Monday, January 22, 2007

Quad 44 & 34 upgrade-service & upgrade-kit

Dada electronics is proud to anounce the 44 upgrade-kit and revision-service.

The problem with the 44 is the fact there are different versions. Some versions used dual (TL072) opamps, other version used single-opamps.

After several tests we decided to use Burr-Brown OPA134 and OPA2134 to replace the TL's. See the data-sheet for more info.

The opamps are very stable, they reject HF feedback and they are designed for audio. At the voltage-level and the amplification-factor in the 34 or 44 they perform better than teh (more expensive) OPA 604 and 2604.

They are also less critical for the power-rails.

The following products will be available in the Dada Webshop next week:
  • Quad 44 upgrade
  • Quad 44 upgrade-kit
Stefaan

The following components are replaced in the 44 (depending on the version and the configuration):

On the PSU-board:

  • 2x 47mF 63V capacitors
  • 2x 1000mF 25V axial capacitors
  • 1x 100mF 16V capacitor

On the Tone-control board:

  • 5x TL072 replaced by BB OPA2134 with feet
  • 6x 100mF 25V (instead of 68mF 6V3)

On the Radio-input board:

  • 2x TL071 by OPA134 with feet
  • 2x 100mF 25V

On the CD/AUX board:

  • 1x TL072 by OPA2134 with foot

On the Disc-board:

  • 2x TL071 with OPA134 with feet
  • 2x Wima MKS4 2,2mF 50V

On the Tape-replay board:

  • 2x TL071 by OPA134 with feet
  • 2x 100mF 25V

7 Comments:

Anonymous Anonymous said...

Contents of 44 kit(e.g. SN16861/2, OPA 134/2134, caps)? Can't find anything on www.dada.com so far.

8:52 AM  
Anonymous Anonymous said...

sorry, Dada Webshop, of course

9:03 AM  
Anonymous Herman said...

Ik heb Douglas Self eens gevraagd of het zin had die opamps in mijn 44 te vervangen, zijn antwoord, nadat hij het schema van de 44 bestudeerd had;
'I can only conclude these TL071 opamps are not being well used. The huge-value resistive attenuators on the inputs will degrade the noise whatever opamp you use.'

9:40 PM  
Blogger Stefaan said...

Hallo, Herman,

Dan zou je het verschil eens moeten horen!

In 30 jaar is er heel wat vooruitgang gemaakt in het ontwerpen van audio-opamps, geloof me vrij.

Wat de "Huge value resistive attenuators" in de ingangen betreft, bij de AUX/CD-ingang is dat een 390K weerstand met een 100K naar de massa, dat lijkt me niet overdreven.

Bij de "Radio" input heeft men geen serie-weerstand en een 1M weerstand naar de massa.

Het gevolg van de design is dat men een zeer hoge ingangsweerstand heeft hetgeen uitstekend is bij het gebruik van eender welke input-bron. Moderne chips kunnen de zeer lage signaalspanning best aan.

Men mag PW niet onderschatten hoor!

Ik ken die Douglas niet maar blijkbaar heeft hij nog niet naar een 44 met OPA134's geluisterd.

Stefaan

11:50 PM  
Blogger hd38 said...

Hello Stefaan !
All the modifications you suggest in this upgrade are higly valuable and do improve a lot the sound.
I would suggest another useful mod : replacing the WEAK 7.5V zeners D404 and D405 with 5W models (1N5343B) does improve the stability of the tricky and unstable selection switches of the 44 which is a frequent problem on this preamplifier.
Hope this helps,
cheers from Grenoble, Hervé

3:13 PM  
Blogger justin wood said...

Hi Stefaan,

I am delighted with the fantastic improvement to my 405-2 with the Dada upgrade package…...it is a stunning difference!

In the mean time, I am very interested in doing something to bring my 44 pre-amp back to life. I have emailled a few photos of my 44 which is Serial Number 20392 as you mention on your web-site that 44s came in various states of modification over the years of manufacture. I noticed that most of the op-amps on the boards are marked TL071CP (plus various other markings such as 027AC, 535B, 240AB or 223AC)….I guess these would benefit from being changed along with some of the capacitors. As you will see in photos some of the capacitors (the red ones…) have leaked a bit like the ones in my 405-2! The printed circuit boards in my 44 are marked as follows: Phono 4C (400uV, 100R, 22nF) – 12542.5, Radio – M12511.2, Aux – M12511.2 Tone control board – M12512.9, Main central board M12436.5

I am sorry to fire off all this data to you but perhaps the pictures may be of use in any case. If you do start producing kits for the 44 I will be very interested to be a DIY guinea-pig!!!

Very best wishes,

Justin Wood

2:25 PM  
Anonymous K. Tham said...

Hello Stefaan,

I recently acquired a Quad 44 Serial No 2926 and did the upgrades as per your recommendations such as capacitor replacements and using the OPA134. I am quite pleased with the performance over my Quad 33/303 combination. I use the Quad 44 to control my Dynaco 70 tube amplifier. Thank you for providing such a generous service for Quad fans.

Along the way I made some other physical changes as well to the Quad 44 such as mounting TR400 and 403 vertically and installing finned heatsinks. The motherboard showed signs of discoloration due to the heat from the power transistors. There is not much room between modules using this technique so some electrical insulation is required on the foilside of the TapleReplay boards to prevent accidental shorting.
Since I use my PC as a jukebox to source the music, I also installed a Ground Loop isolator to filter out the low level hum from the PC on the audio connection between the PC and the Quad 44. The isolator is effective for my listening. I used an isolator from MCM Model 50-9040.
I also replaced the original Volume control with an Alps Blue RK27 dual audio pot. I located this in a local parts store. The shaft is not quite long enough so I must do some mechanical work to accept the original Quad knob.
Right now i am still in the experimental stage with the Quad 44 as I do the upgrades one at a time. I have owned this unit for about 2 months now.
In summary, I like my Quad 44 and the sound it produces. I also like the factory worksmanship of the Quads I own. It is a lost art!

Regards,
K.Tham

6:54 PM  

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