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In Reply to: RE: Mac C11/C22 owners..A question? posted by Michael Samra on July 01, 2009 at 13:21:14
Michael,
I've had two C-22's and I can't say that the bass has been a problem but here's the full history: The first original C-22 did sound thin but still good and after checking voltages I found that the B+ supply was low. I rebuilt that one with original spec can lytics still available at the time, good quality polyprop film/foil signal caps and replaced the rectifier.
The result was clearly a more full bodied sound that was almost too thick and rich for me.
I had EV Regency speakers at the time and I did have the bass and treble controls advanced one click on each channel and the bass trim on each channel up about 1/4 turn to boost under 100HZ.
The second C-22 sounded OK but I rebuilt that one knowing that it was just a matter of time before something would give out. Again I used original spec can lytics, replaced the rectifier but this time I used a mix of inexpensive metalized polyester and polyprop signal caps and I was more pleased with the overall sonic results. I still used one detent click of bass and treble and had the bass trim pots up about 1/4 turn.
The amp was always a Mac C-22.
When I switched to Altec Model 19 speakers I found that I didn't really need any bass boost other than 1/4 turn on the bass trim pots but I retained the one click of treble boost.
If I do use bass boost from the C-22 bass tone controls it's just too much at times and that's probably the tuning of the Model 19's where 50-60 HZ can be strong.
My biggest complaint with the C-22 is the detent tone controls. When I switch to say a Scott 299A or 299C sometimes the ability to adjust the bass and treble in less than a 4db detent step is useful with some source material.
I've tried other preamps like a solid state Luxman,HK Citation lV, Fisher 80C's and a Levinson ML-1 and I can't say I thought there was more bass than with the C-22's.
I found that changing amps and turntable/arm combos had more to do with the bass in my system than the preamp.
Dave
I forgot to mention that I never needed to use the loudness control on either of the C-22's I had.
Thanks Dave
Thats what I wanted to know and I didnt sweep it yet but I totally rebuilt it but the bass is non existent until the loudness is clicked on and then I have to back it down one or even two notches to make it natural..I think I may have a resistor out in the loop or maybe a connection I had missed.Its so beautiful sounding tho and I hope its not the black gates I am using in the doubler causing it..The thing is I am using a pair 220uf BG power tanks in place of the two 40uf doubler caps.
If the power supply waveform isn't pretty,neither is the sound in most cases.
I should mention that the second C-22 I'm now using did do some strange things and it drove me nuts for a while because the sonics were from staggering fantastic to out of alignment AM radio with a 3" speaker. I never knew what to expect when I turned the system on so I finally bit the bullet and went through it reflowing solder on every connection and cleaning tube pins and sockets. I flooded the heck out of all the pots and switches with alcohol, contact cleaner then De-Oxit and worked them 20-30 times during each flooding. Whatever it was it's been OK for months now. But now and then I work all the controls and switches several times and it may be mind over matter but it seems to sound better after that. LOL Who knows.
All six 12AX7's in it were NOS Telefunken smooth plates that are now about 8 years old. I found that older EI 12AX7's I have that are branded RCA sound very nice in it too. Our pal Jim says they were made on the old Tele machinery so they are like Tele's.
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