Regarding NAP clones, there can be a substantial difference in sound quality if assembled as they come, with substitute VAS transistors. The trick to Naim sound quality is the happy coincidence of Mr Vereker using technically "wrong" transistor types originally. Most clone kits though, came with cheap substitutes for the Zetex types ZTX653/753. Though 2SD667/2SB647 were commonly supplied (15pF) the Zetex pair are a huge 30pF Cob and the difference is audible. Sadly, the substitution of low capacitance transistors makes a mess of the Naim sound, the PRAT etc. such that you wind up with something lacklustre in comparison. Note that Naim still use this trick- it's essential.
Like many who have posted in this thread and weren't aware of the errors, you could have reason to be dissatisfied with your clone, particularly if you were familiar with the originals. Perhaps this explains or clarifies why you may be looking to improve it.
If you haven't considered it before, why not just replace the wrong semis and try again with the original type. Whilst you're at it, replace the driver transistors with MJE253/243 too but be aware that the schematic widely circulated on the web and used as the basis for Ebay type kits, is for the NAP 250. The NAP 140 is unregulated and a little different in that it includes some decoupling caps and also uses some different resistances to set the bias level and offset of the input and VAS stages, compensating for the lower supply voltage.
Like many who have posted in this thread and weren't aware of the errors, you could have reason to be dissatisfied with your clone, particularly if you were familiar with the originals. Perhaps this explains or clarifies why you may be looking to improve it.
If you haven't considered it before, why not just replace the wrong semis and try again with the original type. Whilst you're at it, replace the driver transistors with MJE253/243 too but be aware that the schematic widely circulated on the web and used as the basis for Ebay type kits, is for the NAP 250. The NAP 140 is unregulated and a little different in that it includes some decoupling caps and also uses some different resistances to set the bias level and offset of the input and VAS stages, compensating for the lower supply voltage.
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Fortunately, the other semis aren't so critical to sound. For example, you could just as easily use On-semi's BC549C as the LTP. I've tried this in the past with (Motorola) versions having similar high gain, matched for a low DC offset. You could easily conclude that nothing was any different. On-semi (Motorola) made them by the same process as BC239C so you could expect that to be the case.
I think we know that Naim used several different types of power transistors over the original product lifetimes but settled on Sanken's LAPTs and still use them in TO3P format. I don't think there's much virtue in the original power switching types (Solitron ) compared with Sankens but if you must have original 1970's sound quality, that's where I'd look.
but I like the idea. I don't have kit lying about to experiment with at the moment but it seems easy enough to try this out using, say cheap 2SB647, 649 or BC640, BD140 with a 15p or greater diode.
I think we know that Naim used several different types of power transistors over the original product lifetimes but settled on Sanken's LAPTs and still use them in TO3P format. I don't think there's much virtue in the original power switching types (Solitron ) compared with Sankens but if you must have original 1970's sound quality, that's where I'd look.
That's cheating
but I like the idea. I don't have kit lying about to experiment with at the moment but it seems easy enough to try this out using, say cheap 2SB647, 649 or BC640, BD140 with a 15p or greater diode.These are just large, for signal transistors, in a small package.
https://www.onsemi.com/pub/Collateral/NZT753-D.pdf
https://www.onsemi.com/pub/Collateral/NZT902-D.pdf
I would try mje243/253, Cob=50pF.
But has anyone analyzed the Naim circuit in spice? With 4000 posts I scanned a few but did not find any *.asc files.
The schematics I found contain "errors" that may be part of the magic?
BTW, 24-0-24VAC produces ~67VDC peak to peak which is over the limit for old 2n3055s and similar, but I suppose blowing up your amp regularly was par for the course in those days. I know I did it a lot back then.
https://www.onsemi.com/pub/Collateral/NZT753-D.pdf
https://www.onsemi.com/pub/Collateral/NZT902-D.pdf
I would try mje243/253, Cob=50pF.
