Reel to reel deck directly to power amp ?

Almarg, if you’re saying that .775 volts is enough to drive an amp, you’re more mistaken than the rest.

I certainly didn’t say that, and I was not addressing the Technics deck you referred to. (Although there are in fact some amps that can be driven to full power by less than 0.775 volts, the Coincident Frankenstein and Coincident Dynamo being examples). And for that matter I didn’t express agreement with Ralph’s statement that +4 dbm would necessarily be adequate.

Regarding Inna’s questions that followed my post, let’s wait for Ralph to confirm (or correct) my understanding of what the dbm numbers mean, which I’m not completely certain of.

Regards,
-- Al

Next step could be asking Ralph to custom make playback head tube preamp or maybe playback head/phono stage unit, and match it precisely to his amps, and match the amps to speakers. Now that would be high end.

I have an Atma-Sphere MP-3 that has switchable RIAA and IEC (15ips) EQ settings. While the linestage has the standard gain, Ralph has mentioned a number of times that this can be configured as a unity gain tube buffered output. Seems like this would meet your needs. I have used mine for a number of years now with the transport section of an Otari MX-5050, the signal taken directly off the tape heads. I also have the pro-sumer version of the deck that has the integrated preamp circuit with volume control. I can’t recall if I ever ran that directly into an amp, but guess I can check and report back here if anyone is interested.

Sure, I am interested, if it is not too much of a bother that would be great. What is your amp ?

I have several amps here. Atma-Sphere M60s, Music Reference OTL and RM-10, Electra-Fidelity A3-500, Acoustat servos. Give me a bit of time, I will try it on the existing set up first with the Acoustat servos. If that doesn't work I'll swap in my box speakers and try the other amps.

Ralph hasn’t responded yet about the dbm question I raised, so I did some further research and it appears that what I said was correct. dbm in this context represents decibels above 1 milliwatt into 600 ohms. So the voltage numbers I calculated were correct.

It also happens that the 0.775 volt maximum output of the Technics deck that was referred to corresponds to 0 dbm, since 0.775 volts into 600 ohms corresponds to 1 milliwatt.

So the bottom line is that with some combinations of tape decks and power amps it will be possible for the power amp to be driven to full power, and with some combinations it will not be possible. Generally speaking a problem is likeliest to arise in cases in which the amp is high powered (and most or all of its power capability is actually required by the user, at least occasionally), since there tends to be a **loose** correlation between the power capability of various amplifiers and the input voltages required to drive them to full power. Although there are many exceptions to that, of course, where a higher powered amp may require less input voltage to be driven to full power than a lower powered amp.

Regards,
-- Al