Pricing for Quad revision by Dada Electronics

We use the best components and we work together with the best specialists.

After a revision there is a 1 year full warrantee (excluding transportation costs).

This is the pricing (in Euro) for the Quad-revision/upgrades:

• FM3: 85,-
• FM4 including battery: 95,-
• 33: 135,-
• 303: 165,-
• 303 including High-end board-set: 385,-
• 306: 185,-
• 34: 155,-
• 44: 185,-
• 405: 185,-
• 405 including Dual power-supply board: 285,-
• 510: 185,-
• 520 (f): 195,-
• 606: 195,-
• 606 MK II: 225,-

The Do-It-Yourself kits with support remain @ the same price:

• 33-Kit: 22,-
• 34-kit: between 30,- and 58,-
• 303-Kit: 74,-
• 306-Kit: 74,-
• 405-Kit: 80,-
• 405-Kit with Dual Mono PSU: 195,-
• 606 Basic kit: 65,-
• Other Kits: Ask for a quotation

Dada Electronics has all Quad (33 to 909) parts & replacement transistors in stock.

Documentation & 7/7 support by experts are free.

You can order a revision for your Quad or a Do-It-Yourself kit with support & components in Dada's European Ebay shop , Dada's American Ebay Shop or Dada's Australian Ebay shop.

Stefaan

Quad 405 replacement transistors

This is the complete list. The original Quad transistor is in Italics our preferred alternative(s) are in Bold.

Click on the hyperlink to see the Datasheet or to buy the transistor in the Dada Electronics Ebay shop.

• TR1: BC214C - BC559C BC560C BC415C
• TR2: ZTX304 - BCX32 BC682 BC546B MPSA06 2N5551
• TR3/TR4: ZTX504 - BC556B
• TR5/TR6: BC214C - BC560C BC415C BC559C
• TR7/TR8: 40872 - 2SA740 BD242C 2N6134 TIP42C BDX78
• TR9/TR10: 17556 - 2SD424 2SD676 2N3773 MJ15003

All Quad 405 replacement parts are available from the Dada Electronics Ebay-shop or send an e-mail to info@dadaelectronics.eu.

Quad 303 replacement transistors

This is the complete list. The original Quad transistor is in Italics our preferred alternative is in Bold.

Click on the hyperlink to view the datasheet or to buy the transistor in the Dada Electronics Ebay-shop.

• TR1: 38494 - 2N3055 MJ15003
• TR2: 38494 - 2N3055 MJ15003 (or Push-pull alternative* MJ15004)
• TR3: 40411 - MJ802
• TR100: BC154 - BC560 BC214C
• TR101/TR107: BC109 - BC109 BC237C BC184K
• TR102/TR103: U17219 - BC546B ZTX304
• TR104: U17229 - BC556B ZTX504
• TR105: 38496 - BC461 2N5322
• TR106: 38495 - BC441 2N5320
• MR 100/101/105/106 can be replaced by 1N4148

* The 303 can be modified to a PNP/NPN Push-pull amplifier using the Dada Electronics or standard boards.

All other Quad 303 replacement parts are available from the Dada Electronics Ebay-shop or send an e-mail to info@dadaelectronics.eu.

Eduardo Niebla chooses Dada's 405 revision

We revised Eduardo's 405.

He uses it in his studio to monitor his recordings.

We used the Dada dual-mono power supply and Burr Brown OPA627 opamps.

Edouardo wrote:

"Received my Quad 405 with your upgrade plus the Velleman K4700 loudspeaker protection.

The packing was very secure, well done!

The sound now is much more open and extended; bass to trebles through the whole spectrum are very clear and rich. A very wonderful sound. I'm very very happy . I now can hear very clear my mixing and recording work in much more detail.

Thank you very much for all you wonderful and professional work - I have no hesitation in highly recommending your upgrade services and give you 10/10.

Best wishes to you all (I'm definitely a happy customer)."

Click on the picture to visit Eduardo's website.

