I have a question regarding the implementation of the BA-3/B and BA-2 FE's as modules. In passing the signal from a standalone unit containing the FE, does the signal wire need to be grounded. I realized as I was putting the two FE's in their seperate enclosures, that the BA-3 only had a single signal output, whereas the BA-2 has a signal output plus the requirement for a feedback signal. If it is necessary to ground this output, then i will have to use an RCA for BA-3 and XLR for BA-2. I know that in the same amp, this requirement for grounding does not exist, but was unsure if passing the signal from one case to another required it. I have a umbilical chord made of 4 pin Speakon connectors bringing earth and signal ground as well as associated DC connections from output stage and PSU.
Referred to the Fairchilds.
($5 for J313/K2013 is expensive, they do $4.5/pair in Japan
)I have been mulling over this same problem. I think you need to take the ground from the BA-3 via an interconnect to the star ground of the power supply of the power board. My problem with this is that you will need another high quality interconnect ie, one from the pre-amp to your BA-3 and then another from the BA-3 to the power side. I think this arrangement is more likely to cause signal problems (interference) than using an external power supply feeding your BA-3 inside the power output chassis. I am favouring the latter idea now.
Chris
Should know tomorrow if I can get hold of the mosfets. However, I have been making good use of my time by putting together a Salas regulated power supply for the BA-3 (or the BA-2 if I wish).
Chris
IF done properly, I don't see why it would be any different than a usual preamp/amp setup. If I like what i hear, I will probably go to a passive volume control as the BA-3 will become the new "preamp". The reason I like the idea is ease of construction on FE options. If you can run it off the PSU of the output stage, you drop building complexity and interchangeability becomes simple. Connections can be as short as 1-1/2' feet.
If you're concerned about grounding issues, then you really should just stick to XLR balanced signal interconnects. I would not recommend speakON for line level signals, but rather restrict that connector to power and speaker interconnects.
RCA was designed as an interconnect within a single chassis. The unfortunate fact that it was abused to link multiple chassis is a mistake of the consumer market. If you use XLR balanced instead, then these grounding issues that you describe fall out (provided that you properly wire your XLR outputs and inputs).
Unfortunately, I don't know what to suggest for the preamps and amplifiers that do not support balanced I/O. Personally, I am limiting my DIY experiments to balanced, so that means skipping the unbalanced designs or modifying them for balanced. There are plenty of balanced designs from Nelson Pass to keep me busy, so I'm not fretting over the limitations.
The Speakon connectors are to bring the DC power and ground to the FE module from main amp case with output and PSU and is not for interconnects. It allows the use of one PSU for multiple FE choices.
That seems fine. I thought I read "signal ground" on the speakON in one of your earlier posts, so I was only raising issue with signal grounds in that context.
I have mine set up as a separate preamp gain stage, with a separate passive source selector and volume control. I also have a separate BA-3 power supply. It all works noiselessly and without hum.
I have a three-conductor power cable connecting the BA-3 power supply to the BA-3, and the F4 power amp has its own internal power supply. I have star grounds in both the power supply and the gain stage, with copper bus bars as you can see in the picture.
The passive front end, the BA-3, and the F4 are all connected with standard RCA unbalanced interconnect cables.
An externally hosted image should be here but it was not working when we last tested it.
The white cable is the power cable, which permanently joins the P/S with the BA-3.
I learned this from my uncle, who hand-built some of my first electronics: The most reliable connector is no connector at all!
It's certainly a little inconvenient to have two enclosures tied together like this, but you also do not have to worry so much about corroded or failed connectors in the midst of all the other DIY variables.
Totally agree with the no connector design, from signal to power where possible. However, easier on the back if you can separate them when bending and lifting. Young man's game this.
The speakon connectors are well designed being very similar to an Eichmann RCA plug, which are highly regarded. It was designed for professional audio who also happen to be big on balanced cables signal protection and preservation. Of course much of this is dismissed by audiophiles because it eliminates the possibility of selling uber expensive interconnects and cables. I will be able to compare both implementations as I am building two output stages and will have two BA-3 Few boards.@
Agreeing with everything this morning. I am just fitting a Speakon socket for an external power supply. I like its solid connection and also the size of its connection points which allow flexibility when connecting different cable diameters. On interconnects I am just developing one myself and am investigating patents etc. Of course mine works so much better than all the others.
Check out the powerCON product line at Neutrik. They look to be equivalent to the speakON. The entry level connector is spec'd at 20 A and the next level is 32 A !!
About the only shortcoming is that they're not rated for disconnection or connection under load, but I hope nobody plans on yanking the power to their BA-3 without powering down the supply first.