Yes ,I'm talking retail products. They appear and go unnoticed for a small money. They are built exactly like Naim just in plain black shoe box .Typically british design from 80's and 90's .Fast paced and little warmer sounding than Naim due to Mosfet output stage but the same design philosophy. Also similar parts choice.
They're expensive and hard to come by Tantalums, those.
You can see the appropriate positions on the Naim clone boards by matching up the parts. If you check out the schematic at the foot of Neil McBride's first page or reproduced several times in this thread. You'll see where they are used - in the signal path at the input, inverting (feedback) input, current source and also in the output protection circuit which is omitted in clones and original amp. mods.
Watch who you tell about tantalums in audio application. Some get very twitchy and relate tales of explosions with overvoltage and bad sound etc, etc. Some criticisms are quite justified but much is mindlessly repeated folklore
I doubt i will use them all...i need to check my supplies and see what I actually have..it has been a while since i looked at them, in a box in a closet somewhere....i may have a few to spare if someone here would lile to try them...i was just lucky to get them and there is no use in saving them if they are really something others might enjoy....
Up and running
Made up an amp using two of these boards, works great. Two power supplies with speaker protection, all off ebay. Mine came with Sanken output transistors, dont know if they are fake or not but there is bags of power and the DC offset is only 11 to 15 mv and they balance up nice bias wise. Time will tell!
microx
Made up an amp using two of these boards, works great. Two power supplies with speaker protection, all off ebay. Mine came with Sanken output transistors, dont know if they are fake or not but there is bags of power and the DC offset is only 11 to 15 mv and they balance up nice bias wise. Time will tell!
microx
Bias
How many mV are you measuring across the R29/30 0.22R resistors when you set your bias? i have the Sanken big fat transistors too.
Did you have any problems with the board being misprinted and have need to change the transistor mounting?
Not that it will make much of a difference but I happen to have every resistor value for this amp in PRP low TCR 50ppm resistors...i think I am gong to build it with all PRP and drop some Caddocks in place of the output resistors (have a few of these too). Also gonna swap the lytic input cap with a Tantalum.
For the 68uf caps on the board...any harm in increasing these to 100uf? Again, I have some Nichicon KZ or cerafine caps i could replace these with.
I have an extra Chipamp.com PSU kit from a dual mono I never used...any thoughts if this would be sufficient for this amp? Has a total of 20,000uF. I could add another bank of caps if needed.
Jeff
How many mV are you measuring across the R29/30 0.22R resistors when you set your bias? i have the Sanken big fat transistors too.
Did you have any problems with the board being misprinted and have need to change the transistor mounting?
Not that it will make much of a difference but I happen to have every resistor value for this amp in PRP low TCR 50ppm resistors...i think I am gong to build it with all PRP and drop some Caddocks in place of the output resistors (have a few of these too). Also gonna swap the lytic input cap with a Tantalum.
For the 68uf caps on the board...any harm in increasing these to 100uf? Again, I have some Nichicon KZ or cerafine caps i could replace these with.
I have an extra Chipamp.com PSU kit from a dual mono I never used...any thoughts if this would be sufficient for this amp? Has a total of 20,000uF. I could add another bank of caps if needed.
Jeff
I think most of us don't really want to know either but the evidence is that they can't be genuine because of the new condition yet poor marking on long obsolete parts.
Just enjoy your work and later, try some substitutes like genuine 2SC 5200 as previously supplied or any modern, high Ft audio power transistor. You can expect to pay more than the kit is worth for suitable genuine SANKEN M200 parts but you may be surprised that the TO247 transistors they offer are the same chips in a smaller pack, for a lot less money. At the power most peoplre really require, these are fine IMO.
Would I be right in thinking you haven't seen the schematic that specifies the original values?
You can't under-rate caps. Use the specified voltage on the schematic or higher because Tantalums are known hazardous if abused with high voltage. However, the input cap normally floats with little voltage across it unless a DC fault occurs in either source or amplifier.
I just replaced all the blue 10uF/35v tants in my naim pre and 3 power amps.
the recomended ones are Kemet T356:
Buy Tantalum Solid T356 radial tantalum capacitor,35V 10uF Kemet T356G106K035AT online from RS for next day delivery.
hi,
I have buy on ebay a nap140 pcb clone type without emitter resistor. (nap series standard)
My idea is to replace some transistor with others.