Stefaan

Quad 50D & 50E Connectors available now

We found the original manufacturer of the 50E and 50D connectors.

The company was willing to make a small batch for us from NOS (new old stock) parts.

So these are new connectors.

The input connector for the 50E and D are the same, the output connectors are different.

Now you can restore these magnificent amplifiers to their original glory.

The connectors are available in the Dada Electronics Ebay-shop.

Joost

High-end Audio-grade Opamps available again...

Dada Electronics has the hard-to-find High-end Audio-grade Opamps in stock again.

Click on the links for pricing - quantity - datasheet from our Ebay-shop. We ship within 24 hours.

These opamps are the ideal choice for Quad (pre-) amplifiers from the 34 on. Because of the power-supply rails you would rather use the OPA134 in a Quad 134 and the OPA604 in a 44.

Stefaan

• Burr Brown OPA134 (for Quad 34, 44 ao.)


• Burr Brown OPA2134 (dual opamp for Quad 34, 44 ao.)


• Burr Brown OPA604 (for Quad 44, 405 ao.)


• Burr Brown OPA2604 (dual opamp for Quad 44 ao.)


• Burr Brown OPA627 (for Quad 405 ao.)


• Analog Devices AD797 (for Quad 405 ao.)

Dada Electronics is specialised in Vintage & High-end audio.

Installation instructions 405 Dual Mono Psu

This post explains the installation of the Dada / JPE dual power supply for the Quad 405. The PSU and the tools are available in the Ebay Webshop.

Joost & Stefaan

Introduction

The power supply is a fully functional replacement of the original supply. In a standard 405 the secondary windings of the transformer are combined to form a single supply. In post 405 amplifiers, like the 606 each channel has its own supply. There are two reasons for this new design. First it is necessary to support the more elaborate protection circuitry in the successors of the 405, second, it lowers the mutual interference of the two channels. By building the amplifier as a four pole device it also reduces earth loops in the cabling systems.

Preparation

Start with a clean bench and the necessary tools. Although the Psu board is not very sensitive for static electricity, discharge yourself by placing your hands on the bare metal of the chassis before you touch the electronics. Or ware a special bracelet connected to the chassis. Read this instruction before you start working on the amplifier.

Tools

· Philips (Posidriv) no 2 screwdriver
· Soldering iron, 25W, a soldering station with temperature control is the best
· Wire cutters and clippers
· A DC multimeter

Removing parts

For easy access: remove the top, bottom and side plates of the amplifier.
Remove the wiring from the capacitors and the rectifier bridge. Cut the wires where they are entering the cable beam. Remove the capacitors and the clips. Remove the Rectifier bridge. Remove all wires from the secondary windings of the transformer, leaf the blank connecting wire in place on each secondary winding. Also remove the wires to the speaker terminals.

Mounting the Psu in the chassis

Place the plastic self adhesive feet in the corresponding holes. Clean the area where the feet are to be placed with a solvent. Mount the board after the wires are soldered to the connecting pins, by removing the protective tape. and push the board firmly in position. You can always remove the board from the pins.

Basic wiring

In this setup we only implement the power supply as a dual supply. The Din connector and the earth connection at that point will stay in place. Also we reuse the earth connecting point at the location of the old rectifier bridge. Connect the wires as shown in the diagram. Start with the wires on the Psu, place the Psu in the chassis and connect the other wires. Also connect the power on led to the two pins, because there is already a series resistor on the power supply, short circuit the resistor on the small Pcb at the underside of the amp.

Building a floating amplifier, for the advanced user!

To gain full benefit of the double supply, a more complicated route has to be followed. The chassis to earth connection on the Din connector should be removed. Also a new central "earth" point on each amplifier module is necessary. This is created by removing the centre screw on the heat sink, use an special transistor isolation washer (on the heatsink side) and a new screwand nut, M3x15 (all from a TO220 transistor mounting kit) between the head or the nut (depending of the way the screw is inserted) and the heat sink. Use a copper or steel washer on the Pcb side to ensure a good contact. In this way we can connect wires to this point without making any contact with the heat sink and the chassis. For best results only use the isolated cinch connectors and remove the wiring from the Din connector. If you have to use the Din facilities use the spare pin for a second signal earth connection. Because of a printed circuit layout issue in modules numbered M 12368 and earlier, connect the input earth wire also to the new central point on the heat sink. In the original setup this is done by connecting the earth wire to the chassis in the Din connector. On later issues this is not necessary.

