Using a Variac to power amp your CJ amp

[MLAS]

A question about powering up a tube amplifier which has no provision at all to slowstart.
I have an old Premier One b amp with no slowstart provision.
As I flip the switch my UPS on my PC installation (not my audio rig) goes in batterymode so much juice from the AC uses this amp that the standard European 230 Volts sags a lot.
I have two Thresholds S/500's too (on the Watkins woofers on my Infinity's) that behave just the same.
I think it is a good practice now to power up my amps with a 23 Amp Philips Variac a kind of manual slowstart.
At about a 100 Volts (almost have way to the 220 Volts I prefer) I pause for the filaments of the tubes to heat up.

Any other thoughts on this matter?

[AnotherJohnson]

None of the tube amps I’ve had have had a slow start feature, though all have benefitted from a 15+ minute warmup.

I have a big variac left over from some non audio experiments from many years ago, but would not have thought to use it in the audio system. How clean is a variac’s power?

If you like it, it would seem harmless. Maybe it would extend tube life …

If it came down to tube life or sound, I would put sound first. If it sounds the same with the variac, then let us know if you get 5 years out of power tubes instead of 3.

[admin]

If it was designed to start without a "slow start"/warm up, then I don't see why it would be a problem. I would be cautious with supplying the incorrect designed voltage into the unit. Although I doubt "under-volting" the unit would do harm, I'm not sure how it would be of benefit either as tube warming should happen regardless, just faster with full power. Interested to hear what other people think.

As for why the voltage is dropping a lot is another issue. There can be a short transient drop when the unit powers on due to a large trainset current pull, but this should last only a fraction of a second. If the entire system is below recommended voltages after this initial transient drop then I think the actual house wiring needs to be looked at.

I would make sure that the system startup and shutdown direction is correct,.. ie, start with source, and then move along the chain towards the speakers for startup and backwards for shutdown.

[MLAS]

Thanks for your swift answers admin & AnotherJohnson.
Much appreciated.

The dropping of the AC Voltage is normal when already two amps are on and then I switch on the CJ PREM One. I had the same problem with my EVO 2000 when the big open relais switched on and my AC Circuitbreakers switch of.
Now I have old AC fuses and do not have this annoying behavior anymore only my very sensitive UPS thinks there is a brownout when the huge PREM ONE switches on.
My reasoning is that the softstart will prolong the life of the tubes and electrolytics because it stresses the amps a lot less and I can limit the AC to 220 Volts which this old equipment is designed for.
In the US you went from 117V to 120 VAC I believe. We're started at 220 Volts and are nowadays 235 VAC that's relatively speak-en a greater increase than the 3 Volts in the US.
I do not hear any difference with Variac in place. This Philips is very silent and the PREM one makes (also without the Variac) more noise...

[AnotherJohnson]

The voltage regulator circuit should mitigate a lot of these issues.

It is fairly common in the US for audiophiles to buy elaborate power line conditioners to deal with variations that they believe they can hear.

Is that common in your neck of the woods too?

It has not been an issue for me, but I know others are sensitive to it.

[admin]

MLAS,
I'm a little concerned about what you describe. All things being equal, fuses typically blow faster than breakers trip. Are you sure you are not overloading the circuit that you have your equipment on? Did you replace the breaker with an equally rated fuse? Any chance that breaker was a GFCI breaker, those can be finnicky and often trip.

The breaker tripping is telling me that the circuit is being overloaded. That is a safety concern and should be investigated. Some older homes just don't have the wiring to support high current loads or it just might be too much for it to handle. Do you know how much power the system is drawing when it's on? I have one of those cheap killawatt meters and they are helpful in determining how close I am to the tolerances of power draw.

[MLAS]

MLAS,
I'm a little concerned about what you describe. All things being equal, fuses typically blow faster than breakers trip. Are you sure you are not overloading the circuit that you have your equipment on? Did you replace the breaker with an equally rated fuse? Any chance that breaker was a GFCI breaker, those can be finnicky and often trip.

The breaker tripping is telling me that the circuit is being overloaded. That is a safety concern and should be investigated. Some older homes just don't have the wiring to support high current loads or it just might be too much for it to handle. Do you know how much power the system is drawing when it's on? I have one of those cheap killawatt meters and they are helpful in determining how close I am to the tolerances of power draw.

