To start out, this is a great thread. The following is only my opinion on some of the above ideas. I really want to continue to exchange these ideas and discuss any and all implications. If this leads to some heated discussions, then I say GREAT. I have found that the best understanding of a topic comes from defending one's position. I hope this thread can enlighten us all to the wonderful world of DIY audio. And now my ideas.
Ehider, I can really relate to your enthusiam. I can remember when I 'discovered' the differences of crossover components. I also agree with Trelja about the simplicity of a crossover for his (tube) application. (and yes you are a DIY'er) Neither approach is fundimentally more correct than the other. My experience indicates that to get good results with a simple crossover that the drivers and cabinet must be selected VERY carefully. This may not be possiable when you are trying to modify a speaker you already own. In the latter case a zobel may be the ticket at the expense of power consumption.
On the topic of circuits, it is not always safe to just replace transistors in an amplifier with what is percieved as better units due to the possibility that you may change the stability of the amp. If the transistors are wider bandwidth, you might make your amp into a high powered oscillator and smoke your speakers. If one has access to an oscilloscope, the stability of the modified amp can be easilly checked. The bias current of the output stage will also need to be adjusted in some cases. I agree that the difference can be audible, but we must be careful! I recall where a friend of mine was told to increase the size of his power supply caps. He did, by a factor of 10, including some caps that were not in the power supply, and now the unit is dead. A lot of this DIY stuff is very easy to implement but common sense must be applied.
It is also a super cheap tweek to replace the resistor in the differential input pair with a current source. I have done it a dozen times and every time I am blown away with the improvement. Siliconix may still make a current source 'diode' that looked just like a reistor. It was simple to replace the resistor with the FET current source as long as you knew the correct value of current source to buy. I will research the availability if anyone is interested. The Aragon 8008BB already has current source transistors in the input stage but I don't know about the other models. Please let us know about the input configuration of any models you are familar with. BTW there are several easy mods for the 8008BB.
I have not heard of putting caps across the fuses. I must admit this is so simple that I feel stupid for not thinking of it. If the unit has DC power supply fuses (like the 8008BB) the caps would help to deliver transient currents to the board and ultimately to the speakers. The only place I would not put a cap is across the AC line fuse. On second thought, that might help get transient current INTO the power supply! Let's hear (see) everyones ideas on this. The cap would need to be small enough that it would not power the unit if the fuse blew, but large enough to help get transient current around the fuse. Are there any implications we need to watch out for?
Trelja, there are many people that believe the cold weld is the way to go. WBT makes an RCA that does not use solder. My many years in the aircraft industry has me very familar with the crimpers you mention. They are very pricey!
THIS IS A SUPER THREAD! Maybe we can get some of the non believers to try some of the DIY cables or some simple cap modifications and listen for the difference. Under the controlled conditions of their own system they may begin to understand what Walt Jung told me "Everything makes a difference".
I enjoy looking at schematics, quite often I get an idea or learn of a new part from looking at them. If you can get me a schematic I will be willing to try and assist anyone with a mod of their electronics. My business does take me out of town all the time but I will respond to email as fast as I can.
Chris Owen
[email protected] (work)
Ehider, I can really relate to your enthusiam. I can remember when I 'discovered' the differences of crossover components. I also agree with Trelja about the simplicity of a crossover for his (tube) application. (and yes you are a DIY'er) Neither approach is fundimentally more correct than the other. My experience indicates that to get good results with a simple crossover that the drivers and cabinet must be selected VERY carefully. This may not be possiable when you are trying to modify a speaker you already own. In the latter case a zobel may be the ticket at the expense of power consumption.
On the topic of circuits, it is not always safe to just replace transistors in an amplifier with what is percieved as better units due to the possibility that you may change the stability of the amp. If the transistors are wider bandwidth, you might make your amp into a high powered oscillator and smoke your speakers. If one has access to an oscilloscope, the stability of the modified amp can be easilly checked. The bias current of the output stage will also need to be adjusted in some cases. I agree that the difference can be audible, but we must be careful! I recall where a friend of mine was told to increase the size of his power supply caps. He did, by a factor of 10, including some caps that were not in the power supply, and now the unit is dead. A lot of this DIY stuff is very easy to implement but common sense must be applied.
It is also a super cheap tweek to replace the resistor in the differential input pair with a current source. I have done it a dozen times and every time I am blown away with the improvement. Siliconix may still make a current source 'diode' that looked just like a reistor. It was simple to replace the resistor with the FET current source as long as you knew the correct value of current source to buy. I will research the availability if anyone is interested. The Aragon 8008BB already has current source transistors in the input stage but I don't know about the other models. Please let us know about the input configuration of any models you are familar with. BTW there are several easy mods for the 8008BB.
I have not heard of putting caps across the fuses. I must admit this is so simple that I feel stupid for not thinking of it. If the unit has DC power supply fuses (like the 8008BB) the caps would help to deliver transient currents to the board and ultimately to the speakers. The only place I would not put a cap is across the AC line fuse. On second thought, that might help get transient current INTO the power supply! Let's hear (see) everyones ideas on this. The cap would need to be small enough that it would not power the unit if the fuse blew, but large enough to help get transient current around the fuse. Are there any implications we need to watch out for?
Trelja, there are many people that believe the cold weld is the way to go. WBT makes an RCA that does not use solder. My many years in the aircraft industry has me very familar with the crimpers you mention. They are very pricey!
THIS IS A SUPER THREAD! Maybe we can get some of the non believers to try some of the DIY cables or some simple cap modifications and listen for the difference. Under the controlled conditions of their own system they may begin to understand what Walt Jung told me "Everything makes a difference".
I enjoy looking at schematics, quite often I get an idea or learn of a new part from looking at them. If you can get me a schematic I will be willing to try and assist anyone with a mod of their electronics. My business does take me out of town all the time but I will respond to email as fast as I can.
Chris Owen
[email protected] (work)