K&K Audio / Lundahl Transformers

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My Xmas project - From KT120 to DHT

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Posted on January 15, 2015 at 21:33:34
fiacono@optusnet.com.au
Audiophile

Posts: 31
Location: Melbourne, Australia
Joined: May 21, 2003



I previously posted my PP KT120 using Allen Wrights front end, 6h30 cascodes directly coupled to KT77 driver tubes using all Lundahl transformers.
Not completing happy with the sound I went back using 6SN7 front end, very similar to K&K implementation, with CCS on both the cathode and tube voltage regulators. The KT77 was replaced with paralleled 6SN7, (6BX7 is no longer manufactured) and that extra gain avoids adding an additional preamplifier. The KT120 was replaced with EML 2A3’s mesh plates with CCS on the cathodes - new lower voltage power supply was required. The whole amp sounds like a different beast. No harshness and very pleasant to listen to. The 6h30’s sound a little bright and edgy for my liking.
Frank

 

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RE: My Xmas project - From KT120 to DHT, posted on January 16, 2015 at 07:18:12
KevinC
Manufacturer

Posts: 2984
Location: NC
Joined: April 19, 2001
 Nice project Frank, and (in my opinion) a really good choice of tubes if that's enough power for your listening needs! It was obviously a nearly complete overhaul of the wiring and much of the mechanical. Not a task for the timid!

Yes, 6N30P tubes are a job to tame down, although it's much easier without the cascoding. We spent much time determining the plate voltage and current and ancillary parts needed to get the balance right. I still would like a less dry sound than these give, but haven't been able to get there without compensating for it somewhere else.

Kevin Carter
K&K Audio
www.kandkaudio.com

 

RE: My Xmas project - From KT120 to DHT, posted on January 20, 2015 at 05:45:15
coolhand
Audiophile

Posts: 537
Joined: June 5, 2006
 I've found that the early production 6h30P-DR sound notably less aggressive than current production, just more balanced all round.
However an essentially direct equivalent in virtually all cases, which sound significantly more liquid & mellow are the Russian 6N6P, although they tend to have a much higher rate of mismatching triodes, so screening is required if relevant to the application.
Then again they're so cheap that it's no drama to buy a dozen and pick the best !

 

RE: My Xmas project - From KT120 to DHT, posted on January 20, 2015 at 06:04:36
KevinC
Manufacturer

Posts: 2984
Location: NC
Joined: April 19, 2001
 The 6N6P is indeed more mellow sounding. However, it's a good thing that they are cheap, too, as they last a fraction of the time that the newer 6N30P lasts!

The pre-Sovtek 6N30Ps are less "sharp", but frequently become significantly microphonic early in their audio careers. They've also become dauntingly expensive in recent years.

Where is that perfectly voiced input triode with low plate impedance, moderate gain, and availability at less than USD10? (yes, they exist only in my and, perhaps, your imagination) ;+))


Kevin Carter
K&K Audio
www.kandkaudio.com

 

RE: My Xmas project - From KT120 to DHT, posted on January 23, 2015 at 19:50:29
fiacono@optusnet.com.au
Audiophile

Posts: 31
Location: Melbourne, Australia
Joined: May 21, 2003



Those EML 2A3 mesh plates required a good home, been lying around the house for quite a number of years, original purchased for drivers. Using CCS with IDHT as drives made little difference. Power output level satisfies the wife. Now she wants one for the TV, I’m thinking of a smaller version all IDHT, it’s just for watching movies – any ideas?
Be placing an order soon for more amorphous core transformers (before the US dollar gets too high against the Aussie), amorphous core makes a big difference.

Frank

 

2nd coolhand's suggestion, posted on January 24, 2015 at 18:46:42
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 You might want to try the 6n6p, more Rp (about 2K) but similar tube. I have a line stage that uses them and really like the sound. The 60's production 6n6p with the square shaped getter are the best I've found.

twystd

 

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