Output Transistors
*mj21194 (vceo=250v Icm=16A Pd=250W hFE=40 fT=4MHz) ---> mj15003 (vceo=140v Icm=20A Pd=250W hFE=60 fT=2MHz)
----
Driver Trasnsitors
*mje243/253 (vceo=100v Icm=4A Pd=15W hFE=80 fT=40MHz) ---> mje15032/33 (vceo=250v Icm=8A Pd=50W hFE=90 fT=30MHz)
---
Pre Driver Tansistors
*ztx753/653 (vceo=100v Icm=2A Pd=1W hFE=200 fT=140MHz) ----> mje340/350 (vceo=300v Icm=.5A Pd=20W hFE=100 fT=???MHz)
?mpsa 92/42 (vceo=300v Icm=.5A Pd=.625W hFE=80 fT=50MHz)
---
Others
BC239C (vceo=25v Icm=.1A Pd=.35W hFE=300 fT=140MHz) , ZTX108 (vceo=30v Icm=.1A Pd=.3W hFE=170 fT=115MHz)
*BC550 (vceo=45v Icm=.1A Pd=.5W hFE=300 fT=100MHz) ---> MPSA06 (vceo=80v Icm=.5A Pd=.625W hFE=100 fT=100MHz)
* = shown on schematics from ebay seller
(I would use the least number of different type transistors)
with supply of +/- 40V max ideal power on load is 8 ohms = 100Wrms / 4 ohms = 200Wrms
(real power with vcesat and emitter resistor...) 8 ohms = 75Wrms / 4 ohms = 145 Wrms
in the worst condition (2 ohms load) each transistor has to dissipate 200W maximum (20A)
Output and driver seem good replacement to me
the others a little less
I have buy on ebay a nap140 pcb clone type without emitter resistor. (nap series standard)
My idea is to replace some transistor with others.
Output Transistors
*mj21194 (vceo=250v Icm=16A Pd=250W hFE=40 fT=4MHz) ---> mj15003 (vceo=140v Icm=20A Pd=250W hFE=60 fT=2MHz)
----
Driver Trasnsitors
*mje243/253 (vceo=100v Icm=4A Pd=15W hFE=80 fT=40MHz) ---> mje15032/33 (vceo=250v Icm=8A Pd=50W hFE=90 fT=30MHz)
---
Pre Driver Tansistors
*ztx753/653 (vceo=100v Icm=2A Pd=1W hFE=200 fT=140MHz) ----> mje340/350 (vceo=300v Icm=.5A Pd=20W hFE=100 fT=???MHz)
?mpsa 92/42 (vceo=300v Icm=.5A Pd=.625W hFE=80 fT=50MHz)
---
Others
BC239C (vceo=25v Icm=.1A Pd=.35W hFE=300 fT=140MHz) , ZTX108 (vceo=30v Icm=.1A Pd=.3W hFE=170 fT=115MHz)
*BC550 (vceo=45v Icm=.1A Pd=.5W hFE=300 fT=100MHz) ---> MPSA06 (vceo=80v Icm=.5A Pd=.625W hFE=100 fT=100MHz)
* = shown on schematics from ebay seller
(I would use the least number of different type transistors)
with supply of +/- 40V max ideal power on load is 8 ohms = 100Wrms / 4 ohms = 200Wrms
(real power with vcesat and emitter resistor...) 8 ohms = 75Wrms / 4 ohms = 145 Wrms
in the worst condition (2 ohms load) each transistor has to dissipate 200W maximum (20A)
Output and driver seem good replacement to me
the others a little less
re bias
I measure 4.4,mv across R29 etc, this does not work out by ohms law to 38ma measured in the + line as that is the total for the amp not just in the o/p transistors . Also my rails are 44-0-44 as I had some 30-0-30ac trannys so that will make a small difference. I would stick to the cap values but better quality is never bad. I will change only the input cap for non electrolytics.
microx
I measure 4.4,mv across R29 etc, this does not work out by ohms law to 38ma measured in the + line as that is the total for the amp not just in the o/p transistors . Also my rails are 44-0-44 as I had some 30-0-30ac trannys so that will make a small difference. I would stick to the cap values but better quality is never bad. I will change only the input cap for non electrolytics.
microx
Hi, It seems you like the metal output transistors and MJ21194 are about the fastest common types but nowhere as fast as Naim parts or the Sankens or Toshibas offered in the kits. This is a very important element of Naim sound and you really need faster parts than those you opted to substitute.
The "predriver" or actually VAS transistors are not capable of the dissipation required with 40V rails even. Any small TO92 or the E-line ZTX types are on the limit with 1 amp max. current rating so a small-signal type like the MPSA 42/92 will not deliver full drive without smoke. If you can't use the Zetex types, you'll need TO126 video drivers like KSC 3503/KSA1381 from Fairchild. As discussed in many threads, they must have very low Cob, very high Ft and Vceo needs to be at least 100V.
It's fun to make substitutions but it is better not to cause problems or spoil a good thing. Sure, some people want to try the NCC 200 style amp. which is a different sound using some common parts but as modules, you could expect some part matching you perhaps didn't anticipate.
BTW, quite enthusiastic power predictions there - if Naim ever got near them, they would have been amazed!
thanks for the advice schematics from seller is attached.Hi, It seems you like the metal output transistors and MJ21194 are about the fastest common types but nowhere as fast as Naim parts or the Sankens or Toshibas offered in the kits. This is a very important element of Naim sound and you really need faster parts than those you opted to substitute.
