Hello,
I want to build a nac 42 preamp clone and search for a circuit with mods,
can somebody help me to find it?
Pls with a description of the right capacitors, which are the best for the circuit.
A other question I search for the transistors ZTX384/214 and it's not possible to find it, which transistors can I use also to replace the ZTX?
Thanks in advance
Regards
I want to build a nac 42 preamp clone and search for a circuit with mods,
can somebody help me to find it?
Pls with a description of the right capacitors, which are the best for the circuit.
A other question I search for the transistors ZTX384/214 and it's not possible to find it, which transistors can I use also to replace the ZTX?
Thanks in advance
Regards
Sure thats easy.
Start your search here.
Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.
Start your search here.
Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.
ZTX384/214
BC550/560 might be a suitable replacement. Correct or better parameters and correct pin outs
BC550/560 might be a suitable replacement. Correct or better parameters and correct pin outs
Thanks!
I will take this both.
But I see there are existing BC560/550 and BC560C/BC550C, can I also take this both?
Regards
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I found that the 3 versions of the BC550/560 (ABC) has a different value
A: min 125 max 260
B: min 240 max 500
C: min 450 max 900
Which one is the best in my case for the NAC42 ?
These high voltage drivers are better suited for use in the power amplifier VAS, rather than low level circuits. That's not to say they won't work at all but the types already suggested will be better in the NAC preamp design.
If you search in the right places, you'll see that "C" grade parts are specified; http://www.acoustica.org.uk/ then navigate to More Naim stuff/The Naim DIY preamp mods bible.
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Hi Ian,
I can find only the BC550/560 but not index "C".
Is the BC550C and BC560C the right choice and the best choice?
At the specified supply voltage of 24V, BC549C/559C (if available) would probably work fine too. You don't show us where you live so it's pointless trying to suggest where you should be looking to buy components. However, as obsolete, through-hole transistors go, you should have no trouble finding BC550C/560C at professional parts distributors like Mouser, Digikey, Farnell element 14, RS components and many other authorized independent distributors - world wide.
Don't rely on Chinese Ebay stores because you don't really know what generic part or fake is really inside the unbranded stuff you buy. For example, your 2SD667/B647 won't be genuine anyway - how would you know what they really were? Here's my current order for genuine Fairchild /On Semi parts as an illustration of what to buy - other brands use different suffixes to describe leads and packing variations:
Don't rely on Chinese Ebay stores because you don't really know what generic part or fake is really inside the unbranded stuff you buy. For example, your 2SD667/B647 won't be genuine anyway - how would you know what they really were? Here's my current order for genuine Fairchild /On Semi parts as an illustration of what to buy - other brands use different suffixes to describe leads and packing variations:
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Hi Ian,
Thanks for your reply.
I live in Germany, I will order the parts from RS or reichelt.
Regards
Hello,
a question about the transformer which I should use for the preamp.
I will use a power board with lm317 to create the 24VDC with two 10000 capacitors.
The transformer which I want to buy has 2x24V with 15VA, do. you think it is enough power
Or should I use a transformer with 30VA?
Regards
a question about the transformer which I should use for the preamp.
I will use a power board with lm317 to create the 24VDC with two 10000 capacitors.
The transformer which I want to buy has 2x24V with 15VA, do. you think it is enough power
Or should I use a transformer with 30VA?
Regards
A NAC 42 preamplifier has only a tiny power requirement of maybe 50 mA for the gain and buffer stages of both channels so you don't need much more current than this, even with additional boards, as fitted in the original. A 100 mA supply would be plenty, allowing for a signal relay and maybe a LED indicator as well. This means only a 5VA transformer or even less is necessary and 2,200 uF smoothing caps are plenty at that sort of current - 4,700 uF will be plenty of overkill too.
The main issue with transformers and preamps is a need for shielding to avoid the introduction of hum and AC line noise. So any transformer type, plus the mains and rectifier wiring for a preamp needs to be well shielded and kept well away from sensitive signal circuits, which is why Naim simply used the amplifier power supply as a raw DC source and the preamp was thus well isolated from AC noise.
