I made a set of useful PCBs. They are intended to mount large (big really big) film capacitors: WIMA DC Link ones!
I use the cost-effective 45μF/600V (MF Part No. DCP4I054507ID2KYSD) in many of my boards as the last capacitor in the filtering network. This is a 2 pin device, however when you go larger like the 80μF/900V (MF Part No. DCP4N058009JD4KYSD), this one has 4 pins and bigger size. The PCB for the later can also accommodate the smaller DC Link of 45μF/600V. The boards have turret or 2mm banana plug connections and an INS-1 Nixie indicator with its associated resistor. Finally a bleeder 3-5W resistor can be added.
The smaller board has the size of the Source Follower PCB. It can be mounted below it or can be used independently. Can fit a variety of PIO/Film capacitors for decoupling or for AC interstage coupling.
Speaking about the Source Follower PCB, I made also a new batch of PCBs as run out of the original ones. I made a minor modification and improvement by adding an LED indicator before the top MOSFET drain. This works in the same way as the gyrator Rev08 PCB. Can be used for normal operation or for A2 current source indicator. Also added an extra PIO/Film 100nF decoupling cap to be mounted under the PCB to decouple the high impedance node to the power supply:
I really like the cap boards. I tend to use the Panasonic EZP-E series, but after checking Mouser, it looks like the Wima DC-LINK pp caps are a bit less expensive.
I presume the INS-1 is in parallel with the cap, with a dropping resistor in front of it, of course?
Thank you for all the posts, pictures and insights into this building method.
Since we’re on the subject of bypass caps here’s a brief shootout I just did on the cathodes of my 300b outputs. In order of preference:
– Vishay DC Link Cap, 40uF, 900v
– ICW SA Clarity Cap, polypropylene, 47uF, 630v
– RS electrolytic 100uF, 450v
– ICW PW polypropylene cap, 40uF, 160v
– Aerovox motor run cap, polypropylene, 40uF, 450v
The DC Link caps were a clear improvement on all the others – audibly more detail and better timbre to voices and instruments and a generally more involving sound. The two ICW caps were similar – smooth but flat and quite veiled in sound, rather boring in fact. The bigger Clarity Cap (it’s very big in fact) was a little better but still rather flat. The RS electrolytic surprised me – it wasn’t as smooth as the Clarity Cap but it had more life and was arguably more involving though a little coarser. This is just a generic old cap with many years on it. The motor run cap was flat and boring and a little coarser than the ICW caps but otherwise fairly similar to the PW cap.
Conclusion – get some DC Link caps! The sound improved quite noticeably. I’ll be ripping out all my ICW caps, which have a good reputation and are sold as “audio” caps. I won’t be doing a shootout of electrolytics, but I imagine there’s room for improvement there. They were better than I expected, though outclassed by the DC Links.
Very interesting findings Andy, thanks for sharing your experience. I’m glad you confirm the DC link preference as I’ve done myself. Perhaps I was lucky and fast tracked my comparisons by trying them long time ago. Anyhow, they are probably the best in terms of value for money. I use them on all my filtering stages (last capacitor of the supply filter) and cap multipliers. Also for cathode bypass should be a good choice as you confirmed.
Having the PCBs made is a great thing to facilitate stacked mounting or mounting in general
Cheers,
Ale
Hi,
In the 300B SE Amp – main schematic, ar C1 and C4 shared between the stereo channels? One each per build, right?
Hi, yes. I shared both C1 and C4 between the channels. In my 47 driver version of this amplifier, I added a 100nF film decoupling capacitor between +B and GND of the hybrid-mu follower boards