Checks before switching on the amplifier

Before connecting the red and black wires to the amplifier modules check the voltage of the power supply. Connect the amplifier to the mains socket. On the red wire there should be 50V referring to the chassis or the module earth point. On the black wire there should be -50V. If you installed the Psu as a fully floating device, check whit an ohm meter if there is no connection between one of the green wires and the chassis. Also check if there is no connection between the green wires of the two channels.

Appendix 1 Basic wiring
Appendix 2 Fully isolated wiring

Quad 34 Upgrade kit launch

We launched the upgrade & revision kit for the Quad 34 - in 4 versions up to now.

In the 34 before serial number 8000 there were 12 TL071 opamps, in the 34 after serial number 8000 there were 8x TL071's and 4x TJ072 dual opamps. The configuration of the electrolyt capacitors is different as well.

As we will replace the TL071 and TL072 with Burr Brown Audiograde chips we had to launch different versions.

We also wanted to offer the choice between the OPA134 (and 2134) and the OPA604 (and 2604). So there are 4 versions in total available in the Ebay-shop.

(Click on the version to go directly to the Ebay-shop)

• S/N up to 8000 with OPA134
• S/N up to 8000 with OPA604
• S/N above 8000 with OPA134/OPA2134
• S/N above 8000 with OPA604/OPA2604

We will also launch a version where the (4) output-opamps will be replaced by OPA627 or AD797 as well but we still have to do some tests in the coming weeks.

Stefaan

Quad FM1 - FM2 revision notes

Despite their external appearances being so different, the Quad FM1 and FM2 tuners are internally almost identical.

They are both very well-regarded FM tuners and are still capable of delivering a quality FM sound when in good working order. The guidelines for renovating these are basically the same as for any piece of valve equipment.

The notes below also include the results of a lot of experience with these two tuners in particular.

But first a WARNING: valve equipment contains lethal exposed voltages: in the case of the Quad valve tuners, there are a couple of hundred volts DC.

Don't attempt any internal measurements or repairs unless you are aware of all the appropriate safety precautions. Dada Electronics accepts no responsibility.

1. Replace all the resistors attached to the HT line with 1 watt carbon.
These will typically have drifted higher in value, and the larger the value the larger the drift.

2. Replace all the red Hunts capacitors in the (larger) IF/audio section.
These will typically have increased in value by 200% or more, or decreased in value by 50% or more. Replace with ceramic.

3. Replace all the electrolytics that are easy to replace. Replace the main PSU capacitor if you get funny noises, or low or unstable HT voltage, or it shows up badly on an ESR meter: otherwise leave it alone.

4. Don't disturb anything inside the (smaller) RF section if you can help it, regardless of the above. Otherwise you are up for an RF realignment at least.

5. Check the anode and cathode voltages of each valve against the voltages shown on the circuit diagram. If the anode voltage and cathode voltages are both out, replace the valve. If just the anode voltage is low, check the grid voltage of the next stage: if it is high, you have a leaky coupling capacitor between the two, so replace it.

6. Always use the same values, or as close as possible, when replacing components, except that you can double the values of the electrolytics apart from the main PSU electro. Always observe the correct voltage ratings for capacitors.

7. Don't attempt any kind of alignment unless: you really know what you're doing; you have the necessary equipment, i.e. an oscilloscope and an RF sweep generator; and you're aware of, and prepared for, the consequences of damaging a tuning slug, which are fatal for the tuner. The alignment instructions in the owner's manual are barely adequate even as a last resort, and won't give you minimum distortion, or decent stereo.

