API 500 Series DIY??

Hoof wrote:

API stuff is 1.5" wide, as I'm sure you know. Sounds like your rack is not compatible.

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Yes, I think they are 1.5" spacing but......I never intended to put a 512 or 550 into my rack. This is DIY! Also, you don't see too many 500 racks for sell. They also use edge connectors which I don't like. So, I built everthing from the ground up and use high guality DIN receptacles as found on many high end consoles. I acutally looked into getting a used rack at the begining but choose to build it all. Lots of work but worth it.

Regards,
Jeff

Sounds great daveng. Especially considering you've done the whole backplane thing and a discrete amp.

If you've put that much work into it and its an original design with a new opamp it would seem a shame to just give it away if the opamp revision one isnt so hot.....I would keep working on the amp until you nail it and then see if you can make it competitive, if not give it us!!! haha

I like your idea though and by going with a slightly wider module you can get more stuff in (slightly)....thats why I'm looking at 8 in a rack at 8-10HP width do between 40-50mm.

Interested to see some pics if you sort it out.

FH, I agree on the whole switching DC-DC...the headroom is not that a big deal (for a few extra dB) especially with a nice 1:2 O/P trafo ala API. Although if its biased to run optimum at 24V maybe he felt the sound was worth the hassle?

clintrubber - if you have a good lead to surplus sub racks in holland I would be really interested, I'm over there a couple of times a year (dutch missus) and could also easily get stuff sent to her folks.

New Schroff subracks look like £100 here from Farnell, any better leads would be much appreciated?

Cheers Tom

[quote author="TomWaterman"]

clintrubber - if you have a good lead to surplus sub racks in holland I would be really interested, I'm over there a couple of times a year (dutch missus) and could also easily get stuff sent to her folks.

New Schroff subracks look like £100 here from Farnell, any better leads would be much appreciated?

Cheers Tom[/quote]

Hi,

The 'surplus' I wrote was actually shorthand for the stuff I sometimes find in the bin at work, and it doesn't show up that much - but at least more often than I'm in need of a new box :wink:

The stuff I'm talking about goes like this, a rack of years ago with some stompbox-clones (you'll love or hate the colour but it's of course not the original colour - that's just blank Alu):





I'll always keep an eye on that stuff and when supply is good could let you know. Note though that the box shown is actually compiled from several to give one somewhat decent box with usable panels without too many holes at the wrong places.

Bye,

Peter

Crazy looking rack peter.

What else you going to put in the gaps?

If you ever find any cool stuff at work you dont need I'd be interested and if I've got some cash could take it off your hands - as far as subracks go I'll be looking for complete boxes only though, so I expect I'll get some from Schroff in due time.

Cheers anyway!
Tom

[quote author="TomWaterman"]Crazy looking rack peter.

What else you going to put in the gaps?[/quote]

So many plans... :grin: But no direct plans for filling the gaps. Maybe another fuzz. Or a dual VCA-module, but for my synth-like boxes I'm actually using another cheesy colour so I shouldn't mix those up.

BTW, while this rack looks & likely is a mess, there's some thought behind it, like using 'metal'-sockets for signals & black plastic sockets for footswitch-connections.
FWIW, there's now a Dynacomp & Orange Squeezer, the other one is a Superfuzz-clone combined with the EQ-part of a Boss FZ-2 (which is on its turn.... a Superfuzz-clone :wink: ) This is a wicked fuzz that everyone should face at least tree times a week...

If you ever find any cool stuff at work you dont need I'd be interested and if I've got some cash could take it off your hands - as far as subracks go I'll be looking for complete boxes only though, so I expect I'll get some from Schroff in due time.

Cheers anyway!
Tom

Click to expand...

As you'll understand, please don't hold your breath but I keep watching. And once I find something it won't cost much.

