Moscode 300

Discussion in 'Audio Hardware' started by gss, Oct 13, 2017.

  1. gss

    gss Forum Resident Thread Starter

    Location:
    New Jersey
    Hi, all:

    I’ve always been a integrated amp guy, so the world of separates is new to me, and I have some noobish questions on the topic.

    Was super lucky enough to find a Moscode 300 yesterday in the thrifts. A little dusty, but seemingly in fine shape. Ideally, I’d like to bring it in for a check-up, but right now I want to use it a little and get a feel for it.

    Initially, I just plugged in my Google chromecast audio and off it went. Sounded great. Super clean, maybe some distortion in certain passages in the left channel, but hard to explain. Might just be warming up an d coming back to life after a period of dormancy.

    However, controlling the volume through the apps is a little strange. The output is super hot at low settings. Not much volume nuance there.

    I really wanted to try it with vinyl, so I plugged in my old ART DJ Pre II anc connected my Magnepan MG-IIs. Two things:

    Sound was a little on the hard side. Not bad, but...

    The volume was pretty high even though the gain trim on the ART pre was at -10db. Same volume issue.

    So, how does a fella control the volume when using separates?

    I have my Marantz 2325. Can I somehow use the phono pre that with the Moscode?

    I guess the question is: how can I explore the Moscode now with what I have. Feel free to peruse my equipment details.

    Thanks in advance for the help!
     
    33na3rd likes this.
  2. dirtymac

    dirtymac Forum Resident

    Location:
    Exile, MN
    Congrats on the find!

    There's a decent chance your Moscode 300 will need to have some tubes replaced and perhaps a little more work done as well. If you can't get the tubes tested locally, I strongly recommend TC Tubes. They'll let you know exactly what's going on with the tubes for not much money at all and whether you should keep them or replace them. If the latter, they have plenty of options and can help you out. tctubes.com vintage vacuum tubes

    In the meantime, I believe your Marantz has a 'Main Out' set of connections. You can use those to hook up your Marantz to the Moscode and prepare to have a far more authoritative, slightly warmer, sound (I have a Marantz 2230 and once owned a Moscode). Volume would be handled via the Marantz.

    Not sure if you should have powered the Moscode up with a variac or not as the Moscode is a hybrid amplifier. Maybe soneone else could weigh in on this.
     
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  3. 33na3rd

    33na3rd Forum Resident

    Location:
    SW Washington, USA
    I've had my Moscode 300 for 30 years now. Many other amps have come and gone in our listening room, but our 300 is a keeper.

    As you've already found out, the 300 has a lot of gain. It also has an input impedance of 247 k ohms, which means that it works extremely well with a Passive Preamp.

    The designer, George Kaye, still repairs and modifies these.

    Kaye Audio: Repairs and Upgrades of Fine Tube Electronics by George Kaye

    George has worked on ours a couple of times, and it is now a dual mono unit with a 176,000 uF supply.
     
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  4. gss

    gss Forum Resident Thread Starter

    Location:
    New Jersey
    Thank you both for the info.

    I did hook it up using the Marantz main out. The volume control on the Marantz did indeed work as expected.

    Sound was good. Still chasing a little phlegmy soemething in the left channel.

    Took the tubes out to dust them tonight,as I was rubbing them with a damp cloth...the writing rubbed off! What was the factory stock?

    Thanks!
     
  5. 33na3rd

    33na3rd Forum Resident

    Location:
    SW Washington, USA
    Sorry, I do not remember!

    A stock 300 takes a pair of 6DJ8/6922 & a pair of 6FQ7/6CG7. The modified 300 takes 4 6FQ7/6CG7's. The modified units were supplied with tubes from RAM. RAM puts their own logos on the tubes, so I don't know their origin.
     
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  6. gss

    gss Forum Resident Thread Starter

    Location:
    New Jersey
    Well, perhaps this unit was never modified as the tubes were not four identical. It was two and two.

    Does this unit require biasing?
     
  7. 33na3rd

    33na3rd Forum Resident

    Location:
    SW Washington, USA
    Sounds like a stock unit.
    The tubes do not need to be biased, they are input/driver tubes. Only output tubes need to biased and the 300 uses mosfets for output duties. The mosfets do have bias controls, but that's not something the average owner needs to mess with.

    If you switch the tubes from their left to right positions, and the "phlegmy" sound follows, then you can bet that it's one of the tubes needing replacement. If you switch the tubes around, try to wait a few minutes before powering them back up. Tubes are pretty hardy, but they don't like be powered up and down in quick succession.
     
    gss likes this.
  8. gss

    gss Forum Resident Thread Starter

    Location:
    New Jersey
    Good idea about switching them around. I imagine the right set powers the right speaker and vice versa.

