I have a theory what happens when we switch off one polarity of the PSU. Could be tested rather safe also by soldering in a 50 Ohm ballast resistor, cartridge NOT connected, switch off one polarity, then measure the input DC offset and get the offset current by DC Offset / 50.
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Actually the offset trimmer is a differential shunt feedback loop. It should also lower distortion in the input stage.
In any transient or failure scenario conditions worth looking at. But the offset trimming grid is high impedance and the current will go through the 33R I guess. So 150mV max input offset in any disaster case?
I hope so. I really have to test this to be certain. Could be also Ube plus 150mV, that was my first guess.
If you like it or not, for the faint at heart there is always the option to put a high value elcap on the input. I build a D.Self like pre-pre with bipolar Black Gates at the input that sounds much better then many think. The best substitute i found are bipolar Nichicon ES.
The "natural" input impedance of the Paradise is in the 10kOhm range so using a 10kOhm ballast resistor we can come away with a 10uF foil.
Yes, do try it at power on/off, especially at off cycle the lytics don't extinguish in perfect sync, and on (-) or (+) rail disaster case. Many people are going to be involved, some may use small boxes, push the regs CCS or deprive correct ventilation, whatever. So you can give them info about risks if any, and recommendations.
Sure good idea. The best start is of cause build the beast, then put on a ballast resistor in the range of the DC impedance of your cartridge, then measure the input , THEN put on the cart. This does of cause not prevent fatal failure that happens in the future.
I do not know if i was super careful but you know that the first two years of MPP i tested a lot of transimpedance inputs that had considerable DC offset sometimes. I never fried a cartridge. Maybe luck.
Anyway, guys, stuff careful, triple check, do modifications LATER, when you know more about the principles involved, DO NOT DO STUPID THINGS, common sense is enough.
Anyway, guys, stuff careful, triple check, do modifications LATER, when you know more about the principles involved, DO NOT DO STUPID THINGS, common sense is enough.
Just a tought
Component matching is not that critical in Paradise (again due to good design)
nevertheless matching transistors is required for best results
We are going to have 200 + people matching
OF those 200 not many have TOY curve tracer or Atlas componet tester.
Maybe simple matching metode wuld be apreciated
Component matching is not that critical in Paradise (again due to good design)
nevertheless matching transistors is required for best results
We are going to have 200 + people matching
OF those 200 not many have TOY curve tracer or Atlas componet tester.
Maybe simple matching metode wuld be apreciated
Where can we get one of those ?
I use my DMM Hfe function to select BC's... do you believe this is not enough ?
I like it Peak Electronic Design Limited - Atlas DCA - Semiconductor Analyser - Model DCA55 you can order online or using local dealers as indicated on the web site.
Have a look at Peak Atlas DCA - Semiconductor Analyser - Model DCA55 - Peak Electronic Design Limited - YouTube
Price should be 71 Euro (or less 🙂).
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Get this one 🙂 http://www.peakelec.co.uk/downloads/dca_faqs.pdf (did your Google break down, the ATL guys use Geegle Urban Dictionary: geegle 🙂). And, Yes, includes Jfet's. The manual can also be found online.
O.k. I only did read it did do (at the least something with) jfet's. Still it got me interested, the Dutch distributor asks 50 Euro's ex Vat (that will be around 60 Euro inclusive), that seems a very reasonable price. I think I get one, even with jfet's (by recognizing the legs) it gives you a simple go/no-go test while stuffing boards. Anyone wants to comment on his/her experience with this device? Please let me/us know.
Tells if its nJfet or pJfet and which is gate. Especially at the currents and voltages it uses to save the battery it can't differentiate even non symmetric ones. Good for a quick go/no-go for unknown or dubious after incidents. Its good it has the flying leads and random order that is ergonomic. Another thing is that uses too much Ib at mA region for BJT's Vbe. Its battery life isn't stellar for systematic sorting of parts in some production run, all in all is a handy device, I use it from time to time but it did not help with unipolars.
I use the Peak Atlas too and the Peak Atlas ESR tester. For BJTs i think it is good and i use a PSU. It eats batteries for breakfast.
It is not that hard to select J-Fets ether. On DIYAUDIO i have seen jigs.
Some J-Fets are definitely not fully symmetrical. I just had a problem when i beta tested the XCEN Bal to Unbal converter. The negative input gave me 2dB more gain then the positive input. I found that i had inserted one 2SK246 the wrong way. I then measured this Fet in both directions and found that Idss was considerable higher in the correct direction. Inserted into the XCEN with the correct polarity gave me the same gain on both inputs.
It is not that hard to select J-Fets ether. On DIYAUDIO i have seen jigs.
Some J-Fets are definitely not fully symmetrical. I just had a problem when i beta tested the XCEN Bal to Unbal converter. The negative input gave me 2dB more gain then the positive input. I found that i had inserted one 2SK246 the wrong way. I then measured this Fet in both directions and found that Idss was considerable higher in the correct direction. Inserted into the XCEN with the correct polarity gave me the same gain on both inputs.