Hi
As a result of a new thread about Musical Fidelity Ebay amplifier board
I looked up and found the following. MARANTZ MA-9S2 150W+150W 8ohm stereo amplifier kit WLX | eBay
One pair Power amplifier board base on Marantz MA-9S2 amp 300W +300W L17-35 | eBay
Looking at the diagrams they have completly different resister values to each other and the original Amps circuit diagram.
How much difference can the circuit be from an original ?
Has anyone tried either of these items? with success ?.
As a result of a new thread about Musical Fidelity Ebay amplifier board
I looked up and found the following. MARANTZ MA-9S2 150W+150W 8ohm stereo amplifier kit WLX | eBay
One pair Power amplifier board base on Marantz MA-9S2 amp 300W +300W L17-35 | eBay
Looking at the diagrams they have completly different resister values to each other and the original Amps circuit diagram.
How much difference can the circuit be from an original ?
Has anyone tried either of these items? with success ?.
Similar boards have been around for a long time. They are certainly not clones, as they are not balanced and the circuit is much simplified. Strictly for the adventurous.
The PCB's may be good but that would be the only thing I trust. The parts will likely be low grade or fakes
Hm I am am bit curious by the responses.
Firstly the seller Along 12345 etc has a feedback of 20370 n ish? Probably more than the sum of most of this community. Does this indicate a poor quality seller ? Whilst I have purchased from them previously the failure of the LJM item was down to the design IMO. I did note that ONE Naim clone was reported to have gone faulty withing 24 hours.
Have you any evidence that these are fake parts or is this just a generalized opinion.
More to the point which parts do you believe to be fake? Their are hardly any expensive parts in it. The 3 pin common transistors are mega cheap anyway. Probably one fifth the cost of the resistors I will be using? I nwill probably heatsink them anyway.
Any audiphile would be more concerned about the use of the likes of LT 072 chips in the design. Even I can remember that they were considered brash approx 45 years ago,
or am I mistaken. Also noted that someone does an upgrade ? of the Kit and I think it just an improved op amp.
Having researched a LOT more and found someone seemed happy with the smaller version and they thought it was a genuine clone ?
I have now proceeded to purchase these boards and will post a report on its received and finished performance one day which may be helpfull to someone?.
Also will be adding soft start pre power supply and loudspeaker protection circuit but not a balanced input. More akin to the original but the internal will probably be better than the original. The parts were not around at the time of the original.
I would appreciate any genuine technical opinions on the 350 watt design .
The number of low grade silicon diodes worries me, replacement by schottkys or cree. ?
thanks Dave
Firstly the seller Along 12345 etc has a feedback of 20370 n ish? Probably more than the sum of most of this community. Does this indicate a poor quality seller ? Whilst I have purchased from them previously the failure of the LJM item was down to the design IMO. I did note that ONE Naim clone was reported to have gone faulty withing 24 hours.
Have you any evidence that these are fake parts or is this just a generalized opinion.
More to the point which parts do you believe to be fake? Their are hardly any expensive parts in it. The 3 pin common transistors are mega cheap anyway. Probably one fifth the cost of the resistors I will be using? I nwill probably heatsink them anyway.
Any audiphile would be more concerned about the use of the likes of LT 072 chips in the design. Even I can remember that they were considered brash approx 45 years ago,
or am I mistaken. Also noted that someone does an upgrade ? of the Kit and I think it just an improved op amp.
Having researched a LOT more and found someone seemed happy with the smaller version and they thought it was a genuine clone ?
I have now proceeded to purchase these boards and will post a report on its received and finished performance one day which may be helpfull to someone?.
Also will be adding soft start pre power supply and loudspeaker protection circuit but not a balanced input. More akin to the original but the internal will probably be better than the original. The parts were not around at the time of the original.
I would appreciate any genuine technical opinions on the 350 watt design .
The number of low grade silicon diodes worries me, replacement by schottkys or cree. ?
thanks Dave
In which design? The one by Marantz, or the "genuine clone"? Did you check what opamps were used by Marantz in the servo? 😎
marantz ma 9s2 clone boards on ebay
Short answer yes. Yes Ive I checked for hours but it looks as they designed discrete circuit in the original.. Only reason I gave it thought was the person who suggested a mod. I Re looked at his "mod" and it seems its a clone he was modding. So this is one thing I may try at very little cost.
I also once had a hybrid amp and this I used to test sonics of op amps easily. (1980s- 2000)
The huge benefit of my hours of study (I am now mentally very slow) The Original amp uses lots of schottkies everywhere. Personally I discovered how much they improved sonics in 1982 from Ben Duncans advice. Along with Vishay foil resistors. Never looked back .
I have heard this original amp demonstrated in trade shows years ago and it always impressed.
I also just discovered whilst rengineering the box in preperation that my surge protection circuit has a small variable trimmer. As this unit always seemed to power through at switch on, then click again seconds later, I assume this is a time delay adjustment.
Short answer yes. Yes Ive I checked for hours but it looks as they designed discrete circuit in the original.. Only reason I gave it thought was the person who suggested a mod. I Re looked at his "mod" and it seems its a clone he was modding. So this is one thing I may try at very little cost.
I also once had a hybrid amp and this I used to test sonics of op amps easily. (1980s- 2000)
The huge benefit of my hours of study (I am now mentally very slow) The Original amp uses lots of schottkies everywhere. Personally I discovered how much they improved sonics in 1982 from Ben Duncans advice. Along with Vishay foil resistors. Never looked back .
I have heard this original amp demonstrated in trade shows years ago and it always impressed.
I also just discovered whilst rengineering the box in preperation that my surge protection circuit has a small variable trimmer. As this unit always seemed to power through at switch on, then click again seconds later, I assume this is a time delay adjustment.
Found original type of op amp?