Dada Electronics Australia specializes in valve and solid-state tuner
alignment: mailto:dada.australia@bigpond.com. We also refurbish and align the sterep decoders that go with the FM1 and FM2.

Esmond Pitt
Dada Electronics Australia
Copyright (c) Esmond Pitt, 2008. All rights reserved.

Dada Electronics lab "Speakers"

We wanted to show you the "speakers" we test the amplifiers with at full power for several hours.

Instead of noise they produce heath, 2x 400 W RMS.

Joost developed them, inspired by modern architecture...

Stefaan

Dada Loudspeaker Protection & Delay pre-announcement

Dada Electronics and JP Engineering are proud to pre-announce:

The Dada High End Loudspeaker DC protection with delayed switch-on, fast switch-off. (this is the first pre-production version, after the first ten units, real production starts. Size 24 x 89 mm. Product specifications might be changing. )

• No switch-on/off noises like “Plop” or “Pmp” anymore.



• Protects your valuable speakers against DC voltage from the output of your amplifier when something is wrong. Outperforms the original 405 'Clamp' circuit. The clamp board or components on the modules can be removed. A led will be used to indcate the activation of one of the protection circuits.



• Designed for Quad transistor amplifiers, but can be used with almost any other transistor amplifier up to 500W RMS.



• Fixed delay: 4 a 5 seconds. Other values on request. The switch on delay in a Quad 34 or 44 is not needed anymore.

• AC detection: Immediate switch-off when mains power is removed from the amplifier. The AC detection is done via an optic coupler so no ground loops or other related problems.



• Runs on the DC power supply of the amplifier 35 - 90V DC. Can be used with the Quad 303 as well, as with most other power-amplifiers. No separate mains power needed.
  Less mains-power leads inside the amplifier means less induced hum.



• Audio Grade loudspeaker relay (the only one we know of) - very low contact resistance, double contact, one heavy duty and one gold plated silver contact, the gold contact closes after the heavy duty contact and opens before the heavy duty contact.



• DC sensing and protection must be used when you have an amplifier with symmetric power-supply. It can be switched off by removing a jumper, when you have an amplifier with output-transformers and a single power supply or output-capacitors. With this option the relay contact can switch the loudspeaker without any galvanic connection with the rest of the amplifier.



• Mono design. The unit can be used with amplifiers which are built as four pole devices, like the Quad 520 and 606 range. Or when a 405 is fitted with our double PSU in full floating mode. For use in a Stereo amplifier you should use 2 modules.

Placement of the unit in a 405, it will fit beside the modules. Firmly connected to the bottom cover with self adhesive feet.

Quad FM3 Service Notes

Quad produced some 50,000 FM3 tuners between 1971 and 1982. So there are plenty of units out there, so it is well worth while developing a service approach. This article is the result of having three customer FM3s on the bench at the same time as well as my own unit, which I’ve owned for 20 years but am only just renovating now.

The FM3 should not be confused with the similar-looking FM2, which is a valve unit based on the original FM tuner that goes with the 22/II valve equipment (of which 7,500 were built between 1968 and 1971: they are now much sought after). The FM2 and FM3 are clearly marked as such on the back, and the FM2 has the stereo indicator on the left and the tuning lights on the RHS of the scale: the FM3 has them the other way around. The FM3 is a solid-state tuner with excellent performance.

There are three principal variations of the FM3:

s/n up to 5885: This series uses a two-IC front end and a Motorola MC1305 stereo decoder.

s/n 5885-9,9999: This series uses the same front end and an MC1310 stereo decoder.

s/n 10,000 up: This series uses a single-IC front end and the MC1310 stereo decoder.

Within each series there are also minor variations detailed in the Service Manual, the most interesting being that for a short period in 5885-9999 a different tuning gang and tuning scale were used, with ‘MHz’ appearing in the centre of the scale instead of at the right-hand end. I’ve never seen one of these.

