Add rectifier tube to yaqin mc10l? What size is best?

[bichela]

I am not sure if this should go in power supplies or not. It is a power supply question for a Chinese valve amp.

I am considering this Amp or the Yaqin Ms5881a. From studying the schematic of the Mc10l it appears to use two solid state bridge rectifiers on the B+ supply. The diagram I show does not show a B+ delay relay in the circuit. I was considering buying one of these and replace the bridges with full wave diode rectifier tubes. I am uncertain of the best tube for this application. I want to harden this beast to protect from being damaged by a EMP (ElectroMagnetic Pulse) caused by a Solar Corona Mass Ejection (CME). A Rectifier tube would also protect the 6N1s and the EL34 tubes from getting hurt from a full B+ prior to proper filament warm up. I also am considering installing a DPST switch that would allow me to manually cut in the B+ after the filimanents are at working tempratures.

If anyone has done this already. do you have a working schematic diagram of your design?

Personally I am leaning towards the Ms-5881a as I have a tiny apartment and my JBL speakers work fine wi a sounddesign solid state 8Track reciveri at 24 watts. (8 track unit needs work, I just use it as the power amp to my Optimus SSM-1250 4 channel mixer. I tried an old Voice of Music monoblock/speaker amp and plugged one of my studio series JBLs into this amp. Cranked up to its max the speaker was okay but not too loud. it sounded like it was starving. The old amp in this case was a single ended Class A rated at 12 watts maximum output. The boxes built in speaker (two way) appears to be rated for 4 watts at 8 ohms, these crank something fierce. My JBLs are also 8 ohms, therefore impediance isn't the issue.

what the above test did was confirm that 12 watts, single ended, is too wimpy and I can bet 52 watts would give me an eviction notice from my landlord I am partially deaf already, when it comes to determining how LOUD things are.. it is better to stick with the middle ground. I need to preserve the hearing I stil have.

[Globulator]

Originally Posted by bichela

I am not sure if this should go in power supplies or not. It is a power supply question for a Chinese valve amp.

I am considering this Amp or the Yaqin Ms5881a. From studying the schematic of the Mc10l it appears to use two solid state bridge rectifiers on the B+ supply. The diagram I show does not show a B+ delay relay in the circuit. I was considering buying one of these and replace the bridges with full wave diode rectifier tubes. I am uncertain of the best tube for this application. I want to harden this beast to protect from being damaged by a EMP (ElectroMagnetic Pulse) caused by a Solar Corona Mass Ejection (CME). A Rectifier tube would also protect the 6N1s and the EL34 tubes from getting hurt from a full B+ prior to proper filament warm up. I also am considering installing a DPST switch that would allow me to manually cut in the B+ after the filimanents are at working tempratures.

If anyone has done this already.

No one has ever done this, the Yaqin has no issue with switch-on except occasionally blowing the 1A fuse it's fitted with.

I'm guessing the EMP and CME questions are a joke, but seriously there is no space and no need to use a tube rectifier.

[Miles Prower]

Originally Posted by bichela

The diagram I show does not show a B+ delay relay in the circuit. I was considering buying one of these and replace the bridges with full wave diode rectifier tubes.

If you intend to do that, you'll have to replace the entire power supply. Hollow state diodes have way higher forward voltages than any Si diode (tens (many) of volts as opposed to 0.7V). Use the same power xfmr, and you'll be way too low on Vdc.

You also will probably have to replace the ripple filter capacitors as well since Si diodes can source more current (even a small Si diode can source 5 -- 10A of Isurge, whereas even something as beefy as a 5U4GB can source just 1.0A per plate) and can use bigger reservoir capacitors.

If you are really that intent on glowy bottle kewelness, find another amp that already uses hollow state diodes (or add a 5U4GB or something like that, and a filament xfmr, and pretend).

[bichela]

Originally Posted by Globulator

No one has ever done this, the Yaqin has no issue with switch-on except occasionally blowing the 1A fuse it's fitted with.

I'm guessing the EMP and CME questions are a joke, but seriously there is no space and no need to use a tube rectifier.

No, I was serious. Looking at the few pics of the undersides of either the Mc5881a or the MC10l. you are right about the space limitations.

1A mains fuse? that would mean that at 120VAC. it draws 120Watts! Perhaps that is fine once it hits steady state. Most of the tube gear I have had over the years use a Slow-blow fuse.

[Globulator]

Originally Posted by bichela

No, I was serious. Looking at the few pics of the undersides of either the Mc5881a or the MC10l. you are right about the space limitations.

1A mains fuse? that would mean that at 120VAC. it draws 120Watts! Perhaps that is fine once it hits steady state. Most of the tube gear I have had over the years use a Slow-blow fuse.

You were serious? Then you can stop worrying, an EMP of the magnitude to blow silicon diodes inside your amp will render your car, computer, electricity supply, phone lines, banks etc broken so the amp will be low on your priority list, especially as the fix will be a new 2$ silicon diode for it.

Contrast that with the last CME that affected the earth - it needed long wires to build up any voltage/current - telegraph lines, hardly going to affect your hi-fi amp internals.

Also silicon diodes are tough - even a 1N4007 can take a 25A pulse.
Additionally a fast B+ turn on (ahead of filament heating) does not usually do any harm at all, unless the coupling capacitors are not rated high enough voltage. Cathode stripping is a myth!

If you really want a chinese amp with tube rectifiers there are some on the market, like the Bewitch series for instance - look for Bewitch 6550 etc.