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  • Legit 70’s Firepower: The Marantz HD-770s

    2015 - 04.17

    Marantz HD-770 top-end drivers and L-pad array

    As posted about previously, I had encouraged my drummer to get the Marantz HD-440 speakers, since I have very much enjoyed owning a pair of their big brothers, the HD-770s. The “High Definition Series” speakers have walnut veneer cabinets and were built sometime in the 70s. In the Marantz 25th anniversary catalog (dated 1978) they are for sale as the medium tier product underneath the “Design Series”. For a mid-tier product though, these are extremely nice. And as an aside, that 25th anniversary catalog is a feast for the eyes if you’re into this kind of thing… here is a link to it at HiFiEngine.  You’ll need an account to view it but it is easy to create one… it’s worth the effort to check out that super sweet catalog.

    It’s clear they put some thought into the design of these units. The most attention-grabbing feature for me was the 1″ dome driver, which is labeled as a tweeter. I’d call that a misnomer though, since the overall frequency response is given as 33-22kHz +/- 3dB @ 125W of “program material”. Crossover Frequencies are 750, 2300, 5000Hz so that 1-inch “tweeter” is handling 2.3k-5kHz.  I have always been a big fan of dome midranges for their lifelike sound, especially on anything of an earthy, organic variety like acoustic guitar, piano, or exposed vocals. Dome mids do a great job of putting those things “in the room” with you. Interestingly the HD-770 has a stated efficiency of 90dB which is very high for a speaker depending on a 12″ woofer to handle the low end, since the woofer is almost always the limiting factor on efficiency and high efficiency woofers are relatively rare in larger sizes.

    marantz HD series lineup... HD-770s are 2nd from the left

    From the factory HD series units were supplied with a “Vari-Q damping acoustical plug” which you could insert to tune the port if you wanted to change the bass response. The trade-off was more definition in the 50-75Hz range, at the expense of anything below. My speakers were bought secondhand off Craigslist and did not come with this accessory. I see some on ebay with the mention that the original foam is long gone… a running theme. Like the HD-440s, the woofer foam on the HD-770s also crumbles away with time. In my case the previous owner swapped out the original woofer for a replacement driver instead of re-foaming it. This can easily be spotted by the convex woofer dustcap; the original was concave. Given the apparent attention that the Marantz engineers paid to driver selection, I wish he had re-foamed the original. If an opportunity ever presents itself, I would like to acquire the original driver and restore these to their intended stock configuration, although the replacement is doing just fine for the time being.  After searching a while on eBay that seems like a pipe dream though, since a pair in need of re-foaming recently sold for $227.50.  That says something though–one, the original drivers were good and two, the market of people out there enthusiastic about keeping theirs in prime condition remains hot.  My set is also missing the metal ring which mounts around the largest woofer, which is too bad because it does look cool.

    The HD-770s have a three-section resistor (aka L-pad) control panel on the front which allows you to individually adjust the volume of the super tweeter, dome midrange and cone mid-bass drivers. When I built the green speakers for my brother I definitely learned that L-pads are a tremendous asset to any speaker design. They really allow you to tweak the “voicing” of the sound to whatever suits your liking. It can’t be over-emphasized just how much of an impact this has on the sound. Put it this way: never again would I built another set of speakers without L-pads.

    These units have a really funky grille, which has brown fabric which comes outward at the center. I can’t decide if they look cooler with out without the grille on, so I keep the one closer to the door equipped with the grille to protect it from passing foot traffic and the one near the window exposed so I can enjoy the neat appearance of the drivers. Hopefully these units will last me a long time. They are certainly ready to pump out some serious dB’s but still have a soft touch for nuance at the same time. That’s a real nice combination.

    no grille... ... or yes grille?

    New Infrared Shooting, March 2015

    2015 - 04.12

    Happy to report that I’ve finally gotten out and done some more shooting on my Infrared-converted Canon XTi.  I don’t use this camera near enough so when we planned a camping trip, I knew this was my chance to get some great captures out in nature, where the IR SLR really shines.  Here’s a gallery of my favorites.  Some are color-shifted to appear blue instead of red, a few I left red and one is black’n’white.  Enjoy:

     

    A VHS Dubber’s Dream, and a Stereo Pre-Amp Sleeper: The Yamaha AVC-50

    2015 - 04.11

    Having acquired the KM-209 Kenwood power amp, I knew I needed a pre-amp to power it. Since it would be in the living room hooked up to the cable box, I knew it also needed to have a remote control. I’ve never been super into surround sound, so I figured I’d look for something stereo-only. Naturally I wanted to get something older, hoping for a better build quality than modern products… and I didn’t want to pay much. After spending a decent amount of time searching for untis with those qualities, it became clear the best deal would be a receiver or integrated amp which had pre-amp outputs, since a strict pre-amp is overtly aimed at the hi-fi crowd who will spend money for discretes. Remotes began to appear in the early 80s so I looked there, and ended up zeroing in on the Yamaha Natural Sound series.

