Startup "strangeness"

Hardware questions and issues with the FV-1

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FUCHSAUDIO
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Startup "strangeness"

Post by FUCHSAUDIO »

I've been discussing this with Frank via e-mail, but figured I would put it out to the masses:

Has anyone experienced FV-1's that start up sounding poor ? By that I mean almost underwater or chorus-like sounding ? I'm using one of the built in reverb presets with an output volume and a dwell (decay) control on a plug in daughterboard. A simple header to the main amp board. Power lines are clean, plenty of bypass on the daughter board, same crystal Frank uses in his boards.

Some units seem to require a restart (for lack of a better term). If you basically interrupt or bump the power (flip the power switch off then back on), the chip resets and sounds as it should (which is great sounding btw).

I'm about to revamp the daughter board board (after a few hundred boards) and really need to nail this down and am looking for ideas...be glad to share the layout for anyone who wants to look it over for any obvious layout glitches I might have done wrong. I'm "an analog boy in a digital world.."....love the FV-1 RIP Keith.
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frank
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Post by frank »

You need to talk to the crystal maker. Every crystal manufacturer cuts their crystals to their specs so you need to talk to their support people to see their recommended circuit for making sure the crystals start up properly.
Frank Thomson
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FUCHSAUDIO
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thanks Frank

Post by FUCHSAUDIO »

Appreciate the input, and in no-way am I suggesting you haven't been helpful and awesome to work with. Can you clarify "recommended circuit for making sure the crystals start up properly." It's just the FV-1 and a couple of caps on the crystal terminals. Can you elaborate ?
Improving guitar tone, one player at a time....
frank
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Post by frank »

I cannot elaborate as I did not cut the crystal, you MUST contact them and ask their tech people. Emailing me and posting here will NOT solve the issue if it is a problem with the crystal starting properly, only contacting the crystal manufacturer can help.
Frank Thomson
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Sweetalk
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Post by Sweetalk »

I'm using inexpensive and super-generic crystals and never noticed what you did on the startup. The crystal circuit is only a 22pF cap to ground as recommended on the datasheet.
FUCHSAUDIO
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This is the crystal I'm using

Post by FUCHSAUDIO »

http://www.digikey.com/product-search/e ... 00-8301-ND

Are you using something else sweetalk ? I had the single 22pf, added another, but same issue.
Improving guitar tone, one player at a time....
Sweetalk
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Re: This is the crystal I'm using

Post by Sweetalk »

FUCHSAUDIO wrote:http://www.digikey.com/product-search/e ... 00-8301-ND

Are you using something else sweetalk ? I had the single 22pf, added another, but same issue.
Yeah, it might be something like that. Try another brand or type of crystal, play around with the caps values. When you have the distorted signal, the clock signal have any differences with the clock signals when the signal is OK?.
Did you consider power issues?
FUCHSAUDIO
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Post by FUCHSAUDIO »

Power is 3.0 V clean, regulated, locally bypassed on the daughter board. It's supplied by a L78L33ACZ with a 47uf output filter (minimum required). The same basic artwork is used in a reverb pedal that sometimes (although rarely) does this same thing and uses a 9V external plug in supply and the same 3V IC regulator and crystal.

The raw supply starts as 10 volts, regulated to 8 volts for relays, regulated to 6 volts for vacuum tube heaters and regulated to 3 volts for the digital board.

Frank mentioned that "maybe the supply comes up too slow" due to large input filter, but not sure if that should matter since it's happened on units powered off other types of supplies. I can e-mail the layout if anyone wants to have a quick look for obvious "niggles".....

I just noticed Digi-Keys chart for the crystal calls for lesser values of crystal start up caps. Does the chip contribute anything to this value ?

http://www.digikey.com/product-search/en?FV=ffec2182
Improving guitar tone, one player at a time....
Sweetalk
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Post by Sweetalk »

FUCHSAUDIO wrote:Power is 3.0 V clean, regulated, locally bypassed on the daughter board. It's supplied by a L78L33ACZ with a 47uf output filter (minimum required). The same basic artwork is used in a reverb pedal that sometimes (although rarely) does this same thing and uses a 9V external plug in supply and the same 3V IC regulator and crystal.

The raw supply starts as 10 volts, regulated to 8 volts for relays, regulated to 6 volts for vacuum tube heaters and regulated to 3 volts for the digital board.

Frank mentioned that "maybe the supply comes up too slow" due to large input filter, but not sure if that should matter since it's happened on units powered off other types of supplies. I can e-mail the layout if anyone wants to have a quick look for obvious "niggles".....

I just noticed Digi-Keys chart for the crystal calls for lesser values of crystal start up caps. Does the chip contribute anything to this value ?

http://www.digikey.com/product-search/en?FV=ffec2182
I was thinking in a low-startup power line... Try to take the 3V3 line from the raw supply, not from another regulator (or that's what I understood). I NEVER noticed that strange startup in any of my pedals or prototypes. I'm using a 78L33 in TO-92 package with a 100uF output cap from a standard 8,3V power line (9V after a protection diode in series).
FUCHSAUDIO
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Post by FUCHSAUDIO »

All regulators draw from the raw supply, they are not cascaded. Sorry if that was unclear. The 3.3 has a few ohms (less than ten) to reduce the I/O voltage a little.
Improving guitar tone, one player at a time....
Sweetalk
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Post by Sweetalk »

Mail me the layout if you like, maybe there's a little thing you're not taking care of
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