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Custom Linestage by Murrow & Birkeland

71.220.200.105
Posted on October 19, 2009 at 18:45:05
Hank Murrow
Audiophile

Posts: 125
Joined: July 13, 2000



This project drew on the innovation and dedication of the whole Bottlehead team. At VSAC in Vancouver, I displayed my mockups of a 300B amp and 6C45Pi linestage(w. MQ iron) while running my Glow One SET into Omega speakers in the Craftsman’s Room. I had been collecting Mike’s tasty parts for eight years to build a Soul Sister line stage and Blues Master amps; but busy with my job as a potter, I never could seem to get the iron hot and something built. At VSAC, Doc introduced me to Paul Birkeland, fresh from teaching the amp-building class, who agreed to turn my eight-year collection of parts into a Final Music System(Ha!). We decided to work on the preamp first, using a pair of I.A.G./Sowter transformer volume controls, and 6C45Pi tubes driving MagneQuest B7 Cobalt outputs, all fed by a very trick shunt-regulated power supply using EL84s(kudos to PJ!) for a sort of Soul Sister/Kugelis on steroids. Once the circuit was designed, a 17.5" x 10" x 2" h. box was drawn up by Paul, reviewed by me, and sent to Front Panel Express for machining. My friend Mark Nelson machined the knobs for the source and 28-step volume controls, which will be driven together by a belt internally, the belt will slip to adjust balance thus obviating the need for a pot(saw this first on Wardsweb's Foreplay, thanks). The knob on the right controls six inputs, and there are 2 pairs of RCA outputs and a pair of Neutrik outputs on the back panel, while a Neutrik headphone output resides on the front panel. The pic of the unit shows how all this looks with the Auricaps sitting just behind the signal tubes.

RE: Custom Linestage by Murrow & Birkeland, posted on October 27, 2009 at 05:17:13
AnandR
Audiophile

Posts: 688
Location: North Carolina
Joined: September 8, 2003
 Good work. Similar idea at link below. Tried the 6C45, too dry for my ears. But perhaps you have found the sweet spot!

Best,
Anand.

RE: Custom Linestage by Murrow & Birkeland, posted on October 28, 2009 at 12:12:51
Hank Murrow
Audiophile

Posts: 125
Joined: July 13, 2000
 Dear Anand; I did not find this circuit to be dry, detailed yes, but I don't hear dry. Perhaps because we used Horace Atkinson's TVCs at the input, and maybe they allowed the sound to be richer from the 6C45Pi tubes. The linestage IS fully burned in because it lived at Château BottleHead for awhile, being compared with Dan's big TL-404 implemented headphone amp. One mention though, I was stunned at the rendition of bass notes through the Sennheiser HD600s, The Telarc vinyl edition of Holst's Wind Band Suites revealed drum whacks with plenty of snap, skin sound, and impact.... qualities I have not heard since I auditioned this disc on John Tuckers big system. However, I have only had the preamp for three weeks, so much listening needs to occur before I will be certain of its sound. So far, it sounds great! And I will report back with more later.
Cheers, Hank

How do you like it?, posted on October 20, 2009 at 21:02:57
gluca
Audiophile

Posts: 749
Location: SomeWhere Islands
Joined: February 17, 2005
 I mean... I used 6C45pi and I found it a bit dry if such a word makes sense in audio. OH?! Yes, me too, I will be using beeseven.

Neat building, kudos!

Gianluca

RE: How do you like it?, posted on October 20, 2009 at 22:45:21
Hank Murrow
Audiophile

Posts: 125
Joined: July 13, 2000



I love it so far, but my only serious listening has been done with the Senn HD600 phones. Bass is rock solid, soundstage(if you could call it that with cans) is wide. My hearing is not extended enough to comment on the highs, but sweet comes to mind. The most stunning thing I am hearing at present is the details discovered on discs I thought I knew well. It is a real joy to hear these subtle musical cues, that were before only heard in live performance. I attend a lot of live musical events from opera to recitals to jazz concerts...... almost all acoustic in nature. This linestage seems to have the headroom that live performance has always had for me. I think those cobalt B7s are very special, and Paul's power supply keeps noise out of the sonic picture. Here is a pic showing it sitting on my piano. More later......

RE: Custom Linestage by Murrow & Birkeland, posted on October 20, 2009 at 18:39:34
nerdorama
Audiophile

Posts: 328
Location: Seattle
Joined: February 2, 2002
 Hank,
Looks great. Hope you get lots of enjoyment.

Paul,
Great work. Hope you had as much fun at the estate sale as I did.

Regards to all,
John
De gustibus non est disputandum
Oh yeah!!!, posted on October 20, 2009 at 23:09:42
Caucasian Blackplate
Industry Professional

Posts: 4444
Location: Seattke
Joined: June 18, 2004
 I am just trying to figure out what to use first...

RE: Custom Linestage, under the hood., posted on October 19, 2009 at 19:19:56
Hank Murrow
Audiophile

Posts: 125
Joined: July 13, 2000



In this shot, the extensive power supply can be seen filling the left side of the chassis, with the IAG/Sowter TVCs at the top and the 6C45Pi circuits between them. C4S boards below those, then the Auricaps and the MQ B7 Cobalt outputs in the center. As can be seen at the top, there is room for a drive belt to connect the TVCs together while allowing for slippage to adjust balance. Again, thanks to Wardsweb, whose elegant projects are shown in the BH Gallery.

RE: Custom Linestage, details., posted on October 19, 2009 at 19:22:58
Hank Murrow
Audiophile

Posts: 125
Joined: July 13, 2000



A bit more detail in this shot of the power supply with EL84s and their circuits at the top left next to the TVC, and the power tranny at bottom left with its circuit boards. Left channel signal circuits at the right here.

RE: Custom Linestage, last look., posted on October 19, 2009 at 19:37:51
Hank Murrow
Audiophile

Posts: 125
Joined: July 13, 2000



Paul has almost finished the second piece, which is a custom Eros phono stage using MQ Ni B7s, another trick power supply, and V-caps for coupling. Soon to come is a pair of mono blocks now being drawn up to use my EX0-03 plate chokes, BCP-16 Ni grid chokes, and MQ TFA 2004 Jr. Cobalt-sliced outputs. I'll post these as Paul delivers them. For now I can report that the preamp is totally quiet, and listening through the refurbished Sennheiser HD600s is wonderful. Paul is an exceptional builder, who I recommend heartily if you have no time to do these projects and want something special. While I cannot approach the pride many of you have in building your own gear, I trust that all will forgive me for posting Chapter One of the Murrow/Birkeland story here.

Here is the result in its present configuration, until the custom Eros phono stage is ready to sit underneath, and the Marchand 24Db/Octave Xover sitting underneath both. I love the Sennheiser HD600s with this preamp...... tons of drive, and silence in between the notes. Thanks to each BH and MQ devotée that posted their comments on both Forums during the past eight years..... a bit of each of you is in this piece; and Paul Joppa, Doc, Mikey of course...... and Paul Birkeland who literally made it happen. Kudos to All!

Cheers, Hank Murrow

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