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I just purchased a new Rogue Audio Tempest II that sounds quite good with my gradually breaking in Silverline SR17 version III.However ,I did notice that with the passive preamp that should have driven the Stereo 90 to a full 90 watts did not happen.The unit can be turned up full without even a hint of clipping and basically sounds about as loud as my 3020 NAD that I am using to break the speakers in at night. When I contacted Rogue they thought the NOS tubes(which come standard with this preamp along with EH KT88 output tubes) in the preamp section may not be putting out the required 1.0mv to drive the power amp section of this integrated amp(which again is the Stereo 90) to full volume or anything close (see link below)My problem is… are these NOS tubes which Rogue wants to replace with conventional EH brand tubes contributing to the absolutely gorgeous sound I am hearing from this amp?How much in the way of sonics am I going to lose with the EH which will give me a least the 1.0 mv I need to get the full power out of the amp .Is there a alternative that will give me the supposed better sound of the NOS tubes & the 1.0 mv or better output to get the full 90 watts that the Silverlines could use even though they have a 89 db efficiency .They also possess a 4 inch voice coil in the bass driver that could use a little power to get it going .,Any suggestions would be welcomed however first check out the dismal output of this amp when using the NOS tubes. I hate to give up with this amp because of this if there is a tube that will match the sonic qualities of NOS tubes(whatever thier advantage maybe) & still have enough output to drive the internal power amp to 90Wps….that would be ideal. Will the EH they are sending do the trick? Or at least come close….perhaps I am worried about nothing but then why would they go with the NOS tubes?
Thanks
Bill
PS...check out this supposed 90 wps per channel amp using NOS tubes on the 4 input tubes.
http://www.soundstagemagazine.com/measurements/rogue_tempest_ii/
Follow Ups:
If I'm up to speed on your situation, you are using a passive preamp to drive the amp section of an integrated amp. In doing so, you are not getting any gain out of the passive and the amp section of the integrated is having to be driven by the source component through whatever length of resistive interconnects you are using and resulting in an impedence mismatch between the components.Given the situation, you could either try Rogue's suggestion or try different interconnects that are shorter and less resistive...or both.
Preamp tubes are critical to the sound and I suspect you will notice a difference in sound (maybe better, maybe worse) but I would opt for NOS tubes over any Chinese tube every time.
The older models had 4 and 8 ohm speaker selection. Are using the right one?"I did notice that with the passive preamp that should have driven the Stereo 90 to a full 90 watts did not happen"
This sentence suggests something is wrong with the preamp. Does it have an active and passive preamp? Also preamps do not "drive" amps ina power sense. The power comes from the power amp side.
"The unit can be turned up full without even a hint of clipping and basically sounds about as loud as my 3020 NAD that I am using to break the speakers in at night."
This sentence suggests you don't have a problem: it seems to contradict the first sentence.
"My problem is… are these NOS tubes which Rogue wants to replace with conventional EH brand tubes contributing to the absolutely gorgeous sound I am hearing from this amp?"
What? A passive preamp doesn't use tubes, now I am more confused.
The NOS tubes are 6SN7s? This amp also uses 12AX7s. That implies an active preamp section with 1 driver and 1 output per channel. I am guessing. Very good NOS 6SN7 tubes will sound "different" than newer 6SN7 tubes in some circuits and show no or only a small difference in other types of circuits. In general an active preamp (or a passive) will influence the sound.
Rogue is a good company. Send them your tubes, so they can test them. But hey, check the impedance you are using first if it still can do both 4 and 8 ohms speakers
Frihed:
You are correct this is rather enigmatic. Why use the integrated Rogue and bypass its own preamp. The built in preamp is what makes an integrated a true bargain. As you are well aware many preamps of high standing cost as much as this amp. I have had to use the option of using the preamp only from an SS integrated amplifier. It was still an active preamp. Active = yeilding a signal higher than the 2.8 MV or less source. I was able to get things to the same levels fairly easily.
Are you saying the preamp voltage is not important in terms of what the amplifier output signal is? I don't think that it is purely an additive function. If it were a only few milivolts you ar correct it would have little or no audible effect. I think the amplifier's ability to produce output on a scale many logs greater than the input voltage is not a linear function but raises the voltage in an exponential manner, along with other variables which may also be non linear terms. The resultant diminution would be critical in terms of how much distortion you will experience at your preferred SPL.
In a tube power amp the output distorion becomes audible at fairly low levels as a general rule, not every amp hold the flames. In using a purely passive pre or a source directly into the power amp you have to be cognizant of the demands you put on it to drive the load you use.
BTW earspeakers as you know operate at very low voltage levels and amplification may afford to bypass elements in conventional amps.
I also wholeheartedly agree the tubes used will alter the sound quality dramatically for better or worse but not the output level theoretcally, if the same tube type is employed until the tube is burning out. Not without tube rolling to a lower gain or other parameters depending where in the circuit the change is made, such as the new tube type's current pass thru.
Hi There,You read this differently than i did. I didn't and still don't see the part about using another preamp. My only point was to say, I was really confused but i wanted to help.
The only substantive point i think i was trying to make was that the effects of tube rolling depends partly on the circuit. In some circuits, rolling tubes has little or no effects; in others it can have a huge effect.
Dear Frihed:
Asolutely true, I cannot alter the gain in my ARC SP6B. I read in an archived search that this has been an issue many find troubling. The technical reasons given were way beyond my pitiful understanding. If anyone can explain it in "Amps for Idiots" terms I would be very grateful. Thanks
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