Resurrecting a very old thread here, as my questions are related. Will try posting my questions here first before opening up a new thread, if needed.
I understand from the postings that the phono input on an RM5 preamp can be used on it's own with a mm cartridge. For those of you with experience, has it worked with a high output mc carts as well? Roughly, how high does the output of the cart need to be to work properly with this preamp?
I understand that if the cartridge output is too low, you need to add something like an RM4 headamp or a SUT. But I'm just trying to figure out what sort of carts will work well with the RM5 on it's own.
There is no simple answer to the gain/cartridge question. Total system gain and noise are dependent on the total system. You can have too much or too little gain however noise alone is determined by the
first stage in any system unless there is some horribly noisy component after the first stage. From a noise point of view a cartridge of 0.5 mv will work fine with an RM-5. There is no problem with running the volume full up if needed or using high gain in the line stage. There will be a great difference in volume between sources however. If you want to make them similar we sell an attenuator that will bring the loud sources (usually the CD) down.
The other way to make volume settings similar and reduce noise further is to use the RM-4 head amp. That was its intended application. It has enough gain to make the phono and CD inputs very close. I don't feel the RM-5 sound changes much with the gain setting. There were some preamps made without the gain switch but the place for the switch and resistor are still on all boards. We put jumpers in which can be replaced by a 4 position DIP switch. We can do that for you and go through the preamp and make sure it is up to spec.
There are a lot of noisy preamps out there because some designers pretend that a 12AX7 is a good phono input tube.. it is not. A 6922/6DJ8 is about 6 dB less noisy than a 12AX7 and the lowest noise tube one can reasonably find. That's why I started using it in 1978. Look how long it has taken some to get the message and some haven't yet.
Right now I am focused on the OTL amps, tape repro amps and the school. A preamp will come along someday. In the meantime we do have an inexpensive, very nice line stage available.
http://tubeaudiostore.com/tubepreamp.htmlWe are also doing a lot of custom work and will make preamps at pricing competitive with what is going on in the current market place.
