Audio Research I/50

I heard the i50 at the Florida Audio Expo last month and I knocked out by the sound. I was ready purchase the amplifier until I found out that amplifier’s balanced inputs are not compatible with a signal beyond 2 volts. Most every DAC that has a fully balanced design, sounds best from its balanced output and nearly all normally output voltages well over 3volts. According to ARC, normal balanced voltages will over drive its input stage. The i50 is not even compatible with Audio Research’s own DAC9 if balanced connections are employed. It was likely a design oversight to incorporate balanced inputs on the i50. This was disappointing news.

what U think guys comparing this to a Leben CS-600 or CS-600X? or with a traditional SET 300B or 300B XLS?

JBL 4349, Zu or Klipsch pairing.

A great video that answers many questions regarding the I/50 . 

@malibu457 , the reason there is no auto bias is because there isn't room to fit it , I saw a very interesting video on Youtube where they explain the ( few ) trade offs due to price but mainly design limitations in that chassis , which apparently wasn't originally an in house ARC design but elsewhere in the MacIntosh Group .

Balanced Audio Technology VK-3000SE (replaced by VK-3500 which is, I believe, same internals in a new box). I used Audio Research for ten years then switched to BAT and never felt I was missing anything. BAT is just pure music. 

I’m an AR I50 buyer and I want easy or auto bias and don’t want to mess around with tubes, changing or rolling tubes. The tube rollers and tube biasers may want to focus elsewhere.

But I really want the AR sound in something I can afford and a simple good looking integrated ......and the proof is in the listening - when I heard this amp driving Maggie 1.7i speakers the sound was clear, detailed, spacious and sounded terrific.

I will admit that if it were me buying an i/50 I would prefer easier bias. But as a tube amp owner for over 20 years (all ARC other than an Ampsandsound Nautilus), bias does not normally drift very. much in a stock set of tubes. Everything changes is you swap out tubes. ARC obviously did not bring the i/50 to market for tube-rollers. 

With a push-pull pentode design, bias adjustment is vital but again, the consumer could easily get two years of use out of the amp before needing new tubes and bias adjustment. FWIW,  my SET HK Citation-based Ampsandsound Nautilus does not offer any bias adjustment whatsoever and does not need it as a matter of circuit implementation. And that is regardless of being able to swap tube types for the power tubes and rectifiers. 

Somebody asked why ARC didn't "just include" auto bias in the i50.  Because it costs.  And it would then compete with the more expensive models.  

I don't know if this is how they did t, but the old Classic 30, 60, and 120 amps used a servo...an inexpensive chip...to maintain bias once set.  That's what Raven did on their $5k integrated. 

Auto bias circuits have been done for years.  But is the "auto" when it is static, while the tubes idle?  What happens when you turn up music?  Or tubes age?  Or one tube goes a LITTLE whacky? Or maybe it was whacky when you bought the amp?  

I had a chance to listen to the Audio Research I/50 at John Rutan's place last weekend. It was driving Vandersteen VLR CT's with a pair of REL T5/i's. Source was an Auralic Altair G1 I believe. 

Very engaging system that really left me wanting for nothing. When I asked Jeff what the sonic differences were between the I/50 and the Rogue Cronus Magnum III he said the I/50 was more lush, romantic and tubey in comparison. 

I may ask John for an in-house demo of the I/50, but I'll probably hold off until the winter. As my upstairs listening room can get hot!  

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Anyone try the manual bias procedure yet ??

another downside is that the voltage is not switchable.

@malibu457 

ah, but how does it sound?

+1

ah, but how does it sound?

I assume they were trying to hit the $5k price point and auto bias would add a couple hundred? Maybe it really only needs biasing if you use different tubes and this isn't a product they expected tube rollers to buy? Metro hipsters may be more apt to just use it as is? It really does sound good. Can it sound better with different tubes? Most likely, but the price then goes up. AR touts their tube testing and matching in the Darko video. They want to keep it all in house. Even advertising trying different tubes like Upscale does for Primaluna gets people thinking about it. Upscale sells "upgraded" tubes, AR sells replacement tubes. 

has anyone compared this to say a Cayin CS55 at less than half the price or a Willsington R8?

so why would Audio Research create this problem by not adding auto bias for a user who is new to Tubes? it seem that their target audience is the affluent 20 something  metro hipster. dropped the ball on that one.

