Thursday, 19 July 2012

Quad 303a2 5 pin XLR outputs

The outputs of my 303a2 and the cabling colour codes I have assigned for identification (colour codes are nothing to do with original designations - just for my benefit). This is viewed from the CABLE side and not the pin side of the plug.



Pin 1    ground       no connection
Pin 2    low freq +  red
Pin 3    low freq  -  blue
Pin 4    high freq + green
Pin 5    high freq - black

This will be updated with Neutrik Speakon designations when I have done that modification

Saturday, 23 April 2011

New Loudspeakers - Castle Kendal 2

Having lived with the Kef 104s for a while now, much as I have loved having them, they are too big and bassy for the room. In addition, I don't have grilles for them which is leading to aesthetic friction as the experiment moves into being a permanent fixture. To see if anything could be done to resolve this, and to satisfy my next curiosity, I have replaced the 104s with a pair of Castle Kendal 2s. In case you don't know them, they are a medium sized stand mount unit, two way with a front bass port. I have had these for a while now taking up space. They needed re-foaming but I found a very cheap pair of other shabby Castles with the same drive units locally, swapped them over and now had a working pair. As a two way loudspeaker, they are frankly rubbish. The first word that came to mind was charmless. Several more were gutless, messy and indistinct. The benchmark is still my trusty pair of Epos M5s. These are bookshelf speakers but sound better than many standmounts I have had.
Anyway, I stripped the electronics from the Castles, covered the input hole with perspex and finally fitted the Neutrik Speakons I kept threatening to do with the Kefs. At last I had done it properly!
I have to say that the Castles sound much better now using the bi-amp arrangement of the 303a2s than they did before. I would actually say they are a slightly better solution than the Kefs. I still find them too bass heavy at a volume I like so I hurriedly moved onto to changing the bass lift of the amps from normal to low.
This has allowed me to turn up the volume a bit but I'm undecided what difference this change has made and whether I detect a thin sound or tinniness now.I will persevere with this new arrangement for now, if necessary put the bass lift back up to normal and perhaps try messing with the foam in the speaker cabinets to tune out some of the extremes.
On a positive note, the clarity you would expect from bi-amping is there still, the pace of the Castles is much better than the previous dull and lethargic sound and there are still a few tweaking options to try. Some of them are re-levelling the stands and isolating the cabinets from the taller stands I am now using for the Castles.

Thursday, 27 January 2011

303a2 Project

Having acquired a pair of faulty 303a2 amps without the matching LS3/7 loudspeakers, I wanted to see what bi-amping is all about. I chose the 303a2 because firstly they are cheap and secondly I have rebuilt quite a few 303s so whatever the faults are, I must have at least a 50:50 chance of sorting it out.
The first thing I did was a standard re-cap. I put pairs of BHC Aerovoxes in each for the output stages and as I remember the other caps are mainly Panasonic FMs for these (I might have used a few Nichicons but I prefer the Panasonics usually)
I built up the Cannon mains leads from some vintage mess I had lying around and bought a pair of basic XLR to phonos for now.
The main problem was working out how the speakers are wired and what speakers to use. At the moment I am using a pair of Kef 104 originals which have the crossovers bypassed and the cables are directly soldered to the drive units. I'll change this to incorporate some Speakon connectors to make them a bit more convenient. They are cabled with generic bi-wire 79 strand to the 5 pin XLR outputs of the amp.
There is plenty of opportunity for cabling upgrade of course but frankly I needed to find out how and if it works before spending more on it.
One of the amps powered up fine after the re-cap but the other one kept blowing the fuse. After some dangerous experimentation and mains arcing, I found the cap across the transformer windings was shorted. I've removed this now but intend to replace it in the future.

The current state:
1   both amps work
2   I am running them from a 33 (another of my re-cap specials!) having altered my XLR cables to 4 pin DIN
3   There is surprisingly little mains hum (even though I have paid no attention to ground loops etc and shielding)
4   music plays through the speakers

What do I think?
For a first attempt, it's not too bad. The cone on one of the 104s is a bit saggy so there is some grating of the coils sometimes but it depends how bassy the music is. The sound seems MUCH sharper than just using a standard 303 with the crossovers in place on the Kefs, but I am quite keen to improve the bass drivers before passing final judgement. I find the sound quick and smooth but I wonder if there is some midrange missing. I've not listened to music for a while really so should do a side by side with my Epos speakers (which I love - they're only little but really punchy)

Next tasks:
Side by side comparison with the same source and music
Replace caps across transformer
Try fresher bass units
Install Speakons into the Kef cabinets (if I'm keeping them of course)
Rewire them into my Meridian pre

UPDATE
I have wired this up with the Meridian instead (with a new pair of phono-XLRs) and I have to say the 33 is such a great amp. I've listened to quite a few pre-amps lately from Naim, Linn and now Meridian but the 33 produces a much nicer sound in this combination in my view. The Linn seems a bit clinical and the Meridian is a bit 'nothingy' but on the bright side has the benefit of remote control. It gives me the opportunity to maybe use the bass lift functionality in the AM8/15 filters to liven it up a bit. I'll probably wait until I have stabilized the speaker cone situation first though!

Tuesday, 25 January 2011

Quad 303 output capacitor colour codes

Right+     Yellow/Red
Right-      Brown/Red
Left+       Yellow/White
Left-        Brown/White