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In Reply to: RE: Lazarus basic preamp posted by fpharryc on December 17, 2016 at 23:09:24
So for the phono section a Dynaco PAS3 schematic will be helpful but not completely accurate.
If I recall right the Lazarus had a set of simple solid state regulators.
The line section is a 12AX7 where the first stage of gain is direct-coupled to a cathode follower output, much like the Last PAS (which was anything but...).
I've fixed a few of them but I saw the last one a good twenty-five years ago...
Follow Ups:
If we're talking about the same preamp, Allen Wright said:
"That unit's design was a direct ripoff from me"
Link to Allen's Asylum post is here and also below.
Here's the Last PAS phono (with David Vorhis corrections indicated), line stage and filament supply schematics, if anyone is looking for them. I may have the Vorhis / Jung regulated B+ schematic too, if someone needs it, although I showed it to Allen Wright once, and he wasn't too fond of it.
Note that for C43 and C44 in the filament supply, I use two 120,000 µF caps. I've had several people tell me that much capacitance shouldn't make an improvement, but it does.
- which would suggest that he had the design in the early 1980s.
I just remember working on several Lazarus preamps decades ago and being struck at how similar they were to the Last Pas preamp.
But thought I'd at least link to the late Mr. Wright's take on the situation.
I've always liked the sound of my Last PAS. The phono is OK, but the line stage I'd consider very good, certainly better than my stock PAS or Audio Research SP3-A-1.
I've often run a similar line stage, but dropped the negative feedback and used a 12AU7 (with values optimized for a 12AU7). It seems to sound better and has more voltage swing.
And had one guy tell me that it looked like a guitar grunge-box circuit.
No matter how it may look on paper, it sounds very good, better than my stock PAS and ARC SP3 etc. as I mentioned.
I wrote to thank David Vorhis (who sometimes posts here on the Asylum) for putting together such a detailed, well written article on modifying a Dynaco PAS. He took the time to write it like a kit assembly manual, rather than simply posting a couple of schematics and saying, "Have at it". I needed my hand held when I built it way back when. I don't know if I would have attempted it if he hadn't laid it out the way he did, and to have it turn out so well was gratifying.
-
You agree with the circuit's guitar grunge box assessment?
Nah, I'm just kidding, Ralph. It's always a pleasure interacting with you here on the Asylum
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