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Low plate resistance vs. reputation for 'good tone".

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Posted on November 16, 2010 at 11:15:45
Iczerman


 
ECC99 vs. 6sn7.

I could utilize both for driver duties in my 2a3 amplifier.
Both will be biased at -4 volts. ( got a good preamp)
Mu of both is 20. Supply voltage for both will be ~140v.
Plates in parallel in ecc99 RP is 1.15k ohms.
Plates in parallel in 6sn7 is apporox 3.75K ohms.

6sn7 has a reputaion for "good tone". Plenty of NOS to choose from.

Ecc99..er....not that much. Not that many....um..only 1(?).

Which would be the best choice?

 

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RE: Low plate resistance vs. reputation for 'good tone"., posted on November 16, 2010 at 11:37:57
danlaudionut
Audiophile

Posts: 5158
Location: Schenectady
Joined: June 6, 2002
Iczerman

I found the ECC99 more dynamic and bold.
While the 6SN7 is more laid back and melow.
Depends on your preference and system.

DanL



 

RE: Low plate resistance vs. reputation for 'good tone"., posted on November 16, 2010 at 11:59:17
Jim Womble
Audiophile

Posts: 202
Location: Tennessee
Joined: December 15, 2004
I have used both as driver for 2a3, and both sound good. The 12bh7 can possibly sub for the ecc99 if the op point isn't too hot, and sounds as good as, if not better, than either if you can live with the lower gain. Only issue I had with ecc99 was section to section matching wasn't all that good, and they sounded (for lack of better term) icy when used in a differential application (pp driver in amity pp 300b). However, when used as a single section, or in srpp, they sound very good, although they do need 12-18 ma to sound their best, in my opinion. I presently use ecc99 in a srpp line stage, and single sections driving triode strapped el84 (sep amp). I am building a pp el84 that is going to use ecc99 gain stage dc to ecc99 concertina inverter. I have built three different 2a3 amps using 6sn7 as the driver, and all sounded very good, so really, you can do very well with either tube.

 

RE: Low plate resistance vs. reputation for 'good tone"., posted on November 16, 2010 at 18:38:50
Gingertube
Audiophile

Posts: 534
Location: South Oz
Joined: October 8, 2004
I have used the ECC99 in two (2) amps.

The first was as a driver for a 300B. This choice was based upon some work done by a local designer Scott Thompson who did a scholarly comparison of 6SN7 vs ECC99 for driving 300Bs. Scott's website no longer exists, unfortunately but the paper he did showed relative distortion values etc. and clearly showed the "technical" superiority of the ECC99 over 6SN7 for that (driving a SE 300B) application.

Later I built a pair of Menno VanderVenne VDV70/100 (the 100W version). I did some tube rolling and simple experiments with those mono-blocks. One change I found made quite a difference (improvement) was to replace the 12AU7 common cathode amp + concertina splitter with an ECC99. This may have been due to the fact that I triode strapped the Parallel Push Pull EL34s for 45 Watts out instead of 100W and the load on the concertina splitter would have been more "difficult" with the EL34s in triode mode. Those mono-blocks have been sitting on my shelf for the last 5 years waiting for me to rebuild them into something better (parallel push pull 300B).

As a "SWEEPING GENERALISATION" (and we know how dangerous they can be)I am of the opinion that 90% of the "Bad", "Poor Sounding" amps out there (both SE and PP) are that we due to inadequate driver stages. A lower rp driver tube is a good start in fixing these issues.

Just one mans experience - I certainly have a batch of ECC99 on the shelf for the next project.

Cheers,
Ian

 

RE: Low plate resistance vs. reputation for 'good tone"., posted on November 16, 2010 at 19:31:08
kurt s
Audiophile

Posts: 1137
Location: California
Joined: October 12, 2009
After trying 26, 27, 01A, paralleled 12AX7, 6SN7's, ECC99, 5687, 6GK5, 12AT7, 12AV7, 6N1P, 6922, Amperex PQ 7119 and many others driving the 300B, the obvious winning choice was the 7119 for me.

