[boycephoto]

Thanks for you post Ron. 

[boycephoto]

I have noticed the same thing Wayner describes, when with the line voltage chagnes it directly changes the bias voltage on my Ultimate 70.  So, should we have a voltage stablizer on our audio equipment? 

I have photographic darkroom (I don't use it any more) that includes a voltage stablizer between the wall AC and the enlarger.  It keeps the light output consistant while exposing photo paper to give consistant exposure and color quality from print to print.  Hum, I wonder what the output capacity of that stablizer is? Probably not enough for an Ultimate 70.  It might induce noise?  I will look into that. 

Dave

[Wayner]

It would be nice to have a variac.

Wayner

[Wayner]

Today I went to Radio Shack and bought a Kill-A-Watt module that can, among other things, read out AC ine voltage. We are running 117.3 volts right now. This is a way cool tool!

 

Wayner

[Wayner]

Yesterday was a very interesting day of study. I found that the voltage went from 116.3v up to 122.2 volts in about a 12 hour period. It was a very hot and humid day here in Minnesota, and at the "beer thirty" listening time, the voltage was was bouncing between 116 and 117 volts. The ASTM standard is 120V +/- 2.5 volts which makes the window 117.5 to 122.5 volts. I don't think we were heading towards a brown out, but we were seeing lots of demand, probably from air conditioning units all across the midwest states.

What does all of this mean? Well, if you decide to set your bias on a day like yesterday, it's going to be a bad biasing job. If the voltage is around 117 and you set the bias at 1.56, when the voltage is closer to it's normal reading, the bias will be about 1.64 or higher. At 122 volts, I estimate that the bias voltage might hover around 1.70. I'm sure Frank must know the math, but you can see my point about correct bias procedures.

I do recommend buying this Kill-A-Watt device, it's only $30 and has a whole range of neat functions on it, like total power consumption, true power and even cycles per second. Not that this values are way out there, the extremes could be hard on the tube. The real story is that you should set your bias to 1.56 for the average voltage you experience during your usual time of listening. And that requires a little study.

Wayner 

[Wayner]

I had a nice talk with Frank today about several topics and this one came up, related to the Ultravalve/U70/I70 and really any tube driven products. It's probably a nice idea to give the tube pins and sockets a nice shot of Deoxit-5 every once in a while. It's just a good preventive maintenance idea that perhaps we have forgot about, until something weird happens.

As I have learned from experience, much of any problem arises from contact degradation. Deoxit-5 solves lots of these problems. I've seen other folks recommend gel type conditioners and stuff like that...leave that for your hair. Deoxit-5 is also great for RCA interconnects and pots.

Wayner 

[NagysAudio]

OP - All Chinese and Russian rectifier tubes are trash, all of them. Unless you can find a JAN designated NOS tube, I would stay away from tubes in general. Just take the blown-up tube out and stick some diodes into the tube socket, being VERY careful in observing their orientation. It will be more reliable and sound better than any Chinese/Russian tube.

[NagysAudio]

I didn't read the whole thread, looks like AVA HiFi has already suggested the diode trick. What I'm puzzled by, is why use the tube at all at that point? I would personally just leave the diodes and get rid of the tube all together.

[NagysAudio]

Wow, I just read Wayners posts... Voltage varying from 116VAC to 122VAC makes virtually zero difference. Bias varying from 1.56 to 1.70 also makes virtually zero difference. Geez!

[Brett Buck]

I didn't read the whole thread, looks like AVA HiFi has already suggested the diode trick. What I'm puzzled by, is why use the tube at all at that point? I would personally just leave the diodes and get rid of the tube all together.

  To avoid the huge voltage spike when the rectifier comes in at full blast when all the tubes are still cold.

     Brett

[avahifi]

Nagys, your advice to just replace a rectifier tube with a diode pair is not good.

If you do that, four very bad things happen to the circuit afterwards, if it was designed for a rectifier tube.

First, the slow turn-on will be defeated and the output tubes and capacitors will be fed full bore B+ voltage before they have warmed up.  This will shorten output tube life.

Second, there will be a substantial B+ voltage overshoot before the output tubes warm up and conduct, this can exceed the voltage rating of the tubes and the power supply capacitors.

