Tube biasing question

[AnotherJohnson]

That’s great!!

FWIW, the bias circuit isn’t in the signal path, but it controls what is in the signal path. It is essentially telling the power supply what and when. So it is not entirely irrelevant. It may be responsible for your improvements.

[Big Dog RJ]

Ah, I see... ok in that case, probably this is what's also contributing to the added quietness and transparency.

Previously, there were very minute hisses, farts, pops, clicks & ticks going on but mostly when my ear is pasted to the panels. Now, after this service plus all necessary adjustments done with actual measuring and monitoring equipment, these noises are gone!

I was also told that these amplifiers are pretty old, hence the very first LP series monoblocks that came out, along the same line as the LP66s, LP70s, 140m, 260m and so on...
So it seems, that after a while, typically over a decade or so, these intricate parts that contribute to bias circuits and voltage monitoring may require adjustments, that is if there are any problems. OTOH if there aren't any issues then just keep playing tunes. It's not only the caps and resistors and power supply components that may need replacing.

After all, this particular LP series amplifiers are labelled as CJ's Vintage gear, so might as well keep them in tip top condition for long as possible. Really happy and impressed with the overall improvement.

Cheers, RJ

[AnotherJohnson]

Previously, there were very minute hisses, farts, pops, clicks & ticks going on but mostly when my ear is pasted to the panels. Now, after this service plus all necessary adjustments done with actual measuring and monitoring equipment, these noises are gone!

Usually the type of noises you’re describing are from the small tubes in the first stage.

Even new ones can be noisy … this is the main reason to buy tubes that are burned in and screened for low noise.

I can’t tolerate an audible noise floor.

FWIW, ARC, CJ, and Upscale do the best job of supplying tubes that will delight someone who wants factory level neutrality and noise floor. Obviously CJ and Upscale for CJ. ARC and Upscale for ARC. If you’re tube rolling, there are lots of other grab bags to reach into … you might get lucky.

[AnotherJohnson]

I was also told that these amplifiers are pretty old, hence the very first LP series monoblocks that came out, along the same line as the LP66s, LP70s, 140m, 260m and so on...
So it seems, that after a while, typically over a decade or so, these intricate parts that contribute to bias circuits and voltage monitoring may require adjustments, that is if there are any problems. OTOH if there aren't any issues then just keep playing tunes. It's not only the caps and resistors and power supply components that may need replacing.

Yet people still chase premier 8s, etc.

At least the LP series is 21st Century.

Parts values can drift over time. Time and temperature affect their aging. Personally, I think when you’re not warming up or actively listening, it’s best to turn the gear off.

The higher quality parts that CJ uses in their flagship gear age better than run of the mill parts. But nothing lasts forever.

My LP275Ms, which I bought when they were about 10 years old, came to me directly from JF at the factory … restored, upgraded to KT120s, and with a warranty. I know “the ARTs are better,” but … these are awfully darn good. I’m happy with them and would only consider parting with them due to their weight.

[roberto]

AJ is right about those odd noises. Usually are the small tubes. They look awesome and the quality sound must be impressive.
Enjoy them RJ...a big woof for you from another old wolf...

Happy listening!

[admin]

Looks great. What kind of power cable are you using?

[roberto]

Looks great. What kind of power cable are you using?

I was curious too. It looks thin, not a heavy gauge. Just a little question dear RJ: after one hour of playing the music, and if you touch the AC connectors plugs of the cable to the amp or to the mains AC, are they a just a little bit warm?

Sorry to stick my nose where I perhaps I should not! We are learning from you!

Happy listening!

[AnotherJohnson]

Maybe it’s an optical illusion, but on my phone screen it looks quite thick. Maybe gauge 12 or fatter.

Question for the power cord guys: Do you believe that 1 meter of passive power cord in the gauge of the house wiring or fatter can change the character of the power supplied by the grid to the house mains? And if yes, help me out and explain.

The best power cord would seem to be no power cord, no? Hardwire the amp to the house mains from the grid. Typical house wiring is not fatter than guage 14. The biggest influence might be the duplex, it’s fixings, and perhaps the prongs and their fixings.

I know our ears are the best judge. CJ seems to think their hospital grade cords are plenty good. And simple measurements readily show that even the LP275Ms don’t draw more that a couple of amps with normal loads and volume levels.

So RJ … what are you using?

I’m using JF’s cords.

On the ARC I’m using their OEM cord, which is extremely fat.

FWIW, the ARC official listener believes that aftermarket cords impact sound.

[admin]

I really don't think that gauge has to be low (ie thick high amp tolerable) for our equipment. Simply put, even our "high powered" amps don't draw significant current that would be even a modest power cable couldn't handle. The "amp ratings" on extension cables that you would buy at the hardware store really are limited by current due to overheating issues, ie too thin a cable and too high a current = high temp and risk of fire.

I think the power is going to be much more influenced by things like line noise, grounding issues, voltage fluctuations, etc... And regardless of how thick that cable is going to be, the limiting factor is often the plug. In the US, most standard plugs and house wiring are not going to support more than 15 amps. I've actually built my own power cables to experiment and I put a triweave of 3 full 15 amp cables on it. In other words, the "wire portion" would be rated to handle 45 amps. But of course I'm limited by the plug so even if theoretically I put that much current on the cable I would either trip the breaker or burn my house down as their would be a fire at the plug or some other area inside the walls of my house.

Here is the cable: https://www.conradjohnsonowners.com/vie ... php?t=1153

So the question comes down to: Do I hear a difference with various cables? Well, in all honesty, in my system at least, none whatsoever. But hey, I think my cable looks cool and it was a fun DIY project.