I have a Kill a Watt type of energymeter and my system draws 750 Watts when idling that's on a 230 VAC line no more then 3.1 amps.
Our vacuumcleaner, washingmachine etc draw much more when in service.
It's the initial current draw of the CJ's that makes the GFCI breakers trip (you can buy another GFCI breaker with another characteristic) or the UPS sensing device inside concluding that we have a brownout.
I've had a pair of Krell KRS-100 's Class A amplifiers that draw 750 Watts per chassis when minding their own business, when idling.
This 1.5 kW did not trip any device because it took them 7 seconds to let the relays kick in that connected the outputdevices with the PSU.

Softstart, protecting the tubes and capacitors and 220 Volts max is my goal to achieve with this old equipment.

[MLAS]

The voltage regulator circuit should mitigate a lot of these issues.

It is fairly common in the US for audiophiles to buy elaborate power line conditioners to deal with variations that they believe they can hear.

Is that common in your neck of the woods too?

It has not been an issue for me, but I know others are sensitive to it.

To my knowledge power-line conditioners only remove VAC anomalies(I've got four of them, one big one for the amps, two German smaller ones for the pre-amp and DAC) and another one for the CD Transport. They should clean the power but I never noticed real improvements. The 5A small fuse in the my KEMP amplifier filter once blew when I forgot to turn down the volume on the pre and I lowered the needle on my turntable with my CJ EVO 2000 amp on.
That's it.
I just bought a PowerStat Variac Type 1256DU, with a max rating of 30 Amps (Superior Electric Made in the USA), with input 240VAC & 0 - 280VAC output.
It was NOS unit so pristine and in a the original box with the original papers like the manual, registration card and a on 1:1 scale cutout-paper for making the top and bottomplates of this bare unit.
Contacted Superior Electric for the enclosure on the side (7 small vented panels I counted that those can be attached via pre-drilled holes and screwwindings inside them) and a case around the AC in- and out connectors terminals and 30A Limitron fuse (plate made out of mica or Bakelite it seems) with one hole for the input AC cable and a bigger hole the output AC connector. The 30 Amp Limitron fuse (Bussman or Eaton probably nowadays) will be replaced by a lower rating when possible. A little fun project so I can power up my whole household with this unit I reckon

[roberto]

Hola,

What you are seen when turning the Premier on, is the power supply capacitors acting. There is no need to use a Variac. Also, the Variac is a tool for service, not an all time to power the amp. There is no harm charging the caps, and also the noise is harmless to the speakers. If you are generating a heavy transient to the speakers perhaps it is coming from other component, not the amps.

Because the tubes are off when you turn the amp on, there is not transient. The first thing to turn on and wait 30 seconds before you turn the Premier on. This way it is impossible to generate a transient to your speakers.

Remember, the last thing to turn on in yours system are the amplifiers. The first thing to turn off are your amps and wait 30 seconds before you turn off the rest.

Happy listening!

[MLAS]

Hola,

What you are seen when turning the Premier on, is the power supply capacitors acting. There is no need to use a Variac. Also, the Variac is a tool for service, not an all time to power the amp.

I know, it's for technicians to power up old equipment when they are uncertain about the condition of the various parts inside especially the electrolytic capacitors in conjunction with a dimming bulb and ammometer of course.
I have such a device from the GDR: Stelltrafo LS010 very handy.

There is no harm charging the caps, and also the noise is harmless to the speakers. If you are generating a heavy transient to the speakers perhaps it is coming from other component, not the amps.

I never turn off the upstream devices in my audio setup only when I go on vacation. I only switch of my amplifiers because of the power intake when idling @ 750 Watts. I do not agree with your assessment regarding the brute force on/off cycling of my three amplifiers. It's stressful and by powering it in a very controlled matter prolongs the life of the units. Friend of mine has 8 Mark Levinson ML-2 Class A amplifiers in his Levinson HQD system (Decca high units, two Quad ESL55's and two Hartley woofers. They consume an insane 3,2 Kw when idling and he switches them on with two big Variacs for 30 years now and never serviced the units other then some silver Sprague axials I believe that went sour.

Because the tubes are off when you turn the amp on, there is not transient. The first thing to turn on and wait 30 seconds before you turn the Premier on. This way it is impossible to generate a transient to your speakers.

There's definitely a transient in my AC grid and I wish CJ had also a delay built in (like a bit in the EVO 2000) for first properly heat the filaments of all tubes and the the B supply. I did not speak about any transients noises in my Infinity's regarding the Premier One b (which is a NOS device which I bought three years ago with the original crate so pretty new), but my Threshold S/500's do generate an unpleasant 'thumb' in my speakers when turned on with the Rockerswitch in front. Now there is total silence when I turn the dial of the Variac.

Remember, the last thing to turn on in yours system are the amplifiers. The first thing to turn off are your amps and wait 30 seconds before you turn off the rest.