Would love to hear more from your hands on listening session with the i50. I heard one driving Maggie 1.7i briefly and thought it sounded great. 

A local dealer let me take one home for a few days.  I thought it was great, especially for the price.  I wanted to order one but there's a 2 month+ wait and I have a Leben on order that I have a 5 month wait for.  I was using the ARC as a temporary amp while the Leben was being made. I still may get one once the DAC module comes out in June. They are not auto-bias. You need to flip it over and do it manually as someone already said. That's according to the dealer.

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I am sure there IS tube break in, but it is not 600 hours.

do you sure that after changing to a new tubes there is no an additional break in?

600 hours is talking about the amplifier break in and it is the one time event.

one of the weird things is that arc saying that the amp will work at it's best after 600 hours of using it.
on the other hand that average tubes life is 2000 h.
so it means that 30% percent of tubes life you don't get the best potential.
btw, the 2000 hours they are talking about is only when you playing music trough the  amp, or also when it on, but idle?
 

No meters, I don’t believe. 

Darn, I thought I heard something about self-biasing in a factory tour last September. If there are meters-can't recall, that would at least tell you when they need adjusting right?

@stone1 Thanks for asking. I mentioned age as I second @chris_launder ’s observation that the multiple colors offered and relatively low pricing for an AR unit is meant to attract new and younger listeners to the brand. I bring this up specifically because I too wonder whether they expected the tube bias issue is something with which they either didn’t want to task young listeners (with no tube experience) and/or assumed even the mention of it would confuse or put them off.

I don’t see why they didn’t just apply auto-bias as a unit that people will assume needs a service tech and is a danger/pain to bias is probably even more off-putting than just saying, "hey, this unit does it for you with cathode bias." Even if hardly adjustable fixed bias sounds better, a lot of young listeners will still think the AR unit sounds appreicably better than most solid state to the degree that it’s worth checking out this old-timey exoticism. The VT80SE (with auto bias) sure does speak for itself.

We’ll see.

Don't worry. They are on listening and I guess they will get the SE version pretty soon.

There is no problem in general with manual bias.  To my way of thinking having to turn the unit upside down and taking the bottom off to reach the bias pots is prehistoric.  Even my 40 or 50 year old Dynaco ST70 has the bias adjustments performed from the top of the unit, without exposure to other rather lethal areas of the amp.

Place the multimeter probes on the amp, turn the bias screw to the correct reading, or a little less than the manual recommends as oldhvymec alludes to, and done in 5 seconds.

@ Transience

how to your opinion is the Linear Tube Audio soundwise compare to an arc around this price point ?
and what is the reason for this:
"be more agreeable to the younger listeners"

@ Transience 

That's great. Let us know how you like the I/50. The Graham LS6 speakers are very nice. My assumption is that the two should be a good match. I agree with you on the Octave amps. They have implemented a unique and easy way for all users to bias the tubes. 

I just ordered one for a second system and look forward to providing more clarity on the biasing issue from my AR dealer.

I agree that brands like Linear Tube Audio that provide complete audio bias around this price point would generally be more agreeable to the younger listeners their branding cultivates. Even my truly high-end SA Lab integrated auto-biases its 6550 tubes, and that is meant for experienced listeners. This said, I always liked manually biasing my Octave Audio (great bias readout) and Rogue (less so) tube amps, which should be telling of how others will experience this, as I am under 40 and lack comprehensive experience with the servicing of mechanical gear relative to other fields (i.e., automobile / home repair).

In addition to assessing ease of use and seeing if I can access a service manual, I will report on how the I/50 performs in my second system, using Graham Chartwell LS6 speakers that seem to strike an appropriate price and specification balance with this unit.

i hope that sometime soon there will be a comprehensive review, in a serious magazine/site   about it's sound quality 

The i50 is a really nice looking unit, and it's nice to see AR release a product available to those with somewhat more modest means. It is a little strange that they release a product for what could be described as entry-level (per cost...not in the quality sense) with manual bias setting, but requiring it be done by a technician. 

The skeptic in me wonders if this is a way for AR to have consumers build relationships with dealers by design (with the benefit of recurring revenue), a'la John Deere or any modern automobile.

There is an advantage to having trim pots in certain places. When you have a product like AR, you don't want anything to look out of place, collect dust that is difficult to clean and certainly not around trim pots. Mr. Clean Jeans with his Q-Tips and micro cloth could move things. As a bulletproof design. I'd hide it too. LOL

OLD design almost always hid trim pot under the bottom plate (if there was a plate) or through a hole in the top that was covered with a metal or wood cover.

