If you will hear any untoward hf stingy stuff, first suspect the PP local rail decouple maybe fighting with the Maida.
Tom the designer uses 10uF after his 21th century Maida. Mine is 4.7uF. Apparently it has no issues with a capacitive load. We'll see and hear... Hopefully this weekend.
LM317 Maida would ask for some output side ESR, but LT3080 Maida would probably not.
"I have had great trouble with my original Maida regulator (based on National Semiconductor LB-47 using an LM317) driving a capacitive load. That started my quest for a better regulator to begin with. With this 21st Century Maida Regulator, I have loaded it with up to 47 uF on its output without start-up issues as long as a resistive load was present. I need to ensure that the same is the case when starting up into a purely capacitive load." - member tomchr
The Bendix 5992s arrived today. They sound pretty much like I expected, based on my experience with other Bendix tubes. Very clean and smooth, with a lot of air around the instruments and more fine detail revealed.
I'm pretty much done on the breadboard. I ordered a case for the toroid and will see if I can get the power supply and circuit on a 17 x 10 chassis without noise issues. If it's still a problem I'll off-board the raw DC supplies.
One last question--is it worth switching to Cree Schottkys?
I'm pretty much done on the breadboard. I ordered a case for the toroid and will see if I can get the power supply and circuit on a 17 x 10 chassis without noise issues. If it's still a problem I'll off-board the raw DC supplies.
One last question--is it worth switching to Cree Schottkys?
Their tonal counterpoint should be Ken Rad 6V6GT/T (VT-107A)
SiC Schottky diodes have excellent specs. Worth a try I guess. There are also dual diode TO-247 parts like the C6D16065D.
Remember, in a four diodes full bridge rectifier each diode sees AC peak as reverse. In other words secondary RMS x 1.414.
In a two diodes and center tap scheme each diode sees AC peak to peak as reverse. In other words secondary RMS x 2.828.
SiC Schottky diodes have excellent specs. Worth a try I guess. There are also dual diode TO-247 parts like the C6D16065D.
Remember, in a four diodes full bridge rectifier each diode sees AC peak as reverse. In other words secondary RMS x 1.414.
In a two diodes and center tap scheme each diode sees AC peak to peak as reverse. In other words secondary RMS x 2.828.
Oh, interesting about the Ken-Rads, thanks. I have a pair of Sylvania VT-107, very nice.
So for the Schottkys I was thinking the 1200v ones?
So for the Schottkys I was thinking the 1200v ones?
I have those Sylvanias too. Very nice, sharper characteristic than my RCA blacks which are more mid-range oriented. Likeability depends on synergy goals with the rest of the system, on music genres more often played, and mood.
You may go for 1200 PIV diodes in case it will be needed for higher rail center tap future builds, but for this one even a 300 VAC secondary will only give 424 V PIV to them in a four diode bridge like yours.
What is the spec of your transformer's HV line secondary?
You may go for 1200 PIV diodes in case it will be needed for higher rail center tap future builds, but for this one even a 300 VAC secondary will only give 424 V PIV to them in a four diode bridge like yours.
What is the spec of your transformer's HV line secondary?
I love that you are invested in this preamp and have tried so many of the options. ;-) It's very helpful! I plan to build a version for a dear friend who is casting about for a good preamp for his SE system now. He is a complusive tube-and-cap swapper, so his will have a terminal strip for inserting output caps at will. ;-)
My toroid is 275-0-275, so 600V Schottky would be enough? They are much cheaper. ;-)
My toroid is 275-0-275, so 600V Schottky would be enough? They are much cheaper. ;-)
If used as just 275 into four diodes bridge it will only give them 390 PIV. So 600V spec is enough.
If used as 275-0-275 into two diodes and center tap it will be 780 PIV. Then you need higher spec.
If used as 275-0-275 into two diodes and center tap it will be 780 PIV. Then you need higher spec.
By the way, can you post a rather close photo of those Bendix 5992s in action? I am sure all readers would love to see.
LOL! Sure, here they are on the crappy breadboard. ;-)
Finished! Put into service last night. What can I say? The Salas 6v6 preamp makes me happy. 300V b+. 150 on plate. 8 on cathode.
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It turned out really well. Congratulations. What type rectifier is that beautiful National Union NOS? GZ34? How high raw DC it achieves from the 300VAC tap? The 6V6s should be 70's Soviet 6Π6C. Rich tone tubes, only not all samples proved long lasting. I had one gone noisy early, same happened to a couple of friends. But they used to be offered very cheaply online and we had enough good samples for replacements.
Thanks! 5Y3.
My reg only goes up to 311 it seems. So I thought I'll pop in the 5Y3 to lower it. And then I thought...let me see if I can get the heatsink warm (I can't) by dialling down to 300vdc.
They are Soviet made in 77. Can't find my Tungsol (Re-Issue Russians Really) that I used in the first one. Would be nice to compare.
With the 5y3 something like 330. With the GZ34 370 or so. But there is some resistance 47R each leg pin 4 and 6. Choke is 65R. And I made a ct with 47 ohm on the 5VAC supply to tap the b+ start from (Just because I like to do it)
My reg only goes up to 311 it seems. So I thought I'll pop in the 5Y3 to lower it. And then I thought...let me see if I can get the heatsink warm (I can't) by dialling down to 300vdc.
They are Soviet made in 77. Can't find my Tungsol (Re-Issue Russians Really) that I used in the first one. Would be nice to compare.
The Tungsol Russian reissue is clean and even, non edgy, more honest. The old 6Π6C thickly smoked glass is bit romantic and beguiling, little less transparent but a beauty for strings horns and female voices tone. A very likeable tube. The cleaner a PSU and speakers the more wholesome a classic tone tube balances out.
Don't want to give you work. But do you have a list somewhere on all the types etc you have tested. I have a local supplier that has some RCA pairs. And some other brands he does not list. I'd like to ask if he has certain brands.