My interpretation of the REDD 47

Hello,
my name is Michael, I am from Mannheim, Germany. I am a member in this forum for 1 year now and this my first post.
Thanks to this great place I have been able to finish this project with success. I´ve been reading everyday I guess.
So here we are and I want to let you see some pictures of what I have built. There are some things that will be changed
sometime (new faceplate), but for now i am satisfied with this result.
Thank you, Michael

Another one of the inside.

And the front.

And sorry for my bad english

Your english is just great, Micheal. Congratulations on your build. I do like the blue faceplate, maybe black bolts instead of silver would look good too! 

Well done Michael. Excellent looking build.

Cheers

ian

Welcome  Michael, nice work! Is this your pcb design?  8) Cheers Thorsten

rock soderstrom said:

Welcome  Michael, nice work! Is this your pcb design?  8) Cheers Thorsten

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Yes, it is my PCB Design.

ruffrecords said:

Well done Michael. Excellent looking build.

Cheers

ian

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Thank you, the 48V supply is your circuit.

I´m in the process of building one redd47. Can you comment on your gain/attenuator set up? are you using and output attenuator?

I will use the exact same output transformer. how do you like it on this project?

nice build!
Rafael

12afael said:

Can you comment on your gain/attenuator set up? are you using and output attenuator?

I will use the exact same output transformer. how do you like it on this project?

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I think you mean the output attenuator. There is a 6 steps 600 ohms bridged T-pad attenuator with -30 -24 -18 -12 -6 0.
Gain setting is just like the original. OT works great.
greetings

Congratulations ! 

If somebody is interested in.

and THD

Nice build, is +-5dB fine gain control from revision on original schematic and works this way?
Cinemag lately got pretty expensive for one set or so shipped to EU, have you compared Lundahl input to any other transformers?
CMMI-7C sounds excellent in this preamp, high level input for 1% THD often comes handy too because it is clean to high levels. People consider Lundahl as very transparent, maybe they think about amorphous C cores, not classic mu metal like in this one. My guess is both manufacturers must have something in 1:7 or 1:10 ratio of similar quality and sound, haven't tried it beside their output and line input.
If one of the heatsinks is for heater regulator it could be bigger. I got a bit too high temperature rise another preamp which takes less current heater. Checking temperature on both would help.

ml-project said:

Yes, it is my PCB Design.

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Where did you get the PCB for the Lundahl?

Nice work!

My3gger said:

Nice build, is +-5dB fine gain control from revision on original schematic and works this way?

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The fine gain is from the original, but it does not work as a expected. It is about +- 1,5 dB. For me completely useless, so i will cut it out.

My3gger said:

Cinemag lately got pretty expensive for one set or so shipped to EU, have you compared Lundahl input to any other transformers?

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I had no possibility to try out other transformers.

My3gger said:

If one of the heatsinks is for heater regulator it could be bigger. I got a bit too high temperature rise another preamp which takes less current heater. Checking temperature on both would help.

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There is no heater regulation at all.

Greetings, Michael

tommypiper said:

Where did you get the PCB for the Lundahl?

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I made it.

Greetings,  Michael

Well done, Michael. One thing I noticed, though. You should NOT solder the earth wire to the screw/lug, only. Soldering is ok if the the wire is additionally mechanically attached in a way that it cannot get lose. It sounds silly, but it´s our VDE regulations which dictate more or less to use a "Kabelschuh" for this connection.
Drop me a pm if I should describe it in german.