Auto bias sucks. I use it but I install trim pots on Macs. I BIAS cool. Unless I'm doing a lot of late night low volume listening. I still bias and listen. If I can keep the SQ and bias cooler I do. Why? pretty simple, the cooler you bias the longer the valves last.

BUT that is just part of the story. It also stops the power valves from breaking up sooner than they would have with the higher bias. Distortion! HF distortion, and LF both suffer when you start to crank it. The higher you go the worse it get, then you run out of gas. 

If you scope bias the actual watts created can double. Cary Six Pacs are a good example. Factory bias is 220-240ma per 6 valves. 50 wpc. Scope and alignment increased power on demand output to 100+ wpc and COOLED the bias to 160ma for 6 (lets say) EL34s.

So what do I get out of the deal being able to bias my own units?

1. A lot longer valve life, you can see why. Lower bias, lower volume, longer life.

2. Less distortion. Cleaner sound, COOLER running. 

3. More horsepower, the amps will play louder and cleaner before distortion sets in or the tubes break up.

Side note: 

I had WE 300 (116a) amps they were my fathers. That is what he left me. His snap-on tools, and Western Electric Amps. 

I learned how to maintain those valve amps. The 300WE valves that were in it were used. I had 4 new, and one used sets of valves. In 15 year of playing those watt sucking pigs close to every day, 2 sets of valves still had over 50% valve life. I know I put 30,000 hours on those amps easy. My father over 30,000 hours. He had them 20 years. He used the same set of valves all that time. 2 set were never used and I never did wear out the set my father used.

How long do valves last?

I have original Mcintosh valves in a 1968 MC225 less one 12AX7.

BTW you still have to bias most SS ampt too, you know.. :-)

Regards

it's really  inconvenient but at least there is an option to bias.
a friend of mine, a very experienced technician with tube amps said that there is also a disadvantage in auto bias.
sometimes you cant use other brand or type of tubes when it's auto bias.
for me the i50 is still an option.

@runwell

I wish I could answer your question correctly. I’m not a technician just an audiophile. I’m not 100% sure why tube amps drift out of bias. If it is just about the tube or if it also about the amplifier? I believe the bias can change at anytime during the life of the tube. I don’t think there is a period where it preforms at exactly the same level over a long period of time. This change is not necessarily an indication that a tube is nearing the end of its life. This is just my best guess. I am sure someone else on this thread can clarify it better than I can.

Also, thanks for asking Audio Research directly and posting their response. I’m confident now this amplifier is not for me. Why are the trim pots hidden on the bottom of the amp? Turning over the amp, taking off the bottom cover and then we can check the bias? I suppose anyone could do that but who really wants to? I thought Audio Research said that a trained technician is supposed do that? Or is that only when the tubes are replaced? But why? If the tubes need adjustment then why can’t the owner also adjust the new tubes themselves? Makes no sense. The bottom line is that Audio Research should have designed this brand new amplifier with the trim pots on the top of the amp poking through the top plate. Make it easy for the user. Just like 90% of all other tube amps do.

To answer your last question. I assume that after unplugging the amp, turning it over, then opening up the bottom plate that you’ll have to plug it back into an electrical outlet again. It’s the only way to check the bias. Why AR didn’t mention that in their reply to you? Odd. Furthermore, the fact that the bottom plate is opened up and the unit is plugged into a wall outlet is a warning. Especially to new users. Can you say potential lethal voltages? 

With my vt100 MK iii, we adjust the bias while the amplifier is connected.

Why for I/50,it need disconnected and do adjustment? I do not know.

I get the reply from Audio Research regarding I/50,

"Dear James

Summary: The I50 is not auto bias. The tubes should rarely need to be biased on this product but if it needs to be checked, the unit needs to be disconnected, turned upside down ,and the bottom cover removed, then there will be points to connect a voltage meter and read the settings. There is a small pot to turn with a plastic screwdriver that will adjust the bias. We are working on written instructions for this as well as a short video. Those will be available in the near future."

@mezzanine 

       I have a question for you. If the power tube 6550 bias is very stable. Is that to say, the tube is ok for use and not even near the end of lifespan?

@mezzanine +1

We must have the ablity to bias by ourself or auto bias,it is bottom line.

