Redd 47 Mic Preamp

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JBB

Active member
Joined
Sep 19, 2013
Messages
35
Location
Russia, Moscow
Redd 47 Mic Preamp


REDD47.jpg



Photos of the project: http://jbb.ru/47/

The scheme used is this: http://jbb.ru/schematics/47-shem.htm

The layout used is this: http://jbb.ru/schematics/47-layout.htm


The original scheme looks like this:

REDD47.gif



********************************************************************


Accessories purchased in different places:

Transformers Audio: http://www.sowter.co.uk/ 

Resistors and the transformer supply: http://www.partsconnexion.com/ 

Switchman: http://www.hairballaudio.com/shop/index.php?cPath=25

Attenuator: http://www.hairballaudio.com/shop/product_info.php?cPath=27&products_id=65

Case: http://collectivecases.com/redd47.html  - This also fits: http://www.diy-racked.com/diy-talk/viewtopic.php?f=7&t=196

Capacitors and other trifles bought for eBay and Tubedepot.



A few pictures from the field work:

First up was assembled layout of this amplifier:
a.jpg


Potestit layout with different versions of Circuits and correction scheme went on to the final phase:

b.jpg


c.jpg


d.jpg


Audio examples:

http://forum.guitarplayer.ru/index.php?action=dlattach;topic=277266.0;attach=933730

http://forum.guitarplayer.ru/index.php?action=dlattach;topic=277266.0;attach=933731


 

ruffrecords

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GDIY Supporter
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Nov 10, 2006
Messages
14,771
Location
Norfolk - UK
That is a beautiful piece of construction. So neat. Where did you get the right angle brackets for the tubes or did you make them yourself?

I am always curious about specifications. Did you actually measure the specifications you quoted?

Cheers

Ian
 

JBB

Active member
Joined
Sep 19, 2013
Messages
35
Location
Russia, Moscow
Angle brackets for the Tubes I bought at the local construction market. By radio electronics they have no relationship.



First there was this:

index.php




After setting it turned out:

index.php



Other settings are the same as stated.

 

JBB

Active member
Joined
Sep 19, 2013
Messages
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Location
Russia, Moscow
I was interested in only two main characteristics of this device.
Frequency Response and Total harmonic distortion.



Total harmonic distortion: (white line)

index.php


 

Moby

www.mobytransformers.com BV.8, Bv.11, Bv.12, T14/1
Joined
Jun 3, 2004
Messages
2,017
Location
Serbia
Great build. Thanks for sharing the layout :)
 

JBB

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Sep 19, 2013
Messages
35
Location
Russia, Moscow
Forgot to warn. To get a flat frequency response, need to remove the C4 and R6. C9 can deliver 10p . The scheme and The layout there are some differences in this place.
 

JBB

Active member
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Sep 19, 2013
Messages
35
Location
Russia, Moscow
I'll try to find out where it is possible to buy such angle brackets.
How I to find out, be sure to let you know.
 

Moby

www.mobytransformers.com BV.8, Bv.11, Bv.12, T14/1
Joined
Jun 3, 2004
Messages
2,017
Location
Serbia
I made similar brackets (sorry no pic) in the local metal work shop. Not a big deal. mine were brass made and they were relatively cheap. 
 

muffy1975

Well-known member
Joined
Mar 21, 2006
Messages
330
Location
UK
Hey,

can you detail how and where you added the T attenuate and all the other pots? They are not on your layout.

Michael
 

müx_micro

Active member
Joined
Aug 30, 2005
Messages
41
Location
sweden
Nice one JBB!  :) Very neat layout.

(I have seen similar mounting brackets on ebay. Simply search for noval mounting bracket.)
 

JBB

Active member
Joined
Sep 19, 2013
Messages
35
Location
Russia, Moscow
I refused to use the attenuator. I use a ribbon microphone. It has very weak output signal. Therefore, I have nothing to regulate.
 

Kingston

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Joined
Nov 1, 2005
Messages
3,712
Location
Helsinki, Finland
Flawless execution. I really like the fact you took the time to present the specs with all the possible details.

Maybe this will set straight the misconception of "tube warmth". THD+N spec and frequency response as shown here is broadcast and even solid state territory and clearly indicates what it was designed for.

PS. I notice you are using some RME product for measurements. It's possible to use RMAA software with 88.2-96khz setting with it. Just set your sound card sample rate from the control panel first, then configure RMAA with the "MME" type drivers. Remember to always set the correct sample rate before starting RMAA software. You will be able to see if the unit is doing funky things above 20khz. :D You can even do 192khz, but there is some low level hash at the very highest "dog" frequencies from the RME card itself to skew the measurement.
 

JBB

Active member
Joined
Sep 19, 2013
Messages
35
Location
Russia, Moscow
I was not interested in the results of measurements of THD + N spec and frequency response. I was not going to do them.
This amplifier is initially not the most attractive technical Specifications.
I felt a lack of treble. Therefore was forced to take measurements to determine the cause.
I also did measurements at 96khz, and 192khz. The results were a little more accurate. But, it does not matter.
 

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