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I purchased these from an audio dealer for $6600 and then spent $4k on mods. Low ball offers will be declined. Thx.
Listing price is per monoblock. Will only sell in pairs. I have two pairs. Each amp in each pair was meticulously upgraded by Jennifer Crock at Jena Labs ($2k per amp), pushing the performance to SOTA competing against $30,000+ amplifiers (I replaced my Constellation gear with these). Spaciousness and PRAT increased, and the veil and electronic haze was completely removed. Details on modifications below, but in a nutshell, all "last mile" wiring etc was replaced with top shelf materials. Reason for sale: I am now running my Magnepans with flagship Luxman class A amps. I was going to bi-amp my second system's speakers (TAD CR1) with these (amazing combination...four modified marantz amps driving the TADs), but instead am running a full Air Tight system instead (Flagship Air Tight Mono Amps at $65k...better in warmth and harmonics than Marantz, but not as good in control and punch as Marantz...I would be happy with either, but no one was willing to buy the Air Tights from me, so hence the sale of the Marantz monos).
Description of JENA Labs upgrades as provided by Jennifer (co-owner/engineer):
Marantz power amplifier mods. Model 9 for Podeschi
Just as in good medical practice, the first role of planning any modification is FIRST, do no harm. We try to honestly recognise the positive merits present in any given piece of gear, and then discover the shortcomings that come along for the ride. We then try to find a way to mitigate the shortcomings in as reasonable a way as possible.
The Marantz 9 amplifiers are very nice to start with. It is pretty clear to me that the basic topology of the circuits and the basic implementation is really pretty good. Upon examination we find that some of the passive parts, though good and better than average, are not to the very best quality, and that if substituted, more of the positive traits inherent in the amp will be heard. In support of that notion the following work was performed...
AC inlet. We removed the 2 conductor IEC AC power inlet and replaced it with a high quality 3 conductor part that has been fully Immersion Cryogenic treated right here at JENA LABS. The ground terminal of the inlet was also connected to the chassis for improved safety as compared to the ungrounded original.
Binding posts were replaced the highest quality parts available from Cardas, the 100% full Rhodium binding post system. Like all the parts we install, these have been fully Immersion Cryogenic treated. Behind the binding posts, the original single runs of rather generic stranded wire was replaced with multiple wire runs of our 18 Gauge Ultra-Wire.
Signal input jacks, both the RCA and balanced XLR, were also replaced with the top of the line Cardas parts, all rhodium contact surfaces, with Teflon dielectric. As with all the other parts and wire, these too are fully Immersion Cryogenic treated in house here at JENA LABS.
Input wiring in the original amplifiers was rather complicated. The signals from each of the 3 jacks first routed to the main input board, and then were sent via connector and harness and yet another connector off to another sub-board that carried a 4 step volume control ("attenuator"). In order to simplify the signal path, we eliminated this off-board trip to the sub board, eliminating a large number of junctions and excess parts in the signal path that do nothing to improve the sound..so we got rid of that. A single connector on the main audio board was fitted with Vishay Daly CMF series metal film resistors to retain the proper hot to ground impedance, as that functions was present on the now-removed sub-board, The 3 input jacks deliver the signals to the main input board, where the signal now stays, and they are still selectable via relays that are operated by the input selector switch on the front of the amp. The flexible nature of multiple inputs is retained. All the small signal wire used in this section is JENA LABS 22G UltraWire.
Each electronic sub section of the amplifier has excellent power supply bypassing at each place of load, but the main filter bank that works right off the rectification, is not fitted from the factory with local bypass caps. Though completely essential, due to the presence of bypassing at each load zone, our years of experience have told us that to add proper, rather large bypassing right on each of the large main caps, will result in a small, but audible improvement in clarity. We use new-old-stock Reliable Capacitor film caps from our private stash for these bypasses, as they have a proven track record of excellent sonic performance in this application, and incredible freedom from any failure mode.
One last thing we address is a small amount of metallic ringing present in the metal structure of the amplifier. Judicious application of Cascade Audio Engineering VB-2 vibration blocking self-adhesive sheet, results in the damping of these stray ringing modes.
In the end the Model 9 Mk 1 amps are topologically intact, and retain the full reliability of the original design. We have addressed a few issues to get the signal into and out of the amplifier boards in a less colored manner than the factory wire and connector interfaces offer. The result is a sound from the amplifier that only improves upon the hearing of the excellent qualities present in these amps. We have a little more detail and articulation, with a little less stress and edge, We have a larger more expansive overall sound field, with more delicate and easily located individual sounds within that larger field. The bottom end sounds a little more extended and authoratative, but loses non of the warm and friendly nature that it starts with. The extreme highs are clear and fast, with no sense of grittiness, or added fatigue-inducing stress.