Bye,

Peter

Mr Hayward MAY have a spare one around his garage somewhere (he found one for me when I first joined...) - if you ask him very nicely and send him some postage and beer money he may obliger
Otherwise to fill the rack you may need

Front Panels
£1.80 from Mainline
http://www.mainlinegroup.co.uk/mless/main.php?act=Card&id_element=3685

Big Front Panels
£3.00
http://www.mainlinegroup.co.uk/mless/main.php?act=Card&id_element=3649

Schroff Units £10.00
http://www.mainlinegroup.co.uk/mless/main.php?act=Card&id_element=3778

Have fun

BTW - there is another way (others may be bored at this point)
Why not get some half width rack units in 1RU, 2Ru or 3RU sizes and then use rack strips horizontally to mount them

Hey diyr's,

Recevied the first test panels for my "500" style rack preamps. Everthing fits but the VU led daughter board is very close to bumping into the adjacent module. So I'll need to make a slight PCB adjustment on the next set of boards. All in all it all looks and sounds good.

Also, my newly designed discrete gain block (fits 2520 footprint) works first shot. Initial tests showed almost identical technical performance with an original 2*5*2*0. This includes THD, THD&N, IMD. My unit's frequency response was also very close except it was down 0.5dB at 30kHz. I suspect it's due to my approach at local feedback within the device. Another version and more tests will prove me right or wrong. I also made listening comparsions in a test jig using an original 2*5*2*0*, my gain block and for the heck of it, a 24v 9*9*0. Very little difference between my gain block and the 2*5*2*0. Of course the 9*9*0 did sound cleaner, more pristine. Next will be a blind listening test from another person to eliminate any subjective tendancies on my part.

Sorry for posting more info on my gain block than the 500 rack, but I'll post some more hurdles faced in building the rack later. I'm ordering the entire set of front panels this week and I'll post pics of the full face when I get them.

Fun stuff, this DIY!

regards,
Jeff

daveng,

Congrats! Now I have to ask. 1) Which "original 2520" are you talking about? There are at least 5 or 6 different versions floating around that you could argue are originial and they all sound different in my limited experience. 2) Are you implying that your gain block is a copy of or based on an API 2520? If so, what was your reasoning? (if you care to share)

Hoof wrote
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1) Which "original 2520" are you talking about? There are at least 5 or 6 different versions floating around that you could argue are originial and they all sound different in my limited experience. 2) Are you implying that your gain block is a copy of or based on an API 2520? If so, what was your reasoning? (if you care to share)

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1) I compared my design to "an original" 2*5*2*0. It's one of the black and silver label Huntington N.Y. opamps I purchased many years ago. You're right, there were many versions and I have no idea what circuit this particular one uses! I suspect that the differences are quite minimal when you get right down to it as long as they are authentic. I've not done unit to unit tests either but then again most people don't complain about one 550 sounding much better than another. Its just one part of the sound which is also influenced by the transformers, types of caps, circuit design, etc.
2) My design is not a copy of a 2*5*2*0. There are already people building "clones" and I could easily put together one of those. My design goals were based on 2 benchmarks, the 2*5*2*0 as a minimum and the 990 as a maximum. This may seem strange at first since they are very different, but I'll explain. The first is legendary in "sound" (with the addition of transformers). The second is essentially a masterpiece of design work. I was shooting for the "sound" since I love the sound of API units. I've heard and used both and prefer a bit of color over pristine. Designing a good opamp is not an easy task. It's fairly easy to get one to work, but to get one to sound great and have great specs is another matter. The 990 sounds really good and is technically superior!

Check out my post below for more information on testing.
http://www.groupdiy.com/FORUM/viewtopic.php?p=130951&sid=baaea3d3d84f74fda486f58466696b02#130951

Just for your information I've also done listening tests (using a common jig) to test all of the above including 24v 990's. My listening tests focused on the comparisons of sound but I would be foolish to ignore instrument measurments. Us humans are known to be a bit subjective at times!

Thanks for your interest and kind words
Regards,
Jeff