    So, if I wanted a photo pre that mates well with this amp, what would I be looking for? I imagine it would need a volume control.
     
  9. 33na3rd

    33na3rd Forum Resident

    Location:
    SW Washington, USA
    I don't know what to recommend not knowing your budget or cartridge. For a high output MM something with at least 40-44dB gain, and for a low output MC something with at least 60-64 dB.

    As far as a volume control, you could try the $49 Schiit SYS to see if you like the idea of a Passive Pre.
    Schiit Audio, Headphone amps and DACs made in USA.

    If you decide that you really like the Moscode, I think the Schiit Saga would work really well with it at $349. I plan to get one myself in the near future.
    Schiit Audio, Headphone amps and DACs made in USA.

    I don't know that I would put a lot of money into ancillaries until you've decided that you really like the 300. The Moscodes are very reliable, but unless it's been worked on you've got some 30 year old Electrolytic caps in there that might need to looked at.
     
    gss likes this.
  10. TarnishedEars

    TarnishedEars Forum Resident

    Location:
    Seattle, WA
    How do the mods impact the sound of the amp?
     
  11. 33na3rd

    33na3rd Forum Resident

    Location:
    SW Washington, USA
    Much more bass authority, and extended/cleaner highs. Before the mods, the 300 sounded slightly rolled off at both extremes and just slightly veiled. If you already own a Moscode I think it's a worthwhile expenditure.
     
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  12. gss

    gss Forum Resident Thread Starter

    Location:
    New Jersey
    I see George is still available and doing his mods. I’m not too far from MA, but am a little overwhelmed at his mod offerings. They get expensive quickly. Is it worth it?

    With a couple days through the Marantz, it Sound good, but something is not right. @dirtymac mentioned that the Moscode would make the 2325 more authoritative, and it does not. When I ran the Chromecast through the amp itself, now that was authority. However, I was using my Infinite Slope speakers. I think the problem might be the Maggies. Man, they suck up some juice.

    I’ll try switching the Maggies with the Infinite Slopes and use the Marantz in the preamp section.

    Thanks for the info with the Schmitt products. Not sure I understand the difference between and passive preamp and a (active?) one, but okay...
     
  13. 33na3rd

    33na3rd Forum Resident

    Location:
    SW Washington, USA
    Those are big Maggies!
    The Moscodes were popular with panel speakers owners back in the day, I used to run mine with a pair Acoustat 1+1's to good effect. But a thirty year old stock amp may not be up to the task now. I think a modified 300 with larger power supply caps would be up to the task, but I can't guarantee it.

    As far as the price of the mods, I think it was worth it. But I've got different ears/room/ speakers. You might hate what I like.

    Your Marantz 2325 is an amazing amp. I don't know that a stock 300 would be more authoritative. The power rating between the two units is very close. There should be a sonic difference between the two due to different topologies.

    Both the Schiit's that I linked are passive, they provide no extra gain as an active does. The difference between the two is the quality of their volume controls, and the Saga is buffered which allows one to use it with long cables or a solid state amp with a low input impedance.

    Here's a good tutorial about pros & cons of passives from Tortuga Audio who manufactures really sweet passive preamps. I run one of their units in my system.
    Is a Passive Preamplifier Right For You? | Tortuga Audio
     
    Last edited: Oct 15, 2017
    gss likes this.
  14. gss

    gss Forum Resident Thread Starter

    Location:
    New Jersey
    Wonderful info @33na3rd! Thank you for all of your thoughtful advice.

    Wish my 2215b had a pre out. Would be a match made in heaven.
     
  15. gss

    gss Forum Resident Thread Starter

    Location:
    New Jersey
    Just a quick update. I'd put the Moscode aside for a few months, but I'm going to upgrade my turntable cart, so have pulled it out to experiment a bit with it. I return to my original problem, however...

    The only phono preamp I have right now is an inexpensive ART DJ Pre. Even with the volume down all the way, playback is LOUD! It also seems a hard and brittle.

    Why? Why isn't the preamp totally turning down the output of the Moscode? I don't expect audiophile playback from the ART, but I've had it for ten years, and its always been great using for a quick hook up, or for testing something out.
     
  16. gss

    gss Forum Resident Thread Starter

    Location:
    New Jersey
    Any takers on my last questions? I'd recently read that the Moscode will work best with a passive preamp, which the ART is. Any reason why there is so much signal still coming through?
     
