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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

PSA, Do NOT buy this tone control PCB from ebay.
PSA, Do NOT buy this tone control PCB from ebay.
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Old 8th August 2019, 12:38 PM   #1
ValvesOfSteel is offline ValvesOfSteel
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Join Date: Jul 2019
Default PSA, Do NOT buy this tone control PCB from ebay.

I purchased this one to modify for a guitar amp, waited a month for it to come from china (it only cost about $3.50 and I got an insta refund so it's not a HUGE deal, but bad product is bad product.)

Don't need power supply passive front amplifier tone sound palette PCB DIY kits | eBay

The kit was missing one of the 222 caps, I only really need a single channel so once again, not a big issue, but still, missing parts.

Also, the PCB looks good, but appears to be made of some space age material that actively resists solder! Getting a good join to the pads was a nightmare even with flux paste! And then the kicker, cutting a lead from a freshly soldered resistor, seems the solder stuck this time, because the whole pad and track, including the next pad for the pot, ripped clean out of the board!

I am going to rat an old CD player PCB in case I need the other 222 for some un knowable reason, and I soldered a wire link between the broken traces, so I can still use the kit, but so far it's been a nightmare of wasted time!

Very telling that when I submitted the return request in ebay, I got an insta refund and a message saying "keep it". Obviously this is a common issue!

Spend a little extra and get something a little better, I certainly will be next time! XD

Last edited by ValvesOfSteel; 8th August 2019 at 12:40 PM. Reason: forgot the bloody link to the aution! Derp!
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Old 9th August 2019, 03:33 AM   #2
Fast Eddie D is offline Fast Eddie D  United States
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Join Date: May 2010
Location: Skokie Il
A tone stack for a guitar is completely different than a bass - mid - treble tone control for hi fi. You can find a lot of different tone stack schematics (most I've seen are passive) on the web that you can build on perfboard (or even make your own PC) for probably less than $10.

Passive tone controls need to be driven by a low impedance source and they only work when driving a high impedance buffer. They have a large insertion loss (10-20 dB). There are lots of active tone controls that use just one op amp that have 0 dB insertion loss and work so much better than this poorly thought out piece of junk.

All the caps are ceramic. You need to use more linear caps (film caps) in the tone control section. Ceramic caps are horribly nonlinear and introduce lots of distortion when used in filters. This thing doesn't have a chance.
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Old 9th August 2019, 03:40 AM   #3
nigelwright7557 is offline nigelwright7557  United Kingdom
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Join Date: Apr 2008
Location: Carlisle, England
I buy my project pcb's from China from JLCPCB and PCBWAY and they have always been good. A few times I have wanted to change through hole components and managed to get the components out with removing tracks.
Maybe you were just unlucky and they bought in the cheapest possible rubbish pcb's ?
I am on a Facebook pcb group and get inundated by hundreds of Chinese pcb suppliers.

I would recommend getting a circuit and laying out your own pcb then get it made by one of those I mention above. Usually $5 for 10 pcb's 10cm by 10cm and choose a cheap postage method if your not in a hurry.
PCBCAD51 download or CDROM 2019 version out now https://www.murtonpikesystems.co.uk
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Old 9th August 2019, 03:50 AM   #4
Fast Eddie D is offline Fast Eddie D  United States
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Join Date: May 2010
Location: Skokie Il
You want to use capacitors like this MKP2D021001B00KSSD WIMA | Capacitors | DigiKey not ceramic.

I googled "tone stack circuit" and hundreds of circuits popped up. Some are based on "classic" tone stacks (Marshall etc) and are very simple. I'm sure you could find something to work for your application.
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