Meeting a High Priest of the world of hi-fi BS.

[raleighnut]

The one you had done 15 years ago will soon require new caps for the power supply and the output coupling, the small ones on the amp boards can wait a little longer.
The 4 big caps on the 15 year refurb, are they blue in colour? They live between the transformer and the rear panel. Its been 20 years since I worked on a 303 but IIRC the 4 original smoothing caps on the power rails are 2,200uF each. Many people fit 4,700uF/100V when the time comes, the extra capacity does help with transients, yer 1812 overture cannons, large dynamic range music.
If you or a friend can solder those caps are an easy replacement, its solder tag connections, contemporary caps in large values are physically smaller even than 15 years ago and may need packing pieces in the clamps. Short lengths of split poly plumbing tube work well.
303 is still a sweet amplifier, Dada electronics in Belgium manufacture modded boards for them and for the 405/405-2, vintage Quad is very popular in Holland and Belgium for why I do not know.

Yep they are the big blue uns, the ones in the other Amp are a similar size but mounted the other way up, when funds permit I'll be sending the older one off to Huntingdon to be so modded.
The 303 is becoming more popular as time goes on and is now matching the price of the never 'current dumping' 405/405-2 you are right about them lacking a bit of 'oomph' but my solution of using 2 seems to mitigate that a lot, I'm also wondering about changing to the 1v output on my 44* as the output is shared between 2 channels on the poweramp but I'll have to see what QUAD think of that

* the 44 is a very late mk3, very similar to the mk2 but with some small differences, all the 'modules' are Din and Phono equiped but EU regs also changed the earthing arrangements with the signal inputs now being connected to ground, this means the poweramps now have only 2 connections similar to the old 33's spec usin a 3 wire powerlead causes hum. This change occurred after serial number 35,000 I think (mine is in the 38,000 range of the 40,000 built)

 

[bagpuss]

What my boss thinks about my Bose.....

 

[Teamfixed]

Who made this circuit up for you anyway?
Bought it in a shop?
Ooh what a horrible shoddy job they fobbed you off with
Surprised they let you have it in this room anyway
The acoustics are all wrong
If you raise the ceiling four feet
Put the fireplace from that wall to that wall
You'll still only get the sterophonic effect if you sit in the bottom of that cupboard!
I see you've got your negative feedback coupled in with you push-pull input-output
Take that across through your red head pick-up to your tweeter
If you're modding more than 8
You're gonna get wow on your top
Try to bring that down through your preamp rumble filter to your woofer
What'll you get?
Flutter on your bottom!

Taken from the "Song of reproduction" by Flanders and Swann.
www.youtube.com/watch?v=7fJmmDkvQyc

I have been quite into hifi on and off over the years, I built a pair of Kef Concerto speakers back in the 80's. A B39 bass, B110 and T27 tweeters. They were very good but too big so I ebayed the drivers for good money. I now use an ancient Sugden amp with Kef Coda bookshelf speakers which does sound pretty good.
I bought the speaker cable from B&Q which is also pretty good haha.

 

[raleighnut]

What my boss thinks about my Bose.....

View attachment 561948

Ah Bose, my mate had a set......................not my cup of tea

View: https://youtu.be/xxJNsYeJdaQ

 

[randynewmanscat]

I'm also wondering about changing to the 1v output on my 44* as the output is shared between 2 channels on the poweramp

See if I have this right.
You have two 303 and one 44. L out to one amp, R out to the other, you split each input to feed L&R channels of each amp (common)? You output each 303 into one cabinet with 2 drivers? You feed each driver with one channel? The crossovers in the cabs are passive, they are electrically separate? 44 L>L+R 44 R>L+R?
1.0V output from the 44 should work without problem if my above assumptions are correct, you will have a little more grunt, not much but some.
Its not worth trying to get extra grunt without modifications that involve design changes, some keen audiophools with a soft spot for Quad transistor amps make the output complimentary and use 250W/20A MJ15003/4 transistors, the originals are less than 120W I think.
If you don't have a soldering buddy with a little knowledge its not an option as it requires "other works" and there is always the Quad 405-2, less work and faff.
405 are very very fine when modified according to Bernd Ludwig and Keith Snook evolution's, they still sound Quad which just means good really but they are better, the noise floor is lower and they can handle 4 ohm loads unlike the vanilla version with the crappy current limiters.

 

[randynewmanscat]

I have not been through this thread but I guess this has made an appearance already.

