martin manning wrote:I'm sure there are some folks scratching their heads wondering why it sounds good and doesn't hum or oscillate, and also how unlucky they must have been to build an amp that did! I suppose that this isn't a particularly high gain design, and so maybe it's not all that sensitive.
I didn't know I was doing it wrong so maybe it didn't matter.
With V1 gain stages cascaded it's considerably higher gain and still very quiet.
What do you think of the switch wiring I posted above?
martin manning wrote:I'm sure there are some folks scratching their heads wondering why it sounds good and doesn't hum or oscillate, and also how unlucky they must have been to build an amp that did! I suppose that this isn't a particularly high gain design, and so maybe it's not all that sensitive.
Yup specialy with the 1-wire mod,I don't see how its not a humming squealing mess.FM Is the only explanation I can come up with
One the subject of inserting a jack into the normal channel as mentioned above.
Does this do anything more than switch the 1M resistor? I would think since the gain stages are cascaded, the rest of the circuit is being utilized even without the jack.
Reason I'm asking is, after a few weeks with the amp, I've found that I can dial in a nice crunch and then add the jack and it takes it to a really nice lead drive. It doesn't get noticeably louder, just changes the distortion level.
It would be nice to be able to add a couple of relays that would switch both the one-wire mode and effectively open the switch on the Normal input jack giving ma a wide range of tonal options from a foot switch.
Or, I could leave the one-wire mod on a switch and just use a single relay for the Normal channel switching.
I have the 11V tap off the PT that I didn't use. I could adapt it to power the relays pretty easily.
The easy way is to switch the jack to the input resistors of either path.
The 1-wire is controlable and more gain than will fit in a semi if you add the simple master then split V1b signal 470k/470k. Super distortion extra plus plus.
martin manning wrote:I'm not sure what you have in there now... Can you post a schematic?
Hi Martin.
All I've done so far is the one-wire mod.
Moved the wire from the Bright vol wiper to the ground lug beside it, then added a 1M from the same wiper to what was the junction of the two 68K resistors on the Normal channel...it's a single 33K on mine since I have only one Normal and one Bright input.
Reeltarded wrote:The easy way is to switch the jack to the input resistors of either path.
The 1-wire is controlable and more gain than will fit in a semi if you add the simple master then split V1b signal 470k/470k. Super distortion extra plus plus.
Thanks Miles.
I remembered that the donor amp had a foot switch. I revisited the schematic and it turns out there are 3 DPDT relays on the board and they were powered with rectified DC off the 11Vac tap I mentioned. But it seems easier and cleaner to power the foot switch with a wall wart and connect it with an XLR cable.
Here's what I came up with to make the one-wire and input resistor switchable. I'm pretty confident in the one-wire switching on the right but not sure about the input R on the left...I've read descriptions about how those Fender style inputs work but they still baffle me a bit.
Peace,
Mark
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Here's a clip of the 1-Wire tones I want to switch between. This was played on my sunburst Strat I posted in my Bassman build. I set up the crunch tone and then got thee lead tone by only inserting the 1/4" plug into the Normal jack. I panned the crunch to one side and lead to the other. Superior Drummer wasn't playing nice this morning so it's just guitars and bass.
I just remembered what worked best for me when I was messing with that. I split the brite signal 50% with a 470k/470k divider and fed the unused 68k input resitor with that signal. I think I also used a 100p or 250p over the ground leg of that divider and a 100p plate bypass for the brite stage.. something like that.
Switching was as easy as routing the pin to either point in the circuit and grounding the brite channel feeding the input resistor so the noise goes bye bye in normal mode..
I'm sure there are many more than one "one wire" mods. Grounding the wire from the bright channel wiper puts in a low-pass like Reeltard talks about. Other versions use the bright channel as the input stage and take the signal to the normal channel by splitting the mix resistors and running the 470R/470p to the normal channel input. From there it's just a couple of tweaks to get to the high input on a 2204 Master model.
Mark, I think plugging a jack into the unused input is just lifting the 1M connected there from ground, which will increase gain a bit and move the LF roll-off down.
Thanks guys! I chose this flavor of the mod because it was very easy to reverse if I didn't like it.
Can you guys confirm my relay diagram?
The Input Resistor Relay (left relay)
In the shown position, the 1M is connected to ground as if the Normal jack were empty.
When the relay is switched, the 1M is bypassed as if the 1/4" jack were inserted.
The 1-Wire Relay. ( right relay)
The shown position has the wire from the 470K going to ground and the 1M connected to the wiper engaging the 1-Wire mod.
When the relay is switched, the 1M is taken out and the 470K is connected to the wiper as it normally would be. Should I ground the 1M or just leave it unconnected?
Reeltarded wrote:To do exactly what? Yeah, I need more coffee.
Normally a HI input would see that 1M reference. Is that the answer?
Be back for scolding later.
There are two different 1M resistors involved. The question was regarding the 1M in the 1-Wire mod relay. When it's in the circuit it's connected to the wiper of the Bright vol. When it's not, should I leave one end unterminated as shown in the diagram I posted or take it to ground with the unused relay contact?
