New Tubes

[newmill]

I have what might appear to be silly question for you guys. When purchasing new tubes for my Ref75 SE, should these be purchased from Audio Research, or , from an online tube store? Are there any potential pit falls either way? Can I rely on good matched set if I don't buy from ARC? Also, can I purchase directly from ARC or do I have to go through the dealer? As you can tell I have never bought new tubes before. Thanks.

 

[Nemal1]

I may be wrong here only speaking from a Uk perspective, but you purchase tubes via the country distributor, but you are paying an additional overhead and profit cost as a consequence.

I have always used RAM Labs tubes for my spare/replacements.

There are several companies selling matched sets for specific amps and preamps etc but I’ve no experience with any of those.

 

[gadawg58]

I have had good luck buying from Upscale Audio and The Tube Store for my tube gear. Both offer tube matching.

George

 

[trekpilot]

I used TC Tubes in St. Paul, MN when I re tubed my VT100 MK III. I gave them the numbers off of the tubes I had from ARC and they were able to send me as set of tubes that were very close to the ARC numbers.

Scott

 

[lem321]

I have what might appear to be silly question for you guys. When purchasing new tubes for my Ref75 SE, should these be purchased from Audio Research, or , from an online tube store? Are there any potential pit falls either way? Can I rely on good matched set if I don't buy from ARC? Also, can I purchase directly from ARC or do I have to go through the dealer? As you can tell I have never bought new tubes before. Thanks.

The tubes purchased directly from Audio Research may be the "gold standard" as far as replacement tubes for your ARC equipment. They may have the most rigorous matching and testing procedures of tubes anywhere. You know you're going to be getting high quality tubes that will allow your ARC components to function as intended. Having said that, their tubes are also the most expensive in my experience. For example, KT150 tubes can be had usually for around $100-$120 dollars each from many online vendors. ARC will charge about $250 for the same tube. Why is that? I suspect they throw out a lot of tubes that don't meet their rigorous standards and their tube testing is involved. In my case, one of the eight KT150 tubes in my 250SE failed after about 1300 hours. The other KT150s were fine. I needed a tube that would match the one that failed. So, I was able to send ARC the two numbers written on the tube and they sent a replacement that closely matched. FYI, ARC has their own proprietary system for matching tubes, so those numbers mean nothing to me or anybody else. If I had to replace a whole matched set, I'd probably go elsewhere because of cost (e.g. Upscale Audio).

 

[newmill]

I ordered a set from the tube store. They are about half price compared to the dealer quote I received. Your replies were extremely helpful.
I have kind of a follow up question though. Other than tube failure, how do I know when to replace the tubes? They are able to bias perfectly, but I think this is more of an equalizing or balancing between the tubes. I am uncertain how to assess the tube degradation, and have no way of measuring. I am not 100% certain of the hours on the amp, but I can give a pretty good estimation based on tube hours on the preamp. the amp was purchased as an in store demo unit. Thanks.

 

[lem321]

I ordered a set from the tube store. They are about half price compared to the dealer quote I received. Your replies were extremely helpful.
I have kind of a follow up question though. Other than tube failure, how do I know when to replace the tubes? They are able to bias perfectly, but I think this is more of an equalizing or balancing between the tubes. I am uncertain how to assess the tube degradation, and have no way of measuring. I am not 100% certain of the hours on the amp, but I can give a pretty good estimation based on tube hours on the preamp. the amp was purchased as an in store demo unit. Thanks

I generally will change tubes no later than the expected lifespan of the tube if not sooner. For the KT150, ARC reports that it should last 3000 hours although some people have extended their use beyond that time. I noticed in the ARC 75SE manual, life expectancy is stated to be only 2000 hours. The stated bias is very similar in both the 75SE and 250SE at 65mA or about 27 watts of the 75 watt rating so I would expect KT150 tube lifespan to be comparable. Maybe in switching from the ARC Ref 75 to the ARC Ref 75SE manual, the lifespan of the previously-used KT120 tubes (2000 hours) was not updated (?).

I don't believe the 75SE has a hours counter, so your best bet is to use the hours counter on your preamp as a measure of amp hours. Since you bought a new set of tubes, why not just replace the old set with the new ones and use the original ones as a back-up. OR, if you don't hear much difference in sound quality, put back the old ones and use them up first. One advantage to placing the new set in service is that any faulty tubes may reveal themselves and you might be able to return them within the seller's warranty period.