  17. 33na3rd

    33na3rd Forum Resident

    Location:
    SW Washington, USA
    I don't know for certain, but looking at pictures it would appear that at it's lowest setting that the ART DJ's volume control only lowers the signal by -10dB. One of my passive preamp's lowest setting is -64dB, and the other one goes down to -70dB. I don't think the ART's volume control goes down low enough to use it as a preamp before a power amp. I think the ART's volume control is more to fine tune it to your cartridge's output gain.
     
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  18. Panama Hotel

    Panama Hotel Forum Resident

    Location:
    Eastern Seaboard
    could be an impedance matching problem?

    Also, from what 33 has just said, I don't think your preamp is performing the attenuator functions of a passive preamp that's set up to handle line sources. It's more of a phono EQ network/cartridge output trimmer that's designed to be plugged into another preamp (be it active or passive) designed to mediate output between a line stage and a power amp. The ART doesn't attenuate signal enough on its own to be plugged directly into a power amp.
     
    Last edited: Apr 5, 2018
  19. gss

    gss Forum Resident Thread Starter

    Location:
    New Jersey
    That makes a lot of sense, @33na3rd. Then, what kind of passic preamp would best suit the Moscode 300?

    And to make the question even more complicated: what passive preamp - with a phono section - would best suit the Moscode 300?
     
  20. 33na3rd

    33na3rd Forum Resident

    Location:
    SW Washington, USA
    I'm not aware of any modern passive preamps that also have a phono stage built in, that doesn't mean there aren't any though. The "Muse Model One" preamp had a great phono stage, and had the option of being used as a passive, but those were built in the late 80's and early 90's.

    Here's a cheap passive pre on ebay that you could try, just to see if you like the Moscode. You could hook your ART DJ to this, and then run the passive pre to the moscode.
    Nobsound XLR/RCA Balanced Passive Preamp Pre-Amplifier Audio Volume Controller 985953492488 | eBay

    Have you tried using the preamp outputs of your Marantz into the Moscode? Might be a way to give the Moscode a listen before spending money.
     
    Last edited: Apr 5, 2018
  21. 33na3rd

    33na3rd Forum Resident

    Location:
    SW Washington, USA
    I forgot that you did try your Marantz earlier.

    Sorry about that!
     
  22. 33na3rd

    33na3rd Forum Resident

    Location:
    SW Washington, USA
    I seem to be quoting myself a lot today! I did indeed buy myself the Schiit Saga, and it's an amazing piece of equipment!
     
  23. gss

    gss Forum Resident Thread Starter

    Location:
    New Jersey
    Well, @33na3rd! It was still a great suggestion.

    You made me redo the Marantz thing, and it sounds pretty great, but as was posted before, I don't know if it's better than the Marantz, just as good and different. FM is coming in loud and clear.

    I don't think I was to use the two together, but it does sound good. That Schitt preamp is a real contender. Thanks for the suggestions.

    e
     
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  24. gss

    gss Forum Resident Thread Starter

    Location:
    New Jersey
    Also, @33na3rd: you’re using the Saga with the Moscode, right? Then, I imagine you’re just using the Saga to control the volume, correct?

    How does that pre - with the Moscode - compare to other preamps you’ve used with that power amp?

    Also, while the Saga doesn’t have a phono pre, I could always plug a phone pre into the Saga, right?
     
  25. 33na3rd

    33na3rd Forum Resident

    Location:
    SW Washington, USA
    At the moment, I'm actually using Saga with Schiit's own Vidar, another delightful over achiever.

    But to answer your question, here's a list of preamps that I've used with my Moscode since 1987.

    Audio Research SP-12RM, really thin sounding. Sold it.
    Counterpoint SA-2000, not too bad. Sold it.
    Melos SHA Gold, actually very nice! One of my favorites. I still have this one for headphone use.
    Audio Research LS2B, sounded nice after an hours warm up. Sold it.
    PrimaLuna Dialogue 3, nice sounding unit. Sold it.
    Modwright LS-100, pleasant enough. Sold it.
    Muse Model One Preamp, very nice phono stage, active line section a bit veiled, but passive section very transparent. Still using this one for it's phono unit.
    Tortuga Audio LDR3.V2, very nice! Still own this one.
    And lastly, Schiit Saga, sounds as good or better than the others at only $350. I'm using this one everyday.

    Yes, you can easily plug a phono pre into the Saga. It has 5 pairs of RCA inputs. I have my DAC, and two phono units plugged into mine.
     
    Last edited: Apr 6, 2018
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