Much of this is affected by your design layout but are you considering a full DIY project or the little on-board powered, all-in-one kit seen at Ebay stores?
The main issue with transformers and preamps is a need for shielding to avoid the introduction of hum and AC line noise. So any transformer type, plus the mains and rectifier wiring for a preamp needs to be well shielded and kept well away from sensitive signal circuits, which is why Naim simply used the amplifier power supply as a raw DC source and the preamp was thus well isolated from AC noise.
Much of this is affected by your design layout but are you considering a full DIY project or the little on-board powered, all-in-one kit seen at Ebay stores?
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Most Naim preamplifiers take power from a single +24V DC regulated supply in the power amplifier (older models are simply tapped off the amplifiers own +ve power rail) so they don't need a transformer. In the real Naim product lines, there is an option of adding a HICAP, FLATCAP or SNAPS separate power supply instead but these are not cheap or simple ways of adding a small DC supply.
As you seem to be talking about an Ebay clone kit, why not look at what the kit suppliers and builders choose? In a finished product build, I think it is a 22V, 20VA R core type transformer but any low noise transformer type will work fine, as long as it is well separated from the sensitive preamp circuits. I would use a standard 12+12V, 7 or 10VA sealed toroid to make up a regulated 24VDC supply. The transformer will fit directly to a PCB, even a stripboard one, which ensures short leads and a compact, relatively safe assembly if the mounting and mains wiring is secure and sensibly spaced.
Caution - do not rely on stripboard PCB conductor spacing for mains wiring. Cut closely spaced tracks away so that there is plenty of insulation between mains and any other conductor. If you are uncertain or inexperienced with mains wiring, don't take risks - use the safety of a 24VAC plugpack, wallwart etc mains adaptor instead. I even use an old 30VDC HP printer power supply for example. If the supply is followed by a good regulator, there are seldom any concerns for what is used for the input, either AC followed by a rectifier, raw or regulated DC. So long as there is always at least 4VDC headroom above the required 24V DC output, a linear regulator circuits or 3 pin IC regulators such as LM317 or 7824 will remain functional.
As you seem to be talking about an Ebay clone kit, why not look at what the kit suppliers and builders choose? In a finished product build, I think it is a 22V, 20VA R core type transformer but any low noise transformer type will work fine, as long as it is well separated from the sensitive preamp circuits. I would use a standard 12+12V, 7 or 10VA sealed toroid to make up a regulated 24VDC supply. The transformer will fit directly to a PCB, even a stripboard one, which ensures short leads and a compact, relatively safe assembly if the mounting and mains wiring is secure and sensibly spaced.
Caution - do not rely on stripboard PCB conductor spacing for mains wiring. Cut closely spaced tracks away so that there is plenty of insulation between mains and any other conductor. If you are uncertain or inexperienced with mains wiring, don't take risks - use the safety of a 24VAC plugpack, wallwart etc mains adaptor instead. I even use an old 30VDC HP printer power supply for example. If the supply is followed by a good regulator, there are seldom any concerns for what is used for the input, either AC followed by a rectifier, raw or regulated DC. So long as there is always at least 4VDC headroom above the required 24V DC output, a linear regulator circuits or 3 pin IC regulators such as LM317 or 7824 will remain functional.
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Hi Ian,
Thanks again.
I look for the blue sealed toroid transformer with 2x24V with 15VA, should be enough.
I Will also use a power supply board with two LM317 for the right voltage 2x24V separat for
each channel.
I not understand what you mean with "do not rely on ...", pls can you describe it with other words.
If you mean the distance between the transformer and the preamp board, I will make a separate housing for the power supply board with the transformer.
Regards
dsch
Thanks again.
I look for the blue sealed toroid transformer with 2x24V with 15VA, should be enough.
I Will also use a power supply board with two LM317 for the right voltage 2x24V separat for
each channel.
I not understand what you mean with "do not rely on ...", pls can you describe it with other words.
If you mean the distance between the transformer and the preamp board, I will make a separate housing for the power supply board with the transformer.
