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Nope.
Use the BA-3 as your preamp.
Sorry, I left out a detail or two for context. I understand that the BA-3 is necessary to drive the F4, but I neglected to mention that I also have an a40 and will probably be building an Aleph-J soon, or some other amp
How will the BA-3 work as a pre in front of other amps like the a40 ? I'm thinking it will quickly overload them.
In terms of flexibility, am I better off make my pre from the DCB1 instead of the BA-3?
WADR, you can NOT have the crossover after the two stereo BA-3 front ends because the F4 amps have no voltage gain. An active crossover like the First Watt B4 or B5 has only about a 7Vrms output/channel. You'd only get ~ 6 wpc out of each F4 that way. Therefore, the crossover will have to feed each BA-3 front end, which, in turn, the F4 amps need to get fed from. In my case, my DAC will feed the crossover. Maybe Zen Mod or Nelson need to chime in. Then again, I could just be a babbling idiot.
to integrate or not...
I have not the memory to recall the output impedances of the BA-3 and DCB1 (anyone help me out here if you know them) but I am guessing the DCB1 will have a lower output "Z".
IF you are driving long cables or even shorter high capacitance cables (do measure them then the DCB1 might represent a sonic improvement assuming you need no gain at all. Maybe.
The advice to keep each unit in a seperate box applies here so that you have these options! Build them together in a single box and you save some cabling but loose options...
I have not the memory to recall the output impedances of the BA-3 and DCB1 (anyone help me out here if you know them) but I am guessing the DCB1 will have a lower output "Z".
IF you are driving long cables or even shorter high capacitance cables (do measure them
then the DCB1 might represent a sonic improvement assuming you need no gain at all. Maybe. The advice to keep each unit in a seperate box applies here so that you have these options! Build them together in a single box and you save some cabling but loose options...
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Jim & Russell, This is causing me to rethink my plans a bit. I have put a bit of effort into my DCB1 circuit (have populated the board with 4 nice relays for input selection, and have an LDR based volume control already integrated), so I'd like to as much of this as possible with the BA-3.
Here is my thinking: I can make some small modifications to the DCB1 board to retain the input selection and nice volume control that it has and skip the onboard jFETs (there is always another nice use for a matched set of 4!) that are used for the buffer and pass the volume controlled input signal directly to the input of the BA-3. Then, since I'm no longer using the jFET buffer, I can use the nice shunt regulated power supply from the DCB1 to power the BA-3.
So, my question is how LOW can the voltage go on the power supply of the BA-3 and still have it work well? The BA-3 articles talks about 20v and 15v supplies. The DCB1 provides +/- 10V rails, though this can be modified to be higher. I am currently using a 15v transformer, but have a 20v one laying around that could be substituted.
Here is my thinking: I can make some small modifications to the DCB1 board to retain the input selection and nice volume control that it has and skip the onboard jFETs (there is always another nice use for a matched set of 4!) that are used for the buffer and pass the volume controlled input signal directly to the input of the BA-3. Then, since I'm no longer using the jFET buffer, I can use the nice shunt regulated power supply from the DCB1 to power the BA-3.
So, my question is how LOW can the voltage go on the power supply of the BA-3 and still have it work well? The BA-3 articles talks about 20v and 15v supplies. The DCB1 provides +/- 10V rails, though this can be modified to be higher. I am currently using a 15v transformer, but have a 20v one laying around that could be substituted.
I understand, and that isnt a bad thought...might eliminate the slight popping I have on selector switch. I've got a hypnotize and mezmorize loaded boards in a drawer some place....one of the two has a bunch of relays on it...seems like at least one person here used the power supply off one for a BA-3 pre I believe. I'll be watching your efforts, but I would prefer to raise the voltage on the DCB1 rather than lower the voltage on the BA-3, guess it depends what you populated the DCB1 with. I think I will dig mine out and start thinking about it. I dont see the DCB1 sounding better than BA-3 as pre, but I'm wrong plenty often! Using the power supply and switching relays from the DCB1 sounds solid as well.
Russellc
I think you are going to need more voltage. The higher the voltage rails, the more voltage the BA-3 FE can swing. I think Nelson mentions in the article that below 18V is wasting your time.
It is possible to get a new transformer, probably a 24V or 28V transformer, and recalculate the resistor values for the Salas shunt portion of the DCB1 and use that to supply the BA-3. I am not sure if the relays for the switching and such on the DCB1 will work with the higher voltage however...you better check.
On the other hand, I've run a BA-3 based preamp with both LM317/337 regs and a Jung Super Reg at both 30V and 24V rails. The difference was not great. Seems to me the BA-3 might not be that sensitive to power supply quality although I did run a CRC filter in front of both the supplies.
Not w/the BA-3. I have built the Salas phono with dual mono shunts. Sounds good but no, I haven't compared 317/337, Jung reg and shunt directly. The Salas shunt did sound better than Alkaline batteries in the phono stage though.
In my experience the BA-3 hasn't been influenced to a large degree by power supply (or power cords)...maybe it has good PSRR? I know it's designed to be used as the front end of a power amp using the power amp's unregulated supply. Maybe that has something to do with it.
I did read an article a while ago comparing the Jung Reg, Salas shunt, LM317, maybe another reg, I can't remember. The test used a Borbely Jfet preamp. It was a blind listening test. I think the preferred reg was the Jung reg. I believe the test was put on by some audio society/group in the USA.
In my experience the BA-3 hasn't been influenced to a large degree by power supply (or power cords)...maybe it has good PSRR? I know it's designed to be used as the front end of a power amp using the power amp's unregulated supply. Maybe that has something to do with it.
I did read an article a while ago comparing the Jung Reg, Salas shunt, LM317, maybe another reg, I can't remember. The test used a Borbely Jfet preamp. It was a blind listening test. I think the preferred reg was the Jung reg. I believe the test was put on by some audio society/group in the USA.
Also, EVUL has started a thread in the pass labs forum about a f5 based headamp...
His headphone amp is pretty similar to the Ba3 fe. Lots of talk in that thread about capacitance multiplier PSUs for that amp. Might be of some interest to you guys for the ba3 fe as well. It is a little over my head but it is interesting.
His headphone amp is pretty similar to the Ba3 fe. Lots of talk in that thread about capacitance multiplier PSUs for that amp. Might be of some interest to you guys for the ba3 fe as well. It is a little over my head but it is interesting.
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I am just about ready to graft my DCB1 Mez board (now just a 21v PSU, input switching and LDR volume control) onto my BA-3 as a preamp and have a few questions about input impedance of the BA-3.
I removed the jFets, 220R, 220k, and 1M resistors from the Mez board, so now it is just a volume control (the LDRs behave as a 25k pot). There is a 1k input resistor and a 47k input to ground for the BA-3. Do these need to remain in place (they seem a little redundant following the volume control), or can I remove these and not expect any strange things to happen?
I removed the jFets, 220R, 220k, and 1M resistors from the Mez board, so now it is just a volume control (the LDRs behave as a 25k pot). There is a 1k input resistor and a 47k input to ground for the BA-3. Do these need to remain in place (they seem a little redundant following the volume control), or can I remove these and not expect any strange things to happen?
I'm a newbie but am curious: At what DC voltage (above 21V) do you supply to your (single-ended?) BA-3? And how and to how much is the bias current set at?