Some folks are able to hear when the sound quality of their tubes starts to deteriorate. I'm not one of them. I suppose if you're into tube rolling and swap tubes out frequently, the sound degradation may be more easily discernable. I track the tube hours on my ARC components fairly regularly. Based on my typical usage (about 35 hours a month), it gives me a general idea when it's time to replace the tubes. As the tube life of the 6H30 tubes is 4000 hours and they're fairly inexpensive, I generally replace them at the same time as the power tubes.

 

[newmill]

Thanks Lem for the detailed replies. Your advice seems very logical, and makes good sense to me. I will likely go ahead and swap out the old for the new tubes soon. I am however, a little bit curious what would have happened if I did the upgrade package on the tubes. Maybe I would have discovered something I really liked, but I haven't heard much from people doing the upgrade.

 

[lem321]

Thanks Lem for the detailed replies. Your advice seems very logical, and makes good sense to me. I will likely go ahead and swap out the old for the new tubes soon. I am however, a little bit curious what would have happened if I did the upgrade package on the tubes. Maybe I would have discovered something I really liked, but I haven't heard much from people doing the upgrade.

By "upgrade," I presume you mean one of the two different tube packages offered at the Tube Store. I've never deviated from the stock ARC recommendations. A number of people on the whatsbestforum Audio Research forums swear by the improvement in sound quality with different tubes. Oftentimes, these special tubes are either no longer available, very pricey or worse, fakes. The two upgraded offerings, the Upgrade and the Ultimate, differ only in the (2) 6H30 tubes. As the Upgrade package is only a bit more than the original, it may be worth trying. I'm not sure paying more than double the price for the Ultimate package would be worthwhile. My feeling about tube selection is that ARC chooses tubes that work well, are dependable, widely available and affordable. If a particular brand of tube was significantly better, I'd think ARC would have specified it. Even with the stock tubes, the ARC products are pretty darn good and that's good enough for me. I'd rather spend time listening to music than rolling tubes.

 

[newmill]

Quick update. New tubes installed last night. Ran for a few hours before listening. Seems a bit of improvement over old tubes. A little more bottom end heft, and a little more dynamic. See what happens after some more useage. I'm uncertain how many hours were on the KT150s. Thanks again for sharing your experiences.

 

[lem321]

Quick update. New tubes installed last night. Ran for a few hours before listening. Seems a bit of improvement over old tubes. A little more bottom end heft, and a little more dynamic. See what happens after some more useage. I'm uncertain how many hours were on the KT150s. Thanks again for sharing your experiences.

Good news. Cheers!

 

[jadis]

The tubes purchased directly from Audio Research may be the "gold standard" as far as replacement tubes for your ARC equipment. They may have the most rigorous matching and testing procedures of tubes anywhere. You know you're going to be getting high quality tubes that will allow your ARC components to function as intended. Having said that, their tubes are also the most expensive in my experience. For example, KT150 tubes can be had usually for around $100-$120 dollars each from many online vendors. ARC will charge about $250 for the same tube. Why is that? I suspect they throw out a lot of tubes that don't meet their rigorous standards and their tube testing is involved. In my case, one of the eight KT150 tubes in my 250SE failed after about 1300 hours. The other KT150s were fine. I needed a tube that would match the one that failed. So, I was able to send ARC the two numbers written on the tube and they sent a replacement that closely matched. FYI, ARC has their own proprietary system for matching tubes, so those numbers mean nothing to me or anybody else. If I had to replace a whole matched set, I'd probably go elsewhere because of cost (e.g. Upscale Audio).

I agree that ARC selected tubes a the gold standard. But for the one that failed and ARC send you a closely matched tube with the other 8 tubes, wouldn't the new tube be always stronger than its pair or partner? Or is that just fine to have it that way?

 

[lem321]

I agree that ARC selected tubes a the gold standard. But for the one that failed and ARC send you a closely matched tube with the other 8 tubes, wouldn't the new tube be always stronger than its pair or partner? Or is that just fine to have it that way?

I'm not a tube expert by any means. My understanding is that closely matched tubes that have similar electrical characteristics allow an amplifier to operate optimally. Although the remaining 7 tubes have more hours, the newer tube is not "stronger" but should perform well with the other 7 matched tubes. Of course, the new tube theoretically will have a longer expected lifespan. Other experts care to weigh in on this?

 

[jadis]

I'm not a tube expert by any means. My understanding is that closely matched tubes that have similar electrical characteristics allow an amplifier to operate optimally. Although the remaining 7 tubes have more hours, the newer tube is not "stronger" but should perform well with the other 7 matched tubes. Of course, the new tube theoretically will have a longer expected lifespan. Other experts care to weigh in on this?