Third, the sustained B+ voltage will go high because the built in voltage drop of the rectifier tube is removed.  This will overbias the tubes, and likely overvoltage them too, along with power supply capacitors and other components too.

Finally, the diode set has no where near the transient line spike immunity and will short on line over-voltages that the tube rectifier can handle.  This can lead to shorted power transformers and worse.

Bad, bad, bad idea, unless the amp in question was designed specifically for a solid state power supply in the first place.

By the way, doing this will void the warranty on our tube amps, and possibly simply just void the amplifier completely. 

Best regards,

Frank Van Alstine

[NagysAudio]

I suppose... It's just that these 4 scenarios might be a little bit exaggerated. I've made quite a few simple tube power amplifiers where the power supply was the simplest possible design: power transformer, bridged rectifier, and a capacitor/resistor filter. never had any problems with any sort of failure.

[avahifi]

Nagys, I suspect you have never made a tube amp that just got a rave review in The Absolute Sound.  I have been doing this for over forty years now and kind of know what I am talking about. 

Please keep your bad advice to other circles and out of the AVA circle please.

Frank Van Alstine

[jtwrace]

Nagys, I suspect you have never made a tube amp that just got a rave review in The Absolute Sound.  I have been doing this for over forty years now and kind of know what I am talking about. 

Please keep your bad advice to other circles and out of the AVA circle please.

Frank Van Alstine

Tru 'dat

[NagysAudio]

Frank - I wasn't putting down your products, I personally think they're great and you're one of the few sane people on AC.

Does anyone know the age of jtwrace? I'm very curious...

[Bill]

Nagys, I suspect you have never made a tube amp that just got a rave review in The Absolute Sound.  I have been doing this for over forty years now and kind of know what I am talking about. 

Please keep your bad advice to other circles and out of the AVA circle please.

Frank Van Alstine

   Absolute Sound? Does anyone actually still read this magazine, let alone believe what it says? I thought these subjective entertainment type magazines would be the antithesis of what Frank believed. I've said it a million times before: if a publication likes your product, it's a good magazine; if it doesn't, it doesn't know what it's talking about. Human nature all the time. The esteemed Audio Critic once did a hatchet job of one of Frank's DAC's years ago. Do you think AVA likes this magazine? Didn't think so.

[Tom Alverson]

Frank - I wasn't putting down your products, I personally think they're great and you're one of the few sane people on AC.

Does anyone know the age of jtwrace? I'm very curious...

Nagys- careful - your question about jwtrace's age could be interpreted as a slam.  If you really want to know, send him a PM.

The purpose of the added diodes in series with the tubes is to increase their reliability by protecting them from the full reverse voltage.  Apparently this has been proven to be effective in practice.  If you can find NOS tubes they may not need this extra help, but the silicon diode (when used in conjunction with the tube rectifier) don't hurt anything and can only help.

Tom

[charmerci]

Please keep your bad advice to other circles and out of the AVA circle please.

Frank Van Alstine

I personally know of a couple of people on AC that have discounted Frank's products (I'm sure there have been more, too if I've PMed two of them.) because of the hypersensitive nature of the regulars here on his board.

Here's one quote - "Charlie,  You are right, I maybe a little too harsh for saying so.  Though if you think about it with the kind of experience one has had, it really hard to have any kind of interest of learning/trying about their gear,etc.... Hope that makes sense. Thanks."

Just FYI.

[Brett Buck]

Yesterday was a very interesting day of study. I found that the voltage went from 116.3v up to 122.2 volts in about a 12 hour period. It was a very hot and humid day here in Minnesota, and at the "beer thirty" listening time, the voltage was was bouncing between 116 and 117 volts. The ASTM standard is 120V +/- 2.5 volts which makes the window 117.5 to 122.5 volts. I don't think we were heading towards a brown out, but we were seeing lots of demand, probably from air conditioning units all across the midwest states.

  I have checked my voltages over time, and yours are a lot more stable than mine. I got as high as about 121 and a low around 108. Over the period of minutes it will go from 112-119, back and forth all day long.

     Brett

[adydula]

Frank,

Will the diodes be going in new Ultravalves from this point on?
or
Is this an optional thing for those that want that extra longevity and protection?

I have the 1N4007 diodes on the way!! ah the smell of flux burning early in the morning!!

All the best
Alex

PS: The new Ultravalve has made me SMILE a lot!