10,000 hours rated, sounds great straight out brand new, tone is transparent and true (ECC99 can be a little lean at first and is far less reliable) and stays that way over time. The most neutral-to-shade-warm and non-fatiguing detailed sounding driver I have used for the 300B.

10, 10Y, 801A might be a real good one for DHT depending on 300B used. My 300B was a KR 300B-XLS, which is another neutral-to-slightly-warm tube. With 7119, the sound is sublime with all the advantages of SET and very little disadvantage to PP. With this high current low Rp tube 7119, it would take the detail of the 10 DHT to surpass it IMO, as it also sounds close to a very good DHT. The big 300B likes a strong drive from this kind of tube for best sound I think.

-Kurt





 

RE: Low plate resistance vs. reputation for 'good tone"., posted on November 16, 2010 at 22:50:58
Lew
Audiophile

Posts: 6921
Location: Bethesda, Maryland
Joined: December 11, 2000
It's interesting to read that all the below, whom I respect, do at least like the ECC99, as I do. I currently use an ECC99 as a CCS for a 6SN7-based driver, but I have been thinking of constructing an Allen Wright SLCF, using all ECC99s, (for CCS, for driver, and for constant voltage source). I had some hesitation to replace the 6SN7 in the role of driver, because that tube has always been a great favorite of mine, but the slightly lower output Z and higher current afforded by the ECC99 makes it tempting. I use cascoded ECC99s as CCSs in my Atma-sphere preamp, too.

 

RE: Low plate resistance vs. reputation for 'good tone"., posted on November 17, 2010 at 00:16:30
danlaudionut
Audiophile

Posts: 5158
Location: Schenectady
Joined: June 6, 2002
Jim

I agree they sound best at about 15mA.
The 12B4 sounds best at the same current.

DanL



 

RE: Low plate resistance vs. reputation for 'good tone"., posted on November 17, 2010 at 02:48:08
GTCharlie
Audiophile

Posts: 971
Location: Philippines
Joined: December 9, 2004
parallel to Ian's experience. Years ago some guys experimented with various driver/exciter for a 1kw TV transmitter. While, a 15w made it work, a 30 watter had better picture quality.

IMHO, choice would depend on need --- one needs just a few mA, and a bit of wiggle and lots of gain for a voltage amp; OTOH, one needs lots of muscle and large voltage swings to drive, say, a 300B. a tube which might be excellent for voltage amp duties might flounder as a driver.

a 1mA, 1M Rp pentode might do very well as voltage amp, but certainly disadvantaged as a driver to a DHT

 

RE: Low plate resistance vs. reputation for 'good tone"., posted on November 17, 2010 at 09:44:10
Tre'
Industry Professional

Posts: 9726
Location: So. Cal.
Joined: February 9, 2002
I love the 6sn7. Used it for a line stage, the second stage in my phono preamp and as a driver for the 300b.

Now I don't have a single stage that uses the 6sn7.

A autoformer volume control did away with my line stage.

I use a 7119 for the last stage of the phono preamp as it has a lower output impedance and slightly more gain.

The 300b sounds better to me with a 5687 driving it. Miller capacitance is harder to drive than some people understand. 80fp of capacitance will have a reactance of only 20k ohms at 100kHz.

The 5687 CCS loaded driver stage has a output impedance of about 2k ohms while the 6sn7 is 7.7k ohms. 2k driving 20k is much better than 7.7k driving 20k.

Remember, if we can't have 100kHz unadulterated then we won't get 10kHz right. Yes I know that the output transformer won't get 100kHz right but that's not license to give up the fight. These things make audible differences.