    In short I was looking for a sleeper: something with great specifications that got lost in the mountains of A/V choices out there, forgotten by the advances of time and the piling-on of unneeded features. And I think I found it. The AVC-50. It’s got inputs from sun-up to sun-down, it’s stereo-only, has a remote, and a killer set of numbers behind it.

    Yamaha AVC-50

    If used as a pre-amp, the AVC-50 has some astoundingly good specs. Specifically it has a 103dB noise isolation between channels and a Total Harmonic Distortion of 0.005% which is… stupifyingly low. That’s not a typo, there’s really two zeros before the 5 in that. That’s very formidible for any pre-amp, even at a snobbish level of audiophile haughtiness. Yet here it is in this obscure seemingly mid-level Yamaha. Sort of strange.

    As to the sound quality, so far I’m very pleased. Between this and the Kenwood power amp that’s doing the grunt work, I can discern a notable improvement in the quality over the outgoing Aiwa. The AVC-50 needed some de-oxit spray to get rid of the crackling when the main volume control was turned, but that was it. I also like the switched power outlets on the back which feed my tape deck and the power amp. Hearing the relays inside all three of them go CLICK when you turn it on is neato.  One thing I do wish it had is tone controls.  There is no bass/treble control and I do miss that, although the speakers it’s driving are already balanced just about right anyway.  It does have a bunch of functions I’m not in need of though: this thing would be amazing for copying VHS tapes back in the day.  There’s a huge amount of video inputs, you can select any audio source while recording video, and it even has a video enhancing circuit with sharpness control.  If you were copying tapes, this thing would have been stellar.

    You could probably find one of these for about $50 if you were patient and persistent. Me, I paid a little extra at $75 to get this one off eBay which came with the remote (many didn’t) and manuals. Although the pictures didn’t really show me, I had a hunch that if it came with the manuals it was probably well-cared for. Indeed it proved to be, and not only did it come with the manual, it also had the receipt for extended warranty (long since expired) and, most interestingly of all, the promotional literature. Retro advertisements can be pretty entertaining to look at sometimes, so I’ve scanned in several pages of this for any who may be interested. The pictures date it. And there’s a lot of effort put into explaining the capabilities of the unit. It’s a long sell. Something that I haven’t seen for a modern product of equivalent standing. Below are all the interesting pages of the large brochure… Check it out:

    Subtle Improvements to the Home Studio

    2015 - 04.10

    I’ve got a cheap set of MXL 990 and 991 microphones that I’ve been using as room mics and overhead drum mics for all my sessions and they’ve been doing well considering how cheap they are.  A while back I saw on the web that there’s a community of people who are into modifying these mics to punch above their weight.  The simplest mod is a capacitor replacement; three ceramic caps which are part of the audio signal path are swapped out for film caps.  I know my way around a soldering iron so this was a slam dunk for $7 a mic.  A few before and after pics are below with audio results on the way later….

    IMG_7197 BLOGIFIED

    Shown above is the PCB with the three new caps sitting beside it, and there they are installed in the image below, noted by the green arrows.  Not the world’s most beautiful solder joints but they’ll get the job done.

    IMG_7200 BLOGIFIED

    Residual Greatness: The Kenwood KM-209 Power Amp

    2015 - 04.09

    So I spent a bunch of time on Craigslist not long ago helping a friend pick out components for his first “real” stereo and when I started doing this I knew that certainly I would come across something for myself that would prove too good of a deal to resist. Predictably that expectation came true in the form of a Kenwood KM-209 power amp from the 80s that I got for just $50. It’s nothing special to look at but it’s got some significant power: rated at 150W RMS into 8Ω with 0.015% THD–from 5Hz to 200kHz (according to HiFiEngine). That’s more wattage than any sane or reasonable person would ever need. And yet here we are.