Servicing these units should be confined to the following unless you have RF and IF alignment equipment (sweep generator, marker generator, stereo modulator, and oscilloscope).

1. Check that +-14VDC is available at the red lead and the long black lead on the underside. Pre s/n 5885 adjust the PSU RVs as necessary; otherwise maybe replace the Zeners and resistors.


2. Replace the two PSU caps with 1000uF/25V.


3. Replace the audio PSU decoupling cap with 220uF/16V or maybe 470uF/16V.
   


4. If you have high-quality poly capacitors available, you could change the audio coupling capacitors C124/125 (C116/118 pre s/n 5885).
   


5. You can consider replacing the emitter bypass capacitor C100 and the composite-audio coupling capacitor C104, both located next to the MC1310, with 0.68uF/16V, but note that Quad used high-quality ‘orange drop’ capacitors in this position so personally I would avoid it unless you know they are faulty. On pre-5885 models these capacitors do not exist.
   


6. Replace the stereo lamp assembly with a 5mm yellow LED in series with 1k2 (or raise R101 to 1k). The green wire should be connected to the negative (short) lead of the LED, the black wire to the positive (long) lead.
   


7. Replace the tuning lamps and assembly with two 5mm yellow LEDs in series with a 1k2 resistor (0.25W will do). The left-hand lamp looking from the front is connected as (4) above; the other one is connected the other way round (because the black wire here is supplying a negative voltage). In all three cases the green wire is ground. The old lamps can be removed complete with their mounting flanges with a pair of pliers: just squeeze the ‘U’ shape together and it lifts out to the rear of the tuner. If you can figure out a way to mount an LED in the panel lamp position, you can also fit an LED there, on the same principle, i.e. also in series with 1k2. Otherwise, if you have to replace this lamp, make sure that the swinging lever is free and doesn’t contact the chassis and earth its supply voltage anywhere.
   

Do not adjust anything on the left-hand RF/IF board (including the part to the right of the metal divider), or anything on a pre-5885, unless you have FM alignment gear. Note that the factory instructions for s/n 10000+ assume you have an ST1000A and don’t tell you how to do it with an ordinary sweep generator.

Esmond Pitt - Dada Electronics Australia

About the Gazember 2x 160W 303

The Quad 303 160W RMS per channel. Part two.

Last Thursday, on Valentine’s Day, I was in Antwerp, as Stefaan sent me an interesting e-mail (nothing to do with Valentine). A customer sent us a Quad 303/33/FM3 set for a check up, all bought from the man whose name should not be mentioned on this blog, (only this time).

Yes, the "Gazember" 160 W 303 was on our workbench. The pictures on Ebay reveal a 303 in a sorry state, in real life as well I can say now. The output capacitor banks are "glued" to the chassis, with wood glue, so they where rattling inside the cover of the 303 after transport.

The extra capacitors on top and beside the original power supply capacitors where held together with an elastic band.

The original trimmer pots where still in place after 40 years.

The solder work is below any standards.

So far for first impressions.

Technical review:

The regulated power supply has been removed, including the 40411 transistor.

The emitter resistors are halved in value by soldering a second pair over the existing ones.

The standard number of current limiter diodes is unchanged.

All the output transistors are replaced with MJ15003, which in itself is a good idea.

There are two rectifier bridges screwed to the chassis, with more extra diodes soldered on top of it.

All the wirering and the soldering looks unprofessional.

Measurements:

Instead of measuring with constant input voltage whe measured the maximum output before clipping, the way it should be done according to IEEE definitions.

If you let the amp clip until the level of square wave output, "almost" any RMS voltage is possible.


A 1 KHz test signal was applied.

The results:

16 Ohm 24W RMS both channels
8 Ohm 42W RMS both channels
4 Ohm 62W RMS both channels

Technical analysis.

By using the wrong (in our opinion) secondary windings from the transformer, combined with the voltage selector on 240V, you will get a power supply voltage of 70 V DC without load.

With two channels at full power, the voltage drops to 62 Volts DC.