See above.

Happy listening!

Thanks you too and thank you for your elaborate responds, well appreciated.

[roberto]

Definitively the transients are generated by the power supplies of the amps. You can build a power relay with a delay timer for each power amp.

With much respect, turn off the SS power amps and turn on the CJ. With all your components on the power the CJ and report.

[roberto]

I forgot to mention that I use my variac on todays electronics, not only on old, to track the bad component.

Happy listening!

[roberto]

B008F3CA-E6AF-4EBC-B6A2-71624815642B.jpeg (230.35 KiB) Viewed 1046 times

SS stages are the one that produce the transients.

[MLAS]

That's the one I have (EVO 2000) and the Premier One b from CJ.
Like the Threshold S/500's they are the "offenders"

[roberto]

Mlas,

As you can guess, the SS power supply of the SS (Solid State) are big capacitance caps, typically 10KuF to 15KuF each. Charging them makes that odd, horrible noise, and might put to walk your woofers.

You could disconnect from the binding post each power amp, one speaker cable from each power amp, power on, wait 5 seconds and reconnect the speaker cables to the amp. This was, your will not have that transient to the woofers. The SS power amps do not drain any current when are disconnected. the open circuit (one cable disconnected) do this on SS. You can't do this on tube amps, the output transformers are always loading the output tubes, and could get damage if a speaker is not connected.

Happy listening!

[Big Dog RJ]

Sounds very confusing...

I would just stick to basics, as AJ and Robbo have mentioned. Another very important point raised by Admin; the CB's are tripping for a reason... that's basically overload.

Yes, your washing machine, vacuum cleaner and typical household appliances take up more AC draw but it's that initial current draw that's causing the problem.
As recommended by Admin, I would look at the wiring in the house and wire a dedicated line solely for the system and nothing else. Not shared with any other household appliances or on shared circuits / CB's.

Do up a good AWG for that AC line, 10A to 15A is more than adequate for domestic audio. Have that dedicated line on dedicated CB's, turn the equipment on in proper sequence and especially last when turning on power amplifiers, wait approx 30 - 40secs before powering up the next. Same as when shutting down, just one at a time with 30secs intervals.

This allows for initial AC draw to go smoothly without interruptions and slowly discharging when powering down. You really don't want to rush things. No point in talking about other people's systems, they're wiring and gear are quite different. Just focus on yours.

If you've already done everything possible and have allocated dedicated wiring for the system and things / CB's are still tripping off then I don't know what's going on. That's probably a JF question or someone who knows specific areas between operating Variacs with CJ power amps.

Hope you sort it out soon, and all is well.
Best, RJ

[AnotherJohnson]

Soft start has not historically been necessary … so the idea that the circuit is challenged by this particular unit makes sense to me.

Maybe traditional variac usage for troubleshooting would be in order. The caps in many high end SS amps are bigger than soup cans. CJ’s amp caps are generally not. The initial draw on turn on of a CJ tube amp should not/ does not need soft start.

I don’t even hear a thump when I turn on my LP275Ms. I have to look at the lights. I think something is shorted within your unit.

[Big Dog RJ]

Yes, that's correct AJ. Infact another make, ARC doesn't use soft-start either. However, I remember on those huge Manley Labs reference amplifiers, they did introduce the soft-start circuits plus an additional circuit referred to as Ever-warm. This involved the tubes idling at a slight warm temp, giving it a lower current so as not to go cold. Then when play resumes, the heaters kick in with full current and ever-warm shuts off giving the tubes full power.
The only thing with this is, I noticed all this extra circuitry didn't make the amplifiers as pure or as transparent as CJ's.

CJ as we all know is pretty simple, well laid out circuits easy to follow and simple. High quality parts, shortest signal paths and clean pure sound, there's really nothing more required. No bells, no whistles!

Hope all goes well with MLas, and he manages to find the right solution.
Cheers, RJ

[AnotherJohnson]

I really think he may have some failing caps, or a burned out resistor. There’s no way to know without some bench evaluation. The variac may be masking a problem.

Let’s face it. That amp is quite long in the tooth.

[roberto]

My personal believe is that the variac is charging the caps slowly and this is the reason why he is not getting the transient, But operating the amplifiers with a variac is NO NO NO!. Those amps are hight power and produce this transient to the woofers. This is normal, but odd noise.

The transient would be always on these amps unless he builds a timer with a relay. Or disconnect one speaker cable oF each channel before turning it on, the power on the amp, wait 10 seconds and reconnect the cables. No transient will be heard.

Happy listening!