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- Oct 10, 2002
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Folks, I believe we have arrived.
This thread is a continuation of this thread:
A DIY Electrostatic amp
started by ericj. Ericj was looking for a reasonably priced, easy to build DIY electrostatic amp that is within reach of diyers who have or want to move to electrostatic headphones.
I did a quick and dirty design on that thread, but this design was only marginal. While we were testing this verion out my consulting practice went haywire for a few months. A good thing as it turned out because while I couldn't work on any electronics for a while this project kept percolating in the back of my mind. The prototype team was remarkably patient during this gap. I want to thank them for their patience.
When I was able to get back to the project a whole new design had evolved along with a new PS. Both designs were much simpler and were straightforward enough to ensure that properly built boards would work without difficulties. The whole design philosophy was "simple but good."
Once again the proto team consisting of ericj, pabbi1, sachu, wiatrob, and me started stuffing boards. And now there are five of these amps working and driving headphones.
We've called it the eXStatA and there are two versions: an all SS version and a tube hybrid that uses 6S4s. The tube version is going into prototyping now.
The same PS will supply either board and the sand and hybrid amp boards (both channels on one board) are the same size with the same mounting holes so you can swap one for the other in a working amp.
A few particulars for now.
1. The rail voltage is +/-300. This number was chosen so that you can use easy-to-get, inexpensive transformers. There is a Hammond transformer and a Triad transformer that fits. The Hammond has the heater winding for the tube version.
2. The PS has two bias supplies: an HV supply that is adjustable from about 340V to about 680V and an LV supply that is adjustable from about 170V to 340V.
3. The boards are: 150mm x 95mm (two channel amp) and 100mm x 100mm (PS including bias supplies).
4. The maximum peak to peak voltage is about 700-800V. This is good enough for many, many situations. Remember that this amp is targeted at intermediate builders.
5. The gain is approximately 1000 give or take some.
6. Balanced or SE input (Edit)
7. The amp is fully DC coupled. No capacitor bass rolloff. In fact the amps have no caps at all in them (Edit)
I think we have met or exceeded the original set of design goals.
The prototypers have been chomping at the bit to post impressions and pics. But, we have waited until all five amps and PSs were successfully built and listened to.
We're going to burn these amps for a while longer just to be sure that their are no problems with use. HV is a different animal from the LV amps that most people build.
I don't have pics because my boards are off with wiatrob getting ready for RMAF. But the other guys should be posting soon.
Thanks for your patience during the gap. We're back.
This thread is a continuation of this thread:
A DIY Electrostatic amp
started by ericj. Ericj was looking for a reasonably priced, easy to build DIY electrostatic amp that is within reach of diyers who have or want to move to electrostatic headphones.
I did a quick and dirty design on that thread, but this design was only marginal. While we were testing this verion out my consulting practice went haywire for a few months. A good thing as it turned out because while I couldn't work on any electronics for a while this project kept percolating in the back of my mind. The prototype team was remarkably patient during this gap. I want to thank them for their patience.
When I was able to get back to the project a whole new design had evolved along with a new PS. Both designs were much simpler and were straightforward enough to ensure that properly built boards would work without difficulties. The whole design philosophy was "simple but good."
Once again the proto team consisting of ericj, pabbi1, sachu, wiatrob, and me started stuffing boards. And now there are five of these amps working and driving headphones.
We've called it the eXStatA and there are two versions: an all SS version and a tube hybrid that uses 6S4s. The tube version is going into prototyping now.
The same PS will supply either board and the sand and hybrid amp boards (both channels on one board) are the same size with the same mounting holes so you can swap one for the other in a working amp.
A few particulars for now.
1. The rail voltage is +/-300. This number was chosen so that you can use easy-to-get, inexpensive transformers. There is a Hammond transformer and a Triad transformer that fits. The Hammond has the heater winding for the tube version.
2. The PS has two bias supplies: an HV supply that is adjustable from about 340V to about 680V and an LV supply that is adjustable from about 170V to 340V.
3. The boards are: 150mm x 95mm (two channel amp) and 100mm x 100mm (PS including bias supplies).
4. The maximum peak to peak voltage is about 700-800V. This is good enough for many, many situations. Remember that this amp is targeted at intermediate builders.
5. The gain is approximately 1000 give or take some.
6. Balanced or SE input (Edit)
7. The amp is fully DC coupled. No capacitor bass rolloff. In fact the amps have no caps at all in them (Edit)
I think we have met or exceeded the original set of design goals.
The prototypers have been chomping at the bit to post impressions and pics. But, we have waited until all five amps and PSs were successfully built and listened to.
We're going to burn these amps for a while longer just to be sure that their are no problems with use. HV is a different animal from the LV amps that most people build.
I don't have pics because my boards are off with wiatrob getting ready for RMAF. But the other guys should be posting soon.
Thanks for your patience during the gap. We're back.
