Paramount 220v version

[Demsy]

I just re-read my older post regarding the 220v Paramount. I asked if there were any steps needed to anticipate the fact that the supplied transformer is 120-240v, while our line voltage here in Indonesia is 220v.

I got this reply from PJ:

"You are probably OK without any changes. The only thing I'd check on is the filament voltage.
When I tested the prototype (I just looked up my notes) I found 5.29 volts DC at 120v/240v. So, proportionally, I'd expect 4.85 volts which is only 3% low - well with even the 5% recommendation, and certainly within the 10% maximum tolerance. A low filament voltage does not becom important until the tube is well worn, so there is plenty of time to make changes if there are any problems. I don't remember what wire is used, but using a larger wire diameter (e.g. 16 gauge) will give the maximum voltage to the actual tube terminals.
If the actual voltage in use is too low for comfort, there are Schottky diodes with a smaller voltage drop than the ones in the kit; a simple change will raise the voltage. But as I said, you have plenty of time - a couple years at least - before you would need to do anything."

And then I read the sticky by PB regarding the additional capacitor between A1 and A4 pins, in case that the filament voltage is low.

I haven't got the chance to check the filament voltage, yet, I run the Paramounts with 230v currently.

But in any case which of the 2 methods should I follow, if my filament voltage turned out to be too low. And are the current 220v transformer different that the ones from 2012, since PJ calculated that even with 220v the filament voltage would stay within 3% of 5.29v (for 300B), at that time.

 

[Paul Joppa]

The capacitor won't change the voltage, it will just reduce the hum (if any) from the filament supply.

It's always a good idea to first check the actual line power voltage, which can vary +/-10% from the nominal value. In some places it is very stable; in others it can vary with the time of day and/or the season - all depending on the electrical system's loads.

 

[Demsy]

Will a low filament voltage cause hum? To my understanding reading the sticky, it is as if the capacitor is a cure for a too low voltage.

 

[Demsy]

I just measured the line voltage, it's 230V and the voltage between the pins A1 & A4 which is indeed very low, 4.45v and 4.49v on the amps.

Please advice the steps needed to bring the filament voltages up, while the line voltage stays at 230v as that is the highest that can be used for the other equipments. PJ, you mentioned using other Schottky diodes with lower voltage drop. Could you help me with the type of those diodes and the necessary steps that I should follow? Or would following PB's advice be sufficient? I lean more towards bringing the voltage up, though.

Thanks in advance

 

[Paul Joppa]

Sorry, I had not read the sticky before. I see some problems with it, so I'll have to consult with PB before we have a solid recommendation. There are several other things that can be done, and once this is resolved we'll put it in the sticky.

 

[Demsy]

Thanks PJ, looking forward to the recommendations

 

[Demsy]

Brought the manual slide regulator from my work, set the output voltage to 240v. Connected the Paramounts and took the voltage between the pins A1 & A4, it's 4.75V and 4.78V. So I would need a line voltage of 250v or even more to have the filament voltage at 5V. What could have been wrong, the transformer?

 

[Paul Joppa]

Your measurement marches what we measured yesterday. There is no fault with either the 120v or the 240v transformers - I was worried there might be so we checked carefully. 4.75v is 5% low, which is well within the normal 10% acceptable variation (though EML for example specifies 3% - not possible without regulation). I have not been able to find an explanation for why the original prototype from 2006 measured 5.27v (we have determined that the power transformer did not change).

We're still working the problem, but meanwhile here is some discussion of how we arrived at this situation and what we are doing about it:

First off, here is the wikipedia article, for further information on this difficult subject:  http://en.wikipedia.org/wiki/Mains_electricity

As you can see from the article, the emerging widespread 230v standard does not mean that anyone actually has 230v power - most systems are either nominally 220v or 240v, and the approved deviations from nominal have been adjusted to allow the old systems to remain in use.

In the US, over the last couple decades that Bottlehead has been in business, we have mostly heard from customers that their electric power was 120v to 128v, with only a few exceptions. Nevertheless, we design for 120v, which is the standard. When we began to offer the higher voltage, we were mostly expecting english-speaking customers from Europe, so we chose the 240v standard as used in England rather than the 220v. We expected voltages to be mostly higher than the nominal, as is the case in the USA. Voltages that are too high cause much more damage than voltages that are too low.

