Looking for some assistance in confirming the identity of this piece I just acquired. The seller listed it as a Marantz 7 clone. Apart from the 6 tube, 3 line 3 phono design I have no way to confirm this for sure. I researched different 7 style schematics and am trying to pin down if its a known design.
Dual bank 350v 220uf Elna Cerafine Japan caps
Elna Cerafine red elctro caps plus some unique kind of copper foil cap in translucent plastic.
Main board is all Wima caps and RN60. Whats interesting is there are resistors of different style and color than the normal RN light brown I'm used to seeing but almost all read RN60.
4 pieces of Philips ECG 5751 and 2 Jolida branded 12AX7. The tube board is mounted vertically towards the front.
ALPS Japan original black beauty large body controls for volume and balance.
Separate toroid power supply enclosure feeding via umbilical to main unit with MUR full bridge feeding the main B+ and separate regulated supply for heaters.
All wiring is very nicely done in what looks to be a teflon wrap over silver (plated?) wire. Closer inspection gives the impression the wire is wrapped like some Cardas where the teflon is wound around another inner conductor to separate them.
I've been very much enjoying the sound and was thinking of using it as a working platform to follow what others have been doing with respect to 7C restorations and mods. Arizona caps maybe a bit more adventure with Teflon foil in some areas.
Any insight into this one is greatly appreciated. The only other reference I have found to it is from an old Audio Kharma post from 2009 looking for details as well.
Dual bank 350v 220uf Elna Cerafine Japan caps
Elna Cerafine red elctro caps plus some unique kind of copper foil cap in translucent plastic.
Main board is all Wima caps and RN60. Whats interesting is there are resistors of different style and color than the normal RN light brown I'm used to seeing but almost all read RN60.
4 pieces of Philips ECG 5751 and 2 Jolida branded 12AX7. The tube board is mounted vertically towards the front.
ALPS Japan original black beauty large body controls for volume and balance.
Separate toroid power supply enclosure feeding via umbilical to main unit with MUR full bridge feeding the main B+ and separate regulated supply for heaters.
All wiring is very nicely done in what looks to be a teflon wrap over silver (plated?) wire. Closer inspection gives the impression the wire is wrapped like some Cardas where the teflon is wound around another inner conductor to separate them.
I've been very much enjoying the sound and was thinking of using it as a working platform to follow what others have been doing with respect to 7C restorations and mods. Arizona caps maybe a bit more adventure with Teflon foil in some areas.
Any insight into this one is greatly appreciated. The only other reference I have found to it is from an old Audio Kharma post from 2009 looking for details as well.
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Do not, under any circumstances, start pulling parts off that board to try to "upgrade" this preamp. That is a single sided board with no solder mask and no through hole plating, so the traces are not going to tolerate much in the way of rework.
You have 6 12AX7s. Two are likely doing phono stage duty, then you have four remaining for the linestage.
When you take a 7C and you design out the tone controls, you are left with something fundamentally different. Even with the tone controls, three 12AX7s would suffice for just a 7C linestage with tone controls. Whatever you have here is something different (which is probably not a bad thing).
You have 6 12AX7s. Two are likely doing phono stage duty, then you have four remaining for the linestage.
When you take a 7C and you design out the tone controls, you are left with something fundamentally different. Even with the tone controls, three 12AX7s would suffice for just a 7C linestage with tone controls. Whatever you have here is something different (which is probably not a bad thing).
Marantz 7 phono has 3 tubes - one is a cathode follower.
Likewise line stage design has 3 tubes - one is a cathode follower.
Note that C stands for cabinet and there were plenty of 7s sold without. 😀
The 7T is the later solid state version.
I expect as stated above the PCB is fragile.
I would enjoy it for what it is, perhaps get some nice Mullard or Telefunken 12AX7A as an upgrade and move it along when you want to do something more ambitious.
Likewise line stage design has 3 tubes - one is a cathode follower.
Note that C stands for cabinet and there were plenty of 7s sold without. 😀
The 7T is the later solid state version.
I expect as stated above the PCB is fragile.
I would enjoy it for what it is, perhaps get some nice Mullard or Telefunken 12AX7A as an upgrade and move it along when you want to do something more ambitious.
Nissei polystyrene. Among my favourite low voltage riia caps.
Marantz 7 IMHO has a very nice phono stage and quite a mediocre line stage. If it was mine the line stage and the Wima caps would be the first to leave the building 🙂
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You provide TONS of useless irrelevant data 🙄 and hide the most important one: the SCHEMATIC.
Please post the one you draw looking at YOUR unit side by side with ORIGINAL schematics to compare them and check whether they match or not.
By the way, I very much doubt the original Marantz 7 used those part BRANDS. 🙄
Not that it matters anyway.
What makes you think that he actually has a schematic for this unit?
And I largely disagree on the other points, they are a useful frame of reference for guys like me who are recommending largely to leave it alone..
And I largely disagree on the other points, they are a useful frame of reference for guys like me who are recommending largely to leave it alone..
Exactly. I have no schematic and limited ability to see all circuit traces to decipher the circuit.
I got the unit for what I felt was a good price, considering those Elna dual caps list for $400+ new and the tubes are 50-60 a piece.
In looking for info before buying I found none so I took a flyer just to get back into having a tube pre. Vaccum State SVP was a previous reference.
Thought I might mod it but based on suggestions I will hold off. Do not have a MM cart or step up so my ability to evaluate this is line stage alone.
My long term plan is to pick up Allen Wrights cookbook and build one of his designs again or use the info to custom make something. I also have some 4P1L tubes on the way for a Moglia or K&K design.
Lots of criticism around here and elsewhere of the Marantz line stage design. I figure start with a variation on a simple 12AX7 design and work my way up through to the latest and greatest. Yet people like Jeff Day and that fellow from SPEC corp seem fond of them. It was those articles that sparked my interest in this unit.
I got the unit for what I felt was a good price, considering those Elna dual caps list for $400+ new and the tubes are 50-60 a piece.
In looking for info before buying I found none so I took a flyer just to get back into having a tube pre. Vaccum State SVP was a previous reference.
Thought I might mod it but based on suggestions I will hold off. Do not have a MM cart or step up so my ability to evaluate this is line stage alone.
My long term plan is to pick up Allen Wrights cookbook and build one of his designs again or use the info to custom make something. I also have some 4P1L tubes on the way for a Moglia or K&K design.
Lots of criticism around here and elsewhere of the Marantz line stage design. I figure start with a variation on a simple 12AX7 design and work my way up through to the latest and greatest. Yet people like Jeff Day and that fellow from SPEC corp seem fond of them. It was those articles that sparked my interest in this unit.
If you need a preamp with tone controls, loudness, etc., then the 12AX7 makes a lot of sense. If you need a preamp that can drive a solid state amplifier, a subwoofer plate amp, or long cables, then the 12AX7 starts to look like an abysmal decision.
This is based on math alone.
Once you build a 4P1L preamp, you will very likely be selling the Sound Explorer.
Do you have photos of the power supply/power transformer?
This is based on math alone.
Once you build a 4P1L preamp, you will very likely be selling the Sound Explorer.
Do you have photos of the power supply/power transformer?