Wednesday, May 24, 2006

And now for something completely different: Leak

Philippe asked if I could do a revision of his Leak Delta 70 amplifier.

It's not a Quad, all right, but it's high-end, it's the same generation and it's made in the UK as well. So I said yes, one should broaden the horizon.

The amp is a pre/power amp that is constructed very well in a modular way. The design is somewhat "outdated" but the electronics look very intelligent. In many ways the power-amp looks like the Quad 303.

A schematic is not available, but it seems to be very similar to the Leak Stereo 70, the eralier model.

Quad Spot (or is it Leak Spot now -;) will keep you posted in the next weeks. All comments and advices are welcome, of course.


Step 1: Replacing the capacitors.

Nowadays capacitors are A LOT smaller than they were in 1969. I found some "New Old Stock" capacitors of the same size, 4700 MF instead of 2000MF as output-caps. This should improve dynamics below 150 Hz.

On the boards I'll have to replace all caps that are in the signal-line.

I love this Leak-job! After revising too many Quads, send me some Leaks or Naims!


Velleman K4700 in Quads? Ed pushes it to the limit!

Obviously the articles about building the Velleman K4700 protection-circuit in the Quad 405 were very inspiring ;-)

Hans was the first to propose an alternative location for the kit but Ed took it very seriously... He built the kit into the 303, the 405 and the 606 and he even developed a box to use the protection-circuit with any amplifier....

It is clear that Ed also will find a box of Antwerpse Handjes in the mail and he is hereby named a lifelong honorary member of Quad Spot ;-)

Do you work for Quad or Velleman, Ed?

Obviously there will be many questions on this subject, feel free to post them as a comment. To be continued....


Take a look and enjoy (click on the picture to enlarge):

In the 303

Note: in the 303 the protection-circuit is somewhat less usefull than it is in the 405. The 303 is a push-pull amp with an output capacitor, so as long as the capacitor won't fail there is no risk of having DC-current on the output, like in the 405, if one of the output-transistors breaks down. But there still is the advantage of the delayed power on/off. And with expensive speakers you never can be sure enough of course...

In the 405

Ed made a metal-adapter to fit the K4700 behind the transformer.

Note: as mentioned in earlier posts the 405 really NEEDS a better protection-circuit. I heard about several people who had their expensive speakers broken when one of the transistors gave it up. The original "clamp-circuit", even in the 405-2 does not react fast enough all the time.

In the 606

Ed even built a K4700 in the 606. This was not an obvious or easy job to do.

Update: An alternative location.

Ed mailed me some pictures of an alternative location for the Velleman in the 606. For Ed's explanations see the comments below.

In a separate box

This box can be used for any amplifier. But it should be switched on/off together with the power-amp, by a general swith or from the pre-amp.

Thursday, May 18, 2006

Building the Velleman K4700 in the 405

And the winner is... Hans Ausems. He will receive a box of "Antwerpse Handjes" by mail the coming days and wins a lifetime Honorary Membership of Quad Spot ;-)

Hans also built 2x 10000MF capacitors in each power-rail (4 in total) and attached the Velleman-kit to it.

Hans will write an article about his 405 revision for Quad Spot in the coming days.


About repainting Quads (continued)...

Hans had his 33, his FM3 and the front of his 303 repainted by a local car-framework company. He payed about 175 Euro for the job.

As you can see on the pictures it was worth it...

Quad didn't use an "official" RAL-color so the color was guessed. Carpaint was used, metallic with transparent mat topcover. All old paint was removed first.

Hans will answer all questions on this subject, just send a mail to or just post a comment below.


Update 24 may: Breaking News! Hans even repainted his ESL's!

Has Hans has a white interiour he wanted a lighter colour for the ESL-fronts. He used dark-silver metallic paint and he applied it with a small roller...

I can imagine there will be some questions about the paint he used or the influence on the sound-quality ;-)


See the before/after pictures below:

Wednesday, May 17, 2006

Quad Spot joins Weblogs Against Racism

After the awful racist crimes in Belgium those last weeks me and my friends who are behind Quad Spot could not stay on the sideline.


Wednesday, May 03, 2006

Can you do a revision of my 405 FAQ's

How can I have my 405 making better music than a new one?

I often get e-mails from people asking "Can you do a full revision of my 405 (2)? How much would it cost? What exactly would you do? How much time does it take?" etc...

The answer is: yes, I can. It used to be a hobby but now I'm starting up a company, "DaDa Electronics", specialised in the revision and upgrade of vintage high-end Hifi.

How much would it cost?

One remark first: a big part of a revision is transportation-cost (forth and back). If you are in the US click If you are in Europe: keep on reading.

For a complete 405-revision I charge 145 Euro, everything included - except transportation costs.

What exactly is included in a complete revision?
  • All electrolytic capacitors (which dry out) are replaced by new ones
  • The power-supply capacitors are replaced with BC Components 10000 MF 63 V
  • The input-opamp is replaced with Burr Brown OPA604
  • The input-circuit is adapted to the new chip (power-supply of +/- 15 Volt, feedback)
  • The input-sensitivity is adapted to your pre-amplifier
  • The complete internal cabling is replaced with wire with better specs
  • The input/output connectors are replaced with high-quality gold-plated connectors, leaving the DIN-input in place, adding parallel RCA-inputs
  • Some capacitors are added to improve the quality of the power-rails, some resistances are replaced with metalfilm 1%.
  • The amp is measured and calibrated with professional lab-equipment
Do you use high-end audiophile components?

No, I don't. I use good quality standard components. If you want high-end components like Nichicon Black Gate 15000MF for the power-supply this can be discussed. In general the effect of "audiophile components" on the sound-quality will be minimal and the price will be high.

Do you replace the transistors?

It depends. In general transistors don't deteriorate like caps do. If they influence the sound quelity they might be replaced (like the power-transistors might be replaced with 2N3773 if necessary).

What if my 405 is broke?

It depends. If the reason is a bad connection, a broken fuse or a broken transistor, this is included in the revision. If the transformer or another essential component is broke it will have to be replaced at an extra cost.

How long does a revision take?

A full revision takes 2 weeks except if there are unforseen problems.

What are the options?

There are several options (see previous posts on this blog):
  • Adding the Velleman K4700 Loudspeaker-protection with power-on delay: 45 Euro
  • Replacing the transformer with a 300VA Toroidal transformer: 94 Euro
  • Burr Brown OPA 627 or 637 chips instead of OPA 604: 70 Euro
  • Changing the 405 to parallel Monoblock 125 Watt: 25 Euro
  • Changing the 405 to serial Monoblock 190 Watt: 95 Euro
  • Adding a symmetrical 0 Dbm input: 95 Euro
  • Having the Chassis professionaly repainted: ask for a quotation
Is there a warrantee?

Yes, there is a 6 month full warranty after the revision. It excludes damage due to transportation or misuse but it includes the complete amplifier, not only the replaced components.

Can you do a revision for other Quad's?

Indeed. I am specialised in revisions for Quads between the 33 and the 606, the vintage B&O receivers and the Revox taperecorder A77.

How to proceed?

Send me an e-mail ( describing the 405. Adding a picture of the inside and describing the pre-amp and the speakers it is used with is very usefull.

To send it to my address (in Antwerp, Belgium) you could remove the top- bottom- and side-covers to reduce weight and transportation-costs. Make sure it is well-packed.