• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Tube rectifier versus 1200v SIC diodes?

Jump to Latest
#83
kodabmx said:
There's a minimum order of 100$ for free shipping here, otherwise it's 8$... I guess they aren't as nice to the UK?
Click to expand...
Actually, you can get free shipping to Canadian addresses from Digi-Key if you order from their US warehouse, which is just across the border in Minnesota. No minimum order and no handling charge.

Here's the same part listed on their US site.

https://www.digikey.com/en/products...69?s=N4IgTCBcDaIOIGEAMYCyAFAygRjAWjDCRAF0BfIA
The details are somewhat hidden on their website, not mentioned under the link to Shipping Rates / Options at the bottom of the page. You have to look under Terms and Conditions.

Here's a thread with the details:

http://www.audiokarma.org/forums/in...hipping-on-parts-orders.739513/#post-10018562
 
#84
Digikey.com redirects to digikey.ca.

Digikey.ca states when using CAD:
"Free delivery to Canada on orders of $100 CAD or more. A delivery charge of $8 CAD will be billed on all orders less than $100 CAD."
When using USD:
"Free delivery to Canada on orders of $100 USD or more. A delivery charge of $20 USD will be billed on all orders less than $100 USD."

I have no desire to "mail in" my order to save 8$ but waste a week. I haven't had cheques for like 10 years.
Cool tip though...
 
#85
andyjevans said:
I've always used tube rectifiers, and am particularly fond of mesh plate AZ1 and AZ11. I've also used hybrid bridges with UF4007 diodes in the negative supply. Preamp HTs are up to around 50mA at 250v. Amps up to 200mA at 300-350v. The first capacitor won't be more than 47uF polypropylene, more like 10uF or less. Supply would be CLCRC. Second cap would be 47uF or 100uF polypropylene.

I'd like to try SIC Schottky diodes in a full wave bridge and I'm looking at something good sounding and above all safe - don't want any explosions. So what's safe for a preamp and amp as above? I've been looking at these:

C4D02120A | Wolfspeed 1200V 10A, SiC Schottky Diode, 2-Pin TO-220 C4D02120A | RS Components Wolfspeed Schottky 1200v, 10A £7.14 5 pack +Vat

I do have a lot of these:
C3D02060F | Wolfspeed 600V 4A, SiC Schottky Diode, 2-Pin TO-220 C3D02060F | RS Components
Wolfspeed Schottky 600v, 4A £8.90 10 pack +Vat

Could these be used as is for a preamp as above, or should I double them up, and if so what resistors and capacitors to use? Is 4A enough for an amp of 200mA?

Basically I want to find out everything possible about using these SIC diodes. I also want to know what sound quality I might expect, if anyone has directly compared tubes and these high voltage SICs.


.
Click to expand...

Andy,

I tried first the famous Valvo AZ1 mesh plate with two UF4007, later AZ1 with two Sic 600V 4A (same diodes as per your 2nd link), now I use 4 Sic 600V 4A without AZ1.

Sounds better with add advantage no heater power tx and no oversized in volts power tx.

Chees
Felipe
 
Last edited:
#88
merlin el mago said:
Andy, I tried first the famous Valvo AZ1 mesh plate with two UF4007, later AZ1 with two Sic 600V 4A (same diodes as per your 2nd link), now I use 4 Sic 600V 4A without AZ1. Sounds better with add advantage no heater power tx and no oversized in volts power tx. Cheers, Felipe
Click to expand...

Reading this I just made up a HT supply with 4 Sic 600V 4A. It works on the bench. I haven't tried it in a preamp yet. HT off load is 330v, so hopefully low enough not to stress the diodes.

It's CLCRC. 15uF > 8H > 68uF > 1K > 15uF. The 15uF are DC Link and the 68uF is Kemet 550v. I could add more capacitance.
 
#90
merlin el mago said:
Andy, I tried first the famous Valvo AZ1 mesh plate with two UF4007, later AZ1 with two Sic 600V 4A (same diodes as per your 2nd link), now I use 4 Sic 600V 4A without AZ1. Sounds better with add advantage no heater power tx and no oversized in volts power tx. Cheers, Felipe
Click to expand...

I've got the SIC diodes up and working to replace the UF4007 diodes. Sounds smoother to my ears and so in theory they're staying. Unfortunately after a few minutes of rather nice music they went up in smoke. So I need a higher voltage or double them up. Back to the drawing board, but at least I know to use SIC diodes now. From the few minutes I could hear, I don't know if they sound better than a AZ1 mesh. I'll order some 1200v parts and hopefully listen for longer next time.
 
#92
Andyjevans are you going to put back in UF4007's and test your ears and personal expectation bias again?

Do you often change parts without doing any technical assessment of whether 'smoke' is a likely outcome? It seems like you still have no technical grasp of whether the new parts will or won't be capable of performing nominally.

Perhaps an observation is that the latest diodes were operating abnormally when you were doing your listening test, and that using them in a normal manner (where they won't stress themselves in to extinction) could provide a different listening situation.
 
  • Like
Reactions: anchorman
#95
ISCMMS said:
What was the nature of the fault?
Click to expand...

Good question. Since I've only been using valve rectifiers and UF4007 I made an elementary mistake about the PIV of diodes. The secondary was 250V RMS, i.e. 354Vp (RMS x 1.414) and I had assumed this was covered by a 600V part, but I had overlooked that for a bridge into a capacitor the equation is 2x Vp or 707v. Plus a bit more like 10-15% for variations, so 800v. Hence the UF4007 working. I hope this calculation is correct since it comes from online tutorials - feel free to comment. So I'll rebuild it with a 1200V SIC diode bridge and/or 8 of the 600v diodes with equalising resistors. A good reminder to always check the calculations carefully.
 
#97
I think I now have the circuit working correctly - certainly hope so! GC02MPS12-220 1200V SIC diodes in place in a bridge.

Sound is promising. Clean and detailed. It doesn't seem to have an intrusive edge to it. First version at the moment - it could be revised further.

The circuit is a simple resistor load with resistor cathode bias and a Kemet DC Link bypass cap. This simplifies the power supply, so a useful alternative to a valve rectifier.
 
#98
These tests are probably of some interest:
https://www.diyaudio.com/community/...er-with-high-frequency-ac.379927/post-6863135To sum up, they show that vacuum diodes are almost completely free from dynamic artefacts, unlike semiconductor diodes. I didn't have SiC diodes available, but their behaviour is probably similar to Si schottky, just somewhat better.
Schottky's do not have stored charges, but they still have a significant capacitance, unlike vacuum tubes
 
#100
With 50Hz, matters will ease thanks to the lower dV/dt levels, but it doesn't mean you are allowed to be sloppy: keep all the wiring around the diodes minimal, minimize the loop areas of critical paths, use snubbers, etc.
And remember than even an ideal diode (like a vacuum one) has the potential to generate disturbances: the process of rectification itself creates discontinuities in the waveforms, and these discontinuities are the source of harmonics.
At a 50Hz repetition rate, the total energy content will be minuscule, but it may still cause annoyances, especially in a sensitive environment like a preamp.
Any semiconductor-related flaw, like trr, tfr or capacitance will come on top of that and make the matters worse.
Do your homework, don't leave anything to chance, and you will be OK. If a mistake is made early on, it will be difficult to fix later, when you discover its effect
 
You must log in or register to reply here.
Top Bottom