525 build thread

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peter purpose

Well-known member
Joined
Jun 3, 2004
Messages
2,082
Location
London
Let's get started with a BOM

http://www.twin-x.com/groupdiy/albums/userpics/525bomupdt3~0.pdf updated again.

and schematic...

525Cschem21sm.jpg
 
Nice Work Peter , thanks for your time on that

Of course it would be good to order all the parts and be
ready for when the boards come !
 
Hey Peter, are you also using a 2520 for the input opamp? These makes for 4 2520s for each unit. Serious job, if all opamps are DIY.
 
[quote author="rafafredd"]Hey Peter, are you also using a 2520 for the input opamp? These makes for 4 2520s for each unit. Serious job, if all opamps are DIY.[/quote]

I think it's 3 per 525...
 
For A3, the sidechain-transformer driver, it'd probably be enough to use a standard opamp with a couple of BD139/140 power booster transistors.

Question: Why not a simple 10K:10K input transformer instead of additional opamp stuff?

Jakob E.
 
[quote author="gyraf"]
Question: Why not a simple 10K:10K input transformer instead of additional opamp stuff?

Jakob E.[/quote]

Room on the board Jakob.
normal_OL.jpg


Large.. http://www.twin-x.com/groupdiy/albums/userpics/OL.jpg
 
Been studying this schem getting ready for the build, and I don't understand what Q5 is doing. Can someone explain?

At first I didn't understand the bias of Q1, but I read the datasheet and it cleared that up.
 
[quote author="Greg"]Been studying this schem getting ready for the build, and I don't understand what Q5 is doing. Can someone explain?[/quote]
At first glance it looks like it is adding an AC signal to the gate to reduce distortion.
 
since peter started his project, i've been working on getting some ap2623 type transformers made. unfortunately, the first supplier i was working with backed out after a few weeks, so now i am a bit behind.

i don't want to discourage anyone from going ahead and buying transformers. but i should have something good available in a few weeks. until then, please do not contact me. as soon as they are available i will post to this thread and post to the black market.

ed
 
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