Doc modding Marantz imperial 7

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu » Fri Dec 08, 2017 1:34 pm

Geoff.R.G wrote:
Fri Dec 08, 2017 12:50 pm
karatestu wrote:
Fri Dec 08, 2017 12:44 pm
Once it is all finished I may box it up neatly (wooden cases) but I am not sure I ever want it to be finished..........................
You could spend just as long experimenting with different case materials and configurations!
Oh yeah, hadn't thought of that one :grin:

Other things to try;

copper, silver plated copper, silver, silver alloy wiring or two plastic cups with string between ?
position of moon when building something
mains cables & plugs
remove the pcb's from everything and use point to point :grin:
series v shunt regulators or super duper regulators
bulk foil resistors v standard metal film
film caps v electro v tantalum (wet & solid) v PIO v polypropylelne
volume pots v stepped attenuators
active v passive pre,
EI v toroid v R core v C core
standard bridge rectifier v schottky v fast recovery
plain capacitor smoothing or CLC or CRC .... or CLCRC ?
hard wiring everything in sight
the whole earthing thing
soft start or not
speaker protection or not
complimentary or quasi complimentary AB or class A or class D , bipolar, mosfet
resistor or diode or transistor biasing
to protect amp output or not - zobel, inductor
to filter the input stage or not
powered by farmyard muck ?
current mirrors ?

I could go on..............
Naim, Linn & Harbeth fanboy

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu » Fri Dec 08, 2017 1:41 pm

Dr Bunsen Honeydew wrote:
Fri Dec 08, 2017 1:26 pm
Take it out and see how much the music improves :geek:
I will wait until I get my LS6 first :grin:

Your NVA design is obviously ok without it. Not sure that is applicable to all designs ? There could be a lot of magic smoke and burnt semi conductor smell coming from my room :think:
Naim, Linn & Harbeth fanboy

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Dr Bunsen Honeydew
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Re: Doc modding Marantz imperial 7

Unread post by Dr Bunsen Honeydew » Fri Dec 08, 2017 1:59 pm

It will be fine using LS6, put that in and see the difference first.

I don't know when you get them as Christmas feck up deliveries are happening already. Two orders of parts from Farnell are lost at the moment, chaos happens every year which is why I normally go away on holiday. Nadia in Russia, so me deciding to do Black Friday means I have to put up with it again (and you lot as well). Next year if as I hope I go back to December holiday will mean no Black Friday next year.

Alfi
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Re: Doc modding Marantz imperial 7

Unread post by Alfi » Fri Dec 08, 2017 2:31 pm

When Nadia's away in Russia you choose to have fun by stressing yourself out with a Black Friday jamboree - indeed, don't do it again you wicked boy!

Just wait until she gets back, then you'll have even more fun explaining the mess you got yourself into! :lol:

:epopc:

Alfi
Heavily modified LP12, Sole VIII sub-chassis, "In Sole" advanced polymer suspension, Ai bearing, PU7, DV20X2, Norton Airpower clone. Technics SL110A, AT 1005, Denon DL301A. NVA Phono 2 MC (2 power supplies), NVA P50 SA, NVA A40 Mk1 power amps, custom birch ply Allison 6/NVA Cube 1 clones, NVA TIS mk2 , SSC, LS6.

antonio66

Re: Doc modding Marantz imperial 7

Unread post by antonio66 » Fri Dec 08, 2017 3:46 pm

karatestu wrote:
Fri Dec 08, 2017 12:35 pm
antonio66 wrote:
Fri Dec 08, 2017 12:11 pm
Excuse my ignorance Stu, does this mean you are using six mono block boards?
Yes, each driver in my speakers has it's own independent amplifier board, power supply, transformer, speaker cables, interconnect back to the preamp. Hang on, that is not strictly true as the two 12" bass drivers in isobaric configuration in each speaker share an amplifier. Hope I have made myself clear. Right speaker bass drivers (2 of) = one monobloc, right mid driver = one monobloc, right tweeter = one monobloc, left speaker bass drivers(2 of) = one monobloc, left mid driver = one monobloc, left tweeter = one monobloc. Six in total.

Some might say that it is overkill and I am not sure what I think of it yet. As I had the parts in stock (as it were) it was easy to try.

