freestompboxes.org

rocklander wrote:thanks... so I guess my real question is, if I was to do a layout with 3X dual (or a single quad and a dual) there's no disadvantage from a sound perspective?

I think MXR didn't have access to any dual op-amps at the time of the first layout. The sound of the chip is pretty interesting as well. This layout is a lot different sounding from the dual op-amp versions, it's more subtle, smoother and not as 'spacey' sounding than the later model block logo layout.

Here's a PCB from the first batch.

This build is using:

Matched 2N5285 transistors instead of 2N5952 transistors.
.047uF WIMA MKS2 film caps instead of .05uF ceramic disc caps
Carbon film resistors instead of metal film resistors.
Texas instrument UA741CP chips instead of National Semiconductor LM741CN chips.
Board mounted 150k resistor instead of the flying 150k resistor.
True bypass switch.
Alpha C500K pot instead of 05C500K pot.

It sounds much better than the stock '74 reissue.

yeah, never mind.. my n00bishness betrays me.. had I bothered to look at tonepad I'd have seen they use dual opamps

Hi
i modded my 74 script reissue with dc jack according to xenrelic schem (see pdf in previuos page); the unit works perfectly but i noticed that there are more highs and the tone is not so warm and full using it with dc jack than using it with battery. This mod should not alter the tone at all (or it is said not to do it); how can it be? did i make any error? (i followed the schematic in pdf. I put dc jack only, no led and 3pdt)
Maybe the battery (tired) gives less than 9V and the effect sounds better? (warmer, bigger, with no high peaks and smoother).
Is there any mod to mimic a tired battery using a dc adaptator?
thank you for your help
bye
hot

nobody?
hot

thi is the phase i always wanted..I've build 2 of them one for me and one for a friend of mine and works like a charm .
anyone knows a good way to intensity pot as well as a speed led? Just to make it a bit more versatile

harrisxr650 wrote:thi is the phase i always wanted..I've build 2 of them one for me and one for a friend of mine and works like a charm .
anyone knows a good way to intensity pot as well as a speed led? Just to make it a bit more versatile

You mean like a depth pot? You replace the 1M resistor between the gates of the fets and the trimmer with a 500k resistor and 500k pot I think... The mod is out there in google land in more than one place I think.

Flashing/pulsing LEDs stink, why do you want one of them (I have no idea about that)

yeap a depth pot i did change the 1M res with a 1M pot in series with a 680ohm res and didnt like the results, from 0-5 the pot is dead and no phase only dry signal, from 5-10 the pot becomes active but i would like to have usable the full range of the pot so i can dial in precise where i want to. Maybe i had wired wrong the pot with the res? I mean when i saw i series i though a connection like "pcb-680ohm res- pot lug 3- pot lug 2 to pcb...
Well about the led... i wanted it so i can see the lfo speed ( and because its cool )

Try a 470K resistor with a 500KC pot for the depth control.

The 680Ω resistor is way too small.

hotguit wrote:nobody?
hot

Check you battery voltage and use an adjustable regulated 9vdc power supply, or use a 1k resistor from the DC+ lug of the DC jack to a (1N5239B) or (ZL9M3) 9.1v Zener diode to ground, a 220uF 25v capacitor and a .1uF 50v ceramic capacitor in parallel with the zener diode for the filter and then the output of the 1k resistor to the 9VDC input of the SP90 board.