Avalon - U5 DI Preamp

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Avalon - U5 DI Preamp

Postby Silent Fly » 27 Sep 2008, 17:36

It is not a stompbox (or an effect?) but I hope you will find it interesting.

I started to draw the schematics but it is too complex for my old brain.

u5_front.jpg

u5_back.jpg

u5_back_front.jpg


The 3 sets of 2 transistors on the left and on above the input jack are BD139 and BD140. The transistors in power section are TIP31GC and TIP31GC. The ICs are LF412CN.
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Re: Avalon - U5 ( DI-preamp )

Postby Bernardduur » 29 Sep 2008, 08:16

+1!

Once played through one and onlu could peek inside to spot the red Wima's..........
Really want one :D

Nice! Dale resistors!
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Re: Avalon - U5 ( DI-preamp )

Postby lohstah » 29 Sep 2008, 10:30

it would be nice to also have pictures of the 2 stand-up boards in the front plus the values of the lil´ yellow capacitors.

cheers,
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Re: Avalon - U5 ( DI-preamp )

Postby lohstah » 29 Sep 2008, 10:34

the board on the left must be the gain-knob-section, and the one on the right the tone control section. in a simplified version of the circuit, the tone-section could be left out as most people use it it set flat anyway...

cheers,
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Re: Avalon - U5 ( DI-preamp )

Postby Silent Fly » 29 Sep 2008, 20:10

lohstah wrote:it would be nice to also have pictures of the 2 stand-up boards in the front plus the values of the lil´ yellow capacitors.

cheers,
lohstah


As requested:
u5_boost.jpg

u5_filter.jpg


I am not sure I understand what you mean by "lil´ yellow capacitors".
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Re: Avalon - U5 ( DI-preamp )

Postby Silent Fly » 29 Sep 2008, 20:13

lohstah wrote:the board on the left must be the gain-knob-section, and the one on the right the tone control section. [...]

Yes - you are right: the board on the left is the boost control, the board on the right is the filter.

lohstah wrote:[...]in a simplified version of the circuit, the tone-section could be left out as most people use it it set flat anyway...

Exactly.
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Re: Avalon - U5 ( DI-preamp )

Postby RLBJR65 » 30 Sep 2008, 03:21

Nice pics!

On the main board pic you can’t read the value of these caps C1, C2, C3, C4, C41, C42, C49, C36, C37, C5, C32, C33, C34, C25, C26, C21, C22, C10, C16, C17, and C20
Also the cap on the trace side under SW2

On the filter board C5, C6, C13, C7, C8, C9, C10, C11 and C14
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Re: Avalon - U5 ( DI-preamp )

Postby lohstah » 30 Sep 2008, 14:36

On the main board pic you can’t read the value of these caps C1, C2, C3, C4, C41, C42, C49, C36, C37, C5, C32, C33, C34, C25, C26, C21, C22, C10, C16, C17, and C20
Also the cap on the trace side under SW2


what i meant by "small lil´ yellow caps", and some more... :wink:

the trace side of the two extra boards would be helpful, too.

cheers,
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Re: Avalon - U5 ( DI-preamp )

Postby Silent Fly » 30 Sep 2008, 19:01

lohstah wrote:(...)

the trace side of the two extra boards would be helpful, too.

cheers,
lohstah


To be entirely honest, I am not overly keen in disassembling, taking the pictures and re-assembling the U5’s boards just for the sake of it. :hmmm:

I may be ready to do it if someone is ready to do something productive with the pictures. E.g. draw a schematic or do some circuit analysis. :thumbsup

Moreover, the boost control looks like a set of resistors that are connected accordingly to the position of the knob. Probably, it is used to set the feedback of the fist stage of the U5. Not exactly a high tech solution where a picture can really give us a useful insight on the technology used to design the box.

The other board is a passive filter that the majority of the people do not use. [smilie=thumbdown2.gif]

RLBJR65 wrote:Nice pics!

On the main board pic you can’t read the value of these caps C1, C2, C3, C4, C41, C42, C49, C36, C37, C5, C32, C33, C34, C25, C26, C21, C22, C10, C16, C17, and C20
Also the cap on the trace side under SW2

On the filter board C5, C6, C13, C7, C8, C9, C10, C11 and C14


I would be more than happy to spend a few hours to open the U5 and read the values of the caps (or any other component) after someone draw a schematics or decide that wants to do something equally productive with the values of the capacitors. Otherwise, I don’t see the reason to have a list of capacitors/values without anything else. :hmmm:

Having said that, if knowing the values of these caps is something really close to your heart, I can invest some time in finding the values – but please tell me what you need them for. :lol:
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Re: Avalon - U5 ( DI-preamp )