With my old transmission line 2 way speakers I moved the crossover to directly behind the power amps instead of having them in the speaker. I could not believe the increase in clarity. Still not sure why it happened. I am going to try doing the same with the tweeter's high pass filter (3.3uf cap) and padding resistor and see what happens. It may or may not be better, don't know until I try. One thing that I don't have to worry about this time is having a bass inductor too near a transformer - hum is the result.
Thanks for that Stu. Placing the x-over behind the power amps is the Naim way I believe. and I read or was told it was the signal from pre was at a lower level. :?:

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu » Fri Dec 08, 2017 3:58 pm

antonio66 wrote:
Fri Dec 08, 2017 3:46 pm
karatestu wrote:
Fri Dec 08, 2017 12:35 pm
antonio66 wrote:
Fri Dec 08, 2017 12:11 pm
Excuse my ignorance Stu, does this mean you are using six mono block boards?
Yes, each driver in my speakers has it's own independent amplifier board, power supply, transformer, speaker cables, interconnect back to the preamp. Hang on, that is not strictly true as the two 12" bass drivers in isobaric configuration in each speaker share an amplifier. Hope I have made myself clear. Right speaker bass drivers (2 of) = one monobloc, right mid driver = one monobloc, right tweeter = one monobloc, left speaker bass drivers(2 of) = one monobloc, left mid driver = one monobloc, left tweeter = one monobloc. Six in total.

Some might say that it is overkill and I am not sure what I think of it yet. As I had the parts in stock (as it were) it was easy to try.

With my old transmission line 2 way speakers I moved the crossover to directly behind the power amps instead of having them in the speaker. I could not believe the increase in clarity. Still not sure why it happened. I am going to try doing the same with the tweeter's high pass filter (3.3uf cap) and padding resistor and see what happens. It may or may not be better, don't know until I try. One thing that I don't have to worry about this time is having a bass inductor too near a transformer - hum is the result.
Thanks for that Stu. Placing the x-over behind the power amps is the Naim way I believe. and I read or was told it was the signal from pre was at a lower level. :?:
No, I don't think Naim have ever put the speaker crossovers right on the end of the power amp. They have done external crossovers but they were attached to the back of the speakers, not on the rack next to the power amps (at the other end of the speaker cable).

With my old B&W speakers I had my crossover actually inside the amp - before the binding posts. Six inches of wire from the amplifier board output but the speaker return wire had to be longer to get to the dirty end of the power supply zero volts . Had to be careful with hum pick up on the inductors though.

Lower level signal from the pre ? If anything the level is quite high or it used to be. Olive series pre amps had a gain of twelve, twelve times that on an NVA passive and three times more than my Avondale active pre amplifier.

The Naim preamps are bandwidth limited - that is probably what you meant :grin:
Naim, Linn & Harbeth fanboy

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu » Fri Dec 08, 2017 9:42 pm

Triamping is really really good with these speakers. Not sure they extra expense would have been worth it if i had not have had all the bits already. There is the extra real estate they will take up and then more LS6 needed and another TIS cable.

I will just enjoy the small improvement it has brought but then the improvement over biamping may be bigger if i had bigger transformers for the two extra amps and TIS and LS6 instead of the crappy naca5 i have had to use.

More experimenting and listening to do........its a hard life
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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu » Mon Dec 11, 2017 3:07 pm

Currently listening with only four monoblocs and the little cabs. I am missing the big bass cube's :cry: but I am currently treating one pair of monoblocs to another psu and regulated front end :dance: Will do the others two at a time and still be able to listen to some tunes.

Now I don't have the big isobaric bass cubes in I am startingly aware of the contribution they make. Not that the little cuboid 3's are doing a bad job at all.
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Dr Bunsen Honeydew
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Re: Doc modding Marantz imperial 7

Unread post by Dr Bunsen Honeydew » Mon Dec 11, 2017 3:30 pm

You have one of the very very few proper, as the inventor envisaged, isobaric systems in the world. Everyone else has the Linn balls up version or copies of it.

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu » Mon Dec 11, 2017 4:43 pm

Well that is all thanks to you doc, otherwise I would have fecked it up and done it as I read elsewhere. :guiness;
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