Hi I have now found what could be the original type as NJM2114.
This will go on my list of proposed mods. Easy plug in. Also have received a circuit diagram which shows capacitors on power rails as 50v?
I note the schottky diodes as 11EQS10 on the original which were the same type as I had originally used as upgrades for a number of amplifiers. I note nowadays the numbering convention seems quite different. and I am struggling to find a code explanation or conversion table.
Going away for a week . Wish it was Cascais .
Dave
Hi I have now found what could be the original type as NJM2114.
This will go on my list of proposed mods. Easy plug in. Also have received a circuit diagram which shows capacitors on power rails as 50v?
I note the schottky diodes as 11EQS10 on the original which were the same type as I had originally used as upgrades for a number of amplifiers. I note nowadays the numbering convention seems quite different. and I am struggling to find a code explanation or conversion table.
Going away for a week . Wish it was Cascais .
Dave
Sadly the boards have arrived ?
Well, the 300 watt 8 output drivers in the picture description were genuine ... The photo was fake? ie only received 4 drivers per board. Description has been altered but not picture?
THE QUALITY IS PRETTY POOR AND I AM DUBIOUS IT COULD WITHSTAND THE SELLERS NEW CORRECT 150 WATT INTO 8 OHM.
Copper track is thin.
It is even thinner single sided board that original fake ljms.l12s.
Soldering is dubious and I will post piccies soon.
Seller has offered to accept returns at my shipping cost after 6 weeks waiting.
I may decide to proceed with this project mainly due to curiosity (sonics)😕
Meanwhile I may look for a decect pair of assembled hi quality sounding boards of at least 120w into 8 ohm.,
Suggestions. Please
Well, the 300 watt 8 output drivers in the picture description were genuine ... The photo was fake? ie only received 4 drivers per board. Description has been altered but not picture?
THE QUALITY IS PRETTY POOR AND I AM DUBIOUS IT COULD WITHSTAND THE SELLERS NEW CORRECT 150 WATT INTO 8 OHM.
Copper track is thin.
It is even thinner single sided board that original fake ljms.l12s.
Soldering is dubious and I will post piccies soon.
Seller has offered to accept returns at my shipping cost after 6 weeks waiting.
I may decide to proceed with this project mainly due to curiosity (sonics)😕
Meanwhile I may look for a decect pair of assembled hi quality sounding boards of at least 120w into 8 ohm.,
Suggestions. Please
Dont bother with it
Short reason why, I eventually decided to try it and spent hours increasing the metal for heating compared with the cool runnings LJM L20 9.2 which I sold on.
Carefully checking everything, I connected just the one board. It was on for only a few seconds with current limiting light bulb glowing at almost full light.
I checked the temp of initial stage heatsinks and they were warmer than I liked.
Test probes for current and DC offset showed .5V DC accross speaker terminal. Not happy at this point. Switched on again for 1 second for second DC reading which was lower at .025mv . Slightly happier , switched on again and then it basically went up in smoke. Blew 2 x 10R and 2 x 33r and ???
Its going back with the other untested one.
Will advise how I get on with seller who does seem an ok person at this point in time. After all he only sells stuff people provide for him. ???
Short reason why, I eventually decided to try it and spent hours increasing the metal for heating compared with the cool runnings LJM L20 9.2 which I sold on.
Carefully checking everything, I connected just the one board. It was on for only a few seconds with current limiting light bulb glowing at almost full light.
I checked the temp of initial stage heatsinks and they were warmer than I liked.
Test probes for current and DC offset showed .5V DC accross speaker terminal. Not happy at this point. Switched on again for 1 second for second DC reading which was lower at .025mv . Slightly happier , switched on again and then it basically went up in smoke. Blew 2 x 10R and 2 x 33r and ???
Its going back with the other untested one.
Will advise how I get on with seller who does seem an ok person at this point in time. After all he only sells stuff people provide for him. ???
MA-9S2 Balanced version clone
The ones I have found on Ali Express are 99% similar to the schematic diagram from Marantz's service manual, they look like one side of a balanced design. Is there anything stopping me from buying four to put together as a balanced stereo version?
The ones I have found on Ali Express are 99% similar to the schematic diagram from Marantz's service manual, they look like one side of a balanced design. Is there anything stopping me from buying four to put together as a balanced stereo version?
Attachments
Getting a bit tired of this argument. How can the two be the same, when there is a ratio of perhaps 10:1 in parts count alone. And it isn't just the more outputs or the balanced topology. What do you think that little forest of HDAMs at the input is doing? Do you see the nested feedback?
Perhaps the Ali circuit works well but its semblance to the amp upon which it is supposed to be based is only superficial. Similar to the Accuphase disaster but perhaps even worse. With the Accuphase i put in some effort to simulate the theoretical performance of the Ali circuit and it was orders of magnitude below the original because of really poor design. Not curious enough here.
I have the kits as well....Looking at the traces on the PCB's, I'm not sure it will withstand the currents with loads lower than 8 ohm.
Also looking at the service doc of the original design, the circuit has been simplified to the absolute minimum and now is only a shadow of the original.
I did not build the amplifier so if anyone has interest I still have 8 kits laying in my shop.
Also looking at the service doc of the original design, the circuit has been simplified to the absolute minimum and now is only a shadow of the original.
I did not build the amplifier so if anyone has interest I still have 8 kits laying in my shop.
Do you have 8 Circuit boards and components? Can you post a pic of a kit, please?
Or send a message with a pic?
Or send a message with a pic?
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HDAM - some preamp stage? Nested Feedback? Please enlighten me. I am Not an experienced builder, that is why I am asking about this design in this forum...
Kits
Do you have the kits with 2 pairs or with three pairs of output power transistors?
Do you have the kits with 2 pairs or with three pairs of output power transistors?