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LL1660 drivers wanted.

205.188.208.104
Posted on October 21, 2002 at 19:30:17
PeterP
Audiophile

Posts: 594
Location: Central NJ
Joined: April 25, 2001
 OK. What's wrong with me? I've tried to like the LL1660/10mA and so far, in this specific amp (KT88/90 SE UL), I haven't been able to beat a simple 6SL7 SRPP (B+300V). I've tried:

1. 6SN7 - S config & as choke (B+ 300V & 400V)
2. paralleled 6SN7 sections - S config. & as choke (B+ 300V & 400V)
3. KT66 triode - S config. & as choke (OK. So I tried & it was pretty good with a choke at 8mA)
4. 76/76 cascode - S config. & as choke (B+ 400V)
5. 76 - S config. & as choke (B+ 190V)
all at various op-points from 3mA to 9mA.

IMHO the best so far has been the #5. Single ended S configuration with a single 76 running with a plate voltage of about 180V and a current of about 7mA. This has better bass than the 6SL7 but not quite the high end sparkle. I can only say that it has more of that tube sound with great mids and bass. It seems to loose out in the upper mids and highs.

Next on tap will be a 76 SRPP (B+ 400V) cap coupled to S configuration.

Maybe I should save this for my next PP and use a 6BX7/6BL7 and a U config??

Any suggestions are welcome. I just had to vent.

Pete.

 

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Re: LL1660 drivers wanted., posted on October 22, 2002 at 01:37:00
45drive45
Audiophile

Posts: 132
Joined: March 3, 2002
 Could it be that you just like the sound of SRPP better??
Music IS about taste.

I too use the 1660/10ma and i must admit getting the 10ma one, does put a severe limit to the type of drivers you can use if u are using the 1:1.125 ratio.

Because of that, SO far I have only tried 6sn7, 6j5(same i suppose), 6c5 and 2c51. The 2c51 I had were noisy so amnow using 6j5. I want to try 6h30 or ecc99 but I hear that they sound better close to 20ma.

 

Re: LL1660 drivers wanted., posted on October 22, 2002 at 02:09:29
danzan
Audiophile

Posts: 43
Joined: October 21, 2002
 Hi
I've also used the 1660/10 with a 5842 in both 1:1,125 (and 1:2.25) at around 9mA (and 15mA) and sound and gain were pretty good compared, i.e, to a SE of 6sn7.
Actually the 1:2,25 configuration with this valve was better.
I'm going in a bit to try this with a PT8 (the splendid DHT used in Orfeo2 and Katelelo, a (better?) friend of the 26)...
In my opinion the 6sn7 SRPP (my dismissed preamplifier used this, B+ @ 300V)), on the other hand, presents soundstage and things a bit too straight forward and kind of crispy.
But, I agree, in music taste matters.
Ciao

 

Re: LL1660 drivers wanted., posted on October 22, 2002 at 04:51:08
KevinC


 
I hope that no one really believes that a transformer coupled stage is the solution to every audio need. As the other guys wrote, follow your ears.

Now about that PP project using the LL1660...

Kevin

 

LL1660 /18ma as SE--->PP with 2c51/5670, posted on October 31, 2002 at 09:19:37
Danny T
Audiophile

Posts: 174
Joined: May 27, 2001
 I use the LL1660/18ma as IT Splitter in my PP KT88 amps and it works great.
This configuration can't be found in the datasheets, it's a combination of Alt-S(primaries) and Alt-T(secundaries)
As driver I use a paralleled 2c51/5670 (separate cathode resistors) that is biased at 14ma.

I use the secundaries as primaries and vice versa,
they're connected as:
primaries: all in serie (alt-S) Bplus-4, 3-5, 2-7, 8-10, 9-anode
secondaries: for PP (alt-U) gound-13-18, 16-grid1, 21-grid2

I asked the Per Lundahl for the specs of this configurations:
Primary inductance approx 70H
Suggested source impedance not above 7.5k for same LF response

 

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