I was hoping to get advice, I have been rolling Rectifier tubes in my two box preamp I am blown away how different tubes change the sound ,I own two sets of Mullard GZ37/CV378 a set of GE 5U4GB both vintage early 1960's and a set of stock Sovtek 5AR4 also have a NOS set of 6H30 DR I am trying in the clean box , both the Mullard's and Dr tubes only have about five hours of run in time but the sound seems defused on the top end ok on the bass the GE Tubes are good in the mids but soft on the highs and bass so far the stock Sovtek seems to sound best ,Dan says try 5R4-GY Tubes, any one tell me about the Mullard's in this preamp I am getting frustrated, thanks
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!
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!
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!
@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.
@bdp24 Amen to that! Tubes do not possess some "magical" property that gives them a distinctive "sound"! An electronic circuit connected to a transducer (speaker or headphone) has a "sound". Not the individual parts! I expounded upon this topic at length some time ago in an earlier post.
Tube brands DO NOT have distinctive tonal qualities! The "golden ear" crowd can throw stones at me! For the record, I have been around tubes and tube gear from young (the Fifties)!
@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.
goffy I use a
NOS Philips 5AR4 rectifier
in my Modwright LS100 preamp , and a
NOS Mullard 5AR4 rectifier
in my Modwright Elysee DAC , haven't had any sound "anomalies" using either; and found both to be better than the stock new production rectifiers
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
"I don't know the tube complement the LS36.5 DM uses. Just thought I'd list the most common preamp tube types!
" He listed it in his opening -
6H30 DR
.
I have done some research. Apparently the 6CG7/6FQ7 will work as a substitute. Same pin-outs, similar GM and capable of 250 volts/plate. Good quality US-made ones are available for a lot less than the pricey 6N30's (correct designation). I use them in my NYAL Moscode 150.
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.
"
@facten : The 6N30 and the 6CG7/6FQ7 are both 9-pin bases. I haven't yet looked at basing diagrams so I can't say for certain that they are identical. I suspect they are! And the Russian tube is likely a copy of the 6CG7/6FQ7 type dual-triode. Not some secret "super" tube!
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!
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!
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