Postby lohstah » 30 Sep 2008, 19:31

Having said that, if knowing the values of these caps is something really close to your heart, I can invest some time in finding the values – but please tell me what you need them for. :lol:


i would be willing to try to trace the whole thing - it might take me some time, since i have shitloads of work and then two bands to work in - but eventually, we might see some results. i would not ask for parts values if i´d not be interested in doing something with them.

cheers,
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Re: Avalon - U5 ( DI-preamp )

Postby Silent Fly » 30 Sep 2008, 20:07

lohstah wrote:i would be willing to try to trace the whole thing - it might take me some time, since i have shitloads of work and then two bands to work in - but eventually, we might see some results. i would not ask for parts values if i´d not be interested in doing something with them.

cheers,
lowstar


This is the answer I was hoping for. :thumbsup

If you start the tracing, I will start finding the values of the caps and the other components. Do you have any idea where you want to start from?

I would leave the two external boards alone for the time being. I don't think they are that important.
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Re: Avalon - U5 ( DI-preamp )

Postby aliparla » 02 Dec 2009, 13:28

Hi!
A couple of days ago I found this topic and I think it's a very interesting proyect.
So, I'm tracing the circuit :wink:

I've finished the back side, and I'm starting now with the tracks on the components side.

Does anybody want to help?


P.S.: English is not my first language, so It's posible that I say some "strange things" :wink:
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Re: Avalon - U5 ( DI-preamp )

Postby Brink » 02 Dec 2009, 17:58

aliparla wrote:I've finished the back side, and I'm starting now with the tracks on the components side.

Does anybody want to help?

If you post pictures then several people will probably start helping.
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Re: Avalon - U5 ( DI-preamp )

Postby aliparla » 02 Dec 2009, 23:07

I'm using the pictures from Silent Fly, and I think I can clone it.

I was thinking of someone who could read the values of the components and start making a list :thumbsup
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Re: Avalon - U5 ( DI-preamp )

Postby okgb » 25 Oct 2011, 16:57

I'm guessing it may have similarities to their mic preamp ? either of which i'd love to see
does look intimidating at first glance
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Re: Avalon - U5 ( DI-preamp )

Postby thedudeabides » 04 Feb 2013, 22:53

Hey guys! First post, EVER.

I wanted to revive the thread and let silent fly know (if he's still around) that I'd happily take this on and begin drawing tonight. Ill post my results when I get done - Feel free to PM me!

As always,
thedudeabides

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Re: Avalon - U5 ( DI-preamp )

Postby Silent Fly » 05 Feb 2013, 11:35

thedudeabides wrote:Hey guys! First post, EVER.

I wanted to revive the thread and let silent fly know (if he's still around) that I'd happily take this on and begin drawing tonight. Ill post my results when I get done - Feel free to PM me!

As always,
thedudeabides


Hi thedudeabides,

Unfortunately, I don't have the U5 any more. I should have some hi-resolution photos of the PCB if you are interested. I'll be more then happy to send them to you. Please feel free to send me a PM with your email address.

I'd love to see how the the last stage of the U5 is designed.
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Re: Avalon - U5 DI Preamp

Postby alexkalibur » 26 Jun 2015, 18:19

Hi guys,
It's been a long time since the last activity on this post.
Were there some improvements on this topic?
Did anyone manage to draw the full schematics of this U5?

Best,
Alex
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Re: Avalon - U5 DI Preamp

Postby Nocentelli » 26 Jun 2015, 22:35

alexkalibur wrote:Did anyone manage to draw the full schematics of this U5?


I think they probably would have posted the schematic if they were so minded.
I had a look over it, but I seem to have a weird mental block over blue resistor colour codes: I can read the cream four band ones at a glance.
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Re: Avalon - U5 DI Preamp

Postby Phil Smith » 19 Jul 2015, 20:15

Hey there!

I think Avalon U-5 is a great device and it would be awesome DIY project.
I've been starting to trace pcb's too (in simple Sprint-Layout 6) and done the main board bottom layer already. Now the top layer is in a process.

2 Silent Fly - thank you very much for photos you've provided! Great stuff! Do you have some other pics of the device inside? I saw you wrote:
I should have some hi-resolution photos of the PCB if you are interested. I'll be more then happy to send them to you. Please feel free to send me a PM with your email address.

If you still do, I can PM you my email address.

So I guess it's time to make BOM some sort... I appreciate any help, specially in resistor color code reading and stuff.

BTW - Filter cans (C1-C4 on the main board) are 2,200 uF / 63 V - you can barely see "2200" on C2 can and quite clear "63V" on the C4 one.

I hope I'll be enthusiastic enough to complete all boards :D
But Filter one will be a pain in the butt cause it has around 50% traces at the bottom layer which not provided.

I've attached screen of my current progress for the main PCB (green for the bottom layer, red - for the top).

Cheers!
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