The "predriver" or actually VAS transistors are not capable of the dissipation required with 40V rails even. Any small TO92 or the E-line ZTX types are on the limit with 1 amp max. current rating so a small-signal type like the MPSA 42/92 will not deliver full drive without smoke. If you can't use the Zetex types, you'll need TO126 video drivers like KSC 3503/KSA1381 from Fairchild. As discussed in many threads, they must have very low Cob, very high Ft and Vceo needs to be at least 100V.
It's fun to make substitutions but it is better not to cause problems or spoil a good thing. Sure, some people want to try the NCC 200 style amp. which is a different sound using some common parts but as modules, you could expect some part matching you perhaps didn't anticipate.
BTW, quite enthusiastic power predictions there - if Naim ever got near them, they would have been amazed!
like this...
http://www.diyaudio.com/forums/solid-state/112453-nap-140-clone-amp-kit-ebay-2.html#post1360062
but with bc550 instead of bc239c, ztx108
PCB is also drilled for output bjt plastic case.
for NCC style add an emitter resistor should be enough simple.
Perhaps a bit more complex to add decoupling for power supplies.
Attachments
Hi VibroKing$
If you go to the Avondale site, you'ii see the NCC 200 differences are more. For instance, a coil is used in the output for stability. When you change an amplifier and its compensation in particular, stability is affected. That version does need it.
If you understand audio design and how to stabilise a power amplifier both electrically and thermally, fine but very few people do and many just simulate until it works acceptably with generic models. In real life, the audio may not be so good or thermal runaway destroys it at some time in the future.
The design you posted is a generalised original Naim drawing covering all models at the time and includes the VI limiters TR7 & 8 which clones do not. I understand that no amplifiers were never exactly to this published design.
There are many choices for substitute parts and I have changed quite a few types for people who wanted to try something else. BC549B,C or 550B,C are generally used at the input and best matched for beta and Vbe as well as possible. This is easy with a suitable DMM. In most cases of substitution, remember that increased beta, Hfe or gain leads to instability. Sometimes it is critical. Check for overheating of parts and the output stage when playing roullette with parts.
The other semis can be BC546, 2N5401 etc. for MPSA06 and TR5, the Vbe multiplier. The drivers need something - anything better than the clone's TIP41/42! There are several good drivers but I found no improvements over originals MJE243/53.(some high-gain types caused oscillation) The problems are VAS and output types and whatever the rationale, slugs like MJ15003 power transistors just don't work properly in the clones. IMO, if you listen with genuine Sanken or Toshiba high Ft types, the difference to the sound in an otherwise capable clone will be obvious and more exciting, if I can put it that way.
If you read back to Ruwe's posts, you'll find a lot of experience and good advice there.
If you go to the Avondale site, you'ii see the NCC 200 differences are more. For instance, a coil is used in the output for stability. When you change an amplifier and its compensation in particular, stability is affected. That version does need it.
If you understand audio design and how to stabilise a power amplifier both electrically and thermally, fine but very few people do and many just simulate until it works acceptably with generic models. In real life, the audio may not be so good or thermal runaway destroys it at some time in the future.
The design you posted is a generalised original Naim drawing covering all models at the time and includes the VI limiters TR7 & 8 which clones do not. I understand that no amplifiers were never exactly to this published design.
There are many choices for substitute parts and I have changed quite a few types for people who wanted to try something else. BC549B,C or 550B,C are generally used at the input and best matched for beta and Vbe as well as possible. This is easy with a suitable DMM. In most cases of substitution, remember that increased beta, Hfe or gain leads to instability. Sometimes it is critical. Check for overheating of parts and the output stage when playing roullette with parts.
The other semis can be BC546, 2N5401 etc. for MPSA06 and TR5, the Vbe multiplier. The drivers need something - anything better than the clone's TIP41/42! There are several good drivers but I found no improvements over originals MJE243/53.(some high-gain types caused oscillation) The problems are VAS and output types and whatever the rationale, slugs like MJ15003 power transistors just don't work properly in the clones. IMO, if you listen with genuine Sanken or Toshiba high Ft types, the difference to the sound in an otherwise capable clone will be obvious and more exciting, if I can put it that way.
If you read back to Ruwe's posts, you'll find a lot of experience and good advice there.
Ian
This is commercial amp from Exposure ,model Super VIII 2x55W from 87'. The amp was manufactured trough the 90's I guess and brand has quite a following in Britain. It is said to sound as well or a little better than comparable NAIM pieces and it's built in similar way. Naim has much nicer casing and sexy glowing logo
I mention it here on Naim clone thread so you guys don't pass it when you stumble on it somewhere. Since it's a niche brand and doesn't have quite following like Naim the prices are reasonable. Company still supplies parts and service , just like Naim.
This is commercial amp from Exposure ,model Super VIII 2x55W from 87'. The amp was manufactured trough the 90's I guess and brand has quite a following in Britain. It is said to sound as well or a little better than comparable NAIM pieces and it's built in similar way. Naim has much nicer casing and sexy glowing logo
I mention it here on Naim clone thread so you guys don't pass it when you stumble on it somewhere. Since it's a niche brand and doesn't have quite following like Naim the prices are reasonable. Company still supplies parts and service , just like Naim.