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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 445

post #6661 of 7523
Quote:
Originally Posted by TrollDragon View Post

I dont think that will happen, others have tried them as power tubes before if you search back through the thread.
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Noted with thanks :)

post #6662 of 7523
Quote:
Originally Posted by mordy View Post
 

The 6SL7 tubes are just plug and play exactly like the 6SN7 and don't need any external PS. IMHO they sound a little lightweight in the bass compared to the 6SN7 tubes when used as power tubes, but still very nice sounding - a light and elegant sound if you will...

 

That's provided the plate voltage is less than 250V.

 

Here are some 33S30 from my collection.

 

 

 

post #6663 of 7523


What a great review and it's been very helpful to me!

 

I liked the stock GE tubes on my LD3, but was hoping for a bit more bass, especially for the DT-880's, so I sprung for the Voshkod 6ZH1P-EV's, which indeed had significantly more bass, but also significantly more in the high frequency range.  These were the cat's meow for the HD-595's, but the mid-range when using the DT-880's was noticeably weak, especially compared to the GE stock tubes.

 

Decided to try the Mullard NOS M8100's and holy cow, what a difference!  Now the DT-880's sound extremely good with improved bass, sweet midrange and enough high frequency response to make a really nice balance.  Not so good for the HD-595's by comparison which now sound muddy and don't have enough top end sparkle.

 

As a result, I'm using a SS amp for the Sennheisers and the LD3 for the DT-880's.  I haven't ventured into the TOTL phones yet as that's still a bit pricey for me, but I have to agree with those that have said headphone technology is still immature in development.  The HUGE differences between headphones and amps is remarkable.  Still loving it!

 

 

Mark 

post #6664 of 7523
Quote:
Originally Posted by rosgr63 View Post

That's provided the plate voltage is less than 250V.

Here are some 33S30 from my collection.









Sorry, what do you mean by plate voltage? Is this affected by output voltages? Here in Malaysia, it's 240v.
post #6665 of 7523

I have used 6SL7 tubes as power tubes without any problems. Even used one as a driver together with the power tubes. The sound is very pleasant; quick and detailed but a little lightweight.

 

At this time I am using a  1954 12SL7 GE (12V version of 6SL7) and a RCA 6AS7G with good results. Since the SL tube plays louder than the AS tube I have to compensate slightly with the balance control.

 

Why this uneven set up? I did something stupid, totally my fault - can't blame anything else, and shorted out one of my 5A voltage regulators. Explosion, white acrid smoke - yuck!!!!  After shutting everything off and after the smoke cleared (exaggeration, but it sure smelled) I saw that the microchip had burnt up and shattered. Had to use my old voltage regulator that only can handle 2A which is just fine for a 12V/0.3A tube.

 

Aerial view of destroyed area:

 

 

Such is the life of a tube roller - full of excitement....

 

Here is a picture of the latest scientific tool in our arsenal - a thermometer with a probe. Through an intricate mechanism it has been attached to my equipment stand. The tip is resting on the transformer housing. Without the fan on, the housing reaches over 90F; the fan lowers the temperature 10 degrees to around 80F. The tie strap serves to hold the fan in place - one of three.

 

 

253-256.jpg

 

When the price is right I am going to try to purchase a 15A voltage regulator - should be enough for two 2.5A 6AS7 tubes. My A/V engineer friend told me that the current draw could triple on start-up.

 

Happy tube rolling!

post #6666 of 7523

Hi I luvmusic 2,

 

Have you tried using the 6832 as a Power Tubes?Thank You!

 

Yes, I tried it. Here is the proof:

 

 

The sound was quite good, but ultimately I found that the bass lacked power and did not have enough slam and impact. For this we need the 6080/6AS7 tubes with the concomitant voltage regulators and power supplies.

post #6667 of 7523
Quote:
Originally Posted by Rossliew View Post


Sorry, what do you mean by plate voltage? Is this affected by output voltages? Here in Malaysia, it's 240v.