But has anyone analyzed the Naim circuit in spice? With 4000 posts I scanned a few but did not find any *.asc files.
The schematics I found contain "errors" that may be part of the magic?
BTW, 24-0-24VAC produces ~67VDC peak to peak which is over the limit for old 2n3055s and similar, but I suppose blowing up your amp regularly was par for the course in those days. I know I did it a lot back then.
Thanx Jeff!
I don't have all the models models. Normally that wouldn't be an issue but I'm worried substitutes are not close enough?
BTW, you know the PS bridges are shorted?
Whilst you could try other modern SMD equivalents, Diodes/Zetex already make both E-line and their own SOT223 versions, as now fitted in current Naim models): url=http://pdf.datasheetcatalog.com/datasheets/diodes/FZT753_FZT753QTA_FZT753QTC_FZT753TA_FZT753TC.pdf]Diodes FZT753, FZT753QTA, FZT753QTC, FZT753TA, FZT753TC datasheet pdf[/url]
As said, you need only the 30 pF of the VAS transistor and current sink for this. However, the thread OP is about Ebay type clones which translates to through-hole parts in order to make retail kits attractive, viable and easy for beginners everywhere to buy and assemble.
The original models didn't use 2N3055 power transistors in the amplifiers, though. Clone makers such as Avondale Audio do use MJ15003 which is somewhat similar but from the outset in the 1970, Naim used power switching transistors such as BDY56,58 as one way to tackle the crossover problem. Then they changed to house-coded types (probably sourced from Semelab in the UK) then LAPT Sanken power transistors in the late 1980s, which they continue to use in domestic models.
It would make an interesting, if demanding project for experienced builders to design and build their own clone of current Naim models - if you had one to reverse-engineer. To all accounts though, the sound of recent models is more tame than the original line-up and samples are also more difficult to acquire for the purpose. A one-off project for an expert with the resources might be another matter....
After a few minor substitutions: (same parts with name variations)
Error on line 18 : d3 n037 n014 1n5621
Unable to find definition of model "1n5621"
Error on line 24 : q5 n004 n003 n001 0 ztx753
Unable to find definition of model "ztx753"
Error on line 25 : q4 n016 n031 n034 0 ztx653
Unable to find definition of model "ztx653"
Note that the bias spreader (Q6) should be a ZTX108, but I never found a SPICE model for that.
Here are the Zetex's I have found:
and the diode:
Cheers,
Jeff.
Here are the Zetex's I have found:
Code:
.MODEL ZTX651 NPN IS =2.218E-13 NF =.9956 BF =230 IKF=2 VAF=100 ISE=2.9E-14
+ NE =1.35 NR =.995 BR =56 IKR=1 VAR=30 ISC=2.971E-13 NC =1.321 RB =.04
+ RE =.075 RC =.069 CJC=51E-12 MJC=.42 VJC=.595 CJE=318E-12 TF =.77E-9
+ TR =27E-9
.MODEL ZTX751 PNP IS =2.715E-13 BF =170 VAF=70 NF =1.004 IKF=2.75 ISE=1E-13
+ NE =1.535 BR =23 VAR=40 NR =1.005 IKR=.55 ISC=5.15E-14 NC =1.13 RB =.07
