• 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.

Hammond vs. James?

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#41
rdf said:
I use the 1628Se and don't recommend it. My samples have severe issues in the 13 kHz range. For more info see:

Both the HV and filaments read high, the latter at 7 volts which I discovered late and after cooking a few EL84's. I might consider a 125se for benching, but I'll never build another serious amp with Hammond iron again.
Click to expand...

Not that I'm a Hammond fan, but don't you think that this might well be due to your house AC being higher than 115V? I measure mine at 124VAC and following the ratio, my Hammond transformer also runs at almost 7V. I might use a power resistor to bring it down, but my Sovtek 6SN7GT's seem to have taken it pretty well so far.


edit: sorry, someone should have read the rest of the thread 😀. beaten to the point.
 
#42
It never occured to me to check Hammond's primary rating. It's 115 VAC, which makes no sense here. My local utility, BC Hydro, specifies a nominal service voltage of 120 VAC with permissible CSA-regulated variance of 110-125 VAC. My outlets measure 120.3 VAC. Explains a good chunk of the variance (the filaments are still high.) Is the American standard generally 115 VAC?
 
#43
100 years ago we had 110 volts, 50 years ago we had 115 volts, now we have 120 volts (the "standard" voltage). I have measured as high as 124 volts. I am using power transformers made by Hammond (Allied Electronics). They are specified for "117 volts". The filament (and HV) voltages tend to run high, even when I overload the secondaries.
 
#44
Yea, just checked. I get 123VAC on a cool summer night here in Pa. In the winter I have seen 128V, on a hot day 113V.

In my part of the world the number of new generators on line in the last 15 years or so, Maybe 0.

Number of new "McMansions" in the last 15 years… Billions and billions

Have something to do with the problem: do you think?..
 
#46
A hot day here in the Midwest- 120V. Last winter- 124V consistently. Really hot days- maybe 117.

Almost makes one wish for a power conditioner. I remember Kofi picking one up at Best Buy or similar. Not a UPS as such, it wouldn't last two minutes in a power failure, but it evens out the fluctuations.
 
#47
Hi Sherman,
Not a UPS as such, it wouldn't last two minutes in a power failure, but it evens out the fluctuations.
Click to expand...
Yes, and they put out a rectangular "equivalent power" wave. Transformer powered equipment really does not like this.

Switching power supplies are looking a little more attractive after reading this thread.

-Chris
 
#48
I have seen some very large size UPS that it's inverter works continuously. It runs from the rectified DC supply from AC and from batteries when the aC is out. This is kind of true UPS.

However, the cost of such UPS is very expensive.

Johnny
 
#49
Hi Johnny,
Yes. I work with those. Someone in my office ordered and installed some 2 kW rectangular wave units. Burned them out on installation test, and the battery packs too! Of course I told them not to and they did anyway (yuck, yuck, yuck). 😀

The normal sine wave models are horrendously expensive, and heavy! Never mind the battery chassis'. Someone thought they could save some money.

The phone switch survived with tripped breakers. (ITT 3100, full tower)

-Chris
 
#53
poobah said:
Same deal... they flatten the sine. Spreads out the conduction angle but knocks down the supply voltage a bit.

Google "Ferroresonant"

🙂
Click to expand...

Hey poobah, are you sure that's true for all? For years we ran on a >10 kW Best Ferrups ferroresonant UPS and they claimed low harmonic content. Most claim to reduce line harmonics.

I don't like SOLAs because they run BBQ hot and in our applications and generate a lot of acoustic noise.
 
#54
No rdf, not sure if that applies to all. They rely on saturation of the core to limit voltage, hence the flattening of the wave... but if there were enough capacitance in the tank maybe that would improve? Or maybe post filtering?

I bet: MORE MONEY = BETTER WAVEFORM

And yes, they do run hot as hell; and they weigh more than I do!




🙂
 
#56
I have three 1500 volt 1/2 amp power supplies salvaged from old tube type transmitters. The power transformers are ferroresonant types. They weigh 75 pounds each. Yes they will warm up the room, especially with light loads. All of those are drawbacks, but the deal breaker for audio use is that BUZZZZZZZZ. Why would you chase all of the hum out of the audio path only to have the transformer make a racket.

When we used to do manufacturing, there was a room full of Solas to run the ATE systems. That whole room went BUZZZZZ for at least ten years. They powered Teradyne, LTX and Data General equipment with no problems. Most of this equipment used linear power supplies (1970's equipment), and ran OK on the solas, but they were in a seperate room to contain the noise.
 
#57
Those ITT 3100 phone systems used ferroresonant transformers as well. They hum like a, well I can't say but they are very loud. Hit those with a standard rectangular wave and watch what happens!

I don't think you need to regulate a tube amp that tightly. Get the voltage adjusted in range and don't worry about it.

-Chris
 
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