View: https://youtu.be/DvswW6M7bMo

 

[randynewmanscat]

Ah Bose, my mate had a set......................not my cup of tea

View: https://youtu.be/xxJNsYeJdaQ

 

[randynewmanscat]

Taken from the "Song of reproduction" by Flanders and Swann.

Raising the speaker cables off the floor with little gantry's was before Flanders and Swanns time then.

 

[raleighnut]

See if I have this right.
You have two 303 and one 44. L out to one amp, R out to the other, you split each input to feed L&R channels of each amp (common)? You output each 303 into one cabinet with 2 drivers? You feed each driver with one channel? The crossovers in the cabs are passive, they are electrically separate? 44 L>L+R 44 R>L+R?
1.0V output from the 44 should work without problem if my above assumptions are correct, you will have a little more grunt, not much but some.
Its not worth trying to get extra grunt without modifications that involve design changes, some keen audiophools with a soft spot for Quad transistor amps make the output complimentary and use 250W/20A MJ15003/4 transistors, the originals are less than 120W I think.
If you don't have a soldering buddy with a little knowledge its not an option as it requires "other works" and there is always the Quad 405-2, less work and faff.
405 are very very fine when modified according to Bernd Ludwig and Keith Snook evolution's, they still sound Quad which just means good really but they are better, the noise floor is lower and they can handle 4 ohm loads unlike the vanilla version with the crappy current limiters.

Yep that's right on the set up, I changed to the 44 from my old 33 a few years back when I got an unexpected windfall (tax rebate) but that was configured the same. I still use the 33 as an 'active' phono pre for the 5.1 Yamaha receiver in the front room as that doesn't have a phono stage (but it's hooked up to the Telly/DVD/BT Box)
I've seen a few 'mods' to the 303 but they generally take away the ability of the amp to take any load (even a dead short) and survive undamaged due to it's design.
The 'limiters'on the 405/405-2 are removable and were only fitted to allow the Amps to work with the ESL 57's without the danger of 'arcing' the panels. I've owned my 33/303 since 87 and the 2nd 303 since about 2007 and have a few friends who also own QUADs

• Geoff - 33 and 405
• Pete - 44mk1 and 405-2
• Willy - 44mk2 and 405-2
• Chris - 33 and 303
• Rachael - 34 and 405-2
• Gavin - 34 and 306

 

[bagpuss]

Almost the same as telling the wife about the cost of your bikes.

 

[raleighnut]

Almost the same as telling the wife about the cost of your bikes.

View attachment 561992

Aye luckily Maz knows and appreciates what my system is worth and what it cost (not a fortune as I've been gradually building it up over the past 30+ years)

 

[randynewmanscat]

• Geoff - 33 and 405
• Pete - 44mk1 and 405-2
• Willy - 44mk2 and 405-2
• Rachael - 34 and 405-2

Are you or those friends aware of the Snook and Ludwig circuit evolution's or the Dada boards that are an iteration of the best of the design?

 

[raleighnut]

Are you or those friends aware of the Snook and Ludwig circuit evolution's or the Dada boards that are an iteration of the best of the design?

Well Pete and Geoff are but both are dubious preferring to trust in the legendary QUAD reliability, there was also the 'Gazember' mods that claimed to massively increase the power output but that led to fragility.

https://quadrevisionspot.blogspot.com/2008/02/about-gazember.html

 

[randynewmanscat]

Well Pete and Geoff are but both are dubious preferring to trust in the legendary QUAD reliability, there was also the 'Gazember' mods that claimed to massively increase the power output but that led to fragility.

https://quadrevisionspot.blogspot.com/2008/02/about-gazember.html

The power increase mods on a 405 are useless unless the beast is made into a different amplifier, same goes for the 303.
As for the Snook and Ludwig mods, they work. Long time ago I repaired and or recapped a few Quad 303 and 405 when I lived in the UK, or rather my nephew did with training. I split the bounty 60/40, good pay for a 15 year old and he learned to solder like a pro. The transformers are a toss up for ebay purchasers as the potting was not the best, some resonate, some don't, 500VA toroidal is a very good cure.
I would put my 405's against any vanilla 405 for reliability, stability and sound, my scopes tell me what needs to be known rather than subjective banter. Just the correct position within circuit of the bridge capacitor was an improvement on the Walker design. The post end of life modifications are a real improvement on Quads own multiple versions.