 

The maximum Plate Voltage 6SL7 can handle is 250V.

6SN7 can handle 300V and 6SN7GTB 450V.

 

If an amp is designed to run the 6SN7 above 250V, you cannot replace them with 6SL7.

 

All this has nothing to do with your mains voltage but the way the amp is designed.

post #6668 of 7523

My 1+ runs 6SN7's and 6SL7's with a plate voltage of around 100V, and I believe the II, III and IV are similar in this regard. So as Mordy said, in our amps, the 6SL7, like the 6SN7, used as power tubes, are plug and play. However, as Mordy pointed out earlier, power tubes are all about power. The 6SL7 simply does not move enough current to provide a satisfying level of bass slam and propulsive rhythm when used as a power tube.

post #6669 of 7523

Thanks for the clarification @rosgr63 and @gibosi !

 

I may try a pair of 6SL7 just for the kicks.. : )

post #6670 of 7523
Quote:
Originally Posted by mordy View Post
 

Hi I luvmusic 2,

 

Have you tried using the 6832 as a Power Tubes?Thank You!

 

Yes, I tried it. Here is the proof:

 

 

The sound was quite good, but ultimately I found that the bass lacked power and did not have enough slam and impact. For this we need the 6080/6AS7 tubes with the concomitant voltage regulators and power supplies.

THANK YOU! And sorry about your REGULATOR!

post #6671 of 7523

 I promised my self no more 6/12SN7's tubes for me but i was tempted by these 2 SYLVANIA  8SN7 GTB for $15 ,2 12SN7  SYLVANIA and PHILCO for $8, 6 12SN7 T-S,GE,CBS Hytron,SYLVANIA and RCA for $29.Is these a good deal? THANKS!

post #6672 of 7523

Received some 6N16B-VR sub-miniatures today. These are the Russian equivalent to the American 6021. Moreover, the VR indicates that these are uber-premium. The major physical difference I see is these have 9 leads, whereas the 6021 and regular 6N16B have 8. And further, the "pin-out" is different than the American sub-miniatures. I intend to mount these into a 9-pin socket-saver using Mordy's ingenious 18-gauge pins.

 

Curiously, there are two very similar numbers, one printed below the tube number, 9109, and the other above, 9103. Perhaps date related? Or perhaps not?

 

 

I believe the circle-M symbol indicates that these were manufactured in the Melz factory located in Moscow. 

 

 

The etched characters appear to be OTK - 73, which leads me to to think that the year of manufacture is 1973.

 

 

And an etched rhombus with the number 14.

 

 

Anyway, hope to get his little guy mounted and start burning it in soon.

post #6673 of 7523

Hi Gibosi,

 

Congrats om the Russian sub miniature tubes - curious to know how they sound. Seems that Meltz is a high quality factory, but I don't really know the differences between the Russian factories.

 

Regarding the OTK designation, my impression is that this is simply a quality control number, and the number is the number of the inspector. Usually you find lower numbers in the single digits. In this case OTK 73 would simply mean "inspected by quality control inspector #73" and I don't think that it has a bearing on the year it was manufactured.

 

I think I saw somewhere that the number inside the rhombus indicates a certain quality level, similar to the US JAN or W designations for military use.

 

Maybe I am wrong on this, but this is as far as I got when trying to decipher this information.

 

Oskari - maybe you want to weigh in on this?

post #6674 of 7523

O.K. Yep, that's MELZ. I agree that OTK is a quality control mark. I've read something about quality levels, too, but I'm not sure about them. Those 910X strings match the YYMM date format. But: Why two dates? Manufacturing date and acceptance date?

post #6675 of 7523

On the eBay listing for these, the pictures show the date with the same format as is commonly seen on the 6N23P, that is "VIII - 80". Maybe into the 1990's the format changed to YYMM? But if so, the two different dates is a bit of a conundrom...

 

http://www.ebay.com/itm/181254560270?

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