Thanks for your input. Makes sense.

 

[jadis]

And I don't know if I'm imagining this or not, but lately, I feel that my fleet of 12 power tubes appear to have dimmer lights now that when they were even for their first year or so. I wonder if this has to do with the tubes all about to give in. 2 tubes died for no reason last week.

 

[Argonaut]

I'm not a tube expert by any means. My understanding is that closely matched tubes that have similar electrical characteristics allow an amplifier to operate optimally. Although the remaining 7 tubes have more hours, the newer tube is not "stronger" but should perform well with the other 7 matched tubes. Of course, the new tube theoretically will have a longer expected lifespan. Other experts care to weigh in on this?

Averaged across the KT’s in one of your REF250SE’s one of them measuring a little stronger than the original stock tubes should not manifest any imbalance … However I would add that were you able to source genuine pre 1990’s 6h30-DR ‘s and 100% measuring NOS GE6550A’s in the power regulation they Will take your Pre and Power amps to another level.

 

[adrianywu]

The importance of tube matching depends on the circuit design. If the tubes run at fixed bias and you can bias them yourself, it is not as important. It is important that the two phases of the output transformer have the same DC current, since push pull transformers saturate rapidly when there is an unbalanced DC current present. Allowing this condition to continue for a long time can result in permanent magnetisation of the transformer core. If the current bias is balanced, the differences in the plate curves of the tubes will only result in increased distortion. It is probably impossible to match the curves of 12 power tubes.
If you are seriously into tubes, investing in a tube tester/curve tracer is advisable. I use this model: https://www.essues.com/etracer/index.php. If you know the operating condition of the tubes in your amp (plate voltage, grid voltage), you can measure the plate current at that point. You can then sort out the tubes into two batches of 6 to try and match the total current of each batch. You can also try to match the plate curves, but I suspect this will be a futile exercise. The machine also allows you to determine useful tube life remaining, gas leaks and other problems. I find it is better just to buy the tubes myself, sort them out and throw out the substandard ones. Even buying from the manufacturers does not guarantee you will get good tubes, and problems can develop only after a certain number of hours of usage. Without a tester, you will end up replacing all the tubes every time a problem arises. If you use tubes for your preamp and especially your phono stage, you would want to test the tubes and pick the ones with the lowest noise and microphony. I use a George Kay small tube tester for this purpose.

 

[jadis]

The importance of tube matching depends on the circuit design. If the tubes run at fixed bias and you can bias them yourself, it is not as important. It is important that the two phases of the output transformer have the same DC current, since push pull transformers saturate rapidly when there is an unbalanced DC current present. Allowing this condition to continue for a long time can result in permanent magnetisation of the transformer core. If the current bias is balanced, the differences in the plate curves of the tubes will only result in increased distortion. It is probably impossible to match the curves of 12 power tubes.
If you are seriously into tubes, investing in a tube tester/curve tracer is advisable. I use this model: https://www.essues.com/etracer/index.php. If you know the operating condition of the tubes in your amp (plate voltage, grid voltage), you can measure the plate current at that point. You can then sort out the tubes into two batches of 6 to try and match the total current of each batch. You can also try to match the plate curves, but I suspect this will be a futile exercise. The machine also allows you to determine useful tube life remaining, gas leaks and other problems. I find it is better just to buy the tubes myself, sort them out and throw out the substandard ones. Even buying from the manufacturers does not guarantee you will get good tubes, and problems can develop only after a certain number of hours of usage. Without a tester, you will end up replacing all the tubes every time a problem arises. If you use tubes for your preamp and especially your phono stage, you would want to test the tubes and pick the ones with the lowest noise and microphony. I use a George Kay small tube tester for this purpose.

Nice insights, Adrian. Thanks.

 

[jadis]

Hi Adrian, these are the original EH matched pair selected by Jadis for my amp. These died suddenly. And there are 2 sets of measurements in each tube. Would you know what these are, like plate voltage, etc?

 

[adrianywu]

Hi Adrian, these are the original EH matched pair selected by Jadis for my amp. These died suddenly. And there are 2 sets of measurements in each tube. Would you know what these are, like plate voltage, etc?

View attachment 87970

129.4 is probably the plate current in mA. B3 probably marks the position of the tube on the amp. Don't know what 11.15 means, but the date of manufacture is sometimes indicated by year and week. Therefore, this could mean 15th week of 2011 (since the other is 10.40, probably 40th week of 2010).