Rectifier Tube Rolling in a Modwight LS 36.5DM
the 5R4GY draws an additional 0.1A filament current, and will drop more voltage at any given operating point. Their stated maximum current capabilities are identical. The 5R4GY is directly heated, 5AR4 indirectly: fast voltage ramp up vs slow. Purported sonic benefits of directly heated tubes. draw your own conclusions |
@goofy you may find this article by Lucas Ficas of Lampizator fame of interest: http://www.lampizator.eu/UPGRADE/upgrade%20noval%20tubes%20to%206H6P.html |
@goofy you are highly unlikely to exceed the current capacity of a 5Y3 rectifier with a preamp utilising 2 6H30 tubes and two shunt regs. OTOH the suggestion of substituting 12A*7/ECC81,82, 83’s/5751’s, 7025’s, 6DJ8/6922/ECC88’s is ludicrous as they are totally different types of tubes with MUCH higher gains and plate resistances and totally unsuited to your preamp (6DJ8 family are less bad but still unsuitable). God only knows how they would bias. Behause they draw far less current than the 6H30 they may also overload the shunt regulator in the pre which is supplied by a constant current source. 6CG7/6FQ7 have a similar gain, but their plate resistance is about 10 x that of the 6H30 and they run at about a third of the current so you would lose a lot of drive capability. The only sub I would suggest trying is the 6N6P, 60‘s Reflektor are very nice. |
Yes don't go all crazy with tube swapping but...well researched substitutions can make a world of difference. I have a Modwright PS 9.0 that came with Sovtek 5ar4 tube. That one blew after a week. I replace it with the same tube...6 months and another blow. I put one last Sovtek in it and worked but sounded like crap. Edgy grainy unlistenable. I'm new to tubes so I started asking Mr. GoogleI settled on NOS Tung Sol 5R4GY which sound so much better. This was not an expensive tube and I learned what rolling could do. Next I popped for more expensive NOS Phillips 5R4GYS and bang Jackpot! Now lets see how long this one lasts |
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I have found more data: same pin-outs and construction, equivalent electrical characteristics. So the Russians just copied the 6CG7 (including its internal shield). Shame on ARC and others for calling it a "super" tube - and boosting the prices! Another audio "myth" revealed as just clever marketing! |
The Russian's have copied and used Western tubes since before WWII. The correct Western designation for the 6H30 is "6N30". Cyrillic " H" is the Western "N". I suspect that they are actually 6CG7/6FQ7's. Certainly the plate voltages (250) and GM are similar! As is construction (dual-triode). I will contact Roger Modjeski for his opinion! |
roberjerman - tubeworld contradicts your finding that the
6H30 DR
and
6CG7/6FQ7
are equivalents " a 6FQ7/6CG7 is electrically similar to a 6SN7GT, but a 6FQ7/6CG7 has 9 pins versus 8 for a 6SN7GT " and from fourwater " To address this problem, the 6CG7 was created which simply put the 6SN7 elements into a 9 pin minature tube. The main difference is that the plates of the two sections are slightly closer together because of the narrow confines of miniature tube. They did add a twist though, since there were 9 pins available, they decided to add a shield between the two triode sections and bring it out on the extra pin. This was used to keep the two sections isolated, which can be especially useful for high frequency use. This made the tube slightly more expensive to make, so later the 6FQ7 was created which eliminated the internal shield. " |
EAR-Yoshino's Tim de Paravicini has talked about how in the "old days" when one tube maker ran low of a given model (tube factories often made an entire years supply all at once, then switched over in production to a different model), they would buy some from a competitor, put their own silk screen label on it, and sent it out. Tube experts like Tim and Roger Modjeski (Ram Tubes, Music Reference) can carefully inspect an unlabeled tube and tell you what factory it was made in. |
@robergerman " If you desire a "different" sound you can try different makes of the other tubes in your preamp: 12A*7/ECC81,82, 83's/5751's, 7025's, 6DJ8/6922/ECC88's, 6SL/6SN7's .. This is a SAFE method!" Not sure what you are telling him as his preamp doesn't take these other tubes. " Tube brands DO NOT have distinctive tonal qualities" So, all tube brands sound alike? Not sure what you have been listening to. |
@roberman, I love your making the point that what is commonly thought of as the "sound" of a tube is more a matter of it’s electrical characteristics and performance in any given circuit than some inherent subjective, "artistic" quality. That electrical performance is a result of its design and construction, which very much determines the sound it creates. I’m sure some will disagree with that assertion. |
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Different rectifier tubes also draw different amounts of current from the power transformer - even though most are all 5 volt heaters. Too much current draw from the 5 volt AC winding will cause the power transformer to overheat and fail! Stick to the original rectifier that your preamp was designed for! |
Different rectifier tubes drop the B+ voltage by different amounts. That's all! This will effect an electrical circuit's operating points. It is best to use the rectifier that particular circuit was designed for! For instance, a 5Y3 cannot be substituted for a 5AR4/GZ34 because it cannot handle the same current! It will overheat (glow red) and fail! You must use a rectifier tube matched to the voltage and current required for that particular circuit. Do not do such a stupid thing as using different rectifiers! Serious damage may result! |