This explains the lower performance with an 8 Ohm load compared to a standard Quad 303.

As a result of halving the emitter resistances the theoretical current limit doubled. This explains the result at 4 ohm load.

There may be 3 possible reasons why "Gazember" made the mistake to state the 303 had 2x 160 Watt RMS:

• He was confused between Ac Peak-to-Peak Voltage and RMS Voltage. Power into 4 Ohm = output voltage under load (both channels) Square / 4.


• Output-power is defined as power before "clipping" or before 1% distortion


• The power-supply has to be able to deliver the total power. In the case of a Push-Pull like the 303 this is 200% to be on the safe side. A 2x 160W would need a 640W PSU.

Advice.

It could be possible that whe are looking at a "Monday-morning" product. So check those units before you buy them, if you like what you see, buy it.

Until it is clear under which conditions the amplifier should be measured in order to produce the promised results, and it has been checked by an independent lab, I have very strong reservations.

And there is still the issue of the "misinterpreted graph" (see my comments in the first article).

Joost Plugge

The original Joost Plugge text - not for publication - can be obtained via info@dadaelectronics.eu only. You will need Joost's agreement to publish parts of the text.

Stefaan

Gazember - continued

Andy Williams added the following information:

I am also involved in the upgrading of QUAD amplifiers and during the course of this I have seen a Gazember. The owner of this had owned it for around 12 months and said it had been returned for repair two or three times and had eventually lost faith in the product.

Opening the case revealed the original 30 year old power and output caps had several low value caps soldered in parallel and the original caps had finally ruptured and leaked onto the circuit boards causing the amplifier to fail yet again. The original large capacitors should have been replaced when serviced, to not do so is just penny pinching and is not in the customers interest as the amplifier would be no more reliable than a non serviced 30 year old 303 which is not what the customer would expect after spending money on his Quad.

The old trimpots were still in place as was the original rectifier bridge however the power supply board had been removed and the current limit increased by removing half the turns on the wire wound emitter resistors and putting them back in place. New resistors of the correct value would have been far more professional and actually easier to fit - again penny pinching at the customers expense. The resistors windings are no longer in contact with the ceramic former and would be far more prone to failure than a new resistor.

I looked at his ebay shop recently and notice he is now selling QUAD's valve powered equipment - I would like to express my concerns to prospective customers of the high voltages involved in valve equipment and the required safety measures that should be followed when upgrading or repairing such equipment. My advice would be to ensure that whatever they purchase, if it has been modified or repaired that it has been done so by experienced qualified technically competent people and not someone who's past record shows a distinct lack of electronic knowledge and know how. These amplifiers can be very dangerous if the work is not competently carried out and could pose a serious electric shock hazard to children as well as the owner.

Regards Andy Williams

Quad 306 Upgrade-service & DIY Kit launch

Dada Electronics launches the Quad 306 Revision-service and the Do-It-Yourself kit. They will be available in the European, USA and Australian Ebay-shop.

The input-filter and the DC Feedback circuit are upgraded to the Quad 909 quality-level.

.

Low-noise 1% Metalfilm resistors give less noise on the base of the input-transistor. For the same reason the TL071 opamp in the DC feedback circuit is replaced by a Burr Brown OPA604 Audio-grade opamp. Also the DC offset is lower than with the original Opamp.

.

All 4 zeners in both channels are decoupled with 100 nF MKT, thus eliminating HF ripple and further improving signal/noise level of the zener's output voltage.

.

The old 4700 µF Power-supply caps are replaced with new 6800 µF caps with low ESR. The higher capacitance reduces ripple and increases stability of the PSU voltage.

.

Finally the input-sensitivity is adapted to modern standards. The original value was 0,375 Volt which is much to sensitive for modern preamplifiers or input-sources. As this is done by increasing the local feedback of the input stage, as Quad did also in the later 707 and 909 models, this also improves overall signal to noise ratio.

.

The kit and the service are available in Dada's Ebay-shop, just click on the links in the article above.

