new build

a 3W single ended EL84 amp for home, work & school

new build

Postby dcribbs1412 » Sun Oct 26, 2014 6:40 pm

New guy
First try at a SE build.
progress pic....a little ways to go
IEC socket has fuse
fuse holder by the switch was a screwup...
I get a hole cover or maybe its a spare fuse holder :))
marked as a Xmas gift for my son

D
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Re: new build

Postby SteveH » Mon Oct 27, 2014 8:34 am

Looking good ! What's the rest of it look like ?
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Re: new build

Postby Shannon Parks » Tue Oct 28, 2014 11:50 am

Does it fit in the Hammond chassis? My initial top plate with the same layout didn't have the side clearance for the output transformer on the lower right. One the released version I plan to squeeze it closer to the other one and rotate it 180 degrees (so the tabs face out).

Shannon
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Re: new build

Postby dcribbs1412 » Fri Oct 31, 2014 9:40 pm

Pics of build in chassis
I used the Hammond 1550jbk
It might be a little bigger
http://www.mouser.com/Search/ProductDetail.aspx?R=1550JBKvirtualkey54600000virtualkey546-1550JBK
Only 1 channel is working wondering if I have the pot wired correctly
orange and white are right and left in... yellow is ground
do both grounds/shields connect on pot?
any suggestions are greatly appreciated

D
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Re: new build

Postby Shannon Parks » Sat Nov 01, 2014 4:05 pm

dcribbs1412 wrote:do both grounds/shields connect on pot?


Yes. You should be able to crank the pot fully CW and measure low resistance at the J1 pins 1 and 4.

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Re: new build

Postby dcribbs1412 » Sat Nov 01, 2014 6:02 pm

Hi Shannon
Yes, I get 96k cranked on pin 1 and 4 of J1
only 1 channel has sound?

D
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Re: new build

Postby dcribbs1412 » Sun Nov 02, 2014 12:17 pm

Using my Iphone and a make shift signal tracer and the schem
I can trace the sound of a 1k sound wave from both the inputs, 100k pot, V1,C7,C8 all the way to the transformers j2 and j3 connections
getting nothing out of speaker outs or headphone jack?
any comments are suggestions are greatly appreciated

D
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Re: new build

Postby Shannon Parks » Mon Nov 03, 2014 10:28 am

dcribbs1412 wrote:Using my Iphone and a make shift signal tracer and the schem
I can trace the sound of a 1k sound wave from both the inputs, 100k pot, V1,C7,C8 all the way to the transformers j2 and j3 connections
getting nothing out of speaker outs or headphone jack?
any comments are suggestions are greatly appreciated

D


1) All the DC voltages look good at V2 & V3?
2) This sounds like the fabled "shorted speaker output connection". Make sure you aren't shorted at the output. Which outputs and chassis are you using? Can you post a pic?

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Re: new build

Postby dcribbs1412 » Mon Nov 03, 2014 9:52 pm

Hi Shannon
You my friend are on it exactly.
this was the " fabled shorted speaker output connection".
re drilled the output holes bigger rewired and boom...both channels of the amp sound good.
BTW all voltages are good V1...272,163,165 V2 and V3...291,287
Speakers suck but that's a future upgrade.
sorry for the unsexy shop table pic

Thanks for your time and patients

Darin
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Re: new build

Postby Shannon Parks » Thu Nov 06, 2014 11:43 am

Cool! I like that you did a DIY top plate with the Hammond chassis. I'll see if I can't release a paper template for those wanting to do this.

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Re: new build

Postby dcribbs1412 » Sat Nov 22, 2014 5:44 pm

Amp is sounding good thanks Shannon
I think my son will find a new appreciation for vinyl records
One stupid question
headphone jack doesn't disconnect speakers?
I plug in headphones and speakers are still working
Did I wire something wrong?
any comments or suggestions are appreciated

Darin
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Re: new build

Postby Shannon Parks » Mon Nov 24, 2014 10:02 am

dcribbs1412 wrote:Amp is sounding good thanks Shannon
I think my son will find a new appreciation for vinyl records
One stupid question
headphone jack doesn't disconnect speakers?
I plug in headphones and speakers are still working
Did I wire something wrong?
any comments or suggestions are appreciated

Darin


This is normal. I used the speaker terminals as tie in points for the overall feedback and a standard TRS jack in order to clean up the design (ran out of space, really). You can add a DPDT switch as the tie in, and speaker "shut off".

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Re: new build

Postby dcribbs1412 » Tue Nov 25, 2014 10:38 pm

Shannon Parks wrote:This is normal. I used the speaker terminals as tie in points for the overall feedback and a standard TRS jack in order to clean up the design (ran out of space, really). You can add a DPDT switch as the tie in, and speaker "shut off".
Shannon

Thanks Shannon
not sure where to "tie in"
would something like this work (without the xlr jack, 1/8" jack and resistors)
any suggestions are appreciated.


D
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Re: new build

Postby Shannon Parks » Wed Dec 03, 2014 9:18 am

Interesting drawing you have there for switching balanced and unbalanced outputs. Maybe have to use that later.

I've edited the hookup drawing to show the DPDT switch, which is just a simple OFF switch for the speakers. Instead of using the R+ and L+ binding posts as tie-in locations, you'll use the center posts of the DPDT, so some large lugs would be handy. Attached the PDF as well as a jpeg preview.

Shannon
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Re: new build

Postby dcribbs1412 » Thu Dec 04, 2014 2:39 pm

Thanks Shannon
very much appreciate this info

Darin
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