It really depends a lot on where you got your new tubes and how well they were matched. That said, I test the bias a couple hours after replacing the tubes. Then about every 25 hours for the first 100 hours or so. The tubes will usually drift as they break in. How much they will drift really depends on how they were matched. Tubes that were purchased from ARC will probably drift a lot less than tubes from Joe's Guitar store.
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The amp is brand new and the tubes are the KT-120's included from ARC. Sounds like I should probably start checking them now. They have about 54 hours on them at this point. Thanks for the feedback. |
It's surprising that Reference models of ARC do not have an auto-bias. Even if the most primitive autobias circuit is implemented, you don't have to worry about biasing for at least half of tube life. I don't clearly understand ARC philosophy beyond that. |
It's surprising that Reference models of ARC do not have an auto-bias. Even if the most primitive autobias circuit is implemented, you don't have to worry about biasing for at least half of tube life. I don't clearly understand ARC philosophy beyond that. The ARC sound is highly resolved, open and transparent. Any additional circuitry that does not advance those goals (or worse yet that detracts from those goals) is not included in their designs. Convenience vs. sound quality I guess is at the core of their thinking. That is my best guess at their thinking. |
I would check the tubes to see if they have drifted a bit. Then I would check them maybe around a hundred hours.
I also own a Ref 110 but I don't use ARC tubes. ARC burns their tubes in a bit before they are matched. This tends to make the matches much better than tubes that are factory matched. The Ref 110 is an excellent amp. I have owned mine for a few years now and it never ceases to amaze me.
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Convenience vs. sound quality I guess is at the core of their thinking. That is my best guess at their thinking.
It's the best phrase to cut corners, but reality is different. |
It's the best phrase to cut corners, but reality is different. I am not sure I follow your logic. Why is the exclusion of a self-biasing circuit cutting corners, if your primary goal is to produce superlative sound from your products and if you believe that the inclusion of a self-biasing circuit takes away from your goal of producing superlative sound. I am not sure I follow Marakanetz. |
inclusion of self-biasing circuit only improves sound. |
I check bias first day of every month on my ARC amp. Tubes from ARC, very little drifting. |
A properly implemented auto-bias system implies digital components, microprocessors, ADCs and DACs. In order to be reliable and not affect sound quality it will increase the price of the amplifier significantly. Also long term serviceability can be an issue, needing trips to the factory.
As I always use tubes pre-conditioned for 50 hours I check bias after the first 100 hours and then every 500 hours. |
Marakanetz...I suggest you read what Microstrip has to say. I fully concur and any self-respecting tube amp designer will tell you the same. All the added microprocessors and digital circuitry will detract from the sonic quality. If you think Audio Research that has been in business for 30 years with too many awards and industry acclaim are cutting corners by excluding a sel-biasing circuit than I don't know what to tell you. |
I have to agree that auto bias is a very convenient feature, but I think it slightly hampers overall transparency. I have also owned the Primaluna Prologue Two and then upgraded to the Dialogue Two (both with KT-88's) and both are lovely amplifiers for the money involved, but after comparing to others in relatively similiar price ranges (Rogue, ARC's integrated) I could definitely hear a more transparent sound in those without auto bias. These differences could potentially be many other things, but on first glance, that is my assumption as to what differs between them electronically. This is not meant to put down Primaluna in the least, again, they are great amps, though I think you pay a small price for the ease of use with auto bias. |
70 total hours of running in so far, I just checked tube bias for the first time on my Ref 110 and three of the four sets were running just a little bit low. Should be at .65mv according to ARC manual and they were running around .61-63mv. I assume this is a very minor/mild drift. I adjusted the three sets that were slightly low back up to .65mv and away we go... I will check again at 100 hours. This was my first time biasing an amp, and I found it to be kinda fun! |
Cmalak,
Why do you thing that it's done by "added microprocessors and digital circuitry"?
1. Autobiasing is done in DC domain and does not affect the signal no matter what kind of components are being used vacuum, solid-state or ICs.
2. Autobiasing could also be done without using any "added microprocessors and digital circuitry" by common cathode resistor(1940's?), but modern means of autobias widely implemented in Quicksilver amplifiers not only save tube life, but apperently improve sound! Stable quiescent grid current is a "dream:" of every tube push-pull amp.
Pardon, but I don't see this as convenience only feature. |
Marakanetz...I guess we will just agree to disagree. |
Yup,
Why not? Autobias will substantially decrease tube demand on the market. Microstrip speaks nothing but the standard marketting words to make an amp cheaper.
How much the price of the unit will increase by introducing common Cathode resistor or few semiconductor elements(modern way)?
This makes the unit plug-n-play with bullet-proof reliability that substantially decreases demand to send the unit for repair.
I explained facts and not opinions or judgements.
For next upgrade try to get Quicksilver's flagship and experience the magic along with bullet-proof reliability.
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Marakanetz...Thank you for your reco of the Quicksilver amps but I am very happy with my crappy ARC Ref 110. It offers horrible sound performance because it does not have an auto bias circuit. But I guess I will just have to do without it. The Ref 110 has gotten awful reviews and 0 awards from all the various audio publications. It is clear to me now that it has to be the absence of an auto bias circuit that explains it all. Oh yes, ARC was trying to save a couple of hundred dollars on a $11K unit because they are in the habit of cutting corners. Their audio engineers are amateurs and they have no clue.
All the best. |
