Heed CanAmp mods. Registered users only can view.. Dec 16, 2006 0:03:45 GMT
Post by PinkFloyd on Dec 16, 2006 0:03:45 GMT
This is where the heat comes from folks! Not so much the transistors but from the 5W 100ohm resistors, put your finger on one and you'll see what I mean! HOT eh? I added a bit of supplementary heatsinking round this are and actually bonded a sink onto the sides of both the 100ohm resistors with stuff similar to JB weld, so powerful is this gear you'll never get it off, the resistors now run warm to the touch so job well done.... the grey epoxy steel looks a bit mickey mouse but believe me it does the job very well.
Next on the hit list was fitting a dip8 socket to enable opamp rolling. I went for a good quality gold plated, turned pin type. The surrounding area is "tight" (to say the least) so you've got to make a bit of space so you'll be able to roll in opamps easily. Move the 100nF cap under the board (the yellow one) and carefully bend the LED legs flush with the front panel.... ensures there's enough room to fit / remove opamps.
2 x 16V 4700uF general purpose Jamicon capacitors are fitted as stock (and in my example were fitted the wrong way round!!) I absolutely detest these capacitors so removed them pronto!
There is also provision for snap in capacitors to be fitted so that's just what I went for........
First in were a pair of el cheapo Suntan 105C 35V 10,000uF. I also swapped out the 2 x 100uF stock Jamicons for a couple of 35V 100uF ELNA Cerafines. HUGE improvement to the sound, the extra capacitance pays off BIG time, and then some.
Suntan 10,000uF and 100uF Cerafines in position.
Satisfied that the 10,000uF made a major improvement I removed the Suntans and fired in a couple of 105C 10,000uF 105C dubiliers... no difference to the sound but a cap I like to use when I can. Also Replaced the stock 1N4002 diodes with UF4007 (1000V) ultrafast types.... again, subtle but noticeable improvements to the overall timing and clarity.
Model number written on the side of the cap.
I've also replaced all the 63V film caps with 400V film caps (polyester) all bypassed with small polyprops (EVOX) (ie: 100nF polyester bypassed with a 10nF polyprop, 470nF nF polyester bypassed with a 47nF polyprop) Most of this is under the board and under board mounted film caps are all supplemented with a blob of hot melt glue (before soldering into position) to ensure strain relief, mechanical integrity.
Another thing I did was replace the "thread" like hook up wire to the head socket with some good quality thick copper gear.... doesn't necessarily sound any better but a bit more of a reassuring look to it as far as integrity is concerned.
From what I can see there's really not a lot else can be done to improve this amp further..... the designer has put all the right holes in the right places but, in parts, populated those holes with cost effective parts..... Alpar (from HEED) has already mentioned that if budget were no object these holes would be populated with more expensive (mostly more capacitance) parts and he agrees "of course it will sound better there's no doubt about that" To put the amp to market at $350US or £250GBP compromises have to be made somewhere. Fortunately it won't cost the earth to populate the holes with parts the designer would have liked to have used if cost were no object.
About £4 for the two 10,000uF caps, a few pence for the Ultrafast diodes, a quid for the heatsinks, pennies for the opamp socket (dip8)........ very cheap but VERY effective mods. The stock opamp is the NE5532 (an opamp I love) some people will call you the antichrist if you even dare suggest they sound good, I think they are lovely sounding devices ;D (and considering they're universally used in most recording studios.........) Do they sound best in the HEED though? A question I'm in the process of answering.......
To date I have rolled in AD-843, OPA2227 and OPA2107.
The three of them each displaying their own unique / signatures / characteristics.
AD-843 - Grainy, raw, open, organic, A realistic wellies and bucket listen, all four seasons in just one day... warm, cold, wet and dry, imagine apples falling off the tree then fast forward to basking in glorious sunshine on a beach.... to my ears 8.5/10
OPA 2107 - Velvety, smooth, easy listening, laid back like an overripe grape basking in the sun, no hurry, don't rush the brush type of presentation..... nice if you like that style..... to my ears 8.5 /10
OPA2227 - best of the bunch in the bass department (to my ears) toe curling depth / extension. Fruity in places yet decidedly mellow in others..... fun 8.5/ 10
NE5532 - Warm, rich, sprinkled with sugar and cinnamon... a doughnut like, easily digestible, fast food, satisfying signature that will appeal to a broad palette time and time again 8.5 / 10
Next up under the hood are OPA627BP (on Bdogs), AD8620 , LM6172 and OPA2111KP.