OK, I think you have the general idea for building clamps but you won't need 10 x 27mm 'aluplate' bar. 5-6 mm thick will be OK. This piece, clamped together with the 3mm chassis bottom plate, should prevent "bowing" when you screw down the clamp bolts. You will need to tap 4mm threads into either bar or fit nuts/bolts from the underside of the chassis for this.
I am uncertain whether Naim used more short screws to secure the bar to the bottom plate. I suspect they would have, to ensure rigidity. However, this requires some workshop skills and thread tapping tools. Maybe its OK for you but not everyone is happy to do this.
The first problem I referred to was actually with the clamp bars. they probably need to be at least 8mm square for rigidity, otherwise they will buckle or crumple at the 4mm hole when you tension the bolt.
BTW, I may have misunderstood you but don't mix thermal grease with silicone rubber thermal pads. The grease is only used between hard materials like transistors and mica sheet, metal surfaces etc.
I am uncertain whether Naim used more short screws to secure the bar to the bottom plate. I suspect they would have, to ensure rigidity. However, this requires some workshop skills and thread tapping tools. Maybe its OK for you but not everyone is happy to do this.
The first problem I referred to was actually with the clamp bars. they probably need to be at least 8mm square for rigidity, otherwise they will buckle or crumple at the 4mm hole when you tension the bolt.
BTW, I may have misunderstood you but don't mix thermal grease with silicone rubber thermal pads. The grease is only used between hard materials like transistors and mica sheet, metal surfaces etc.
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Why not bolt each transistor to the 10mm plate through the mounting holes in the transistors as intended? Naim uses their clamping system to reduce the number of screws and the manufacturing cost as far as I see. You don’t need the top clamps at all.
So you would have 8 bolts, each going through the chassis, the plate, the thermal washers and the transistors.
So you would have 8 bolts, each going through the chassis, the plate, the thermal washers and the transistors.
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Unfortunately, if you go looking for mica washers to to use with the grease and MT200 transistors, there are now very few sources, globally. I bought some from Taiwan about 6 years ago but that's all I found that was good quality. I think most people will be stuck with diminishing amounts of silicone rubber pads so buy those now if you have hoarded these obsolete Sanken types and plan to use them some day.
Follow up on "heat sink" and washers
Hi
Just to be sure.
Between the 10mm (7 mm are ok!) aluplate and the chassis bottom plate, I can use either thermal pads or grease?
The same between the Sanken transistor and the top clamp?
If I use this top clamp, which apparently only serves as fastener of the transistors, and do not have thermal function (correct)?
It is not necessary to use grease here?
It is also not necessary that the clamp have physical contact to the 10mm aluplate?
Then you mention MT200 transistors! Where do they come from? Is those an alternative to the Sancen 2SC2922?
My goal is to build the clone is "NAIMish" as possible, and assume the Sancen transistors are to be preferred! Is that correct?
Ps. I am Danish so there is a little langauge barrier
Hi
Just to be sure.
Between the 10mm (7 mm are ok!) aluplate and the chassis bottom plate, I can use either thermal pads or grease?
The same between the Sanken transistor and the top clamp?
If I use this top clamp, which apparently only serves as fastener of the transistors, and do not have thermal function (correct)?
It is not necessary to use grease here?
It is also not necessary that the clamp have physical contact to the 10mm aluplate?
Then you mention MT200 transistors! Where do they come from? Is those an alternative to the Sancen 2SC2922?
My goal is to build the clone is "NAIMish" as possible, and assume the Sancen transistors are to be preferred! Is that correct?
Ps. I am Danish so there is a little langauge barrier
MT-200 is the package style of the transistor - the standardised size and shape.
Sanken 2SC2922 are good. I got some from Mouser but they are obsolete now and cost me around $10 each. There are others on ebay but these are usually either fake or reclaimed. The 'preloved' ones can be ok, but they are obviously second hand.
With thermal rubber washers no grease is needed. With mica washers or no washers then use grease. Between the aluplate and chassis you would normally use just grease. Rubber is not usually as good a heat conductor as mica+grease or grease alone. Only use grease alone where electrical insulation is not needed.
Yes. No significant thermal function.
Suitable cheap and simple heatsink for Naim clone can be made from what we here in Serbia call aluminium "flah" (from the German word "flach" meaning "flat"). I usually buy 2 meters long piece 80mm wide and 8mm thick and then cut it to suitable lengths. Good side of this mounting method is that nut and bolt can be used instead of threading the heatsink. 250mm piece is about half a kilo in weight. It is absolutely enough for even loud home listening.
Different mounting methods can be seen at the attached photo.
Different mounting methods can be seen at the attached photo.
Attachments
Recent Naim products don't have the same signature sound as older products. Naim sound was crisp and clear but recent products are dark and dull. Here in Serbia almost nobody likes recent Naim products. Whoever buys it keep it for short period and tries to sell it. It's much better to buy Chinese clone boards of old Naim products like NAC42, NAP140 or NAP200. The company changed their whole philosophy of sound.
That's very interesting. Dark, muddled bass, somewhat incoherent mids and treble as if certain sounds were trying to upstage the rest. To my ears it didn't output engaging music.
Has Naim lost the recipe? Is it deliberate?
Exactly. It seems that Julian tuned the products by ear until he got the sound right. After him it's mostly techno approach. There is craftsmenship, user friendlinies, gadgets, etc. but not the sound. Now it's industry, before it was enthusiasm. My friend has Nait XS. He is surprised how bad the sound is. There is no point in using 380VA transformer, huge capacity in PSU if the sound is not right. There is remote control but not decent binding posts. It seems that now quality of sound is of secondary importance. Inside 0f the amp there is many SMD components for which you need magnifying glass to see.
Hi
As mentioned the in earlier post schematic and BOM suplied by ALGAR_EMI (here) is a great help for my NAP 200 Clone build.
But I am very unsure regarding VR1 (adjust bias current). According to my PCB it should be 102 Ohm. As I read ALGAR_EMI's schematic he uses 1KOhm.
I am considdering Piher PT6KV-201A2020 at 200Ohm (link to mouser)
Please let me hear your thoughts.
Best regards,
Thomas
Ps. has anyone considdered autobias?
As mentioned the in earlier post schematic and BOM suplied by ALGAR_EMI (here) is a great help for my NAP 200 Clone build.
But I am very unsure regarding VR1 (adjust bias current). According to my PCB it should be 102 Ohm. As I read ALGAR_EMI's schematic he uses 1KOhm.
I am considdering Piher PT6KV-201A2020 at 200Ohm (link to mouser)
Please let me hear your thoughts.
Best regards,
Thomas
Ps. has anyone considdered autobias?
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