P.S. It is a little weird having all these great 6sn7's I've collected and cherished over the years and now I have no place to use them in my system.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Low plate resistance vs. reputation for 'good tone"., posted on November 17, 2010 at 11:32:08
Lew
Audiophile

Posts: 6921
Location: Bethesda, Maryland
Joined: December 11, 2000
Tre', That was sort of my point. I know intellectually that ECC99, 5687, 7119, etc, should make a "better" driver stage, on paper for sure, but like you I am very fond of 6SN7 and have found it hard to get around its mystique. (In fact, I started acquiring 7119 and 5687 several years ago with the facts in mind, but I have never put the tubes to use. Truth be told, I have a couple of 6900s as well.) Knowing that you and others here do like those tubes as drivers in actual practice is helpful.

 

for what it's worth ..., posted on November 17, 2010 at 11:54:28
mikeyb
Audiophile

Posts: 1779
Location: Minnesota
Joined: November 8, 2002
The 'Miller' capacitance of a 2A3 is higher than that of a 300B - 93 pF versus 82 pF. That of a 45 is lower - 36 pF.

So if I were to choose a 2A3 driver for a 300B, the 'predriver' would see a more capactive load that if it were to drive the 300B directly. Cause for thought.

 

Interesting tube experience, posted on November 17, 2010 at 12:24:14
andy evans


 
I've tried quite a few of your list of tubes. I quite liked ECC99 and 6N1P (also E80CC and ECC40), but would prefer a 6SN7 or even better split that in two and use 6P5GT, 6J5G or 2C22 (7193).

But I'd prefer by quite a long way a 26 direct coupled to a 10Y.

Various variations - 01A, 30sp to a 46, 31 or 71a

Andy

 

Only thing wrong with certain DHT's, posted on November 17, 2010 at 16:38:41
kurt s
Audiophile

Posts: 1137
Location: California
Joined: October 12, 2009
Some are "light weights", meaning their filaments are thin and incapable of decent microphonics, such as using 01A as an input to the next driver.

Less microphonic but not as transparent sounding to me is the 26 with its thicker and more stable filaments (that also requires more current). But, that 26 darkishness is complementary to the 10 slightly bright driver, but the gain is getting excessive for the 26 microphonics with that. This then sets the application for the amp to be for lower sensitivity speakers, a limitation. That is, unless a big effort is made to shield the 26 from vibrations. Or another useful thing might be to IT couple with some step-down to set proper gain overall, placed between 10 and 300B.

Going DHT is demanding over modern IDHT's, and much more costly, bulky, and heavy. But it usually is the most transparent. However, I have some idea that it may not always be since you go from 2 to 3 stages.

But I wish I could hear that 26->10->300B amp. It sounds promising.

-Kurt

 

RE: Low plate resistance vs. reputation for 'good tone"., posted on November 17, 2010 at 17:49:31
bobbyj


 
The plate resistance issue is real, as well explained below. And, the few that qualify, (below or about 2K ohms) DO have perceivable subtle "tonal" differences, even amongst the same type. Not to be left out is also the C3m or C3o triode connected, that performs basically as the others (5687, 7119 etc..)

BBBut...

A semi-recent experiment showed that the mu output impedance of a paralleled 12SL7, yes SL, loaded by a CCS was (is) about 300 ohms. . !
(no new news here)

So, as realized then, now many more "too high" Rp tubes could be
used and then perhaps their "tonal" strengths/weaknesses could then be
forced on to a more level playing field. ie: 6SN7 stashes, are suddenly re-validated.

 

Agreed..., posted on November 19, 2010 at 22:03:42
RC Daniel
Audiophile

Posts: 1852
Location: Brisbane
Joined: November 3, 2002
...and have tried to argue (poorly) that same pint in the past.

Cheers
RC
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

RE: Low plate resistance vs. reputation for 'good tone"., posted on November 20, 2010 at 08:23:11
Palustris
Audiophile

Posts: 1527
Location: Cape Cod
Joined: September 12, 2008
Just last week I taste tested the Amperex 7119 against the Sylvania 7044 driving a 2A3 in a "monkey" and the choice was easy: 7119.

 

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