+ RE =.065 RC =.085 CJE=360E-12 TF =.94E-9 CJC=90E-12 TR =60E-9 VJC=.705
+ MJC=.46
.MODEL ZTX653 NPN IS =3.8206E-13 NF =1.0025 BF =250 IKF=1.15 VAF=154
+ ISE=1.035E-13 NE =1.3642 NR =1.0012 BR =50 IKR=0.42 VAR=38
+ ISC=7E-13 NC =1.19 RB =0.04 RE =0.0875 RC =0.06
+ CJC=45.5E-12 MJC=0.4534 VJC=0.5774 CJE=278E-12 TF =0.78E-9 TR =30E-9
.MODEL ZTX753 PNP IS =3.2007E-13 NF =1.0041 BF =200 IKF=1.6 VAF=76
+ ISE=8E-14 NE =1.57 NR =1.0008 BR =33 IKR=0.45 VAR=51
+ ISC=6E-14 NC =1.079 RB =0.087 RE =0.08 RC =0.07
+ CJC=80E-12 MJC=0.4896 VJC=0.7676 CJE=350E-12 TF =0.86E-9 TR =24E-9
.MODEL ZTX851 NPN IS =1.0085E-12 NF =1.0001 BF =240 IKF=5.1 VAF=158
+ ISE=2E-13 NE =1.38 NR =0.9988 BR =110 IKR=5.5 VAR=46
+ ISC=4.6515E-13 NC =1.334 RB =0.025 RE =0.018 RC =0.015
+ CJC=155E-12 MJC=0.4348 VJC=0.6477 CJE=1.05E-9 TF =0.79E-9 TR =24E-9
.MODEL ZTX951 PNP IS=1.3766E-12 NF=1.013 BF=187 IKF=5.0 VAF=66.3
+ ISE=1.4E-13 NE=1.41 NR=1.0099 BR=56 IKR=0.9 VAR=33 ISC=1.7E-12
+ NC=1.4 RB=0.029 RE=0.020 RC=0.0255 CJC=287E-12 MJC=0.4522
+ VJC=0.4956 CJE=1.15E-9 TF=0.83E-9 TR=20E-9
.MODEL ZTX853 NPN IS =8E-13 NF =0.99 BF =240 IKF=1.4 VAF=200
+ ISE=4E-13 NE =1.27 NR =0.99 BR =90 IKR=1.4 VAR=46 ISC=100E-12
+ NC =1.65 CJC=127E-12 MJC=0.46 VJC=.65 CJE=1.07E-9 RB=.3 RC=.014
+ RE=.014 TF =0.9E-9 TR =20e-9
.MODEL ZTX953 PNP IS=1.6649E-12 NF=1.0139 BF=220 IKF=4 VAF=55
+ ISE=6.2E-13 NE=1.62 NR=1.0107 BR=40 IKR=0.95 VAR=43 ISC=3E-12
+ NC=1.4 RB=0.032 RE=0.0295 RC=0.034 CJC=265E-12 MJC=0.5286
+ VJC=0.76 CJE=1.1E-9 TF=0.8E-9 TR=29E-9 XTB=1.4 NK=0.7 TRE1=.0025 TRB1=.0025 TRC1=.0025and the diode:
Code:
.MODEL 1N5621 D(IS = 1.14436E-7 RS = 0.1 N = 2.300601 TT = 6.52E-7 CJO = 1.412E-11 VJ = 0.4 M = 0.3106097 EG = 1.11 XTI = 7.636 KF = 0 AF = 1 FC = 0.8991 BV = 1.028E3 IBV = 1E-6)Cheers,
Jeff.
after a somewhat complicated passage, it's now pretty much on the right track.I hope they were all good changes, huggygood. Also good that you now have some time for DIY fun
I met an Irish woman who is currently on vacation in Melbourne with her father for the holiday season.
life is Beautiful .
I haven't a boatCareful of those Irish lasses. You'll wake up one morning to find everything you own on a boat....
, just motorbikes Thanx Jeff!
Cool, thanx!
I should have done this before I asked for you models but I found:
Index of /Spice_Model_CD/Vendor List/Zetex
including ZTX108 and ZTX108B.
My simulations claim THD results around 0.03% so I went back to my simulations of the old Sinclair Z30/50 that I had done because it was something similar and something I managed to afford back in the 1970s. And the results are similar even though they used to claim 0.01%.
It used little 4Amp BD187s for outputs and the two PNPs where BC212, ie 200mA. I still have an unused Z30/50 that I got those numbers from. There are two different NPNs that I can't read/figure out. The LTP emitter resistor is only 1.8K and not 18K as advertised but it worked anyway.
