35 responses Add your response
Do you have tube linestage as well? I ask because I tried tube rolling in my Herron VTPH2A with poor results - ended up going back to the ones Keith provided as they clearly sounded the best. However I did roll the two 6922's in my linestage, replacing them with early 70s NOS 7308 Mullards sourced from Brent Jessee and it made huge upside difference. |
You just bought it. Listen to your records and enjoy them for at least a month. Asking about changing an already good setup, is a not a good sign. I tried both versions of the Chinook. It's a great unit either way. Tube rolling is subjective, it can be very subtle,or not noticeable at all depending on your own ears/system. |
You just purchased it. Spend time listening to it, and enjoy it.I've tried both the stock version and the SE. Either way, its a nice unit. Subjectively, tube rolling can change the sound. Depending your own hearing, it can be subtle or you may not even hear it as an improvement. Power cord may also change presentation. |
the best sound I have had from the chinook, was with bugle boys from Holland. quite the musical tube. the other HUGE improvement you can do with the chinook is replace those loading resistors on the rear PCB. From the factory they are metal film. Install some Vishay bulk foils there and the noise floor will drop, you will get more micro detail, and imaging will improve. |
Partsconnexion I got mine here. Huge upgrade. |
Keep in mind that only one of the tubes per channel in the Chinook (6922, I think) is actually being used for gain and is therefore likely to have an affect on sound quality. The other tubes in each channel are used as part of fancy Cathode follower output stages. Cathode followers add no gain, and usually have little to no effect on sound quality, so long as they are in good working condition. Also, I would agree with others who suggest that you listen to your unit extensively before thinking about tube rolling. |
This power cord will knock your socks off for little money: https://www.ebay.com/itm/253018874722 It's great for detail, dynamics and blackness. If you prefer a little warmth, there is this one. |
Tubes of the same type made by different manufacturers do sound different to me. But in my experience differences don’t hold up over time. Then too, same tubes from same maker can sound different from one another; there’s a sample to sample difference. There is no substitute for understanding how the circuit works in the first place. But I admit there are some tubes and makers I really dislike. In my Steelhead I use Siemens CCa for that one gain section. |
The is a certain amount of variability in tubes made by any manufacturer. Buying untested NOS tubes is a crap shoot. The most important and noticeable characteristic is noise. The best tubes have to be selected out by testing each individual tube. The only company I know of that does this is RAM Labs here http://www.tubeaudiostore.com/emission-labs.html I use the Super Low Noise 6922's in my ARC phono amp and they are way quieter than the stock tubes and I mean Way Quieter. They are also super expensive @ $90. But you can choose Low Noise or Standard tubes. In a phono amp I think SLN tubes are a must. This is a difference you absolutely will hear. They have to test 100 tubes to get one SLN tube. Mike |
Apparently the Chinook uses two 6922s per channel. If that’s not correct, stop reading this, because I don’t want to mislead you. If it is correct then you would mess around with the tubes closest to the centerline of the chassis. That’s if it’s constructed like my Steelheadwhich seems a reasonable bet. OR ask Manley which of the two tubes in each channel is part of the gain circuit. They’re cool. As to SLN tubes, who could argue against the idea? Problem is that the SLN characteristic is transitory. And there’s no telling how long it will be before any given tube will go noisy. Also, in the particular case of the Chinook the single gain tube is part of a hybrid cascode where the bottom element is a FET. In such a topology the noise characteristic of the tube section is less crucial to output noise,partly because the tube per se does less work on gain. Not that it still isn’t a good idea to use a low noise tube. |
In my Chinook I like Tungsgram.
https://www.ebay.com/itm/Tungsram-PCC88-7DJ8-M-Pairs-MINT-NOS-JAN-APRIL-1971-Hungary-ECC88-E88CC-sub/160932194464?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649 I also like National. Try Upscale for those. |
I posted last time above that if the chinook is laid out like the steelhead, then the gain tubes are the pair of tubes nearest to the centerline of the chassis looking from front to back. the cathode follower output tubes are to the left and to the right respectively of the gain tubes in each channel. I hope that’s not too confusing. And if it is ask manley or your tube dealer. |
you'll have to find a tech in your area. The replacements are Nichicon XY series film and foil. The originals from manley are metalized film. you can buy the parts from digikey.com https://www.digikey.com/en/products/detail/nichicon/QYX2A474KTP/2117731 It takes 2 min to change the parts, hard part is all the pre-disassembly work first. |
One other thing. I've done a bunch of rolling in my Chinook. The stock Electro Harmonix 6922s are very good. The amp was voiced with them per EveAnna 's tech Chris. Even though I roll tubes like crazy, I do admit that EH 6922s are a quiet tube. They really don't get enough credit. I'm ready to roll after I understand how the machine sounds stock. I try to keep an open mind because I never really know what I will like. I've used inexpensive reissue tubes to great effect, and have found pricey NOS not that great (even when tested and from a great seller). It always depends. If funds are not an option, I'd buy 2 6922s of 3 different makes so you can experiment. |
The Steelhead, and possibly the Chinook, uses a 30 µF metallized film capacitor for output coupling between the phono section and the line section. Then there is a second 30 µF metallized film capacitor between the line stage section and the output. The single most revealing improvement you could make in the circuit is to replace both of those capacitors with better quality and lower value film capacitors. The question then becomes what is the minimum value of capacitance that would be sufficient. So far as I can tell the motorized volume control on the steelhead has a 5000 ohm input impedance. That is very low as volume controls go. Therefore you do need a fairly high amount of capacitance between the phono stage and the volume control. I chose to use 10 µF value, because that will still give you a very extended low bass response. For the output from the line stage to the amplifier, you can use any value that will give you an appropriate bass cut off in conjunction with the input impedance of the amplifier you are driving. So for example if your tube amplifier has an input impedance of 100K ohms, you could use a 1 µF capacitor. For amplifiers with a lower input impedance, you would want to increase the value of the coupling capacitor accordingly. That will give you a bass cut off at 2Hz. In addition to those capacitor changes, you could remove each of two 47 ohm resistors that are in series with the output of the line stage and the phono stage, respectively. Unless you are using very very high capacitance interconnects between your preamplifier and your amplifier, these changes will have absolutely no deleterious effect on performance.To the contrary the improvement in sound quality is very significant, far more significant and lasting than tube rolling can achieve. In my opinion, of course. |
