Quad 520 vs. 520f- what's the difference?

  • No one logged in.

29-Aug-2012 07:20 PM

Glitterbug

Glitterbug

Posts: 73

Hello dear Forum people, it has been a while...

After I unconditionally fell in love with my 510's, I got infected by the virus of trying to get more of the pro studio gear of Quad. I was just offered a 520 in ok cosmetic condition and unknown technical state- supposedly it works, turns on etc. but the seller does not have XLR cables to try it. So it's a bit of a risky endavour, but since it was offered to me for a good enough price to still upgrade and fix it if needed, I am happy to take the risk.

But: it's a 520 and not a 520f. Does that matter? What's the actual difference between them? Is it an earlier version? Are they technically and sonically different?

I want it for driving my second pair of LS3/5a's in the studio.

For those interested: After my 405 was kicked out of my main system by the two 510's, the 405 went into a permanent relationship with a pair of heavily upgraded and modified Celestion Ditton 15XR's which I actually picked up for free (they were on their way into the trash...) and invested in new caps on the x-over, a pair of new Morel tweeters, new wadding and a bit of dead sheet for the cabinet, a second bass driver (that replaced the passive membrane) that I found on ebay for cheap and new internal wires, and together with the 405 they are among the nicest combinations I have heard. Very, very warm yet detailed and thanks to the Morel tweeters, they sing with stunning shimmer and sparkle on the top end, yet the bass is dry, deep and precise. Who would have guessed what these old fellas could be capable of.

Many thanks in advance, Till


  Reply

30-Aug-2012 01:25 AM

EJP

EJP

Posts: 1000

The main difference is that the 520F has provision for fitting a 600ohm input transformer. Thoroughly obsolete in this day and age. There is also a circuit difference around Tr10 in the 520, which is absent from the 520F. See the 520F user manual in the Downloads sections for a few other variations in the 520 series.

Dada Electronics Australia
  Reply

30-Aug-2012 07:11 AM

Glitterbug

Glitterbug

Posts: 73

Thank you for the quick reply! So if I understand correctly, there are no major differences between the two? I want to try to get as close to the sonic qualities of my 510's, that's the reason why I was looking for either another set of Monos or the stereo version of the amp. 

  Reply

30-Aug-2012 08:30 AM

EJP

EJP

Posts: 1000

I'd be astonished if you could tell the difference between them.

Dada Electronics Australia
  Reply

31-Aug-2012 07:48 AM

Glitterbug

Glitterbug

Posts: 73

So I just purchased the 520. I was looking for upgrade kits, but couldn't find one in the shop... upon my search in the blog section, I came across the description of somebody that upgraded two and made monos out of them, yet the parts seem to partially not available in the shop? 

Are there any particular revision challenges with the early 520 amps, other than the PSU caps? Or it there a drop-in replacement that does not require drilling holes? And, are there more online sources on the 510/520? Since it is a less common fellow, there seems to be very little info on it.

Before I order I will wait for it to arrive, let's see what has been done and what condition it's in. 

As always, thank you all so much! I have become a much happier music listener ever since I came across Quad and Dada Electronics.

  Reply

31-Aug-2012 08:49 AM

EJP

EJP

Posts: 1000

I did one up last year, couldn't find any alternative to drilling holes.

Dada Electronics Australia
  Reply

31-Aug-2012 10:06 AM

Glitterbug

Glitterbug

Posts: 73

Is there a tutorial that explains- also in pictures- what and how exactly has to be done? 

  Reply

01-Sep-2012 04:23 AM

EJP

EJP

Posts: 1000

There are some articles about it in the blog.