    Kenwood KM-209

    For a very long time now I’ve had an old Aiwa receiver that’s been the heart of my living room stereo setup. I bought that receiver at Best Buy in the 90s, back in the era when Aiwa minisystems were the bomb and everyone had to have one of those. I admit, the trademark green source buttons with the active one lit in red both looked cool and was quite functional from across the room as well. But an Aiwa is an Aiwa, even if this was their attempt to break out of the minisystem market and be seen as something more legit in the hi-fi world. The receiver is still working, although some of the EQ and DSP buttons seem to have a mind of their own these days.

    Probably what won me over on this unit was the excellent experience I’ve had listening to the Kenwood KA-8300. And also the performance of the Marantz PM750DC Integrated Amp… The KA-8300 said ‘hey Kenwood was actually pretty serious, way back when’, and the PM750DC said ‘products built shortly after the peak of a manufacturer’s greatness can be a great deal’. 80’s Marantz gear worked out pretty good. Let’s give this Kenwood a go. For $50, I couldn’t pass her up.

    The sound is neutral, as far as I can hear.  It certainly goes plenty loud.  As for the unit itself there’s a glowing red display in the center labeled “Power Indicator” which has LED indicators which light up on either side of it for left and right channels. There’s also a toggle switch which lets you switch between 1x and 0.1x for the meters, which is a key feature for power meters.  Nothing exotic or amazing here, but some very solid numbers for a cheap price!

     

    A Relic of their Apogee: The Kenwood KA-8300

    2015 - 04.06

    The Kenwood KA-8300

    Probably the coolest piece of audio gear I have is this 1975 Kenwood integrated amplifer, the KA-8300. Kenwood’s not typically a brand associated with hi-fi now, but back in the day they built some real beasts. And beastly the ‘8300 is, weighing in at 35 pounds. It looks and feels like Kenwood had something to prove with this unit. Power is 80W RMS per channel into 8Ω with 0.1% THD rated from 20Hz to 40kHz. That power rating, being from ’75, is surely conservative. It can also handle 4Ω or 16Ω speakers too, which is somewhat unusual for this time period. The most obvious distinguishing features of the amp are those sweet-looking meters on the front. Watching these is a pleasurable novelty and has actually taught me a bit about the amount of wattage required for typical listening levels…not much! There is a toggle button which swaps the meter range between 3W and 100W. This switch is almost always left on 3W if you want to see the needles bump at all. That surprised me, just how little power is actually used for most listening.

    The KA-8300 has pre-amp outputs which can be used simultaneously with the speaker outputs if you want. When I bought a power amp off Craigslist those came in handy for testing it out. But maybe the most useful feature on this unit are the turnover controls, which are 3-position levers that affect the frequency of the “bass” and “treble” tone knobs. Having the option to move those frequencies around actually makes quite a difference in the usefulness of the bass/treble knobs since it allows the user to tailor the controls to match the speakers being driven. Similarly, the “Loudness” EQ adjustment (which boosts highs/lows for better listening at quiet volumes) has two settings. When listening on the Marantz HD-770s which have a 12″ woofer, setting #2 definitely sounds better whereas on their little brothers, the Marantz HD-440s, switching to setting #1 gave a better bass sound. Loudness is a nifty little circuit which I do prefer to use when the volume is at a low/normal level.

    Although this model was not Kenwood’s top-of-the-line unit, I believe it was only a rung or two below that. For the extreme collector, there is a rare copper-colored faceplace and a slightly higher wattage unit that was otherwise virtually identical in feature-set to this one. Those amps command a much higher asking price but I felt this one hit the sweet spot of equalization features and power for the dollar.

    The KA-8300 is totally built like a tank. The proof is in the pudding too, since when I bought this unit on eBay from a vintage-electronics restoration shop, the faceplate was in perfect condition. As you can imagine, I was quite disappointed to see that it arrived with a bend on the upper right corner despite the fact that the unit was very well pacakged by being wrapped up with bubble wrap and styrofoam around that. 1/4″ aluminum plate doesn’t bend easily and after attempting with a large pliers and channel locks, I gave up and decided to call it character. What I learned in the process is that it would take a lot of force to bend that faceplate, meaning the unit sustained a pretty good impact and has kept right on ticking, functionally. All the knobs and switches work good and I hope this one should be a centerpiece of my audio collection for the rest of my life. Here’s to many late nights of musical enjoyment…

    IMG_5317 v3

    Hot Jams from Recently

    2015 - 03.29

    So it looks like I have the ability to embed audio files, which is sweet!  I should post more jams on here.

