Improved Merrill DCA5.5
RE: What are the best sounding SS diodes for full wave bridge rectification?
You should be fine with a quad of 3 A./600 PIV Schottky diodes by Infineon from Mouser. You can lower the bridge’s cost by using UF5408s snubbed by HIGH WVDC 10 nF. caps. in the negative legs.
Choke I/P filters can produce very nasty kick back spikes. Those spikes can destroy SS diodes of any stripe. You protect the “sand” by using either a HIGH WVDC 10 nF. cap. or an appropriately rated MOV in what would be the 1st position of a CLC filter.
Eli Duttman - El Cheapo
If you can DIY, an “El Cheapo” built using Dunaclone Z565 O/P trafos and triode/UL mode switches will surely do the job. If you can’t build for yourself, see about commissioning a build from Mike Samra or Don Sachs, along with other capable “inmates” from the tube DIY “board”.
Dig into the archives for “El Cheapo”. That setup is good for about 6 WPC with triode wired O/P tubes. UL mode “finals” will get you about 12 WPC.
FYI, Poinz now prefers the “reissue” TungSol 6V6 made by New Sensor at Saratov, Russia, to NOS. ;> ) IF the will to do so is present, tubes every bit as good as those made in “days of yore” can be manufactured today.
Since you mentioned “El Cheapo”, 1 of the early fellows on the bandwagon built with Mullard CV4024s and black plate RCA 12AQ5s, along with Z565 O/P “iron”. Yowzuh!! I’m all in favor of NOS, when it can be sourced without surrendering body parts.
Build an “El Cheapo”! A $500 outlay will easily cover the cost of all parts, including excellent DynaClone Z565 O/P trafos.
Nobody in their right mind uses anything other than SS diodes in a DC filament supply.
With the possible exception of directly heated triode O/P types, DC heating is reserved for preamp, especially phono section, duty. AC heating is the norm in power amplifiers.
Fact, tubes are high impedance, high voltage, low current devices. While it is possible to build without transformers coupling the O/P tubes to the speakers, it MOST DEFINITELY is not the sort of thing to tackle as a 1st project.
You say you want approx. 10 WPC. An “El Cheapo” built with 1/2 way decent O/P trafos will yield 12 WPC and it works without a preamp, when driven by a CDP.
I’ve uploaded the “El Cheapo” schematic. A link to the LENGTHY “El Cheapo” saga is provided below.
Finally, start a new thread on the Tube DIY forum about your ambitions. That “board” is where discussions of this sort belong.
The 12AT7 based small signal circuitry used in “El Cheapo” works with EL84s as well as it works with the 6V6 family. AAMOF, the only change to the “El Cheapo” parts values needed to use EL84 “finals” is in the cathode bias resistor value. :> ))
There’s MUCHO sonic mojo in “12” W. multi-grid power O/P tubes. Is there a bad sounding type? The EL84 and 6V6 say NO.
Yeah, the top cap plate connection puts the type squarely in the enthusiast’s column. Given current product liability law, they could never go into a commercial amp.
That reduced bias and increased sensitivity can be a blessing. Add the EL38 to the list of types an “El Cheapo” style 12AT7 based splitter/driver works with, minus a line stage that has gain.
One of the reasons we went with self bias in “El Cheapo” was to avoid the hassle of adjusting both CCSes and bias.
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