Helium

@Pars, What p/n you used for 47uF cap? Can you please measure voltage across it (at 30VDC power supply)? I have difficulties in finding that rated over 25V.

Well, maybe Kevin knows something I don't know) Anyway, I would use metal-oxide or metal film insted. To be specific, I'm ordering 71-CPF3-D-1. Also I remember AMB clearly discouraged against using wirewound in similar locations in his beta.

Are you using 1 Ohm wirewound type resistor? I would stay away from wirewound type in sigal path due to their high capacitance and inductance.

What's the input impedance of cfa3? And same question for krell ksa5 klone please. My guess is 10K and 50K respectively, but want to reconfirm.

While thinking over building this amp, I'm considering to replace 546B/556B with 550C/560C. I've got a lot of them matched for B22 projects. Could anyone advise if any problems with them (Vceo lower 45V vs 65V, but typ. hfe is higher)? PS will be 30VDC.

Kevin, so is matching them at Ib=1mA OK? (provided that hfe is ~200) Why? They are basically identical, except that MJE can sustain more power (=better), but doesn't have isolated tab.

Yeah, English is not my native language I'm going to use Toshiba 2SC5171/2SA1930 as output BJT. Pinout is same to MJE/MJF. Regarding matching, I'm trying to figure out what Ic or Ib or Ie I should aim at while matching them for CFA circuit. I've got different devices for measuring hfe. One of them declares measuring hfe @ Ic=5mA, others do this @ Ib=10uA, 1mA, 10mA. So I'm a little bit stuck here (Ic vs Ib, and appropriate range). mwl168 mentioned he's running 220mA bias current. Can it be asumed that 220mA is Ie? Maybe Kevin could chime in?

After mwl168 wrote his impressions on the sound, this amp looks very temptating. Ordered 20pcs PCB (SE version, so 4 needed for balanced bridged amp). Plan to use Toshiba BJT as output transistors, as I was unlucky with matching MJE15030 and 15031. Never tried to match MJF though, but I think they are hardly different from MJE.

It might be transistors are heating THAT340 thru copper layers. Are they soldered directy to board, or plugged in sockets?

@Laowei: Just curious, what GG board file are you using? What I'm looking at has slightly different traces layout (was posted 20160224). Can you check yours if its newer?

Yep I'm working for Japanese company, and my eyes got used to seeing that)) whoever edited the file has OS with japanese language pack installed.

Ok, I checked BOM and availability of parts here and there and it seems feasible to build but at enourmous price, almost prohibitive for own use. I guess ttl quantity of listed obsolete parts in whole universe is enough to build 10 units more of this thing. Maybe 15 (provided they are not 'wasted' for other projects). Then they will be depleted forever. I may be missing somehow but last year you mentioned: ===== diy-t2 with current production parts testing now obsolete fets 2sj79/2sk216 replaced with ksa1220/ksc2690 and 2sa1486 replaced with stn9360 ===== How about the progress? I guess board have to be redesigned to accomodate new parts.

Thank you so much!

Kevin, could you please upload the latest BOM (both amp and ps) of DIY T2? Could not find it anywhere.

I think he needs to try another opamp instead of opa445. Maybe DC must be decreased temporarily for another lower voltage opamp, but worth to try.

Why do you guys always refer to 5-mm pitch connectors while the board has 5.08-mm pitch?

Sh*t, I confused Alpha with Alps. Then TKD definitely better of course. Just place order for Alpha version, will contact PCB maker to replace Gerber.

Yes, it's 4,8 x 6,8, and latest rev is 1.5. What's input impedance of 'portable' Dynalo? If it's low, then problem is that 5K RK27114 Alps hard to source, even on Ebay (they seem to disappear completely).

What is exact board dimension of this PCB? Hi Kerry. Is SSDynalo-v1-4.zip from Kevin's depository the latest gerber? SSDynalo-v1-4.zip EDIT: Found, never mind.

wow thank you!

Grounded Grid?

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Could you upload there schematic files as well please?

Kevin, Want to build this board and try it instead of e12. Few questions if you allow: Is trigger offset DC with standard resistors 0.5v? Is it from O+ to O- or from O+ to GND/O- to GND? Is it suitable for non-differentail balanced amps like 4-board B22, 2-board KSA5? Is it suitable for SE amps (like 2-board B22, 1-board KSA5)? Just use R+ and L+ terminals? Input GND taken from where? If it's signal GND, then take it from any board? Can it be left unpopulated?

Thanks.