Quote:
Originally Posted by barretter
I don't really understand what you are getting at when you talk about "adjustment of the RIAA curve from the cartridge and similarly inverting this effect from the modern line signal to the amp" or "RIAA bias adjustment".
For a start if you have lots of 78s from before 1954 they won't have been cut with RIAA pre-emphasis but with each record company's patent pre-emphasis and the same goes for pre-1954 microgroove discs. Which de-emphasis to use is a complete minefield which is why the RIAA (Radio Industry Association of America) introduced their standard in 1954 and succeded in having it adopted by most of the world's record-issuing companies by the time stereo came along.
As far as I can see the only components in the disc input circuit are a couple of 1M resistors which are presumably the correct loading for the two ceramic/crystal cartridges. Is there any circuitry further down the line before the main amplifier which could contribute to equalization of the signal from these cartridges?
|
Hi Barretter
You seem very well read about the historical aspects of record recording standards, thanks for sharing this with me.
To clarify, as far as the phono system entering this amp, this will be via two separate H4F head shells one with the original GC8 78/45 reversible cartridge and the other a new moving magnet cartridge with a robust tracking weight for 33/45 stereo use. The GC8 input is now switched into the amp in its original unchanged level and conditioning and requires no further discussion as this is operating satisfactorily playing all my 78's.
The MM cartridge headshell will be input to the amp via the SPA9 pre-amp. This pre amp has RIAA conditioning, and I have yet to assemble this part of the project.
Hopefully this will also be suitable, and as it stands i do not have any current questions on this.
With regard to the new EXT input (WXAD-10 wifi) I am satisfied I have managed to provide suitable signal conditioning in the form of high/low pass adjustable circuitry prior to the signal entering the SRG600 amp. I am able to tune this signal to respond to signal bias expected by the amp previously (occasional RIAA bias conveyed from the cartridge). To remind you I am using the phono input to the amp and switching the various inputs pre conditioned as previously described. This is working satisfactorily as intended and works well. I do not have further questions here either.
My question was to source a small adjustable amp to trim the differing signals strengths in the final connection to the amp.
The older CD's (via WXAD-10) seem to have lower outputs and I would like to be able to trim these to the same level at the final stage so the amp sees the same level as the newer higher level signals.
It is a simple request to source a line level amp which only has a small adjustable gain so I don't have to couple something together.
It appears no one knows of something suitable so it looks like I will have to do this!
I hope this clarifies my question.