6SN7GTB in MPX-3s and Supras with high-power option
Aug 5, 2008 at 5:55 PM Thread Starter Post #1 of 12

Frihed89

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I have an MPX-3 that allows me to run 6BL7 and 6BX7 models as well as 6SN7GTBs at 450V as output tubes. I have had string of bad luck as a buyer with the first two, so thought I would try some 6SN7GTBs as subs for the 6BL7GTAs and 6BX7GTEs. If you have experience with Tung-Sol v plates, Sylvania Short bottle Chrome top BPs, Long Bottle Raytheon BPs, Japanese Raytheon long bottle GP, how do they sound in relation to the others. (The Tung-sols are very dry, bu very detailed). Are there others you like? Are there any other good subs for the 450V setting as output tubes.

Please this is not a question about other tubes unless they will sub for the high power tubes (6BL7, SBX7, 6SN7GTB).
 
Aug 6, 2008 at 12:58 AM Post #2 of 12

Skylab

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Hi Mac:

My favorite 6SN7GTB is the Tung Sol tall-bottle, brown-base. Nice sounding tube.
 
Aug 10, 2008 at 2:29 PM Post #4 of 12

moredes

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I'm new to this and not real knowledgeable, but from my perspective, I have a coupla questions. What are you using for a driver tube, and what were your "bad experiences" with the 6BL7's and BX's?

I like the BLGTA's for their 'retained' warmth and openness (I know--kind of a contradiction in terms) but I'm using a Mullard ECC32 to drive those, and that tube may account for my favortism. (by "retained warmth", I mean that in comparison between 6SN7's and 5687's, I found the 6BL7GTA's to be almost as warm as the SN's and 5687's--certainly, the BLGTA's are not as 'fully' warm, but they're not thinned so much that I'd describe the BLGTA's as 'less warm'... I hope that makes sense)

I've tried GE, Sylvania and RCA BLGTA's but prefer the National Union (black[?] is that the right name for it?--it's black around the lower half of the glass and the base is black) for their warmer highs above the others. And the BL's are 'way noticeably warmer than the BX's. BX's screech.

From my experience, either of the 6BLGTA (or ...B) is more dynamic and powerful than any 6SN7 in the output ports. Frankly, I don't hear any difference at all between 6SN7GTA's and B's there.... on the other hand, I don't know what problems you encountered when you used the BL and BX's you bought.

As an aside, I found the 6BL7s to be too shrill for input work.
 
Aug 10, 2008 at 4:46 PM Post #5 of 12

sacd lover

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Quote:

Originally Posted by moredes /img/forum/go_quote.gif
I'm new to this and not real knowledgeable, but from my perspective, I have a coupla questions. What are you using for a driver tube, and what were your "bad experiences" with the 6BL7's and BX's?

I like the BLGTA's for their 'retained' warmth and openness (I know--kind of a contradiction in terms) but I'm using a Mullard ECC32 to drive those, and that tube may account for my favortism. (by "retained warmth", I mean that in comparison between 6SN7's and 5687's, I found the 6BL7GTA's to be almost as warm as the SN's and 5687's--certainly, the BLGTA's are not as 'fully' warm, but they're not thinned so much that I'd describe the BLGTA's as 'less warm'... I hope that makes sense)

I've tried GE, Sylvania and RCA BLGTA's but prefer the National Union (black[?] is that the right name for it?--it's black around the lower half of the glass and the base is black) for their warmer highs above the others. And the BL's are 'way noticeably warmer than the BX's. BX's screech.

From my experience, either of the 6BLGTA (or ...B) is more dynamic and powerful than any 6SN7 in the output ports. Frankly, I don't hear any difference at all between 6SN7GTA's and B's there.... on the other hand, I don't know what problems you encountered when you used the BL and BX's you bought.

As an aside, I found the 6BL7s to be too shrill for input work.



First to Frihed 89, the 6sn7gta/b can take up to 450 volts on the plate but the tube is not seeing 450 volts in your MPX3; none of the output tubes are. The high voltage setting in the MPX3 tops out around 400 volts. Most of the later SLAM SE models were set at 375 volts.

By the way, if I had to use 6sn7gtbs I would use the TS tall bottle 6sn7gtb or the Sylvania 6sn7gtb. I like the airiness and neutrality of the TS but the tube can sound harsh at times. The Sylvania sounds warm, rich and smooth but to closed in and dark for my tastes. These are good tubes but, to me, as output tubes they just dont compare to the 6bl7gt.

Secondly, to moredes, a 6sn7gta, say from Sylvania, is no different sounding than a Sylvania 6sn7gtb .... the only difference is the 6sn7tb has controlled warmup. The 6sn7gta was the redesign of the 6sn7gt and the 6sn7gtb added the controlled warmup to the 6sn7gta to make the tubes live longer in TV sets. That is why you dont hear any difference with the 6sn7gta vs the 6sn7gtb.

Thirdly, I agree with moredes, as I stated above, I would take a 6bl7gta over ANY 6sn7gt as an output tube. The 6bl7gtas just have so much more power and a noticeably increased soundstage size. Plus, the 6bl7gta still has VERY good tone as mordes noted .... and less overall coloration to my ears. Two of my three favorite amps use 6bl7gtas as the output tubes. Note: there is no 6bl7gtb. There is the original 6bl7gt and the later redesign 6bl7gta.