Otherwise,the Tube drift,especially for the new tube. How we can ask the technician mutli times for the same issue? 

I am asking this point to Audio research and hopely they will reply me soon.

i also will not buy an amp that  can't control the bias , auto or manually, but i think that this subject still need to be checked.
i don't think you'll have to send it for biasing.
think that the meant is when you replace the tubes, let say after 2000 hours of playin, which to my opinion it's not much, it can be to me after 1.5 year, you can bias it using a technician at your place.
but, yes, if it like that ,it's disappointing. 
 

I was thinking of buying one as well but then I read that it needs to be biased by a trained technician. That really has made me consider not buying it. It makes no sense that a product in this price range, made by a manufacture with such a long history of making tube amps, would offer their latest product like this. Audio Research needs to clarify this. There are some points/questions I'd like to bring up.

1) Why can't Audio Research offer either automatic bias or user adjustable manual bias? Prima Luna offers automatic bias. Rogue and most other companies at least offer user adjustable manual bias. Trim pots next to each tube. Companies like Rogue even include a multimeter readout dial on the amp. Very easy. Four words: User Adjustable Trim Pots. Why not AR? 

2) I've owned tube amplifiers before with manual user bias. I usually checked the bias at least once every 3 months. I can tell you they were always a little off and I always had to readjust the bias to get it back to the optimal bias level. Not all tubes are equal. Some fade out over time quicker and some can even stop working. For AR to basically say the bias is fine for 2000 hours or about 2 years is odd to say the least. Is Audio Research certain the tubes won't drift out of bias within 2000 hours or about 2 years? 

3) Where to send it in to get the new tubes biased? Does AR do it or do we need to find our own "qualified technician"? Some of us may live far away from one and need to box it up and ship it off to one. Very inconvenient. Not to mention the extra cost for the user and possible shipping damage each time. What if a tube goes bad early? More hassle.

As I write this I am more convinced than before that I'm not buying one. It's a shame because I'm sure it sounds great, it does look awesome and it's made in the USA. Perhaps the biasing issue won't matter to some of you. Especially if you have an AR dealer close by with a technician. However, for others I think it will be an issue. 

@dweller Good Point. 

It is really trick things to handle how the power tube is dead or not. 

The most difficult things is the handover amplifier from the prior owner, as I even do not know how long they used it. I want to replace 6550 set this time, as the sound is way beautiful as some one tell me the status pro of the tube will be best just before they die.

For 6h30 tube, Audio research official one is not good for the  sound,I will change it to EH 6h30PI GOLD even the machine is new like my REF 75se.

By the way,I had Classic 120 many years ago, beautiful  sound, just have maintain problem as I was in China that time, so I have to sell to a Engineer who can handle it  by himself.

@runwell - I too owned the VT-100 III. Also the Mk-I and a Classic 60 (the good old days!). I never used them with a preamp that matched their quality, however so never heard them at their best. If you are worried about tube failure, just replace the 6550s after two years. You can send the old set to someone who does testing (like Upscale Audio in L.A. California) and keep the good ones for spares. The 6H30s last a lot longer than 6550 (ask ARC about lifespan). BTW, I had a power tube go out on my ARC Classic 60 and didn’t even notice it (I listen at conservative levels and use a subwoofer). Discovered when I traded in for the VT-100 Mk I.

I owned the VSI-55 years ago. This looks like a redesign of that or the newer VSI-60. Entry level, they say, so likely cheaper parts to keep the price down. Not an ARC basher, I love the products. I wish they would put their best technologies into a low powered amp. 

@dweller  your calculation is right.  

I have  vt100 mkiii and the tube is from period owner, 

Recently I changed all 6550 tube and 6h30 tube, but the old one is not dead. I am wondering how we can found the tubes are almost end and got swapped out?

If I do not prepare in advance,does that damage the amplifier?

although its looks like there is an issue with the bias adjusting, i still think that it’s something to check with ARC
i don't think i'll buy an tube amp without this option

Yes. All of these factors figure into the total lifespan. Some more than other. At the time, I was playing music 4-5 hours a day (more on weekends) and got about two years from ARC factory tubes. You can probably compare tube bias to the idle speed on a car. If your idle is set to 4000 RPM, your gas won't last as long.

@dweller  You said 6550 in your amplifier last about 2 years,it is matter how long time you run the amplifier and how hard the sound make,right?

If some one maintain in low sound level,the lifespan could be much longer.