Dada Electronics Australia
  Reply

01-Sep-2012 09:18 AM

Joost Plugge

Joost Plugge

Posts: 553

Hello Till,

I made a blog post in april 2010 about the 520F and also explained the differances between the 520 and the 520F. Looking for the same psu caps is, I think, a waist of time. Quad also made thesame layout fault as in the 520F. So buy new fresh ones,remove the extra pin's, and redrill some holes. We don't offer an upgrade manual, but with the blog articles and the diagrams from the download section it should be possible to do the job. If not, mail me. Maybe we can produce a third blog post about this very good but rare amplifier range.

Joost Plugge

  Reply

04-Sep-2012 09:16 AM

Glitterbug

Glitterbug

Posts: 73

Hello Joost and everybody else,

thank you for your replies! The 520 arrived yesterday, but it seems to only be half operational. Lights turn on, but upon a first try, only strange, ill noises came out of my speakers. Since I only have my LS3/5a's as passive speakers here in Berlin, I didn't want to go into further testing, I was too afraid to ruin my speakers and turned the unit off immediately.

Looking at the inside, everything looks very good- nothing burned, blackened, etc, and to my amateur eye, everything looks original. The only thing that was changed (for no good reason) was to switch ins and outs- no idea why. But I am also not sure about the configuration of the cabling on the amp boards.

Also, the boards of my 520 look very very different from the pictures on your blog; they also don't have a board revision number. Sadly, also the serial number sticker fell off, but it seems to be a very old version of the amp.

I will send you some pictures via email, and maybe you have suggestions for me. 

I read the revision instruction on the blog, but I have the feeling that a lot of the instructions might not cater to this old fella since the layout seems to differ quite a bit. But again, it's an amateur speaking here.

Looking forward hearing from you, Till

  Reply

04-Sep-2012 09:35 AM

Glitterbug

Glitterbug

Posts: 73

Sorry, there is a revision number on the boards: it's 12828:2.

  Reply

06-Sep-2012 12:37 PM

EJP

EJP

Posts: 1000

They were made in small quantities with lots of variants. Maybe Joost has seen them all, I certainly haven't.

Dada Electronics Australia
  Reply

06-Sep-2012 04:49 PM

Glitterbug

Glitterbug

Posts: 73

I know that there have been endless variants, only problem I have with the revision that I would love to do is that the descriptions in the blog section most likely don't cater to the amp boards I have... and since my knowledge is not that great, I need simple tasks, like: replace r31 with a resistor of this and that value... ;-) but comparing the board I have with the pictures on the blog, the layout is totally different, and components are placed in different places than they appear in the blog post.

Just trying to avoid greater damage on hardware and the untrained technician, meaning, myself... :-D

  Reply

06-Sep-2012 04:51 PM

Glitterbug

Glitterbug

Posts: 73


But I sent Joost (and Stefaan) pictures, and am waiting for him to tell me what to do. So I guess I am in good hands! I feel very lucky though that I found another of these fantastic amps. Even though I would love another pair of 510's eventually...

  Reply

07-Sep-2012 02:17 AM

EJP

EJP

Posts: 1000

If I remember correctly the combine ts are all labelled.

Dada Electronics Australia
  Reply

07-Sep-2012 02:18 AM

EJP

EJP

Posts: 1000

Err, the *compoonents* are all labelled. iPad strikes again!

Dada Electronics Australia
  Reply

08-Sep-2012 06:48 AM

Joost Plugge

Joost Plugge

Posts: 553

Hello Till and Esmond,

I sorted out the differances between the 520 and the 520f, also I find out that a 522 is also a 520 inside, due to work for a other customer. I think Till has all the information to complete the work. If I find the time,I will rewrite some parts of the original blog post.

Joost Plugge

  Reply

08-Sep-2012 09:37 AM

Glitterbug

Glitterbug

Posts: 73

Thanks to Joost's priceless knowledge and insight into the matter, and their great web shop, I will be able to order all the part needed and I am quite positive that I will be able to do the repair / revision myself. Endless praise and thanks to the great Dada people!!! :-D

I will post again once I ordered the parts and finished the work. Keeping fingers crossed that nothing goes wrong this time...

  Reply