OK so I've been a bit slack getting to the second instalment. I actually finished the last coil about three weeks ago and have made the crossovers.

Tip number 1. Wear Gloves!! After the first coil my fingers were killing me. I'd pulled back the skin on my fingertips so hard that it was coming away from under the fingernails. Ouch!!! The gloves I subsequently wore were just normal rubber dish washing gloves. These worked quite well because they allowed me to put tension on the wire (holding the spool) and I no longer got sore fingers

Tip number 2. If you can make the same value with different size formers, choose the one with the lesser turns per layer. My pancake coils were much easier to make than the taller ones.

I think that the reason for tip 2 is that the more turns per layer, the more chance that small kinks in the winding wire will add up to enough to make it hard to get the last turn on for any particular layer. The coils...

Wind my own coils, yeah why not, how hard could it be? Well if you are as much a perfectionist as I can sometimes be, pretty damn hard!!!

I suspect it would actually have been a whole lot easier if I'd not obsessed about getting a low DCR for my coils, and gone with a smaller gauge wire. As it turns out I was (obsessive), and decided to use 1.6mm (~14 AWG) wire.

I originally had thoughts of measuring off the length I needed, clamping one end in a vice and slowly turning the former (in my hands) until I wound it all on, luckily that Idea didn't last very long and I started to think about making a winding jig.

I hit google and saw some pretty fancy jigs, motorised with clutches, speed control, turn counters, that all looked too hard, so I thought about what I actually needed. Georges Transformer winding jig was in the back of my mind too, which gave some inspiration as well

The pictures below are what I came up with. I had...

It seems I have been doomed to not do any of my DIY projects since my main computers hard drive crashed followed shortly after by my laptops (the laptop has had another crash after that, and the drive is now on the way out again!!)

After having to pull the cables out of my chipamp last week and plug the TV into it (because the MythTV box refused to play a DVD and I can't plug the DV18 DVD player direct to the chipamp because it has no volume control) I decided I had better get off my backside and finish my pre/active crossover. I had to do it again tonight as well (plug the tv into the chipamp), sigh...

This is all because my playmaster had something in the pre die again and is only working on one channel and I just haven't been bothered fixing it. I thought that being inconvenienced might make me more likely to finish the other projects but it has been broken for about 6 months

So on Monday I decided that I should re-install Holm-Impulse...

Following on from YARPS I thought I would post the design I have been working on for my active crossover (which is in fact is what the YARPS power supply was designed to drive).

So here I present the Synergy "Active" Crossover. Please note I have only simmed it at this stage (and when I started I knew nothing about active filter design) so there is no guarantee it will work.

Why have I put "Active" in quotes? Because whilst this filter uses active components, for all intents and purposes it behaves like a passive filter. It basically emulates either an LC or a CL passive 2nd order filter.

Why the name Synergy? Well I though it was the best word to describe the differing technologies working together to give the end result

The design goal is to have an active crossover that for all intents and purposes is transparent. That is it does nothing other than split the frequencies at the desired crossover point....

I'm in a way glad that it is taking so long to finish these speakers after my four year break from them! If it had have taken a couple of weekends I would have kicked myself for not having done it sooner!

One thing that having had a four year break does is make it easier to slow down and do things properly, afterall, a month or two is relatively short in comparison

I got over two of the biggest fears with this project on the weekend. One was whether I was going to be able to do the veneering properly (this seems so far not to be an issue) and the other was whether my plans to put a 22mm chamfer on the front baffles was going to work (a test on some scrap MDF worked well). The main thread for the project is here with all the latest pictures

How to finish the veneer is as yet undecided, but I'll worry about that in a few weeks

The next big hurdle after finishing the boxes is going to be getting decent freq response measurements,...

I've long known that the boxes for my current three ways are leaky, more than likely incredibly leaky, but I've never bothered doing anything about it because I intended to build some new not leaky cabinets. Well I haven't and it is probably going to be a while before I do, so today I decided to check the impedance curve for the woofer in box. Thanks to Mick (prickears) for his quest to get to the bottom of his 80 Hz suckout I am finally doing something about my leaks!

The design goal (when I changed to vifa 10" drivers from the original 12" plessey's) was a box tuning freq of about 34Hz. When I measured the impedance today for one of the boxes, the tuning freq was in fact about 30Hz much lower than intended and when modeled with that tuning freq, has a very droopy response starting to roll of from about 220Hz, though the f3 is only 2HZ higher than the inteneded model at 36Hz..

So It looks like one of the diy tasks in the comming weeks will be attempting...

I'm finding DIY'ing a very different ball game now that I have started again. The difference being I have a 21 month old daughter now. Gone are the days when I could sit down for 10 hours straight working on something. I have to take on tasks that I can complete in 2 hours (or work on into the night and suffer sleep deprevation!)

Yesterday I did some more sanding on my speaker boxes, I think I could just keep sanding until the 25mm MDF was only 20mm I better stop soon and get on with the veneering.

Tonight I attacked the problem of the switching thump in the amp. I found some 47uF Nichicon FG caps in the cupboard and soldered them into the negative feedback circuit in the preamp. That brought the DC coming out of the gain stage in the preamp down from -1.1V to about -210 mv. I'm not sure if I will try and tackle getting rid of the rest of the dc, but it is a substantial improvement. The cap basically put between the second resistor in the feedback...

Sanded down the second box so it is now in a state that is close to ready for veneering. Filled the screw holes with filler and also the bottom of the front baffle which was for some reason a mm or so short. can't remember if that was a measurement stuff up or a problem with the saw accuracy, probably the former I'd guess! Actually now that I think about it, it was an assumption that the mdf was really 25mm thick and it was slightly more... Only problem is the filler takes 48 hours to dry, so next weekend before I can start trying to slap on any veneer.

Also attacked the amp again. Plan was to put in the bypass of the preamp. Got most of the way there but was getting too late so left the drilling of the back pannel (for the rca sockets) for tomorrow. All in all it was a worthwhile excercise. The way the input caps were installed was nothing short of shocking, I think I did it to check it was ok, but never got around to doing it properly, I decided to use cat5e twisted...

Glued the rear baffle onto the second of my MTM's today. Had an OH <insert your choice of expletive here> moment just after I placed the baffle onto the speaker. I'd put it on inside out! Now I realise that might sound a bit weird, but because my binding posts are not quite long enough for 25MM MDF I had to route out a few mm to allow me to put the first of two screws on. Anyway luckily I realised pretty quickly and was able to pull it off wipe off the glue, put some more glue down and get it screwed down and clamped without any problems. Would have been a bit of a disaster If I hadn't noticed straight away.

Was planning on putting in the new RCA's to the amp today as well, as a way of bypassing the preamp, but just didn't have the time or the energy. Maybe next weekend

Tony.

Last night I built an earth loop breaker for my trusty old Series 200 100W mosfet amp. It's been annoying me with Hum ever since I moved to the new place. Combination of having the mythtv HTPC and also cable like TV antena that is shared through multiple units. Well it cut it down but it didn't cure it.. The gainclone is dead quiet... the differece? I used an 12 Ohm resistor on the gainclone, and it is running without a pre, the series 200 one I used a 10 ohm as per Rod Elliot's article (and the connection is through the preamp built into the amp. Tomorrow I plan set up a switch and some new "direct" RCA jacks so I can run the HTPC direct bypassing the integrated pre.... hopefully that'll do the trick. If not I'll probably try bumping the resistor up to 12 ohms...

Today I was going to glue the back baffle on my second MTM but it got very gusty and I thought it would rain (my work space is on the balcony, so not good for gluing if looking like rain). So I only...