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 Post subject: Re: "Lacewood" Amp V2.0
PostPosted: 09 Jun 2018, 08:13 
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Joined: 03 Jan 2017, 20:59
Posts: 22
On an other forum someone said the current is too close to the maximum. I can use the 100 mA version for the high frequency driver in my active set-up but it will be limited to this application.

Also i found very nice military brown base RCA 6V6 but on my calibrated Jackson 648 they read about 30%.
Anyway they sound great on my Lacewood, is there any problem using them.

Regards.


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 Post subject: Re: "Lacewood" Amp V2.0
PostPosted: 09 Jun 2018, 10:19 
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Joined: 06 Apr 2009, 10:08
Posts: 1430
Location: US Pacific Northwest
lowhifi wrote:
On an other forum someone said the current is too close to the maximum.
Hooey!

One of the primary considerations for max primary current is core saturation. This is controlled via core cross section, and gapping. The "C" of the transformer core controls the propagation of the magnetic field and the gap dimensions control the overall reluctance of the magnetic circuit. It is this circuit that connects the primary and secondary windings. The core and gap are sized to support a certain level of DC induced flux and present a reasonably small magnetic hysteresis such that the coupling distortion is very low. So when a designer sizes a core for an 'X'mA magnetizing current, he has taken into account both magnetization flux and energy transfer.

The Lundahl LL1663/50mA is sized to cleanly handle up to 50mA DC current AND the signal fluctuations without saturating. (LL1663 data sheet attached) The design point of the lacewood is 43mA total DC magnetization current. This is only 86% of the maximum design specification which likely already has a little design margin thrown in for manufacturing yield purposes.
Attachment:
1663.pdf

Go ahead and use the LL1663/50mA. The amp will have fuller low end performance and will have significantly better transient response. You do not need to worry about core saturation. Trust the designers at Lundahl. They know what they're doing.


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 Post subject: Re: "Lacewood" Amp V2.0
PostPosted: 13 Jun 2018, 14:31 
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Joined: 03 Jan 2017, 20:59
Posts: 22
mike567 wrote:
Boost transformer. 12.6 volt secondary wired in series with the primary of your power transformer will put you in the ballpark.
Use higher voltage till you get what you need.


I have an insolation transformer who had many taps on the secondary, maybe an other solution.

https://www.hammfg.com/electronics/tran ... s/line/169


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