Regards
dsch
Question to this circuit
Hi,
I would like to build this board also and I'm not sure about some points
1. The output is only coming from Q1 or is there a dot between Q1+Q3+Q4 to output?
2. I want to use a 470pf wima mks2 capacitor, is this ok?
3. Is this circuit complete and ok?
Thanks in advance.
Regards
Hi,
I would like to build this board also and I'm not sure about some points
1. The output is only coming from Q1 or is there a dot between Q1+Q3+Q4 to output?
2. I want to use a 470pf wima mks2 capacitor, is this ok?
3. Is this circuit complete and ok?
Thanks in advance.
Regards
Attachments
Earlier, I posted a link to acoustica.org.uk and showed the subdirectories to click and navigate to the preamp mods bible, which includes a clearer NA321 schematic and an updated version, which save guessing which lines are connected or not. I've attached a newer NA321 version so that you can see what I mean. Don't forget that you only have the NA321 gain stage circuit there. For a minimal preamp, you also need the following 20k volume control and NA324 buffer stage to complete a basic, simplified preamp circuit, as you see on the motherboard of Naim preamps. Did you see that link and find the schematics there?
You can use a polyester (MKS) capacitor if you want but for either a 470 or 100pF RF bypass cap, a cheap ceramic disc cap or MLCC type will be better.
What does "do not rely on" mean? If you don't have a browser and can't simply Google "rely on", It means to depend on, trust or believe will be OK.
So "do not rely on" simply means don't trust, depend on or believe is safe to use etc.
To be specific, the copper foil strips on stripboard, Veroboard etc. are very close on some products and 230VAC is likely to short between strips and burn your board, particularly if soldering is messy and there is excess flux - that's why you should not trust it as supplied. However, you can remove or cut alternate strips back, where they are close to the mains conductors, so no big deal to fix. 🙂
@jaycee. Since when has the black shoebox HiFi trade ever been anything but a BS mill anyway? 😀 When I first heard of the SNAPS, back around 1980, I thought it must have been a complete regulated supply for the whole audio system - in view of the price. Nope, just a fancy little low current 24V regulated supply in a standard case, just to do a better job than a cr*ppy 7824. Most of the cost would have been in the packaging, external treatment, special SNAIC lead, artwork and promotional waffling. Yep, I've heard a few systems using SNAPS and HICAP supplies but I can't say they sounded noticeably worse without them.
Then again, some owners are also passionate flat-earth believers who pay plenty of cash regularly for service work - or just keeping their systems attuned to global flatness. 'No need to insult those who pay handsomely for that illusion 😉
You can use a polyester (MKS) capacitor if you want but for either a 470 or 100pF RF bypass cap, a cheap ceramic disc cap or MLCC type will be better.
What does "do not rely on" mean? If you don't have a browser and can't simply Google "rely on", It means to depend on, trust or believe will be OK.
So "do not rely on" simply means don't trust, depend on or believe is safe to use etc.
To be specific, the copper foil strips on stripboard, Veroboard etc. are very close on some products and 230VAC is likely to short between strips and burn your board, particularly if soldering is messy and there is excess flux - that's why you should not trust it as supplied. However, you can remove or cut alternate strips back, where they are close to the mains conductors, so no big deal to fix. 🙂
@jaycee. Since when has the black shoebox HiFi trade ever been anything but a BS mill anyway? 😀 When I first heard of the SNAPS, back around 1980, I thought it must have been a complete regulated supply for the whole audio system - in view of the price. Nope, just a fancy little low current 24V regulated supply in a standard case, just to do a better job than a cr*ppy 7824. Most of the cost would have been in the packaging, external treatment, special SNAIC lead, artwork and promotional waffling. Yep, I've heard a few systems using SNAPS and HICAP supplies but I can't say they sounded noticeably worse without them.
Then again, some owners are also passionate flat-earth believers who pay plenty of cash regularly for service work - or just keeping their systems attuned to global flatness. 'No need to insult those who pay handsomely for that illusion 😉
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