    Here is a recent one (1/25/15) that’s a pleasurable odyssey based on the Steve Miller Band classic “Fly Like an Eagle”.  The recording from this session had several issues, so this mastering leans heavily on the room mics.  Don’t judge my audio quality here.  But the playing is pretty awesome I think.  I’ll call out my highlights to make it a more interesting listen:

    start-2:45 guitar driven intro opens it up

    3:50 some cool delay time changes while playing, culminating at 4:02 (these knob turns produce a high pitch sound that’s like lasers or record scratches)

    4:45 nice buildup into the guitar solo handoff

    5:37 interesting scale/tonal guitar soloing

    6:28+ bitrate distortion on the horn, most obvious at

    7:20+ trumpet/bass/guitar all sync up on unison line, sweet descending bass chords at 8:13 while the guitar is pitched shifted up

    10:07 intense bitrate dips on the horn, leading into huge guitar delay section

    11:22 dynamics come way down for a nice chill section.  Singing bowl taps come in at 11:33+

    12:54+ slow guitar swells of new chords build into the next section, neat bass vibes

    15:00 snare drum comes back, ending the slow buildup, 1/4 chord switch begins

    16:21+ pretty happy with this soloing

    17:11 phrase that jumps up/down, then 17:31 descending phrase that jumps down for final note: both these are “outside my box” figures that were gratifying to hear.  New vocab.

    18:34 meaty guitar punctuation that’s cool

    19:28 first identifiable “into the future” riff from Fly Like An Eagle… I can trace tiny moments of the rhythm for a couple minutes prior but they are quite camouflaged

    19:39 incredibly triumphant “Time keeps on slippin / into the future” this moment,oh yeah.  And the switch to the 4 chord halfway through seals the deal.

    21:06 very mysterious, reverbed-out “into the future”

    21:34 new feel on the drums opens up another chapter of the jam

    21:52 cool descending guitar riffs with the Steve Miller “doot-doos” from the intro the to tune, using the harmonizer although faint

    22:49 “Time keeps on slippin” with a totally unreasonable amount of delay

    24:23 “most people think that / great god will come from the sky / take away everything / and make everybody feel high” Bob Marley quote, played with ascending notes instead of the way he actually sings it.  Hard to hear this but I really enjoy it when listening

    24:42+ cool repeating line on the guitar and varied staccato trumpet trickery; I really dig the complexity and the bounce through this section

    25:48 drums switch over to hip-hop style rimshot feel.  I’m a sucker for this type of groove.  Open 5ths on the trumpet harmonizer

    29:29 self-proclaimed “scale-wankery” on the guitar closes out the final section.

    All in all, it’s a pretty killer jam with a lot of creative quoting and unusual choices in terms of the soloing phrases.   And just because, here’s this awesome album cover with the “Fly Like An Eagle” theme to it, from an earlier session…

    100% Juice

    Electric Trumpet DIY pedalboard, phase 2

    2015 - 03.14

    An update on the pedalboard I’ve been building:

    aluminum ground plane beneath main board

    As you can see in the image above, I’ve installed an aluminum sheet beneath the main board to act as a ground plane, hopefully to dampen any noise and RF interference from the power supply platform mounted below it.  I’ve also rounded off the corners using my router and belt sander, then applied three coats of 2-in-1 stain+polyurethane, with two coats of a wipe-on poly after that.  I liked the 2-in-1 but I’m not so sure that the wipe-on poly really added much.  I didn’t really shoot for a mirror finish though.

    The second image, below, shows the pedal setup for our session on 3-7-15.  There are three new pedals here which I’m renting from  PedalGenie.com, which is a brilliant service that loans out pedals for people who might want to experiment with different effects setups like myself.