More recently we have had customers (mostly outside Europe) who have 220v legacy power systems, and have voltages that drop below the nominal 220 as often as they rise above it. This results in a filament voltage that is indeed low enough to worry about. Yesterday we tested some possible solutions that can be fitted to an already-built Paramount, but I want a little more data before making specific recommendations.

In addition, we are gradually changing our designs in various ways to deal with this issue, without imposing higher costs on everyone.

 

[Demsy]

Paul, thanks for your reply. I'm wondering whether you could give me a list of the measurement of the 120V transformer pins, this way I can easily compare it with my 240v transformer under real 240V line voltage. I understand that 4.75V is still within the tolerance but but please understand that I'm looking for the ideal 5V filament voltage.

 

[2wo]

You could use a Vairac (adjustable autoformer) to fine tune the incoming line. They go to about 110-120% of input.

Or there is a way to use a low voltage, filament type transformer as a buck-boost, I,m sure I have it in my notes somewhere ;D. Maybe someone has a link...John

 

[Paul Joppa]

Paul, thanks for your reply. I'm wondering whether you could give me a list of the measurement of the 120V transformer pins, this way I can easily compare it with my 240v transformer under real 240V line voltage. I understand that 4.75V is still within the tolerance but but please understand that I'm looking for the ideal 5V filament voltage.

We have done the measurement you describe and the secondary voltages are identical with 120v into the 120v transformer and with 240v into the 240v transformer. The winding resistances are also identical.

Our measurements are not complete yet - we just did enough to know that there is no special problem with the 240v transformer, and to know that the capacitor will work for 2A3s but not for 300Bs. I have a couple other approaches in mind, but I need to test them so I know exactly what to recommend. Unfortunately PSUD does not have good enough models for the diodes we are using, so testing is the only way to get accurate results. I believe I will be able to get you very very close to 5.00v for a range of supply voltages below 250v.

 

[Demsy]

Thanks PJ. It would be real nice if the input voltage could be kept at 230V, that way I don't need the slide regulator. I already have 3 voltages at present, 120V for the Dungeness, 230V for my pre-amps, turntable, CD etc. and at the moment 240V for the Paramounts 8).

Also thank you for your suggestions, 2wo

 

[Grainger49]

I'm going to suggest a cleaner and more expensive answer.  Get a PS Audio Power Plant, of any generation.  It can control the output voltage and frequency.

 

[Paul Birkeland]

I'm going to suggest a cleaner and more expensive answer.  Get a PS Audio Power Plant, of any generation.  It can control the output voltage and frequency.

This isn't really a "clean" approach.  If one wanted to resell their amps later, what are you supposed to tell prospective buyers?

How dirty is your actual power?  How clean is the actual output from the PS audio?

 

[Grainger49]

I've been using a P300 for 3 or 4 years.  Here is the thread describing the results:  http://bottlehead.com/smf/index.php/topic,1372.msg9575.html#msg9575

I don't buy Bottlehead equipment for its resale value down the road.  Getting the kit price back seems to be a good deal.  I buy it for its value and sound.

I'm afraid I haven't understood your point.  My point was voltage (and frequency) can be adjusted on a Power Plant.  The OP could raise the output voltage for his Paramounts.

 

[Demsy]

Grainger, our line voltage here is 220v daytime and could go down to 200v at night. For this I already use a 5kVA automatic voltage regulator, which is now set at 220V. I also connected a manual slide regulator, set at 240V, to it. Of course I can bring the voltage up to 250V, but the point is to find out first why the filament voltage is still below the specified 5V even at 240V. I really don't have the desire to keep the chain of regulators in my music room.

 

[Grainger49]

Ok, I had not read that you had brought your input to the Paramounts to 240V and still not brought the heaters to spec.  Sorry!

I'd say Paul Joppa will come up with the answer.

 

[Demsy]

PJ, if the line voltage were set 250V, would there be any negative consequences for the transformator and it's other outputs?

 

[Paul Joppa]

>>> "PJ, if the line voltage were set 250V, would there be any negative consequences for the transformator and it's other outputs? "

No, none.

I have developed a preliminary set of recommendations to give the 5.00 volts with line power of 220, 230, 240, and 250v, and interpolation will allow intermediate voltages to be accommodated. I am not yet ready to post them.

 

[Demsy]

Thanks PJ. Good to know that the recommendations are on it's way!