Leestereo Marantz 1090 Revisited

[hirscwi]

Sound advice - thanks. It's as much of an experiment as anything else.

 

[Leestereo]

The 1090 is completed and ready for the listening test. I've attached the final cap list.

Listening test:

Using Tekton Lore-S speakers and after about 50 hours of break-in. Most of the test was done using Winton Marsalis; Awadagin Pratt; and Chuck Mangione CDs with which I am quite familiar. I also checked out a couple vinlys. This is now a better sounding unit. The treble is much clearer and easier to listen to. Mid-range has a bit more definition and there is a bit more "tightness" to the bass. None of these difference are dramatic, but they are noticeable. I also believe tha changes madea substantial improvement to the phono section. And the unit is quieter now - thanks to the UF diodes.

I attribute much of the change to the replacement of the old ceramics with the much higher grade C0G/NP0 MLCCs. These removed some distortion in critical parts of the signal path. I suspect that some of the electrolytics helped also. A nice experiement would be to replace the electrolytics and perform a listening test. Then replace the ceramics. It's my unscientific view that the ceramics might have more impact than some high-dollar films

Those Tekton Lore-S speakers are very nice!

Its gratifying to read that your impressions of the sound improvements in the 1090 match my own; guess I'm not tone deaf after all!

I agree that the use of C0G capacitors to replace cheap garden-variety ceramics in the signal path addresses the major source of the "harshness" in treble range of the 1090. The analogy of a chain with a "weak-link" for a stereo system with a poor sounding component can be extended to the passive component level: any cheap ceramic in the signal path can be considered a "weak-link" and should be replaced with something better. Similarly, 30 year old electrolytic capacitors should be replaced.

 

[hirscwi]

Thanks for the kind words.

I think your analogy of a weak link is spot on. The 1090 is basically a good design - it just needed some component changes/upgrades.

Yes, I'm very pleased with those Tektons. I have only had them about a month but they are fantastic.

 

[Autobahn]

Hirscwi and Leestereo,

Thank you!!!!!!!!!!!!!!
I just restored a 1090 using info from both your postings, and the difference in sound between before & after the work is night & day!! This receiver is with out a doubt putting out more than its rated 45 watt per channel.

Michael

 

[Magnus Back]

The 0.22µF ECW is an excellent choice and it fits nicely on this part of the P400 board; as long as the high-pass F3 is <5Hz there is no problem.

@Leestereo
Sorry for reviving this old thread. I've been looking at your comments on capacitor selections for input filters.
In reference to the high/low pass filters used in these Marantz amps, why is < 5Hz good for the high pass in this case? And correspondingly for any low pass what would be a good cutoff frequency to aim for?
I assume there are different considerations for pre and power amp sections? At least I see the filtering is different with standard values.

 

[Leestereo]

For RC high-pass filters, a good rule of thumb to minimize distortion within the pass-band, is to use a capacitor that gives a F3 that is 2 octaves below the lowest frequency of interest, i.e. 20Hz. Accordingly, the minimum acceptable target F3 is 5Hz. Further, if the capacitor is an electrolytic type, to minimize LF distortion (see http://www.diyaudio.com/forums/parts/192811-capacitor-measurement.html#post2643470), it is good practice to use a capacitor that is ~10X the size required to achieve the F3=5Hz, e.g., if a 1µF film capacitor is sufficient to give F3=5Hz, an electrolytic capacitor substitute should be 10µF. However, since one cannot assume that the electrolytic capacitor installed in the filter followed this ~10x size recommendation, it is best to calculate the replacement film capacitor size. With a low-pass RC filter, there is a 45° phase shift or delay at the cut-off frequency (F3). Although the audibility of phase delay is debatable, if one wanted to reduce the phase shift at 20kHz to <1%, a F3 of ~1.5MHz is needed. The phase lag can be calculated with -arcTAN (2*π*f*R*C).

 

[Magnus Back]

Thank you, great info!
I assume the 20Hz is chosen because it's ~ the lower limit of human hearing?
It seems we can under good circumstances (headphones and certain types of sound) detect phase shifts up to 10° at > 70dB (SPL) so it's definitely good practice to reduce phase shift.