Concerning the 6bx7gt, the 6bx7gt definitely has a lighter, brighter tonality and an airier sound than the 6bl7gta. I found them somewhat harsh with my original gain tube choices. But, after some experimentation I have come to enjoy the tube. Both the 6bl7gta and 6bx7gt are exceptionally tough tubes. I use the 6bx7gt in my high voltage Supra. The tube works well in the Supra because the output tubes are being driven almost 50% over spec, so consequently, the 6bx7gt warms up. The 6bl7gta warms up too .... to much so with Senns. So, for an allrounder I get the best results with the 6bx7gt for Senn and Grados in this particualr amp.

Finally, you can use a 6bl7gta for gain. But, I dont think the tube works well for gain at all. The 6bl7gta was typically used as a driver tube to drive big output tubes like 2A3/300Bs etc... in integrated amps .... which is why the tube makes such a good headphone output tube. Remember the high voltage SP amps are only high voltage on the output tubes. The gain tube is still running at the default 300 volts with a much lower current bias. The reason I had the original high voltage amp built was because the default 300 volt/ 10 ma bias didnt bring the 6bl7gta tube alive. The 6bx7gt is an even worse choice as a gain tube as the tubes mu/ gain is only 10.

Here is a one off high voltage PPX3 SLAM that uses 6bl7gtas with 9 pin to octal adapters @ 375 volts. This amp is exceptional with woodied MS1's.

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Here is the original high voltage SP amp; an updated old chassis Supra. This one runs at 392 volts but the bias current is a very high 56ma. This amp is a pure powerhouse ....

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HPIM0245.jpg
 
Aug 10, 2008 at 6:13 PM Post #6 of 12

moredes

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Quote:

Note: there is no 6bl7gtb


I coulda swore there was... 'way too many experiments with my tubes, though; I musta got the "B" mixed up with my 6SN7's.

..and here comes "Pandora's Box"...

Earl, why do you have more than one (count'em--three) headphone amps?
In trying to resolve this for myself-- assuming they're all in the same place (or, at least 2 seem to be) from the photos, I'd guess you use different amp/headphone combos for different types of music? If that's true, would you describe your preferences for each type of music?

Thank you.

Brian
 
Aug 10, 2008 at 10:00 PM Post #7 of 12

Skylab

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Earl, can you use a 6BL7GTA as an output tube in a standard/stock MPX3?
 
Aug 10, 2008 at 11:03 PM Post #8 of 12

mrarroyo

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Quote:

Originally Posted by Skylab /img/forum/go_quote.gif
Earl, can you use a 6BL7GTA as an output tube in a standard/stock MPX3?


I asked this same question of Mikhail!
icon10.gif
He said that although the higher voltage would make the 6BL7GTA sound better it was no necessary. Then he sent me two NOS Sylvania 6BL7GTA (tall bottle w/ a black base and green letters).
wink.gif
 
Aug 10, 2008 at 11:16 PM Post #9 of 12

derekbmn

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Quote:

Originally Posted by mrarroyo /img/forum/go_quote.gif
I asked this same question of Mikhail!
icon10.gif
He said that although the higher voltage would make the 6BL7GTA sound better it was no necessary.



The use of a higher gain input/driver tube will drive the 6bl7gta harder and result in the same effect as raising the voltage to the output tubes. The 6sl7gt is your ticket.
 
Aug 11, 2008 at 12:26 AM Post #10 of 12

sacd lover

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Quote:

Originally Posted by moredes /img/forum/go_quote.gif
I coulda swore there was... 'way too many experiments with my tubes, though; I musta got the "B" mixed up with my 6SN7's.

..and here comes "Pandora's Box"...

Earl, why do you have more than one (count'em--three) headphone amps?
In trying to resolve this for myself-- assuming they're all in the same place (or, at least 2 seem to be) from the photos, I'd guess you use different amp/headphone combos for different types of music? If that's true, would you describe your preferences for each type of music?

Thank you.

Brian



LOL!!

Brian, through the years I have become a headphone amp collector. I have the high voltage Supra shown, a Supra Extreme, a MPX3-12 volt option, three PPX3 SLAMs, the high voltage PPX3 SLAM shown, a Mini3 portable. an Extreme-14 amp power transformer option, a plitron power transformer equipped Extreme, a Bottlehead, two heavily modded Doge 6210s, a Sound Quest SQ-84 and a Space Tech Lab 6AS7G. In addition I have owned a Woo 3 and Woo 6 and two Mapletree Ear+s that I didnt like as well as the others and sold. I had a number of headphone amps before I discovered head-fi back in 2002.

The SPs are great with any music and any headphone I like .... 580 /600 / MS1/ MS1 woodied / MS2i / 701. Some of the others only seem to work well with the Senns .... Space Tech, Doge .... but they do fine with any music I like.



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Aug 11, 2008 at 11:31 AM Post #12 of 12

sacd lover

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Quote:

Originally Posted by Gabe Logan /img/forum/go_quote.gif
What is that item labeled "Zap" ?


A Zap Filter discrete output stage modded Zhalou 2.5C dac. Great sound for not a lot of cash.
 

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