If you want a (free) copy of the upgrade/revision manual just send an e-mail to info@dadaelectronics.com.

.

Stefaan & Joost

Listening session

Hans Aussems (NL) upgraded his 2 303's to monoblocks with Dada Electronics' High-end boards. He wrote:

Hi, Stefaan,

Yesterday I visited an old friend after a long time. I know him since we studied Hobo and Fagot at the conservatorium. What we also have in common is our love for listening to music and audio equipment.

I took my 2 Quad 303 monoblocks to listen to them with with his vintage 7-ties Tannoy Dual-concentric speakers which are completely revised by a Tannoy-guru from the UK.

I have to say I was very impressed by those speakers! Despite of my Electrostat-ears this was a very pleasant experience. Many modern loudspeaker-builders could learn a lot from this.

But the best is yet to come: the Quads.

After listening a while via my friend's Rega amplifier we connected the Quads. What a great sound!

The sound is tranquil at all times, without sharp edges or turbulence but with a lot of power and authority. What a dynamic can be realised with those speakers! We couldn't do anything else than listening to our music, stopping was not an option.

The Rega clearly was the lesser one, it did not have the fineness or the natural sound of the Quads.

At the end of the session we also compared with a tube-amplifier but this one had too much unrest, sharpness and distortion.

My friend is completely convinced now of what I knew already: the great capacities of the 303. You can soon expect a new order for a set of 303 Highend-boards.

Hans

A 160W per channel Quad 303?

On Ebay such a beast is for sale, but what is it?

We get a lot of questions about this offering. Can you do that? Yes we can (maybe), but we won’t. See comments.

Can you also glue new capacitors on old ones, and leave corroded trimmerpot's in to place to maximise the profit? Do you also falsify graphs to proof your point? Yes we can, but we don’t.

The claimed 80W RMS in 8 Ohm is easy done, remove the regulated supply, ignore the fact why Quad did design this in the first place, and run the amp on an unregulated 90V supply voltage.

The second part, 160W RMS in 4 ohm is a lot more difficult, if possible. Our advice: check before you buy it, if the unit really deliver this kind of power. RMS, two channels, not peak-to-peak.

Why don’t we do this kind of work?

We work within the Quad design philosophy. We only upgrade and improve things if they really matter and are necessary because of modern speakers and sources.

If you need a 160W in 4 Ohm, buy a 520 series or a 606, 707 and 909. But remember, you need ten times the power to hear a sound at twice the original volume.

Joost Plugge

Who is behind Dada Electronics & the Blog?

We are guys in our 4-ties who have been working in informatics. Strange, isn't it? All 3 of us? Gregg joined us, he wasn't in informatics but in photography.

• Stefaan Verdonckt (BE)

• Joost Plugge (NL)

  

• Esmond Pitt (AU)

• Gregg Deking (US)

Our most-viewed Ebay object is... the Quad 33 kit

the Quad 33 DIY upgrade kit.

We have more than 13.000 Ebay visitors for this 33-kit as we speak and we sold several hundreds of 33-kits.

You can check out the Quad 33 kit on the Ebay US site here.

Depending where you are you will get faster and cheaper shipment from:

• Dada Europe


• Dada Australia & SE Asia


• Dada USA

but you will get the same high-standard components and 7/7 support.

If you want a free copy of the 33 upgrade-manual or other Quad 33 documentation send an e-mail to: info@dadaelectronics.com.

Stefaan

Quad 405-2 AC voltage considerations

From serial number 83000 and onwards Quad omitted the AC mains voltage selector on the Quad 405-2.
I recently checked such a late model Quad. It did not perform well. The power delivery was not on spec. On the outside of the unit there was a marking: 220V. But in real life the unit was wired for 240V. The Quad 405-1 had a selector with 6 positions, in the service documentation of the 405-2, only for four voltages is explained how to connect the wire links to the primary windings of the transformer. In the Netherlands the AC voltage is 230V, this is one of the missing voltages in the documentation, and the other is 130V. Because of the design, the DC power supply voltage of the amplifier is proportional to the AC mains voltage. So 130 V or 110 V does matter! To complete the documentation I drawn the missing link positions. You can also use these diagrams to rewire any Quad 405 and omit the voltage selector with those tiny wires. If you can hear a difference? I can’t tell you, judge for yourself. Before you rewire the amp, check the AC voltage during some weeks, check what is really coming out of the mains socket. Click on the diagram to get a fully detailed version, I also added some colour.

