Doc modding Marantz imperial 7

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savvypaul
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Re: Doc modding Marantz imperial 7

Unread post by savvypaul »

Oft times, when the house lights flicker, here, I wonder if that's just Stu powering his system up, 50 or so miles away...

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karatestu (Wed Aug 26, 2020 6:21 am) • Latteman (Wed Aug 26, 2020 2:46 pm)
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Cracking job :shock: I hope not - one chisel pointed in the wrong direction and whack. A cracked panel after all that work would likely end with a lot of swearing (ffs) and something being launched across the shed.

At first I was going to leave the walls 25 mm thick but decided to be brave and go for 20 mm just to gain a little bit more cabinet volume. Also I was going to leave a 50 mm band all the way around the perimeter of each panel to aid jointing. I revised that and just left the little blocks where I can drill and bolt them.

The thinner I leave the walls the longer it takes as I have to be more careful with the hammer and chisel. Luckily I have a lot of experience with stone and concrete having done a lot of building and landscaping.

Paul - I have to ring the local power station and warn them ahead of switching on :grin: Can power supplies be made that can run on 3 phase I wonder :think:
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Re: Doc modding Marantz imperial 7

Unread post by CN211276 »

karatestu wrote: Wed Aug 26, 2020 6:33 am

Paul - I have to ring the local power station and warn them ahead of switching on :grin: Can power supplies be made that can run on 3 phase I wonder :think:
There was a power cut near me yesterday. Think you are a bit far away and it was the storm. :lol:
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

I have in my cupboard four Avondale soft start modules which might help the power station cope with the inrush current when I flick the switch. Hang on a minute, my amps don't currently have any switches at all :lol: Not even a souce selector or volume control :dance:

Anyway, those soft start modules have never been used since I visited Les in early 2017. Also in my cupboard there are four power amp output protection modules, several Avondale TPR4 regulators, six built ALW super regulators, umpteen PFM mosfet gyrators, a pfm flea regulator, four Avondale power amp boards, four Naim power amp boards, a NAC72 with it's guts ripped out, two hicaps, Avondale 821A preamp boards, several transformers, 32 kendeil caps of 6,800 uf or 10,000 uf.

That just scratches the surface. I think I could make several systems from stuff just laying about in my work room cupboards. I did sell a couple of Avondale power amp boards recently otherwise I would have six of the buggers. I felt a bit sad when I took them to post :cry: Think I have got a hoarding problem.
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savvypaul (Wed Aug 26, 2020 6:51 pm)
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Had a cheeky thought yesterday :think: .

How about trying four 12 inchers in one speaker i.e one behind the other in isobaric loveliness? I could use all the drivers I have and just test it out with one channel. Not ideal but might give me an idea of the benefits (or drawbacks). Doc got up to three in the cubix but who knows, maybe he tried more ?

Of course the required cabinet volume for me would decrease but you have to take account of the volume taken up by the extra drivers. Ridiculous overkill or maybe not :think:
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Re: Doc modding Marantz imperial 7

Unread post by Latteman »

Stop 😂
Focus or u will never finish it😉
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Re: Doc modding Marantz imperial 7

Unread post by Ithilstone »

Latteman wrote: Fri Aug 28, 2020 8:15 am Focus or u will never finish it😉
I do not think that finish is Stu'e ultimate goal ;] - tinkering is!
Nothing to see here...
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Tinkering is fun, trying out new things for yourself is the best way to learn. But I do want something finished at some point before the next decade starts :lol: Then I can start something else.
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Capacitors on the tweeters are still the Russian paper in oil K75-10 but I have wired in some 1 uf instead of the two 3.3uf I had in series (1.65 uf). They are much smaller than the coked can size 3.3 uf which is good. I expect there might be some burn in (hocus pocus) but it sound mighty fine already.

1 uf is much closer to the value I require and it's good enough for farming :grin: . It probably would make feck all difference if I could find a 0.9 uf cap and they don't make em anyway. In fact the tolerance is such that they could actually measure less than 1 uf but I haven't measured them. Can't be bothered with all that bollox.
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

My tweeter fetish is becoming a unhealthy obsession :confusion-helpsos: I'm addicted. Currently got five per channel. Well I say tweeters - two of them are crap full rangers pulled out of knackered portable cd players. They are rear firing and out firing. The best one (Visaton G25ffl) is forward firing, B&W P4 tweeter (one inch metal dome) is up firing and MS902S tweeter (one inch metal dome) is inward firing.

You would think I would be satisfied with the number I have :hand: Well I'm not :roll: I have four Visaton G20sc that I bought from zebbo (thanks) to be used. I was going to replace the two crap full rangers with these and buy four more to replace the B&W and MS jobbies (yucky metal domes).

I never tried a down firing tweeter next to the downfiring magnet out mid bass. Is it worth trying ? Hell yes :dance: What about a hexagonal or octagonal upper enclosure ? :shock: :shock: :shock: Just think about the number of tweeters if one is put on each face - ten if using octagonal :dance: . Will that result in strange phase and comb filtering effects ? Who knows. If it does will it actually make any difference inthe real world rather than just on paper :think:

Some things that people or the theory tell you about certain design choices turn out to be not a problem for me or just plainly inaudible. Well, am I weird or just prioritise things differently to everybody else ? I know when something sounds wrong and adding more tweeters so far has only had positive effects for me.

Only one way to find out. Another 14 visaton tweeters comes to about £700 :shock:
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