My Day improving Audio Equipment

[Light Dependant Resistor]

Hi
Today's work started last night, installing UF series diodes in my 2 Quad 306 power amps.
These diodes are very good for audio purpose making standard diodes well worthwhile replacing.
there are differences in the forward voltage specification between the 4001 - 4004 at 1v vs 4005-4007
1.7v so to replace part for part the UF 4003 is recommended.


in the 306 there are 6 x 1N4003 diodes, D5,6,7,8,9,10 on each channel, if doing this on yours
you will need some solder wick to carefully remove the existing diodes. The 306 has to be the
easiest of Quad amps to work on so is a delight. However this work needs extra care as diodes
inserted and soldered in the wrong way will result in very damaged equipment. There are nice
labels underneath the board showing you where each goes, but no labels on the top board
so you need to very carefully match position from what is seen underneath to what is on top.
taking care with D7 in particular

so 24 diodes later, the improvement in audio quality is very easy to hear.

a nice lunch later.. hmm where else can these go

8 went into my DBX 150x , another 4 into my Pioneer CD player's separate analogue
power supply.

Cheers / Chris

[Firebottle]

Good one Chris, I had only really thought of the improvement in the power supply with UF diodes.

[Sovereign]

Fantastic Chris

[Light Dependant Resistor]

Thanks Alan and James.
The UF series diodes are a huge improvement, I prefer the UF4007 in the 306
they have a what I am hearing as better match to the bridge components.

The 2 x 22R resistors quad use are slightly out, if you want to perfect
the current dumping bridge use 27R and 30R for each channels r24 and r25
and move r35 ideally to the junction of r13 and L1 as was done in the 909
or if you are not that brave to the upper side of r13 as was done in the 606
Quad usually did the 606 mod when amps went in for service, removing
the original placement and adding the 10k resistor bridging the left and far
right leg of T3

So today I am installing a separate digital supply in a marantz CD50
yes the famous TDA1541A Dac. Here I have built up both positive
and negative regulators on a nice piece of stainless steel that serves
two purposes both as a heatsink and as a ground plane.

I trialled this with a sony PSP 5v supply changing the
SAA7310 and SAA 7220 and TDA 1541 5v+ supplies
to come from the sony and thought that's nice, so then
embarked upon doing all of the 7310 7220 and TDA 1541
digital supplies. The analogue supplies I will leave standard
for the moment, as i am researching the AD844 as an I/v

The bank of six 7805 regulators have surface mount 1206 size 0.33 caps on
input and output soldered directly to legs, and ground is the metal heatsink
pin out being vin ground and Vout left to right. i am using a T03 cased
regulator for 15v+ a 7815 and also 5v+ 7805 and 15v- 7915 and have
ordered in a 7905 as there will be some heat dissipation from the
main supply which after rectification is 18.7v+ and 18.7- the
transformer I am using came out of a unused meridian 101 ( will convert it to be
an LDR pre later )

2015-09-05-145618.jpg

[Light Dependant Resistor]

Today I set about changing surface mount op amps in my DBX Quantum
which are placed in the analogue input and analogue output board.

SOIC op amps are often difficult not because of their size, rather because the
tracks they are soldered to are fragile. Standard there are JRC 4580
devices installed in the Quantum that are typically used in tone controls, and
a review of their data sheet finds them to be pretty average for any audio purpose,
let alone a very expensive device like this, so changing them for LM4562 also
SOIC size is very very beneficial.

A quick explanation on how I am presently using the Quantum as
it has so many features, it is a mastering processor usually used
in recording. It has what is called type 4 conversion which
utilises the top 4db of its analog to digital converter to create
an overload region in order to improve dynamic range capture.

Regular reader to the forum would be aware of how much i
praise type 1 DBX, it seems to me to be exactly what is needed
if you want to hear recordings closer to how they truly sound.
On the other hand Type 4 failed to impress me until 5 days ago
when I happened to insert it receiving the tape out of the 150x
and then through the Quantum via a digital link to my
Yamaha CDR HD1500 then back from Yamaha analogue out to the 150x
tape in and console out to ldr preamp and Quad 306's

Well its a combination that is as close as I ever heard
for getting music correct in every way. I was enthralled today
hearing Tord Gustavsen humming along like Keith Jarrett does
on one track and presentation is just so life like now.

So back to SOIC op amps, and changing them, using
solder wick can help, but can also weaken the surrounding
track, what I found was successful was to physically cut
the op amp itself not the legs, if you cut the legs this
strains the tracks, so it momentarily looks horrible
but if the op amp you are replacing is removed by cutting
the plastic frame the legs are then all intact and makes
substitution quite easy if you use a temperature controlled
iron and solder down one leg. I then usually solder the
middle two legs then the outers. If you get solder between
the legs of the SOIC device, just use solder wick to remove.

The UF diodes really prove their abilities with changes today
not forgetting D13 in the 306 a 1N4148 to be changed to a UF type.

More on the marantz CD50 to come.

Cheers / Chris

[Desmo]

...
The UF series diodes are a huge improvement, I prefer the UF4007 in the 306
they have a what I am hearing as better match to the bridge components. ...

Interesting Chris, If you prefer the UF4007 for the Quad 306, then why did you fit UF4003's? was that just what you had to hand?

[Light Dependant Resistor]

Interesting Chris, If you prefer the UF4007 for the Quad 306, then why did you fit UF4003's? was that just what you had to hand?

Hi Graeme
I fitted the UF 4007 in both 306's I listened to one channel with its standard diodes 1N4003 and
in the other channel UF 4007. That way I could assess what changes these diodes made.
what I picked up was more natural sound from the UF 4007 channel, I then changed the
other amps diodes for UF 4007.

The UF 4003 is closer in exact specification to a 1N4003 so advised to use them, however
I have had total success with the UF 4007 in positions D5, D6, D7, D8 D9, D10 and D13
in both 306 amps. I am using a 306 per channel just using the left hand channel of one amp
to drive one speaker and the right hand channel of the other amp for the other speaker
Speakers I use are either gale GS401a or Quad ESL57

Cheers / Chris

[Desmo]

Thanks Chris that clarifies things. I might try the UF4007's then.

I'm currently using a more traditional vertical bi-amping model with one 306 driving the right hand speaker (bi wired) and another doing the same for the left hand speaker. In my case the speakers are B&W P6's. Normally I'd have one of your LDR pre-amps in place, but today I confess I've got a home brew valve pre amp in service ;-)

[Desmo]

Thanks Chris for starting this thread, I've replaced all the relevant diodes on my pair of Quad 306's and you are quite right there is a noticeable improvement in sound. I think they are particularly clearer in the higher registers, but there is an overall increase in clarity. I'm going to do the same trick to my Myst G-Ohm amplifiers which use 1N4003s, and see if they also respond as well.

[Light Dependant Resistor]

Thanks Graeme, don't forget R24 and R25 in your 306's change from 2x 22R ie 44 ohms to 27R and 30R ie 57 ohms

Todays improvement was changing the rectifying diodes and 2 more near the middle of the board, all which were 1N4002
for UF 4007 in a Marantz CD52Mk2 player. Took all of about 15 minutes, and boy what a difference for the better.

My usual test piece of music is Miroslav Vitous Universal Syncopations 1 and 2 and there is now much better clarity with
what individual instruments are doing and stereo separation has improved and just much nicer, given this is a
very good sounding CD player to start with.

The only other change in this player well in fact two changes were assisting the CD clamp hinge with a coin glued to it in the middle,
Marantz also attend to the same style of thing in a CD50, and changing op amps for 2 x dual LM4562.