Kit building Quad 405 Clone

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JonLawes

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Joined 2008
#1
Hello ladies and gents, just a post to introduce myself really!

I am a keen audiophile who has never really had the money to buy myself any nice equipment. Anything I have owned has always been secondhand, and it says a lot about the humble quality of my kit that the highlight of my setup is a pair of matched Celestion Ditton XR15 speakers!

Anyway, I have decided that to teach myself a little more about the workings of an amplifier I would have a go at one of the cheap (and no doubt nasty) amplifier kits from eBay, in this case a Current Dumping Quad 405 clone from Tubeshunter. I work in an electronics based environment so there are lots of people here who can help if I come unstuck, but not many who know much about the audiophile side. They can tell me in depth semiconductor theory but don't know their Linn from their Leak!

So essentially I thought I would log in, say hello, and ask you to brace yourselves for some questions in the future!

Many thanks,
Jon.
 
#4
I was going to use a Quad 33 to drive this, mainly because its borderline affordable and is of around the right era to match my 405 clone! Is there any good reason to hold out for the Quad 34 or 44 in preference? I know they are much newer and may be a leap ahead, but as its only driving this 405 clone will that be so important? My budget is rather tiny...

All advice recieved in good humour! 🙂
 
#5
It really depends on what sources you are going to use.

I originally used a 33 but changed it due to having to use adapters to the DIN sockets.

I changed to a Counterpoint tube preamp which sounded better and had the advantage of phono sockets.


Don't forget to post plenty of pictures of the build from day 1.

Andy
 
#6
I managed to source a pretty well priced Quad 34 Pre-amp, I'm not averse to changing the connectors to something more useable (sorry if that offends any purists!) if required. Its got an MC input card with it. I'll probably mod it to take a CD input, plus an iPod interface I'm designing at the moment. Sorry if that makes anyone feel ill!
 
#7
I scavenged an old hefty heat sink from a broken amplifier today; its quite sizeable but not quite as big as the one you normally see on the front of a quad 306! I need to make a custom enclosure I think, quite looking forward to it.
 
#8
An externally hosted image should be here but it was not working when we last tested it.


Here is a picture of the unit so far. Come up against a small problem as R11 doesn't have the component value written on the board so I'm awaiting the sellers reply to see if he knows it.

Its only mocked up in the photo; the heat sink isn't yet connected to the board, as the absence of power transistors will inform you! I'm a bit nervous; the construction bit I can do but if it doesn't work on completion (which lets face it given the obscure source of the kit) I am not going to be much good at fault finding.

The Big heatsink the two amp heat sinks are bolted to I scrounged off an old amplifier.
 
#10
Nice work. I will be watching your progress on this post.

I own a Quad 33 and 44. I like them both, but prefer the 44. It is a very quite preamp from a noise perspective. Both have great tone controls, but slightly different. I could get technical, but I think personal preference always wins.

I use the 44 in my main system and go between the 33 and a tube preamp I built in my family room.

Dave
 
#13
JonLawes said:
Excellent, what a great forum this is. Thanks guys!
Click to expand...

Hi Jon!
After reading your thread I looked up the seller of the kit, and decided I'd like to give building it a go! However, it would be interesting to know if you got it working before ordering.. 😉

If it sounds anything like the original 405, then you are in for a treat!

Regards
Patrik
 
#14
Its a bit vague, some of the components were wrong. However the board is silk screened with the component values which makes life easier. My boards are almost complete and i plan to test them using bench supplies rather than splashing out on a toroidal transformer until i know it works. Otherwise the pcb looks good, but its easier now i have the 405 schematics. Even now i;'m not sure if I am building a 405 or 405/2.
My other problem is setting the supply rail voltage, i am not sure if its 35 or 50v.
 
#15
I have purchased and built the 405 clone! I have reworked some values so that I can use 2n3055 devices and a reduced supply rail I would agree that there are a few errors but nothing to bad!!!have also used the Tl071 opamp as a front end all in all it sounds ok and represents good value for money
regards Trev
 
#16
JonLawes said:
Its a bit vague, some of the components were wrong. However the board is silk screened with the component values which makes life easier. My boards are almost complete and i plan to test them using bench supplies rather than splashing out on a toroidal transformer until i know it works. Otherwise the pcb looks good, but its easier now i have the 405 schematics. Even now i;'m not sure if I am building a 405 or 405/2.
My other problem is setting the supply rail voltage, i am not sure if its 35 or 50v.
Click to expand...

I asked the ebay seller if it was based on the 405 or 405-2, and what, if any, known improvement's had been incorporated (non-inverting input stage, etc). The answer I got back was the one word "405". So it's probably a straight 405 clone. Not sure why a kit producer wouldn't do the 405-2 instead.. No biggie as one can update it anyway.

The 405-2 with improvements seems like an ideal DIY project anyway. Fantastic sound, few and cheap components, small board, unconditionally stable, no trimming at all, and modest demands on cooling and power supply. Unless Quad is going to go after us all and sue us..

latala said:
I have purchased and built the 405 clone! I have reworked some values so that I can use 2n3055 devices and a reduced supply rail I would agree that there are a few errors but nothing to bad!!!have also used the Tl071 opamp as a front end all in all it sounds ok and represents good value for money
regards Trev
Click to expand...

A few errors may be very bad indeed if you "paint by numbers" on a kit!
Seems like a bargain if it sounds like a real Quad! Did you do the diode mod (I haven't looked into it properly, but apparently later 405s had a diode added somewhere to ease the task for the dumper transistors. I have yet to study the schematics.)

Do you know if all the original protection circuits are implemented as well? (Hmm. the 405-2 has a small thick film plug in board for protection circuitry, which is probably why the clone is 405 only..)
 
#17
I used to retail the 405 back in the seventies and judging from that the kit is the mk 1 i.e with the discrete transistor current limiters not as with the later mk11 a hybrid pc setup
The only upgrade I have done is to fit the tl072 op amp instead of the Lm 311 I did consider the diode mod but as I was after the origional sound decided to leave it out
To be honest I always preffered the 303 to the 405 and only built it because Iwas available !
My mods were to use transistors from the junk pile and as I use Lowther PM6 in audiovector enclosure any thing more than 5 watts is to loud any way the origional supply rail is +50/-50 volts dc and my version is _30/-30 volts dc
regards for now Trev
 
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