On back of Preamp is switch for Low power /high Power I always use on low and wonder purpose of this as I recently had amp serviced and Tech stated that front Red Lights on Model 15 dont come on until you drive loud on High power never had this above 50% as ear drums begin to crackle but never had Red high power lites come on. Question has any one here ever lit these lites on this amp?
Model 15 amp with Model 7 preamp
- Thread starter chasman
- Start date
Brian
An Old Geezer
I assume you are using a 7T. If so I think the hi/lo switch is related to the phono preamp. I do not remember such a switch on the 7 (or 7C, the tube preamp, as some call it).
As for the 15. The light is a part of the circuit to to prevent amp damage in the event that you clip the amp. It was to allow what we'd call a soft clip and was of the same idea as the McIntosh Power Guard introduced later except Mc is more sophistocated. Having had numerous 15s (both early and late production versions), yes I did clip the amps and get the lamps to light. It is impoertant to make sure the lamps have continuity as if not then the amp can easily self-destruct on clipping. It was a problem with the early 15s, and cured to a degree with the later 15s and for the most part the 16 reduced further and with the 16B the design finally was as stable and not any more prone to self-destruction than any other design of the time.
As for the 15. The light is a part of the circuit to to prevent amp damage in the event that you clip the amp. It was to allow what we'd call a soft clip and was of the same idea as the McIntosh Power Guard introduced later except Mc is more sophistocated. Having had numerous 15s (both early and late production versions), yes I did clip the amps and get the lamps to light. It is impoertant to make sure the lamps have continuity as if not then the amp can easily self-destruct on clipping. It was a problem with the early 15s, and cured to a degree with the later 15s and for the most part the 16 reduced further and with the 16B the design finally was as stable and not any more prone to self-destruction than any other design of the time.
Maron Horonzakz
Well-Known Member
The Marantz mod 15 is a great amp...I had six of them...You dont want to stress that amp in lighting the safety lamps....The output transisters are now hard to find...I sold mine to engineer at a TV staton (all 6) and they are still in service.... I now own the newer Marantz Esotec MA-5 monoblocks (6 of them) They should last another 30 years.
Brian
An Old Geezer
Yes, very bad for the amp, for the speakers and for sound quality. Applies to any amp but with the 15 it is more so due to the self-destruct issue. Keep is out of the read and other than things like cap and migrating solder it should last long term. Only other thing some consider is the thermal grease on the outputs. By now it may have dried and not be doing its job as well as it should.
SB Marantz
Well-Known Member
Those lamps are nothing more then a clipping indicator and should not harm the amp if it's ok.
I re-capped mine and tested it at full power on the dummy-load.
I re-capped mine and tested it at full power on the dummy-load.
