I am trying to use a Citation B power amp (circa 1964) in place of my Marantz 9 tube amps as my "summer" amp here in the desert.
I noticed the sound to be good, but the sensitivity is less. The Harman Kardon is rated at 1.6V input for rated power. Curiously, I can't find the input sensitivity specs for the original Marantz 9's. It is not on the brochures I've seen from the company. The reissue from 1996 does list the input sensitivity as 1.3V into 100K ohms.
Looking at the schematic (attached), I see R2 (left channel) and R36 (right channel) in the input part of the circuit which is 2200 ohms. Would this be a good place to start? What value resistor should I use? I may install sockets on the circuit board to experiment with different value resistors.
My preamps are Marantz 7 and 7T. I would like the Citation B to mimic the 9's input sensitivity as close as possible.
Thanks much!
I noticed the sound to be good, but the sensitivity is less. The Harman Kardon is rated at 1.6V input for rated power. Curiously, I can't find the input sensitivity specs for the original Marantz 9's. It is not on the brochures I've seen from the company. The reissue from 1996 does list the input sensitivity as 1.3V into 100K ohms.
Looking at the schematic (attached), I see R2 (left channel) and R36 (right channel) in the input part of the circuit which is 2200 ohms. Would this be a good place to start? What value resistor should I use? I may install sockets on the circuit board to experiment with different value resistors.
My preamps are Marantz 7 and 7T. I would like the Citation B to mimic the 9's input sensitivity as close as possible.
Thanks much!
Attachments
Try setting the impedance switch to 16 Ohms, that's the least amount of feedback therefore higher sensitivity.
Craig
Craig
Thank you Craig. I set it to 16 ohms and did notice an increase in sensitivity. But still less than the 9's. For what it is worth I installed Khozmo shunt type attenuators on my Marantz preamps so I don't know if this may play a role. The are just right for the 9's as they are. But I noticed when I use other power amps I have to increase the volume on the preamp significantly more. The 9's do have a cathode follower gain circuit at the input that's absent on my other amps...
What you actually want is to make the gain of the amplifiers the same, not the input sensitivity.
About the only simple and safe way to do this, is to add an attenuator at the input of the "louder" amplifier.
Sensitivity (in Volts) means how much input signal is required for full rated amplifier output before clipping.
The gain (in dB) means how much the amplifier increases the input signal level. The gain is not the same as the sensitivity.
About the only simple and safe way to do this, is to add an attenuator at the input of the "louder" amplifier.
Sensitivity (in Volts) means how much input signal is required for full rated amplifier output before clipping.
The gain (in dB) means how much the amplifier increases the input signal level. The gain is not the same as the sensitivity.
It makes sense Rayma. Now, the louder amp is the Marantz 9. As it is, I don't want to change that, it is perfect for my preamps. I do want the Citation B to provide similar gain at the same voltage output coming from my preamp.
Increasing the gain of the Citation is not a good idea, since its stability will be affected.
An attenuator before the Marantz is the only safe way to make the gain of the two amplifiers the same.
The attenuator could be external in a small box, or in-line.
It was designed by Hegeman but uses all silicon transistors. The Westinghouse outputs were originally used by the military and very expensive. By the time the Citation B used them they had come down in price considerably...
Thanks for that, but it was Stu's first solid state amp, correct? And the matching Citation A preamp his first solid state preamp?
Gotcha. Thanks for this recommendation. I have an all original Dynaco PAS-3X that I am going to try next along with a Chinese Marantz 7 line stage clone that I modified with some vintage caps. We'll see what happens...
The input impedance of the Citation B is around 15k, which is much too low for tube preamps.
Virtually all tube preamps used with it will have increased distortion, lowered output, and reduced bass response.
Virtually all tube preamps used with it will have increased distortion, lowered output, and reduced bass response.
Even with a cathode follower? The PAS-3X also has a lower output impedance due to it's clever implementation of the tone controls.
I did notice somewhat reduced bass response with my Marantz 7T, but this design although solid-state, mimics the characteristics of the tubed Model 7, almost to the letter...
I did notice somewhat reduced bass response with my Marantz 7T, but this design although solid-state, mimics the characteristics of the tubed Model 7, almost to the letter...
What are the relative positions of your Volume Control between the Marantz 9 and the Citation B when playing the same music via the Marantz preamp? That would give us an idea of how much extra gain you need on the Citation B
Do the comparison with the Impedance switch at 16R as Craig suggested.
Do the comparison with the Impedance switch at 16R as Craig suggested.
A cathode follower provides low source impedance with low distortion for a high impedance load,
but a low impedance load increases the distortion.
Also a tube preamp line stage output coupling capacitor is normally sized for high impedance loads,
since tube preamps are not usually intended to drive low impedance loads, so there will be bass roll off.
The interesting thing is that in 1964, when the Citation B was released, there were hardly any solid state preamps available for the hifi enthusiast aside from the Citation A. Maybe the Hadley 621 and that was it.
The manual for the Citation B says any high quality preamp can be used, not just the Citation A.
I am going to try using a tube preamp and report back...
The manual for the Citation B says any high quality preamp can be used, not just the Citation A.
I am going to try using a tube preamp and report back...
Plenty of gain with the Chinese Marantz clone preamp and no perceivable bass rolloff. So impedance mismatch is not an issue. I'll do some measurements of output voltage at different volume positions using a 1 kHz signal and compare them to my Marantz preamps later...
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Ok. So I listened to the Citation B/Chinese M7 clone combination for a few hours. Plenty of punch in the sound. Great imaging and bass response. Given the M7's generous output I could hear some loss of clarity when pushing it, which is likely the onset of clipping.
Attached is a table I compiled of the relative voltage output of different preamps I've used. Like I said before there is no official input sensitivity of the Marantz 9 original version, only the reissue. My pair, made in 1962, seem to have a lot of gain. So much, that many preamps give very little usable area in their volume controls. Examples are the Audio Research SP-8 (had to install gain reduction resistors), the Dynaco PAS-3 and the Conrad Johnson PV2. My Chinese M7 clone is pretty much unusable as well, although it performs superbly with the Citation B.
Also note the Marantz 7 with the Khozmo shunt attenuator has less output that stock.. This applies to the 7T too, as I have a Khozmo attenuator installed on it as well.. Perhaps the Khozmo works good with the high gain of the Marantz 9 but no so much with other power amps...
Attached is a table I compiled of the relative voltage output of different preamps I've used. Like I said before there is no official input sensitivity of the Marantz 9 original version, only the reissue. My pair, made in 1962, seem to have a lot of gain. So much, that many preamps give very little usable area in their volume controls. Examples are the Audio Research SP-8 (had to install gain reduction resistors), the Dynaco PAS-3 and the Conrad Johnson PV2. My Chinese M7 clone is pretty much unusable as well, although it performs superbly with the Citation B.
Also note the Marantz 7 with the Khozmo shunt attenuator has less output that stock.. This applies to the 7T too, as I have a Khozmo attenuator installed on it as well.. Perhaps the Khozmo works good with the high gain of the Marantz 9 but no so much with other power amps...
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Well. This was an easy one. I simply adjusted the volume knob on the 7T so that it would output approximately 1.5V with a 1kHz signal at the 12 o'clock position.
I now have gain comparable to the Marantz 9's.
I now have gain comparable to the Marantz 9's.