How much do I need to spend to get a preamp that sounds better than no preamp?
@georgehifi And the service Pass service manual for both revisions... https://www.google.com/url?sa=t&source=web&rct=j&url=http://forum.vegalab.ru/attachment.... As you can clearly see, the gain stage isn't on its own ladder. |
His wording on the thing makes it clear at 3:00 you're seeing unity gain at the output, and it's clearly a direct connection to the output, but given the other components in parallel with the input to ladder, there's got to be some small loss to be made up by a small amount of active gain. I'm not saying it doesn't behave just as he suggests, but it's obvious the gain stage shares the ladder all the way down. |
As you can see, I’ve highlighted in red from input to output, if the volume is kept below 3 o’clock it is totally passive and the signal only runs through the source selector and the switched resistor ladder volume control. https://ibb.co/j8uwJn Nelson is right when he said: "The only component in the signal path is wire and switch contacts. At positions below 3 o’clock, the volume control functions as a precision passive attenuator using discrete resistor ladders." "Above 3 o’clock, active gain is ADDED to the output signal in 2 decibel increments, for a maximum of 10 dB,As a result, you suffer the effects of active circuitry only when additional gain is necessary." If anyone want to get one of these Pass Labs masterpieces that he loves himself, good luck as they are very rare and if they do come up used go for quite a bit of money. Cheers George |
An interesting circuit- the output of the follower drives the top of the control; its output (running wide open gain) is thus mixed with the incoming signal. While Nelson's comments are essentially true, they are not the whole story by any means. One weakness of this circuit is the extremely low impedance the source must drive, which in this case is less than 2000 ohms if the schematic George linked is correct. Most sources can't drive such a load at all. |
