Carl_Huff said:
Thanks Carl, I wouldn't know what to do with a .LAY PCB file. My idea was to simply bring the base lead to the edge of the board rather than make specific provision. The only other two connections required would be the power rail, that's easy to get to and the 5W resistor could hang between the device and the board.
Since I am the only one I am sure I can still rig it though.
Thanks for trying. It is appreciated.
Terry
Well fellas here is another rev. It's only 8:30pm here in southern California and I am on a roll. This one ...
#1) Puts all 6 output device diodes in the tempco string.
#2) Changes the adjustment pot in the tempco string to be be 200 ohms - the same as the value of the pot in the LTP.
#3) I corrected the 'Q' numbers of the output devices
Are we getting close?
#1) Puts all 6 output device diodes in the tempco string.
#2) Changes the adjustment pot in the tempco string to be be 200 ohms - the same as the value of the pot in the LTP.
#3) I corrected the 'Q' numbers of the output devices
Are we getting close?
AKSA said:
Hugh,
I agree with you. That's why I use a dedicated tweeter amp and another for the LF grunt. The tweeter amp is really the one that needs to have the finesse and resolving power, - which is usually compromised in high power amplifiers.
Bi amping may seem complex but the final implementation can be quite easy and much less expensive to implement than the equivalent fidelity full range amp.
David
are we agreed that the simple mirror for the collector load is adequate for an extreme ULD?
I would suggest one of the improvements that Hugh (AKSA) or others have proposed.
Adding a resistor and transistor to balance the current drawn by the VAS is one option, or Hugh's diode+? to force the mirror to be more accurate. I suspect the PCB for the first option also allows Hugh's to be implemented.
I would suggest one of the improvements that Hugh (AKSA) or others have proposed.
Adding a resistor and transistor to balance the current drawn by the VAS is one option, or Hugh's diode+? to force the mirror to be more accurate. I suspect the PCB for the first option also allows Hugh's to be implemented.
Carl_Huff said:
Why ?
Both these transistors have very low voltages across them.
In the original circuit, Q3 collector voltage is around 1.2V, and Q4 collector voltage around 830mV due to it's base and collector being tied to Q3 base. Matched high gain MPSA18 will work even better there, but they can be a real pain to match for both HFE and VBE.
SandyK
high voltage parameter compromises many other parameters.
If one does not need high voltage, then usually there exists a better or cheaper transistor that meets or exceeds the other parameters of the HV type.
The general rule is to select transistors that meet the worst case operational voltages expected in the circuit. Some of these can be as high as (V+) + |V-|
If one does not need high voltage, then usually there exists a better or cheaper transistor that meets or exceeds the other parameters of the HV type.
The general rule is to select transistors that meet the worst case operational voltages expected in the circuit. Some of these can be as high as (V+) + |V-|
Let's talk about caps. I am adjusting the PCB to conform to the new schematic and am checking to be sure that the BOM calls out parts that are appropriate to the PCB layout. There is a .15uF cap at 400 volts hanging off of the output of this amplifer. Wouldn't a 250 volt cap like the WIMA MKP4 metallized polypro cap work just as well? It certainly has a smaller footprint on the PCB. Is there any reason to not specify the WIMA part?
Anf then there are all those decoupling caps that I have attached to the collectors of every output device. Wima MKP2 parts fit well there. Any thoughts or other preferences?
Anf then there are all those decoupling caps that I have attached to the collectors of every output device. Wima MKP2 parts fit well there. Any thoughts or other preferences?
with 220uF in the feedback loop the input cap must be <=6u6F.
4u7F would do.
The 220uF is a bit small for my taste, could you leave sufficient room to fit a 330uF here (my preference)?
or
maybe even 470uF for those that like to go even flatter in the audio band.
330uF would allow <=10uF input cap.
470uF would allow <=14uF input cap.
4u7F would do.
The 220uF is a bit small for my taste, could you leave sufficient room to fit a 330uF here (my preference)?
or
maybe even 470uF for those that like to go even flatter in the audio band.
330uF would allow <=10uF input cap.
470uF would allow <=14uF input cap.
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