183 Preamp PCB layout for 1U chassis

[dmoose5835]

Second pass with beefed up +12V rail (1mm/40mils).

Default traces 0.5mm (20mils).

Cheers!

[dmoose5835]

Traces widened and separation improved.
BOM priced as of 28MAR25 with Mouser and other partnumbers.

You are invited to use or kibbitz if you wish.

[Guy77]

Hi.
I was looking at your board in PCB-Way Gerber viewer.
I wanted to ask if these ( yellow arrow) are screw in terminals for the wires connections to the pre amp tubes for example.
Also what are the dimensions of your preamp board?

Thanks!
Cheers
G

Capture.JPG

[dmoose5835]

Hi.
I was looking at your board in PCB-Way Gerber viewer.
I wanted to ask if these ( yellow arrow) are screw in terminals for the wires connections to the pre amp tubes for example.
Also what are the dimensions of your preamp board?

**
Hey, Guy - those are connectors with a 3.5mm pitch from the Molex Ultrafit line:
538-172286-2103 172286-2103 Molex Headers & Wire Housings ULTRAFIT 3.5MM 3CKT HDR VT SGL K NAT TIN
538-172253-6112 172253-6112 Molex Headers & Wire Housings ULTRA-FIT CRIMP TERM 20-22 30MI Form,
538-172256-4103 172256-4103 Molex Headers & Wire Housings ULTRA-FIT HSG SR 3Ckt White
and so forth.

The header goes in the board, then the wire contacts and housing for that connector plug in.
That should make swapping pots and pre-wiring tube sockets easier.

Of course, you can do that any way you wish.

A not-quite-complete BOM is attached.

The board is 375mm x 130mm. I'm planning on 1/8" board thickness and an ENIG finish, but I have to buy five of them.

[Guy77]

Hi.
I was looking at your board in PCB-Way Gerber viewer.
I wanted to ask if these ( yellow arrow) are screw in terminals for the wires connections to the pre amp tubes for example.
Also what are the dimensions of your preamp board?

**
Hey, Guy - those are connectors with a 3.5mm pitch from the Molex Ultrafit line:
538-172286-2103 172286-2103 Molex Headers & Wire Housings ULTRAFIT 3.5MM 3CKT HDR VT SGL K NAT TIN
538-172253-6112 172253-6112 Molex Headers & Wire Housings ULTRA-FIT CRIMP TERM 20-22 30MI Form,
538-172256-4103 172256-4103 Molex Headers & Wire Housings ULTRA-FIT HSG SR 3Ckt White
and so forth.

The header goes in the board, then the wire contacts and housing for that connector plug in.
That should make swapping pots and pre-wiring tube sockets easier.

Of course, you can do that any way you wish.

A not-quite-complete BOM is attached.

The board is 375mm x 130mm. I'm planning on 1/8" board thickness and an ENIG finish, but I have to buy five of them.

Thank you for the detailed information!

Cheers
G

[fred.violleau]

Hey Dmoose5835,

Very interested with your PCBs.
I am switching over to rack preamp builds.
Amp are taking too much space, and Dumble power amp sections re very redundant;
Where do you get your PCBs printed?

Do you have a reference for the connectors on mouser? Never used any of these and dont know how to call these pieces
EDIT : just saw your BOM post, will get through it !
Is it a proven design ?

Thanks for your help!

Fred.

[dmoose5835]

It's NOT a proven design, yet, and have not ordered boards with personal funds yet.

I based the circuit on the MonkeyMatic HotRodDeluxe to ODS conversion PCB - a design that's at least 12 years old.
The topology is pretty constant, so changing the BOMs can shift you among BluesMaster, HRM, Skyline etc variants - and I intend to cook up at least 3 preamps.

I'm also working up a stereo power amp (22W per channel to start).

I don't claim to be a Dumble expert - just starting out on this path. Maybe give me a few months to actually get at least one built before you spend any money on copying me?

[fred.violleau]

Hey dmoose5835,

Your layout references a Hammond PT 1182L6.
How will you get the B+ voltages inline with what is expected dor a D-style amp (200 to 235ish VDC on the plates)?

FYI I have built a badger rack preamp that works fine with a Antek AS-05T200.
Where do you get uour PCB printed?

Thanks;

Fred.

[fred.violleau]

So I see in the schematic you are using a DC to DC high Voltage converter outputing around 300VDC.
I am really curious to understand if there is any effects on the B+ vs a beafier toroid transformer that would get the secondaries up to 300VDC.
Have you messed around with these DC to DC HV units before ?
Is it about the price point?

Thanks;

Fred.

[dmoose5835]

So I see in the schematic you are using a DC to DC high Voltage converter outputing around 300VDC.
I am really curious to understand if there is any effects on the B+ vs a beafier toroid transformer that would get the secondaries up to 300VDC.
Have you messed around with these DC to DC HV units before ?
Is it about the price point?

Thanks;

Fred.

Another AmpGarager used one of these to build an Dumbleator, and they're like, 5 bucks each on the eBay (I bought 5). My thing is trying to fit this circuit in a 1U chassis and this looked pretty good. I do still need to hook one up with a realistic load and see how it does I have time to do that before even being able to place an order. I'll report that result and again when I order boards. Worst case I have to look at the tradeoff between giving each 12xx7 its own DV:DC vs a more proven approach like the londonpower preamp power supply or a bigger toroid.

[dmoose5835]

I almost think I'm happy with this version. The Creepage and Clearance should comply with IPC 2221B now. I did punt and will be using off-board wires for the heaters and high voltages.

[solderhead]

On a related note, what are you using for the 1U chassis?

[dmoose5835]

On a related note, what are you using for the 1U chassis?

Something I bought off eBay:
https://www.ebay.com/itm/285760941690

It's acceptable, so far.