Pio1980
AK Member
It's possible with all class 'A' circuit preamps lacking automuting.
C22 Warning - tube preamps
- Thread starter dewickt
- Start date
62 -- To a large degree, a thump is a thump is a thump, regardless of what topology or design creates it. Relating specifically to cold turn on surges however, unless a SS unit has a delayed mute feature, I would be suspect of ALL such designs (as in, they produce a thump). Vacuum tube designs with vacuum tube rectifiers will generally have no thump, as will not those with SS power supplies and using a CF output stage. It can all get convoluted enough to say that as a general rule, preamp on first, then power amp. Power amp off first, then preamp. The little interrupters that sKiZo recommends then will take care of any quick power surges for all topologies.
Dave
Dave
jbailey930
AK Member
I wait about 1 min for my tube CJ preamp to energize before I turn on the SS Mc2205.
nj pheonix
Lunatic Member
I was thinking along those lines. . Even a schematic with a BOM. It could be breadboarded.
lindstrom
New Member
Where do you get those?Got that covered ... I have a non-latching adapter on my tube stuff that required a manual reset after a power blip.
That gives the amps time to discharge properly and not take a hit. The SS stuff will cycle fast, but that's not really an issue, and we're past the "thump stage" if I wait a bit before resetting the adapter to pass power.
I still say this is one of the best things $20 investments you can make for your system, and peace of mind.
* Doesn't protect against brownouts, just those quick blip blip hits that can overload tube equipment that hasn't had time to discharge properly.
dewickt
Will fix about Anything
Not exclusive to tube preamps, but more common with them. Best example is an unrestored C20, all it takes is some leakage in the output coupling capacitors to make the turn on swing fatal to a DC coupled amplifier. Have also seen preamps with modified outputs (larger value capacitors) cause DC output due to the output loading resistors having to high a value unable to drain off the turn on swing.
Just a good idea with any system, preamplifier on first then the power amplifier.
Just a good idea with any system, preamplifier on first then the power amplifier.
Pio1980
AK Member
Since you asked, I'll take a closeup of the bottom of the board and put it out for anyone to adapt for their own purposes.
This version uses a 12 vac source with a full wave ps, it could run in 6.3 with a doubler ps and no other changes.
And that for most people s common practice. I never really liked macs trigger wire as it seems to turn everything on at the same time.
sKiZo
Hates received: 92644 43.20°N 85.50°W
ooPs! ... added a link to the first post too ..
TRC 90033 Shockshield White Portable GFCI Plug with Surge Protection
And before yall ask ... ignore the "GFCI" part ... what's important for protecting your tube equipment is the "NON-LATCHING" feature. That will trip on a blip, and require a manual reset. These and similar adapters are popular with the trades ... don't want a power saw walking away - or worse - if the power comes back on automatically.
"Long as we're waiting, pass the coffee please"
"Want sugar with that?"
"Sure ... but hold the saw!"
As mentioned earlier, they're rated at 8 amps, and one comfortably handles both my stereo amp AND the mono amp I use on the center channel.
nj pheonix
Lunatic Member
Out of laziness i solved this by accident. I bought some remote control outlet modules . When power goes off they go to off (source)position and have to be commanded on again.
pretty much these though i bought a three pack. No affiliation.
http://www.ebay.com/itm/like/311363135311?ul_noapp=true&chn=ps&lpid=82
pretty much these though i bought a three pack. No affiliation.
http://www.ebay.com/itm/like/311363135311?ul_noapp=true&chn=ps&lpid=82
Pio1980
AK Member
I'll try to get something on this up sooner than later.
Pio1980
AK Member
More pix, I'm working out the skiz in spite of a case of CRS. Any assistance appreciated, this is the 12.6 VAC version. The 6.3 VAC version will have a doubler ps with elyticap values adjusted for acceptable ripple with low storage factor.
Pio1980
AK Member
Last edited:
I doubt it. The C22 was built at a time when amps had output transformers, which naturally block DC from hitting the speakers. While most amplifiers have coupling caps or DC blocking caps somewhere in the signal path, there are some modern ones that don't. I think that McIntosh preamps have not had a problem with DC at the output for many decades. I could be wrong, but it's easily tested with scope, or at least with a meter to see if there is voltage present at the output with no signal passing through the preamp. What amp are you thinking of? Most modern amps that are DC coupled have output protection circuits that will kick in if the amp sees DC at its output. There's also the question of what you would gain with a DC coupled amp. There's no reason to amplify signals that are well below what your speakers can handle. It's a waste of power and potentially dangerous to the speakers. I would add a high pass filter with a DC coupled amp anyway.
On a related note, the Grateful Dead's PA was direct coupled from the mic inputs right up to the inputs of the power amps. It greatly improved the fidelity of the system.
I just almost took my c 2300 to a friends house so he could hear it on his system. I run the c2300 with a 452 but I never would have thought using it on anything non Mc would cause problems, till I saw what was at the top of this thread. I may have hooked it up to another amp one day and was surprised.
Similar threads