    Pedal setup for 3-7-15 session

    The signal chain is:

    Trumpet >

    Eventide Pitchfactor >

    Boss OC-2 Octave >

    Morley Power Wah >

    Fulltone Cylde Deluxe Wah (loaner) >

    Caroline Icarus Clean Boost (loaner) >

    Malekko Bit sample rate reducer >

    A-B splitter forms two paths >

    A: Damage Control Glass Nexus > Line 6 DL4 Delay Modeler > Maestro Phaser > Damage Control Liquid Blues drive > Line 6 MM4 Modulation Modeler > Moog Bass MuRF >

    B: TC Electronic Flashback delay (loaner, on its own signal path for evaluation) >

    stereo summing pedal >

    DI Box

    (Also seen on the floor are an Ernie Ball expression pedal to control the Pitchfactor, and a generic Korg tap tempo to control the MuRF)

    Tycho Monitors, phase two

    2015 - 03.08

    So I’ve been slowly progressing on the small bookshelf speakers that I’ve been building.  Here are a few progress pictures 1. after the front/back panels were routed and glued on and 2. after staining.

    Tycho Mons assembled

    Tycho Mons stained

    Pacifc Coast Extension: Progress Pics Pt.4

    2015 - 02.18

    Time for an update on the Pacific Coast Extension model railroad progress! When last we left off, I had just completed the upper deck benchwork and subroadbed (i.e. flat plywood) over the staging. As you can see in the photos, I’ve now completed the entire upper deck benchwork and subroadbed, which, like many things in this hobby, is a simple sentence to say but a huge amount of work to actually do.

    I’ve also completed the inclined subroadbed which leads from the lower deck to the upper, although all the track is not yet in place there. A small section remains where three tracks of singled ended staging branch off. I added this area since I do enjoy running very long trains–long enough that some of them need to be broken up to fit in the double ended staging below. The wiring is installed for all new track mentioned in here as well. I did miss my self-imposed deadline of completing all mainline trackwork by the end of 2014 although since I only missed it by a couple weeks, I’m going to call that a win. Such deadlines are created to motivate oneself, and in that regard it was a success.

    the mountain loop (furthest "right" in these images)

    An autoreverser has been installed on the newly-completed mountain loop (shown above), although I’ve been struggling to get it to work correctly with the snap-coil switch motors which will allow a train to automatically run endless loops on the upper deck. Right now I’m thinking something just isn’t wired correctly and I need to spend the time to figure that out.

    The incline between decks never exceeded 4.5% as measured with my Micro Mark precision level, an invaluable tool. However it does appear quite steep visually and I know certain trains are definitely going to require helpers or multiple trips to make it up the grade between levels. That’s alright though, I’m okay with that. Real life worked the same way. Now if only MTH would hurry up and make some Boxcab motors.  Shown below is the large curve which will eventually be built into the Mine Creek trestle, and the incline between decks.  The plexiglass is there because that ledge is open to the living room, probably like 20 feet below!  This photo is looking just to the right of the one above.

    Mine Creek and deck connection

    To continue looking to the left of the photo above, here is another view, showing how the laypout wraps around the desk with a window behind it:

    IMG_7131 v2

    Speaking of the trains themselves, there are a few great new additions to the railroad. Foremost of these would be a Milwaukee Road creek series observation car, something available only in brass although fortunately it has been produced several times by different makers in the last several decades. I believe mine comes from the 1980s although I’m not sure. It has already been sent off for a custom paint job to match the Walthers cars, and I intended to further customize it by building an interior and adding lighting.

    Another beaut I’m delighted to have around is an MTH Little Joe in the orange and black freight scheme. Although my railroad is set in Washington state, there is a large amount of scenic overlap between Milwaukee’s Coast Division where the Bipolars ruled, and their Rocky Mountain division where the Joes ruled electric operations. That’s as far as I intend to ‘bend the rules’ at least at this point. Besides, any self-resepecting Milwaukee electrics modeler has got to have a Joe or three around; they’re debatably the most iconic of all Milwaukee Electrics, lasting from the 50s right up to the end.  You can see E73 in the picture below, which shows the staging area:

    IMG_7151 v2

    A few interesting things I’ve learned: Micro Engineering flextrack is great, especially if you use Peco track fixing pins along the edges of the ties, as opposed to large Atlas spikes on the center of the ties. This hides the spikes quite well and makes the track look more realistic. However it does hide the spikes so well you may accidentally do some damage trying to reposition the track later, by overlooking that hidden extra spike you put on the far side of the rail which is nearly impossible to see. ME flextrack also has a very annoying way of shortening the far end when bent even slightly–always check BOTH ends of the track before you cut any rail. And I do mean always.

    I’ve also ordered the supplies to commence with rock building on a large scale, which is a stage of construction I’ve LONG been itching to reach. I will have more details on that stage later this year.