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"Lacewood" Amp V2.0
http://www.diyaudioprojects.com/Forum/viewtopic.php?f=9&t=5736
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Author:  john55 [ 30 Jun 2018, 03:18 ]
Post subject:  Re: "Lacewood" Amp V2.0

Amp has been fired up and has been running for two hours with no problems. So just an early valve death. Thanks for your input Jim_O
230V is spot on for Spain. Thanks Matt for the information for checking out the transformer. I felt a lot easier switching on after completing the checklist on the transformer.

Author:  M. Gregg [ 16 Jul 2018, 09:10 ]
Post subject:  Re: "Lacewood" Amp V2.0

Suncalc wrote:
lowhifi wrote:

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.


LL 1663/50mA?
PP with U/L taps (yes), SE with U/L? am I missing something. Whats the pin configuration for SE U/L.


Regards
M. Gregg

Author:  Suncalc [ 16 Jul 2018, 21:10 ]
Post subject:  Re: "Lacewood" Amp V2.0

M. Gregg wrote:
LL 1663/50mA?
PP with U/L taps (yes), SE with U/L? am I missing something. Whats the pin configuration for SE U/L.

Lundahl LL1663 Data Sheet attached.
Attachment:
1663.pdf

Author:  M. Gregg [ 17 Jul 2018, 07:47 ]
Post subject:  Re: "Lacewood" Amp V2.0

Hi Matt,

On the SE Ultra linear, which pin number are you using to give the ratio for the Lacewood circuit?
The choice is 5-11, 3, or 9. Just wondering what % tap the circuit requires.
Ie is there a compromise.

Regards
M. Gregg

Author:  Suncalc [ 17 Jul 2018, 18:02 ]
Post subject:  Re: "Lacewood" Amp V2.0

M. Gregg wrote:
Ie is there a compromise.
Yes. But it's complicated. The amp's performance is based on the 40% tap used by Edcor on the GXSE. Obviously you're not going to get that with the LL1663.

The default would be to use pins 5/11 for the screen. This is a 50% tap and frankly, the differences between this and 40% are not that major. This is rigidly halfway between pentode and triode modes. I haven't tried it but I doubt most people would notice a difference between this and a 40% tap.

Using pin 3 is up toward a pure pentode mode. It's one half (with windings in series) of a 33% tap or about 16.5%. This actually has a pretty large effect with the 6V6 and it may be a suitable choice, but some experimentation would be required.

Pin 9 is so close to pure triode mode that I would not bother. You would probably be better off running the 6V6 as a triode.

So, yes, compromise is the name of the game. The initial compromise, choosing a different output transformer, drives the next compromise, how to connect. But that's normal in all things DIY. YMMV.

Author:  M. Gregg [ 18 Jul 2018, 05:13 ]
Post subject:  Re: "Lacewood" Amp V2.0

Suncalc wrote:
M. Gregg wrote:
Ie is there a compromise.
Yes. But it's complicated. The amp's performance is based on the 40% tap used by Edcor on the GXSE. Obviously you're not going to get that with the LL1663.

The default would be to use pins 5/11 for the screen. This is a 50% tap and frankly, the differences between this and 40% are not that major. This is rigidly halfway between pentode and triode modes. I haven't tried it but I doubt most people would notice a difference between this and a 40% tap.
But that's normal in all things DIY. YMMV.



Thanks for the answer,

If all else failed, you could drop the CT voltage with a series regulator to get it down.
Yes, the "Close to pentode" tap would be interesting.
I tried the pentode connection using driver supply AKA Magnavox and other variations on a small SE.
Stiff regulated pentode/ Electron stream and diode-triode. (Taste varies :D )

I was interested in your thoughts on the 50%, as you say just a bit different.
Also your thoughts relating to the trade off Edcor Vs the "Better output TX".
Its strange Lundahl don't provide the additional tap for use on the SE version "which is air gapped".
(Not interchangeable / rewireable SE or PP) I guess it’s a cost constraint.

Just something to consider looking at other Output Tx's.
Just a thought, hopefully they bring the terminations for 5/11 out to the connection block on the SE version. :confused:

Regards
M. Gregg

Author:  lowhifi [ 01 Aug 2018, 15:54 ]
Post subject:  Re: "Lacewood" Amp V2.0

I have just received my Lundahls LL1663 but i am too busy with home improvement to think about tube amps.
It is possible to add a switch to choose between penthode and triode? Regards.

Author:  john55 [ 12 Aug 2018, 12:14 ]
Post subject:  Re: "Lacewood" Amp V2.0

I first found DIY Audio Projects about two and a half years ago. I've built the 6EM7 Vertical Amp twice in different cabinets, the 4S Universal Pre-Amp twice in different cabinets, the Lacewood 6V6 V.2 twice in different cabinets and a Baxandall Tone Stack in a wine box. All the builds have been fun and I've had them all in different combinations to find the sound I like best. Friends have bought some of the builds from me and I'm now left with a 6EM7 Amp, a 6V6 V.2 Amp and a Baxandall Tone Stack, all three of them in different cabinets. After many hours listening and a lot of soul searching, I decided that the 6V6 with the Baxandall Tone Stack was the perfect combination. I can't overstate the importance of the tone stack. I know many people say that with bass and treble controls you're colouring the sound, that you're interfering with the pure signal. Well so be it, to my ears (which are a getting on a bit and not as good as they could be), being able to adjust the higher and lower frequencies to suit the listening environment and my substandard ears works perfectly.

So what to do about the look of the equipment. I decided to completely disassemble the 6V6 and the tone stack and rebuild them in matching cabinets. Also space is a problem so I decided to stack them.
Finished the project this morning with the exception of some nice feet for the 6V6.

The sound is perfect. Not a whisper of noise or hum from a relatively cheap pair of speakers. Can't wait to get it connected to my Fostex Back Loaded Horns upstairs.

Author:  Suncalc [ 12 Aug 2018, 21:47 ]
Post subject:  Re: "Lacewood" Amp V2.0

A very cool and unique build. It really looks great! Well Done!

Author:  mwhouston [ 13 Aug 2018, 08:26 ]
Post subject:  Re: "Lacewood" Amp V2.0

john55 wrote:
I first found DIY Audio Projects about two and a half years ago. I've built the 6EM7 Vertical Amp twice in different cabinets, the 4S Universal Pre-Amp twice in different cabinets, the Lacewood 6V6 V.2 twice in different cabinets and a Baxandall Tone Stack in a wine box. All the builds have been fun and I've had them all in different combinations to find the sound I like best. Friends have bought some of the builds from me and I'm now left with a 6EM7 Amp, a 6V6 V.2 Amp and a Baxandall Tone Stack, all three of them in different cabinets. After many hours listening and a lot of soul searching, I decided that the 6V6 with the Baxandall Tone Stack was the perfect combination. I can't overstate the importance of the tone stack. I know many people say that with bass and treble controls you're colouring the sound, that you're interfering with the pure signal. Well so be it, to my ears (which are a getting on a bit and not as good as they could be), being able to adjust the higher and lower frequencies to suit the listening environment and my substandard ears works perfectly.

So what to do about the look of the equipment. I decided to completely disassemble the 6V6 and the tone stack and rebuild them in matching cabinets. Also space is a problem so I decided to stack them.
Finished the project this morning with the exception of some nice feet for the 6V6.

The sound is perfect. Not a whisper of noise or hum from a relatively cheap pair of speakers. Can't wait to get it connected to my Fostex Back Loaded Horns upstairs.

You have really gone all out. Good work.

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