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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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It is currently 17 Jul 2019, 20:42

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 Post subject: Re: "Lacewood" Amp V2.0
PostPosted: 14 Mar 2019, 01:50 
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Joined: 13 May 2016, 02:02
Posts: 129
Location: Javea, Spain
Suncalc wrote:
john55 wrote:
That's saved me a few euros. I was going to order some KT-88s in the new year.
Maybe I'll do a KT88 SE-UL bias optimization study when I'm through with the 6L6. I think it might be interesting.

More work with that beautiful little test jig you've built?


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 Post subject: Re: "Lacewood" Amp V2.0
PostPosted: 15 Mar 2019, 13:15 
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Joined: 03 Jan 2017, 20:59
Posts: 31
I put a .22uf coupling capacitor i had in hand instead of the .1uf in my second Lacewood, any counter indication?
Anyway the .22uf duelund is a great improvement over the .1uf auricap, maybe a little less high frequency.
Regards.


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 Post subject: Re: "Lacewood" Amp V2.0
PostPosted: 15 Mar 2019, 17:36 
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Joined: 23 Feb 2017, 02:02
Posts: 495
In theory the 0.22uF will increase low frequency response maybe bit more base.
In theory it will not reduce hf because 20khz is still way too low for series inductance of capacitor to start killing amplitude


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 Post subject: Re: "Lacewood" Amp V2.0
PostPosted: 17 Mar 2019, 16:30 
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Joined: 03 Jan 2017, 20:59
Posts: 31
Ok maybe it was just my impression or the cap was sleeping for to long. I made tests with a signal generator and a sonometer and there's no real difference if i add a .47uf in serial with the .22uf.

There's a big deal on Duelund caps at partsconnexion until the end of the month, up to 60%, great deal but i will buy only a pair of .1uf of the RS line at 30% to put in my other Lacewood for the lower frequency (i don't want more bass) and use the .47uf for the 4S preamplifier. :headphones:

Matt didn't seems to use fancy passive parts for his projects.

Regards.


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 Post subject: Re: "Lacewood" Amp V2.0
PostPosted: 17 Mar 2019, 16:33 
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Joined: 03 Jan 2017, 20:59
Posts: 31
[quote="lowhifi"]Ok maybe it was just my impression or the cap was sleeping for to long. I made tests with a signal generator and a sonometer and there's no real difference if i add a .47uf in serial with the .22uf.

There's a big deal on Duelund caps at partsconnexion until the end of the month, up to 60%, great deal but i will buy only a pair of .1uf of the RS line at 30% to put in my other Lacewood for the lower frequency (i don't want more bass) and use the .47uf for the 4S preamplifier. :headphones:

Matt didn't seems to use fancy passive parts for his projects. :up:

Regards.


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 Post subject: Re: "Lacewood" Amp V2.0
PostPosted: 17 Mar 2019, 16:58 
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Joined: 20 Feb 2014, 10:35
Posts: 56
Location: NZ
0.47uf in series with 0.22uf = 0.15uf


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 Post subject: Re: "Lacewood" Amp V2.0
PostPosted: 18 Mar 2019, 02:06 
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Joined: 23 Feb 2017, 02:02
Posts: 495
Fancy parts get you better sound, geniune metalised polypropene gets you most sound quality gains and good for low end amps.
Mid high end amp schematics you want fancy caps like erse pulse x.


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 Post subject: Re: "Lacewood" Amp V2.0
PostPosted: 22 Mar 2019, 00:13 
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Joined: 03 Jan 2017, 20:59
Posts: 31
Hello.
I want to know if it's possible to lower the gain on the Lacewood 2.0 i didn't put a volume control on the two i build.

Can i use weak 6v6 without any worries.

Regards.


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 Post subject: Re: "Lacewood" Amp V2.0
PostPosted: 22 Mar 2019, 08:52 
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Joined: 06 Apr 2009, 10:08
Posts: 1586
Location: US Pacific Northwest
lowhifi wrote:
I want to know if it's possible to lower the gain on the Lacewood 2.0
Yes. First, remove the 33µf bypass cap on the driver. This will result in about a 6dB gain reduction. After that, a 250kΩ resistor in series with the input and using a 250kΩ grid resistor behind that on the input will form a -6dB pad to further reduce the overall gain.

The first change will subtly alter the sound. The second will not.

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Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog


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 Post subject: Re: "Lacewood" Amp V2.0
PostPosted: 22 Mar 2019, 16:43 
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Joined: 06 Jun 2008, 18:23
Posts: 5115
Location: Australia
Good to know.

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Projects:"retro2308" - chip based headphone amp | ”Calibre 834” - tube phono MM preamp | ”najah” - Raw 180W Tripath Class D power amp | "Icon" - Shuguang CV-181Z preamp


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