodes in the bridge rectifier.
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Mounting the Green Led that is used to generate the ref voltage for the Current control. Note the long leg is near the hole it will be soldered into this is the Anode.
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Led with the two 10nF caps behind.
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One of the two 33,000uF bulk capacitors note the stripe in the case it is the Negative terminal alway check these or big bang will be louder than the music
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Mounting the Op-Amp AD820.
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The BC337 transistor and the DC offset preset.
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The drive transistors BD139 na BD140, see there orientation and the BD140 is on the right. Solder them closed as the PCB acts as a small heatsink. Also mount the BC337 close but not tight to the PCB. See above.
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Here is the PCB,sI did for Ben, (thanks for the order Ben could do with more)
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On set up insure the IQ preset is Anticlockwise and the DC offset is centre.
PCB 1 , 5Hz - 100KHz Flat PCB 2, 5Hz - 100KHz Flat at full power (15W) in this case.
DC offset -3.2mV 0.3mV
I/P Z 13.5K 13.5K
Damping 1150 1128 with a 250VA transformer tag on.
Phase angle 20Hz - 20KHz -,+ 3.0 deg both PCB,s
Boxed ready to go Ben
Also not the insulators under the MOS FETs a small amount of heatsink compound only OK "U" yes you now who.
Okay I can see everything now and if I tell you what I've done you're probably all want to disown me . All I had to do was turn off The hospital Wi-Fi and let my phone naturally download the pictures via 3G , Oh my goodness I can be so dim at times !!!
Paul Quick, have you finished your build yet with the power supply boards ? if you have do you want to get off your arse and post some pictures and tell us the difference in sound that they make
Hi Colin, on the PSU BoM you have position R13 on there twice with two different resistor values. Should the value be 10k or 3k6? I'm hoping you say 3k6 because that's what I have soldered in place [-O<
A quick update on how my SECA build sounds. My current amp for comparison is an Audio Note OTO SE, and as i didn't have a pre-amp i'm using a Pass B1 clone so i can only comment on this combo together. My preconceived ideas were that the SECA kit would give a more cleaner, more clinical, sound than the OTO, but maybe lose some of the OTO's midrange magic.
My actual findings are that it gives a big open, smooth sound, with more detail than the OTO but not in a clinical or grating way and is easy to listen too. Strings and vocal have good texture and the extra detail makes even well know albums more interesting. Comparing a kit build that's sub £500 against a production amp that's more than £2500 new doesn't seem fair, but it more than holds it's own. The bass isn't quite as well controlled, and the highest highs are smoother, or possibly slightly rolled off i haven't decided yet. Both of these points may well be down to the BI pre/buffer as i haven't heard it in any other systems and have read comments that it can sound a little laid back. Also the addition of the PSU boards may help to control and extend the bass further, but i should be able to comment on that in the next couple of weeks when i add them.
Overall very pleased with the sound of this and believe there's even more to come with the new boards and investigating other pre-amps. I haven't had a lot of listening time with it yet so there may be more thoughts to come if i can get them into words!
Big thanks to Colin, not just for the original design, but for all his help along the way (and everyone else that's helped) so that i could evn get it finished and making music.
That's really interesting reading Simon . Now get your skates on and put the PSU boards in so we all know what difference they make :-) Well done by the way, I bet you feel quite satisfied with yourself, I'm sure your aware but you could easily get £1000 for your Audio Note
Final parts for the PSU boards ordered today so should be able complete the boards by the weekend, then it's just the dreaded metalwork getting them fitted to the heatsinks! Will update once they're in, i'm as curious as anyone to hear the difference they make
As for selling the Audio Note it might be nice to have a valve and a solid state option. I'm quite fond of the old girl.
Great news Simon. You may be the first who has been able to evaluate the addition of the PSU boards, as I don't even think Quickie is being that .....quick. Or maybe he has but I've missed it
Col - I've just realised i couldn't use the base of the chassis as the two transformers take up all the space. I'm sure if i take my time i can mount them on the heatsinks with the amp boards. It would be neater like that and means i can separate a channel completely for testing etc. as it will all be mounted on a single heat sink.
If Quickie has finished the PSUs i'd be keen to here his impressions. If i can find some time this week i'm going to try using a squeezebox touch direct into the SECA thereby bypassing the B1 pre and see what the results are.
I couldn't help but change both the power amp and the pre as the OTO is an integrated. Now I'm trying to figure out what part the pre is playing in the sound.
I should be able to tell you what the differences are between AMP board only and AMP + PSU boards, but I ran without the Tracking PSU for a while and then converted to using the PSU and in between the two the memories faded!
However, accepting that I am biased, I have not heard a better amp in my system and since putting in the PSU I have really not felt like changing anything.
It may be possible to put in a big switch to allow rapid change from the AMP alone to AMP + PSU, I will talk to Colin about it just to make sure that I do not blow everything up.
I built my PSU's and amp boards yesterday. The PSU's are based on a previous BoM so I have more parts on these boards than I actually need. They should be ready tomorrow providing RS Components turn up with a couple of transistors that Farnell mis-picked on my original order.
Colin missed this off the original BoM but I found it very helpful
Post-pizza amp building:
There are a few bits missing from my amp boards that I'll fix tomorrow. Then it's on to the dreaded case metalwork (
Your comments about this amp comparing favourably to your Oto are encouraging Si. I also use an Oto and it would be great if the amp/PSU combo is in the same ballpark. Given the damping factor of these amps I'm expecting tighter bass than I experience with my Oto.
Brumjam - will be interested in your comparison with your OTO. I also thought that the greater damping factor would result in tighter more controlled bass, but haven't noticed that yet. Hopefully the addition of the PSU boards and/or a pre amp upgrade will sort that. What pre will you be using it with out of interest?
Comments
Lovely. Looks like mine. Only very much neater! (And the PCBs mounted sideways of course!)
^:)^
My work doesn't stand up to close scrutiny.
I would love to see your build but I'm in hospital at the mo and I can't seem to see your pictures. Maybe it would help if you put up a photobucket (or what ever you use) link up for me.
Cheers
Oh my goodness I can be so dim at times !!!
Well done by the way, I bet you feel quite satisfied with yourself, I'm sure your aware but you could easily get £1000 for your Audio Note
You may be the first who has been able to evaluate the addition of the PSU boards, as I don't even think Quickie is being that .....quick. Or maybe he has but I've missed it
Hope it all goes well.
I don't suppose you have a Farnell item code for the amp PCB part that sits right next to the DC adjust? It's marked 470R.