That depends if your amp needs gain. If yes, keep the Whammy in the loop, if no bypass it with a switch (but only flip it while off I guess).
Thanks for all this. Final advice:
Is there a reason to put a switch in after the pot to direct the signal to either the Whammy or the amp, or can I just add a wire to divert the signal after the pot to the amp. In other words, is there a problem with having the signal go to both the Whammy and amp if I'm only using one of them?
How do you mount an led to the front of the box (on/off indicator)?
I'll post pics when done!
Is there a reason to put a switch in after the pot to direct the signal to either the Whammy or the amp, or can I just add a wire to divert the signal after the pot to the amp. In other words, is there a problem with having the signal go to both the Whammy and amp if I'm only using one of them?
How do you mount an led to the front of the box (on/off indicator)?
I'll post pics when done!
Hello,
I am building my second Whammy. This time, I will be using 15V transformer instead of 22V. Everything else is the same. What voltages should I be reading when testing the PSU (following the directions on page-1)
- Approximate voltage on C9 + pad and ground?
- Approximate voltage on R13 and R14?
Thanks for any information.
I am building my second Whammy. This time, I will be using 15V transformer instead of 22V. Everything else is the same. What voltages should I be reading when testing the PSU (following the directions on page-1)
- Approximate voltage on C9 + pad and ground?
- Approximate voltage on R13 and R14?
Thanks for any information.
15V rectifies to approx 21V, but the voltage at C9 or R13/14 depends on your regulator configuration. Both naked and LED should be fine, but the resistor reference probably wont get you good regulation.
Just sharing some of my findings....
I have about 20'ish mV on both channel outputs, and then i shorted out C26 & C27, the outputs shot up to 87'ish mV.
I removed the C1 & C5 input caps, and the output now is -1.0mV on both channels.
Then i try to short out C26 & C27 again, i got -1.5 mV on both.
Finally i use back C26 & C27, very happy with -1mV now.
Btw i m using stock opamp that came with the kit, RC4580.
Happy Camper !
I have about 20'ish mV on both channel outputs, and then i shorted out C26 & C27, the outputs shot up to 87'ish mV.
I removed the C1 & C5 input caps, and the output now is -1.0mV on both channels.
Then i try to short out C26 & C27 again, i got -1.5 mV on both.
Finally i use back C26 & C27, very happy with -1mV now.
Btw i m using stock opamp that came with the kit, RC4580.
Happy Camper !
Me too! I had no offset coming into the Whammy and was getting 24mV for the output. I took out C1 and C5 and now it's 1mV. Woo Hoo!
With the input caps out you may very well get less offset because of lower resistance from pot and source all in parallel. The input currents develop less voltage.
Updates on my double balanced Whammies:
My power supplies are at +/- 16.3VDC, using LM317/LM337 pairs, just because I have plenty of them.
I using Fairchildes, source resistors are 4 Ohms, with approx. 0.556 volts across them.
That is about 140mA bias.
Now, my sturdy Al chassis a litle bit warmer than was before, at least.
I using 6.8 uF ERO MKCs on inputs, they doesn't hurt me at all.
Also, I have 22uF Elna Silmic II at position C26 and C27.
Using OPA2604s, my output offsets are below 1 mVs.
Balanced offsets are below than this.
I've mentioned earlier, I don't need gain, so I have about 1.22 kOhm at positions R4/R8.
There isn't any stability issue, even without C2/C7.
I will going down to 1kOhm.
I must have to say, my BOSOZ is now retired.
It is an excellent balanced preamp, the most symple thing you can imagine, but it has limits. I have tear drops in my eyes.
What will be, if my Korgs will be ready?
My power supplies are at +/- 16.3VDC, using LM317/LM337 pairs, just because I have plenty of them.
I using Fairchildes, source resistors are 4 Ohms, with approx. 0.556 volts across them.
That is about 140mA bias.
Now, my sturdy Al chassis a litle bit warmer than was before, at least.
I using 6.8 uF ERO MKCs on inputs, they doesn't hurt me at all.
Also, I have 22uF Elna Silmic II at position C26 and C27.
Using OPA2604s, my output offsets are below 1 mVs.
Balanced offsets are below than this.
I've mentioned earlier, I don't need gain, so I have about 1.22 kOhm at positions R4/R8.
There isn't any stability issue, even without C2/C7.
I will going down to 1kOhm.
I must have to say, my BOSOZ is now retired.
It is an excellent balanced preamp, the most symple thing you can imagine, but it has limits. I have tear drops in my eyes.
What will be, if my Korgs will be ready?
Is this good? Bad? I'm sorry, but you've reached the limits of my electronics literacy. What does this mean in terms of creating awesome music?
The secondary harmonics in the 12k band definitely attenuated to account for the DC offset of the...uh, no. It sounded about the same, but I didn't do a careful A/B test.
LOL! Thanks!
Actually, I have two whammys, almost identical, and I removed C1 and C5 to try. I noticed the same results with regards to output DC offset. From 24 to 1 mV. They are set up for A/B.
If there is a change, it's very subtle to me. I sort think I hear a difference in the lower treble, but I think I might be imaging it.
Now that DC offset is so low, I haven't tried removing and jumping C26 & C27
Even if it doesn't help the sound, removing C1/C5 brings down the cost of the amp by over $6!
Curious about the output resistor suggested to prevent oscillation. The BOM on the 1st page of this thread suggests resistors of 1/4 watt or greater when making a selection. Does this hold true for the output resistors?
There are Dale 100 ohm 3/4 watt and Dale 56 ohm 1/2 watt resistors readily available. Are they both suitable?
Many thanks.
There are Dale 100 ohm 3/4 watt and Dale 56 ohm 1/2 watt resistors readily available. Are they both suitable?
Many thanks.
There have been several mentions in this thread that if you're building the Whammy as a preamp it wouldn't hurt to put a 25 to 100 ohm resistor on the ouputs. It'll help prevent oscillations. I'm not sure this is part of the schematic.