Help with tone sucker

whomeno · May 15, 2020, 09:09:30 PM

I'm tring to build the tone sucker amp from "pual in the lab". Got the board done, but now I'm not sure how to hook the transformer up to it.
I bought a hammond BE2G 24V transformer.
I see there is 2 ac inputs and a ground on the board. so the hot and common would go to the ac inputs? correct and where would I connect the ground wire from the board?

And the schmatic

Asking for the guru's to help me out a little on setting this up.
Thanks

willienillie · May 16, 2020, 03:45:47 AM

The start and finish of the 24VAC secondary go to AC1 and AC2. If there is a center tap don't connect it, a bridge rectifier doesn't use a CT. Board ground would connect to common ground for the whole circuit, along with jack sleeves etc.

antonis · May 16, 2020, 02:51:16 PM

Sorry but I think that you either kidding us or post & forget/ignore your issues..

https://www.diystompboxes.com/smfforum/index.php?topic=124449.0

whomeno · May 16, 2020, 06:31:48 PM

Thanks for the reply and yes I forgot I posted earlier.

iainpunk · May 17, 2020, 08:24:59 AM

in the schematic, the 7808 has two of the same value capacitors in front and after it, although this will probably work alright for you, it's good practice to have different value capacitors to prevent the chip from oscillating and getting hotter than it's supposed to be. i had a 7805 that burned up because of oscillations. i suggest a 22n in front and the original 10n after.

cheers,
Iain

whomeno · May 19, 2020, 10:37:23 PM

Ok 1 last question on this amp. it calls for a 22K pot. auto or linear taper? I don't have a 22K what would be a good value to go with.
Thanks

bluebunny · May 20, 2020, 03:43:18 AM

25K should be fine. 22K is a Europe thing. And I would guess at log. Though the pin designation on the schematic looks just plain wrong - it goes from grounding the output from the preamp to grounding the input to the power amp! Not checked vs. the layout, because not enough coffee...

antonis · May 20, 2020, 05:11:51 AM

Just a question..

In case of you don't feed another circuit from 317 output (like clearly seen on schematic), what's the reason for using 32.5VDC rectified power to get only 8V from 7808 output..??

As for Volume pot, I totally agree with Eric (and I already have enough coffee..)
(also checked and verified vs layout..)

whomeno · May 20, 2020, 06:54:19 AM

Bluebunny.
Can you explain more please? The amp seems to work but hardly any volume.

antonis · May 20, 2020, 07:11:53 AM

Still coffee time for Bluebunny..

Lug 2 (wiper) of Volume pot is permanently grounded..

So, despite of its setting, signal goes to Ground 'cause it's the way of less resistance..
Even in max setting (no resistance between wiper & lug 3) there is some resistance of the following circuit "seen" by signal when sitting on lug 3..
(signals are lazy enough to follow the hard way..)

whomeno · May 20, 2020, 07:31:40 AM

antonis,
Is there a way to fix this? The amp dose work but has low volume, I think the tda2030 is bad. would the grounding of lug 2 and 3 cause low volume?
I am looking at the vero, where is pin 2 grounded at?

antonis · May 20, 2020, 07:41:25 AM

I suppose so..

~~On layout, replace 22K 1 for 22K 2, 22K 3 for 22K 1 and 22K 2 for 22K 3~~

Wait a minute 'cause your layout is wrong ..

antonis · May 20, 2020, 07:54:56 AM

22K-2 is OK..
22K-3 should go On negative leg of C9..(where 22K-1 wrongly goes..)
22K-1 shoulds go to any convenient GND (like where 22K-3 wrongly goes..)

So, just interchange lus 3 & 1 ..

(my poor eyes hurt..)

whomeno · May 20, 2020, 08:02:28 AM

ok Thanks

bluebunny · May 20, 2020, 08:48:43 AM

Quote from: antonis on May 20, 2020, 07:11:53 AM
Still coffee time for Bluebunny..

Lug 2 (wiper) of Volume pot is permanently grounded..

So, despite of its setting, signal goes to Ground 'cause it's the way of less resistance..

Yep, this is what I was getting at, but without the benefit of caffeine.

whomeno · May 20, 2020, 07:06:03 PM

Update... The tda2030 was bad found a tda 2040 i had put it in and sounds good.

niektb · May 21, 2020, 02:24:31 AM

This design bugs me also

If you have a trafo, why not using double-sized (positive and negative) supply? Now you have to put DC-blocking caps and biasing resistors everywhere

And 2200 uF on the output

antonis · May 21, 2020, 06:28:04 AM

Quote from: niektb on May 21, 2020, 02:24:31 AM
And 2200 uF on the output

Good design practice for output of single supply power amp..
(although some experts claim for super-extra-high quality/cost of particular cap..)

On a second look, it indeed is a quirky design..
e.g. Zobel network (Boucherot Cell) R10/C13 values are aimed at some "extra-ordinary" loudspeaker..

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Help with tone sucker