[ppl]

I see no harm in suplimenting Regulation by the low dropout Regulators like the LT-1085 and LT-1033 as long as the Voltage drop is not a Problem. However My self and maby the Folks that Do Virtual battery Type Power supply's are on the Otherside of this issue but that is ok. So My advice is Try Both ways and use whitchever one sounds good to You.

I Am using A single Voltage Regulator in the Prototype of the Latest version of my pocket amp. This is in concert with the Virtual ground Driver since the Regulator's main Porpose is to allow a wide range of wall wart voltages with out fear of blowing 10 volt Rail caps and the AD-8620 opamp. But my investigations of using a Mear MC-7818CT From On semiconductor of Recent date code vs a High performance Linear Tech Regulator intended for Microprocessor use in concert with the Os-Con Caps cant remember the # LT-15XX? look itt up. To get a higher voltage out of low voltage fixed reg's adding a voltage reference between the IC's gnd pin and the Actual Ground but in this case the other Supply rail results in an output voltage similar to the MC7818. But the sound with the LTC was way better and Batteries to me sounded Better to me than the 7818 but i think the LTC was at least as good.

AS for my orig amp schemitic http://homepage.mac.com/WebObjects/F...eSharing1.html

 

[goon-heaven]

ppl: AS for my orig amp schemitic http://homepage.mac.com/WebObjects/...leSharing1.html

There it woz, gorn... I cant see no schematic in there.
No files listed to download in "public", links at top page appear orphaned. Or do I need to wear a Mac?

 

[aos]

Using modern regulators is superb idea. I use them in PDAC - ADP3303 - and they are far superior to 3-pin regulators, in fact at least one if not two *orders* of magnitude on most parameters (line,load,noise,ripple rejection). They do have some SEVERE limitations though, they are almost never available in voltages over 5V making them useless for most audio unless some ingenuity is used. It is usually not possible to add external reference to adjust the voltage. Also, negative voltage regulators are extremely rare to non-existent. Additionally, many of them have input voltage limitations - ADP3303 will die if fed more than 12V, making it even less useful for audio. If you do find some that overcame these limitations, please post the info.

 

[ppl]

see attached

 

[ppl]

was going to post a gif file of the schematic hear but the attach option is not showing up as an option this time

 

[ppl]

third times a charmer

 

[goon-heaven]

Thanks, ppl for the schematic. I'm starting to get a bit nervous now, in case I get my balls shot off for hijacking this thread, and because I'm treading beyond my dim understanding. I can get my head around your treatment of AC on the power lines - looks good. Do you have any notes and device numbers used? I'm not proficient enuf to understand other bits of the circuit. I presume lines from R18-X2-Part2 (the other channel) have been omitted for clarity(or confusion in my case), as well as the equivalent R6-R9,R11/C8(used for feedback?) help...

 

[ppl]

Hear is Version two that just includes the Gain and Supply Isolation this is still an old desigh and like i sed dose not show the Complete power supply as the Schematics showen do. This attachment is what i used for simulation so some components were what was in the spice Lib. like the LT-1122. However the LT-1122 is a great sounding Opamp but i think might be discontinued now. Any way this attachment as well as the others should give you an idea of what is going on

 

[goon-heaven]

Thanks ppl for V2 - looks good enuf to build if components were available - the circuit clearly illustrates the supply isolation between the gain stage and the output buffer. Your comments suggest your designs have progressed since then - care to elaborate?

 

[ppl]

goon-heaven> Parts can be changed like the LT-1122 could be any fet input opamp, I used the AD-825 in that Amp rather than the AD-744 used in the First one. The Only transistor you might have a problem sourcing is the 2N5414 and that was a mistake it should be 2N5114.This is a P Channel JFET and is hard to get But the 2N4392 is still available however the TO-92 types like PN4392 and MPF-4392 are Available. You can also use the PN4392 N channel JFET to replace the pChannel Type 2N5114 (Q7 & Q8) However the Gate, Source connection should be reverced so rather than this connection going to C11 for Q8 it should Go to C6 and the remaining Drain lead that went to C6 is now connected to c11 or just rev from what is showen. also Q7 can be replaced with a PN4392, MPF-4392 types as well just Rev as before. The use of Complimentry JFET's is not a requirement as doing the above will allow use of all N channel Devices. I used complimentry devices so as to have Both the Pos and Neg rails act as curent sources rather than one acting as the current source and the Other as a current sink. Other types that have worked well hear are J111 for the N Channel Devices Q4 & Q5 and type J174 for the P channel devices Q7 & Q8. as for the MPS-A05 and MPS-A55 any pair of complimentry BJT transistor pairs like 2N3904 & 2N3906 or similar 600 Ma rated transistors will work fine. However you should not have a problem sourcing the MPS-A05 & MPS-A55 types and these are the Perfered types as are Types MPS-8099 & MPS-8599. The 2N5484 types used for Q1 & Q2 should be used as this is to Bias the Opamp into class A and are the best devices for this. Hope this helps

 

[goon-heaven]

ppl> Thanks for your notes on possible alternative devices. I am interested enuf to pursue further. Whats best supply voltages? Your impressions of the sound? Good points and weaknesses?