Joost Plugge

Gold - New DACT components available from Dada

Dada now has the DACT CT 2-50K-1, CT 3-5-4, CT 3-5-8 and CT 4-250K-2 in our stock.

Check out Dada's Ebay-shop.

Stefaan

Quad 405 DIY illustrated guidelines - Step 1 to 3

This is the original 405-revision article published on this blog in 2006. We republish it on general demand.

Stefaan

I thought it was time to make an online step-by-step guide for upgrading a 405.

If you are in the US and you are looking for a DIY upgrade-kit, check out www.quad405.com. The guidelines remain the same but you won't have to pay more for low Dollar-rates and high shipment-costs ;-)

As I recently bought a very nice (but very old) 405-2 (thank you Leigh, I hope you had a good time in Antwerp) I will use this one as a photo-model. I will take pictures of everything I do and explain why I do it. All comments and tips are welcome of course.

The revision/upgrade will be a basic one without fancy or expensive things like the BB627, but I'll mention those options in the PS.

Click on the pictures to enlarge.

So here we go...

Step 1 - Getting the components together

This may be the hardest part... Aspecially if you are looking for audio-grade components at an affordable price. The components I will use in this revision are:

BHC Aerovox 10.000 MF 63 Volt for the power-supply. These are quite expensive (+/- 16 Euro each) but in the power-rails we need the best quality. A less expensive alternative may be BC-components or Philips.

• 100MF and 47MF 63V Audiograde capacitors for C5 & C10. In the 405-2 we will need 3 47MF per circuit-board.
• Bipolar capacitors of 10MF (for the clamp-circuit) and 47MF (for the DC-feedback) x2
• Metalfilm 1% 0,5W low-noise resistors for R2 and R6, and probably for R1, R3 and R4 as well (we'll come back to that).
• Burr Brown OPA604AP-chips for the input-channel. We'll need 100NF caps to stabilise the power-supply of the chips and 16V zener-diodes to make the chip feel happy.
• We'll also need some supplies like new fuses, IC-sockets, thermal compound, cables to replace the old cable-beam, LS & RCA connectors, PCB-connectors adl...
• Last but not least: the schematic that corresponds with the exact serial-number. That won't be a broblem: send me an e-mail.

What equipment will we need?

• The minimum is of course screwdrivers, pliers, soldering-equipment and a multimeter
• Better would be a 2x50V lab power supply, a LF tone-generator and a 2 channel scope (but it is possible to do without them)
• Ideal would be a low-distortion sinus-generator and a distortion-meter as well. I don't have those myself (yet) so don't worry;-)

Step 2 - Taking the 405 apart

The first step is to remove the top- bottom- and sidepanels. Sometimes, after 30 years, the screws are hard to remove. The best screwdriver to use is a Philips n°2 with a length of at least 20 cm.

We now understand why Quad made 4 hole's on the left- and the rightside of the backpanel: they were intended to facilitate manipulation of the screws of the circuit-boards.

I don't need to mention it's usefull to keep the screws apart. They can be replaced (they are M4 - which is a standard-size) but of course there is not much use in replacing the screws.

The best way to proceed is to remove the top-panel, then the bottom-panel and then the 2 side-panels.

The first impression of a newly opened 405 is usually a dusty one. This doesn't matter (in this stage ;-).

On the 405 on my table the voltage-selector is at 240 Volt. Switch it to 230 Volt. The connectors will have to be replaced (except the DIN-connector).

The LS-connectors were not only lousy in the first place, they are oxydated and will give a bad conta