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Old 23rd October 2010, 01:57 AM   #1
6L6 is online now 6L6  United States
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Default QUAD 44 Pooge

Hello all!

I'm currently in the beginnings of a QUAD 44 (and 405) Pooge. It's a fairly early one, SN #63XX, I will post the board versions in another post.

I'm starting with the low-hanging fruit, PSU electrolytics, opamps, etc...

So far I have the 32yr old opamps replaced with BB OPA604's on a few of the inputs, and every PSU cap has been replaced. (there's a whopping 5 of them...)

I had to clean up my workspace (kitchen table) before I could take photos, but these seemingly meager improvements have made a noticeable improvement in the preamp. Much akin to cleaning a dirty window, it's clearer, and also less noisy.

Next will be the remaining opamps (which live on the tone control board) and the switching IC's.

I would love to hear from people who have done this and their suggestions for making the most out of this neat old preamp.

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Old 25th October 2010, 01:16 AM   #2
6L6 is online now 6L6  United States
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Ok, here are the promised photos -

Click the image to open in full size.

The QUAD 44, vintage late 70's. What date codes I have found on the components are all 1978-ish. A neat pre in it's day, modular inputs, very interesting tone controls, adjustable high and low-pass controls, and switchless input selection. They changed color sometime in the 80's to a more attractive gunmetal grey.

Click the image to open in full size.
The back of the preamp

Click the image to open in full size.
Here is it with the case off, looking down from the top.

Click the image to open in full size.

Here are the 2 'Radio' (Line-level) cards. The left has new opamps, the right the original. I might play around with replacing the Styro caps, but as they never drift in value, and are pretty good, I wonder if boutique parts will truly make a ton of difference... I will, however, put some RCA plugs on these cards at a later date.

Click the image to open in full size.

MM Phono board. New Opamps installed. It's very nice sounding and fairly quiet, I am going to leave it as-is for the time being.

Click the image to open in full size.

One of the 2 Tape boards. Completely stock.

Click the image to open in full size.

This is the board to which the input boards attach, you can see the rows of pins from the top flanking the switching IC's. This board also contains the PSU caps and regulators, and the aforementioned switching IC's. I have al ready replaced the caps with new Nichicon, and made the filter caps bigger, 1500uf up from 1000uf. I will do someting with that silly little bridge diode, but I am not sure what the right parts to use. Any suggestions?

Click the image to open in full size.

PSU/Switch board from the side. The new caps are plainly visible.

Click the image to open in full size.

PSU/Switch board reverse. Note the heat near the regulators! I will add heatsinks if I replace those components. The row of 4, 14-pin IC's will be desoldered.

Click the image to open in full size.

Board with new IC's installed.

Click the image to open in full size.

The rest of the work accomplished today was replacing these Opamps on the tone control board (including one not in this photo) and a electrolytic cap. (Next Photo)

Click the image to open in full size.

Click the image to open in full size.

Here are the 'dead soldiers' (although everything was operative) PSU caps with bypasses, and smaller electrolytics, 14-pin switching IC's, and a bunch of 32-yr old opamps.

Things to do in the future -

Install RCA plugs on line cards
Replace bridge diodes
Replace and heatsink PSU regulator pass elements

Anyway, as you want to know about the sound, all I can say is that it's great! Updating everything is making it much quieter and more dynamic, the 'fingerprint' of the quad sound is still very much intact, but subjectively it's much, much better. The 'more' dial has been turned up a few notches.

Admittedly, it's hard to give an accurate assessment because the amp I'm using has not been updated yet, as I am waiting for parts, and is rather noisy... But I will cross that bridge when I get there!!

Thanks for looking!
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Old 25th October 2010, 02:29 AM   #3
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I have done extensive mods to my Quad 44. Pretty much what you are doing now but with some additional upgrade to the power supply and other bits. The Quad 44 is my primary listening preamp with my Dynaco St 70 and AR3a's.
If you are interested you can drop me a pm and I can share the changes I have made and the new ones I am doing right now.
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Old 20th August 2011, 03:56 AM   #4
Sir_Rob is offline Sir_Rob  New Zealand
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Hi All

Thanks for all the pics. Ive just purchased a 44 405-2 combo and Im just starting a total rebuild and upgrade job on the 44 1st. Mostly OPA604s a couple OPA134s and OPA627s where appropriate. Most importantly however for these chips to work to full potential the local PS needs a real thorough workover and redesign in key areas as it currently is not up to task for these amps. For instance Ive already moved the bridge rectifier out from under the phono section back to the AC input on the PS board feeding an upgraded regulator setup and distributed decoupling everywhere.

I will post a photo summary later once all the parts have landed and time for the job permits. IMO this PRE has enormous potential without being crazy and just using modern electronic vparts and design considerations that werent available in the 70s.

So please if you can keep updates of your progress coming Im keen to see where you go with this.

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Old 23rd August 2011, 09:16 PM   #5
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Use Metal film resistors - the inexpensive common ones will help - no reason for nude Vishay's or Caddock mk 132
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Old 12th September 2011, 04:30 PM   #6
frank1 is offline frank1  United Kingdom
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I have also done something similar.
I found that modern Op-Amps take more current than the old ones so I had to upgrade the power supply. ( I also didn't like those transistors getting too hot, bolted to just the PCB).
I fitted a new toroidal mains transformer and +/-15v regulator chips on a flat heat-sink spaced off the back of the PCB.
I also fitted phono sockets to the input board brackets.
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