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Mr. Samra, recently you posted a detailed description of mods that can be made to a Mac 2105, one of which I own. I also have an ARC VT 100 Mk2. I interchange them, using the ARC on vinyl and the Mac on line inputs. I have an ARC SP8 pre, and feed the ARC thru the regular op, and the Mac thru the tape head op. Using the tape op, I find that all functions of the SP8 go inoperative except the selector switch. The line signal goes through unchanged apparently, since the SP8 need not be on at all. I assume it is acting as a passive input selector, with volume controlled through the source (TV, DAC, tuner.)
Recently, I decided, as a test, to listen to vinyl through the Mac and the tape op. The SP8's power must be on, but all other preamp controls were again inoperative, even the mute switch. I was curious to see if it would work, and if so, how much volume there would be. Listening, I first tried a recording of "The Sleeping Beauty" by Rozhdestvensky and the BBC, a fine recording but cut at a low level. There was oodles of volume. The volume controls on the Mac, set at 1 o'clock, were fine. I next tried Strauss' "Till Eulenspiegel" with Kempe and the Dresdeners, mastered at a much higher level. The sound almost exploded into the room, and I had to turn the Mac down. Gosh it sounded good. The Mac's sound improved in this configuration, especially in the highs, where more detail was present. It approached the ARC in this respect, with much less sense of a "softer", high-end roll-off.
Questions 1: With the phono through the tape op, am I truly bypassing the line stage of the SP8, except for the selector? Is this simpler circuit path the reason for the Mac's improved sound, and the SP8 really now operating as a phono preamp only? (I tried to attach a pic of the SP8 circuit, but couldn't get it to take. Sorry)
So - I said all that to say this -
Question 2: Will the mods for the 2105 you suggest make the bass better defined? I love the clarity of the ARC's low end, but like the greater weight and richer tone color of the Mac's low end. If your mods make for better definition in the lows of the 2105, then I may be able to get the best of both worlds, with added benefit of the Mac's reliability and fewer tube worries and expense all the way through the system. Thanks for your time and help.
LowIQ
Follow Ups:
ith the phono through the tape op, am I truly bypassing the line stage of the SP8, except for the selector? Is this simpler circuit path the reason for the Mac's improved sound, and the SP8 really now operating as a phono preamp only? (I tried to attach a pic of the SP8 circuit, but couldn't get it to take.
That is correct..You are bypassing the preamp and That allows the signal from the source component phono, cdp, tuner,or whatever component, which is selected on the preamp to be routed to the tape deck input for recording. To play back from the tape deck, or to monitor the recorded signal directly from the tape as it is being recorded, requires a deck with separate record and playback heads, so you then select the monitor or tape position of the preamp's monitor/input or tape/source switch,or whatever similar designation it may have.The sound of the MAC 2105 seemed much more dynamic because you essentially eliminated the preamp section so the signal was being fed directly into the amp.You still had your phono stage,but the line stage was bypassed and just used as a source connector or tie point.
Question 2: Will the mods for the 2105 you suggest make the bass better defined? I love the clarity of the ARC's low end, but like the greater weight and richer tone color of the Mac's low end. If your mods make for better definition in the lows of the 2105, then I may be able to get the best of both worlds, with added benefit of the Mac's reliability and fewer tube worries and expense all the way through the system. Thanks for your time and help.
The mods or upgrades will help all the way thru..New input filter caps and strategic bypass will make the bass tighter,and more controlled and yes,more natural..It will improve the amp from top to bottom.You will still have a slight dynamic loss going thru a linestage but that's true with any added stages in the audio loop.You may want to upgrade the components in the Sp8 possibly.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Thank you for the clarification. Now, what was the date and forum where you posted the mod info for the 2105.I looked but may have missed it. Darn it, I can't seem to remember how to access your posts, though I know there is a way to do so. Sorry to sound so stupid.
The tubes in SP8 are bugle boy and telefunken 12ax7's and vintage Mullard 6922s, all testing well.
Do you have any suggestions as to renewals for caps, etc. in the SP8? Power supply tubes perhaps?
Much appreciated.
LowIQ
I did only two SP8s and this was a while ago.I just did a general rebuild with newer and better filter caps and I put some paper in oil caps in the interim stages and Russian KBGs in the output..Today I would be using Schotky diodes in the high voltage stages as well.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
I found it. It was in the Vintage asylum.
LowIQ
Super.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
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