I suggest that you test each board in isolation as described in the build guide and report back.
Use the voltages shown on the schematic to help you find the issue.
Double and triple check each component.
Thanks - the input boards at least passed the general voltage tests in isolation. I do not have a signal generator to test the gain. I’ll need to dig up the extra components to test the output boards. Will report back.
I figured out my dumb mistake. I had tacked Q104 into the top position on the board for testing but neglected that you have to wire leads down to the the center board location if you do this. I moved Q104 down to the center and everything tests out fine now. Thanks to all who humored my question and tried to help!
Hello. This is my first post on this forum, though not my first amplifier build. I have received those beautiful blue EF3-3 boards (thank you Stuart, and the team) and started gathering the (many) parts. With my selection of drivers (MJE15032/33) no less than eight 470pF mica capacitors are required, and unfortunately they are freakishly expensive (5 euros a piece). Are they really worth the money, or can I use the ceramic caps in some or all positions without sacrificing sound quality? Anyone has some experience on that matter ?
Ronnie.
Ronnie.
https://www.mouser.com/ProductDetail/KEMET/C323C471KAG5TA?qs=h3/j8evtlm2NhwUn9MxL7w== is a decent C0G substitute. These are not quite as good as the silver mica, but should be stable and linear. The JA version has 5% tolerance instead of 10%, but the lead spacing is smaller. If you are careful, you can bend the leads to fit. Just don't crack the coating while bending. 10 cost less than 1 AgMica.
There are less expensive C0G, but the data sheets did not seem to spec the dissipation factor or seem to be recommended for this application.
There are less expensive C0G, but the data sheets did not seem to spec the dissipation factor or seem to be recommended for this application.
Hello folks
today my package from Fireanimal arrived and also the almost lost Ground Lift and T-Ground PCBs
Now I wanted to order the parts of the Ground Lift and T-Ground but I find the shipping prices of Digikey a little bit expensive.
Is there an EU alternative that is cheaper?
today my package from Fireanimal arrived and also the almost lost Ground Lift and T-Ground PCBs
Now I wanted to order the parts of the Ground Lift and T-Ground but I find the shipping prices of Digikey a little bit expensive.
Is there an EU alternative that is cheaper?
Gathering the basics.
While the materials and parts are slowly finding its way to my workshop I have a simple question.
I've ordered some mica To-220 and To-3p mica pads as insulators but what about shoulder washers? Are there quality differences or doesn't it really matter? I've understood the polyamide ones can sustain a lot of heat but the question is,. is it neccassary or not? Haven't found anything substantial about it on the net the be honest.
thx
Coming from downunder.....
Toshiba drivers
While the materials and parts are slowly finding its way to my workshop I have a simple question.
I've ordered some mica To-220 and To-3p mica pads as insulators but what about shoulder washers? Are there quality differences or doesn't it really matter? I've understood the polyamide ones can sustain a lot of heat but the question is,. is it neccassary or not? Haven't found anything substantial about it on the net the be honest.
thx
Coming from downunder.....
Toshiba drivers
I don't think you need shoulder washers with those transistors. The to-220 seem to be the fully isolated packages and only require a tiny bit of thermal paste. The to-126 have isolated mounting holes and can do with only a thermal interface (mica or silicon pads). In Stuart's pictures you can clearly see that he does not use isolating shoulder washers. Note that the mica pads require also a small amount of thermal paste on both sides to reduce the thermal resistance. Only then do they have slightly better thermal performance with respect to silicon pads. I still prefer silicon pads as they are a lot less messy when mounting (and future disassembly).
If you order for more than 55€ shipping is free. I think for Mouser it is 50€. The whole shipping is very convenient by both as they pay the import fees and it's fast.Hello folks
today my package from Fireanimal arrived and also the almost lost Ground Lift and T-Ground PCBs
Now I wanted to order the parts of the Ground Lift and T-Ground but I find the shipping prices of Digikey a little bit expensive.
Is there an EU alternative that is cheaper?
None of the above capacitors are truly temperature and voltage independent. It's a matter of degree. Silver mica has a measurably lower DF, especially at higher frequencies, thus its use in the positions that are intended to suppress high-frequency oscillation. Self resonant frequency is well above 50 MHz, which removes the complications of additional poles in the compensation network. I've measured the DF for some of my mica caps and it is always below .0006 at 100kHz. Same value polypropylene/polystyrene DFs are generally below .001 at the same frequency. The C0G/NP0 measure similarly. More details can be found in Self and in a paper by Bateman. The mica caps are virtually indestructible. If you can afford them and have room they are the very best you can get for time constants. They are also very stable over time.
Some people claim they can hear the difference among capacitor types. However, among the Class 1 dielectrics, I would be suspicious of such claims. Actual blind testing of different capacitors in the same circuit is quite difficult to arrange. If you get into the PET/PTFE and class 2 ceramics, then there is measurable distortion which may be heard.
Personally, I wouldn't sweat the difference among the mica/pp/ps/np0 dielectrics, but then there is an increasing number of things I can't hear. I happen to have a collection of silver micas bought years ago at a ham fest. They've appreciated at least as well as gold. You can still get 100 for 38 bucks on Amazon. However, the collection I got from Amazon recently was missing the 470pF value for some reason.
@wkloppen You will need shoulder washers for the TO-220 packages and possibly some of the TO-126 packages. The MJE340Gs used for thermal compensation have a conductive back and plastic on the top. The TO-247 (TO-3P) and TO-264 do not require shoulder washers, at least for the On-Semi parts I have.
Using a insulated shoulder washer even for TO-126 that have a insulated hole is a good idea, because if your mounting hole is slightly oversize this can allow enough clearance if the transistor is pushed all the way to one side of the hole in the heatsink. The non insulated surface of the transistor can then make contact with the grounded heatsink. Using a insulated washer prevents this.