In my experience if you are trying to get better sound on the "power side", I would look at power conditioners, voltage regulators, and just making sure you are not running the washing machine when you are listening. My two cents on the topic... and that's probably about what it's worth.

[AnotherJohnson]

It sounds like we agree.

[AnotherJohnson]

In my experience if you are trying to get better sound on the "power side", I would look at power conditioners, voltage regulators, and just making sure you are not running the washing machine when you are listening. My two cents on the topic... and that's probably about what it's worth.

ARC makes a big deal about the mains rms AC voltage having an effect on the bias circuit. They set the bias using a 117.5 VAC mains.

The bias circuit sets the control grid voltage. The control grid voltage, and the specific tube characteristics, set the envelope for the output wave excursions, and pretty much (along with the power supply) define the output waveform.

And it’s all transferred to the speakers via the transformers.

So … going after problems with your mains supply is a legitimate pursuit. Our power (we’re supplied by TVA) is pretty stable, but this is not the case from all utilities everywhere.

I’ll never forget the lesson from JF. I had two separate 20 amp circuits installed to run my Krells. Both were on the same ground bar in the same breaker box. I had no hum.

When I plugged in the LP275Ms, I had hum.

JF suggested plugging everything into one circuit at one duplex entry point, using a multi outlet power strip.

I knew he was nuts. But he was not nuts. He was right.

We debated the amount of power needed to run big amps, preamp, and sources. It is not a lot. A 15 amp circuit can handle it. Stable reliable power is more important than access to a steady state 50 amps.

Trust JF. When it comes to CJ products, he is always right.

[Big Dog RJ]

G'day maties,
Was busy enjoying those fine tunes!

Yes, agreed with those points stated, you really don't need to go overboard with power accessories. The main and very important thing is to first of all have a dedicated AC mains line wired direct to the AC mains board on a separate CB and ensure that is fully grounded! This one dedicated AC line doesn't have to be mega powerful either. 10A or 15A is more than plenty, simply because we're talking domestic hifi here, not sound systems for the Super Bowl...

Also acquiring a very high quality AC power board is just as important, and well grounded once again. If you're using more than one power board consisting of a total of 8 outlets, then this is a complicated setup with far too much gear... thus causes other issues. If the case need be then wiring another AC mains for the second power board is much advisable.

With regards to power cords, interconnects and speaker cables, it is a full Nordost power cable loom, consisting of Heimdall 2 on power cords & interconnects and Tyr2 on speaker cables, which I was also using the Frey2 cables.
Sometimes I like both!

These are the pics of the power conditioning accessories but there are no power conditioners as such, I stopped using them a few years back. Now it's just raw AC mains direct into the QX4 unit and then onto the Qbase8 power board. Makes a very fine connection for power accessories.

Re. Robbo, no, none of the plugs ever gets warm or hot, they're cold to the touch... as you know Nordost is tip top quality and their stuff is serious level gear.

Cheers, RJ

[roberto]

Thanks RJ. I just was curious. I do know the quality of Nordost goods.

Happy listening!

[admin]

Very nice. Nordost always looks great and although very expensive, the quality is clearly evident in their products.

[AnotherJohnson]

And the low priced spread at my house.

[AnotherJohnson]

4AC45C52-0A61-4136-9020-D1A7F7F160B3.jpeg (2.33 MiB) Viewed 5530 times

Ikke nordost. Pluggene mine kommer fra sørvest.

[Big Dog RJ]

In fact, I was told by my electrician that the US type plugs are the best. Due to the live pin being larger than the neutral pin. Therefore, this larger pin actually draws the required current, and many audiophiles here in Aus, are changing their Aus plugs to US type.

I was about to do so myself but when he came out last time and tested everything, said was fine. The maximum draw is not even been reached inspire of having all 8 ac outlets utilised on the Qbase8 power board. That's a 10A mains outlet, and the most all the gear is drawing at any given point is only around 5A the most. So plenty more amps to go... I could plug in 4 more monoblocks and still be good to go.

Those original plugs and cords that AJ in using are the best! Simply because they are the standard that CJ recommends. Unfortunately, for us in Aus we don't get those types of cords at all with the cartons. What we get are rubbish cheap looking cords that are similar to the kettle... no good.

At least I was lucky enough to set aside a budget towards proper cabling solutions, and ended up with a full Nordost power loom that's mighty fine.
Cheers, RJ

[admin]

I've also tested maximum power usage using one of those kilowatt meters (such as this: https://www.amazon.com/P3-P4400-Electri ... 111&sr=8-6. Few hundred watts at best. But sometimes that voltage is off from the expected 120v and it also fluctuates. This is a local power supply issue and why I used a power conditioner/voltage regulator.

Those meters are really handy and I recommend everybody own one. It's also fun to go around and see how much electricity your appliances use.

[AnotherJohnson]

Good points about the voltage differences and the effect this has on plugs and wires.

A 10 amp capable circuit at 230 VAC can deliver the same power as a 20 amp capable circuit at 115 VAC.

Incidentally, I love the look of the Nordost stuff. They’ve taken this coupling business to the level of an art form.

[AnotherJohnson]

In the US, transmission on the grid is done at high voltages, and it is stepped down at the point of service. Houses are typically supplied both 120 and 240. The house circuits for high power devices, like heat pumps, clothes dryers and electric ovens or ranges are wired for 240 VAC. The rest of the house, including duplex outlets, switches, and lighting are wired for 120 VAC. The amperage each circuit can handle is dictated by code. A typical 240 will be wired for 30 amps, but there are some 240 circuits that are wired for 50 amps or more. The 120 circuits are mostly wired for 15 amps, but there is also a standard for 20.

In industrial service, depending on need, heavier duty services can be taken from the grid, like 480 3 phase.