I blew up those amps several times and modified it in the process but eventually I threw out the Z30/50 cards and built a typical amp using TIP41/42 drivers and some surplus 2n3771s with 2.2 Ohm base shunts, ie so big the PS can never destroy them.
The Sinclair PS had a cool protection latch-off but I replaced it with an ordinary split supply.
I added an EF to the Sinclair preamp ahead of the tone controls to bypass the Phono preamp for tape input. I used a R-R tape deck in those days.
I never spend money on amps because people gave me blown recievers for free, which I rebuilt.
Today I could afford and design so much more but I have become way to practical, lost most of the passion in my old age. And then there is the lack of great music like we enjoyed in those days. My tapes have become a folder on each computer and my phone, and a thumb drive in the cars.
Cheers,
Steve
Cool, thanx!
I should have done this before I asked for you models but I found:
Index of /Spice_Model_CD/Vendor List/Zetex
including ZTX108 and ZTX108B.
My simulations claim THD results around 0.03% so I went back to my simulations of the old Sinclair Z30/50 that I had done because it was something similar and something I managed to afford back in the 1970s. And the results are similar even though they used to claim 0.01%.
It used little 4Amp BD187s for outputs and the two PNPs where BC212, ie 200mA. I still have an unused Z30/50 that I got those numbers from. There are two different NPNs that I can't read/figure out. The LTP emitter resistor is only 1.8K and not 18K as advertised but it worked anyway.
I blew up those amps several times and modified it in the process but eventually I threw out the Z30/50 cards and built a typical amp using TIP41/42 drivers and some surplus 2n3771s with 2.2 Ohm base shunts, ie so big the PS can never destroy them.
The Sinclair PS had a cool protection latch-off but I replaced it with an ordinary split supply.
I added an EF to the Sinclair preamp ahead of the tone controls to bypass the Phono preamp for tape input. I used a R-R tape deck in those days.
I never spend money on amps because people gave me blown recievers for free, which I rebuilt.
Today I could afford and design so much more but I have become way to practical, lost most of the passion in my old age. And then there is the lack of great music like we enjoyed in those days. My tapes have become a folder on each computer and my phone, and a thumb drive in the cars.
Cheers,
Steve
Do you have SPICE's maximum timestep set low enough? (I use 0.5usec for 20kHz.)
At 1W RMS (4V peak-to-peak over 8 ohms) I'm getting 0.005% 1kTHD and 0.091% 20kTHD.
Cheers,
Jeff.
pre build naim-clones
Sorry if this has been asked before. Ive tried to investigate this, but havent found good posts.
Does anyone have experience with premade clones like this one? I dont have any technical skills, so modding the amplifiers are not an option.
Hifi NM152 MOD Preamplifier + Hiend version Power amplifier Clone Naim Nap200 | eBay
Apparently this guy claims that the clone sounds 85% of the original. Naim NAP200 clone | NAJLEPSZE ODTWARZACZE, DAC, PC audio, DIY
Will i be better of buying a second hand nap-155xs/nac-152?
Thanks for any feedback.
Sorry if this has been asked before. Ive tried to investigate this, but havent found good posts.
Does anyone have experience with premade clones like this one? I dont have any technical skills, so modding the amplifiers are not an option.
Hifi NM152 MOD Preamplifier + Hiend version Power amplifier Clone Naim Nap200 | eBay
Apparently this guy claims that the clone sounds 85% of the original. Naim NAP200 clone | NAJLEPSZE ODTWARZACZE, DAC, PC audio, DIY
Will i be better of buying a second hand nap-155xs/nac-152?
Thanks for any feedback.
Definitely is better to buy the original 155/152. Will sound better, last longer and have resale value. This clone seems too expensive to me for what it is, with half of the components potentially fake.
Evaluating sound in % from some other sound doesn't make any sense to me. I wouldn't trust any review written like that.
Evaluating sound in % from some other sound doesn't make any sense to me. I wouldn't trust any review written like that.