Progress Report:I'm getting signal through. The output is below unity at the moment. The trim pot in the top right doesn't seem to have any effect. The gain pot drastically drops the volume when backing off the gain.
I've tried the 15k resistor at D-2 and E-2 since I wasn't sure with that big 220uf convering the area.
Cool! Thanks for tackling this. I will triple check everything in a couple of days when things is getting less busy here. Which trannies do you have in there?
I used low leakage Russian GT313a PNP Ge trannies and then for kicks, I tried some Si 2n3906. Oddly enough (if I remember correctly), when I was trying 2D and 2E for the 15k, when I had it set in 2D, the bass switch seemed to have a more drastic effect .
The non-working switch could be something to do with the software, maybe. Anyway, changing the type of the transistors (I can't use russians but just those the software has) the roll off affair has changed. It could be ok just like that.
I didn't work on this layout, but I have fun to emulate the circuits, so I try this one looking at the schematic I found. - The gain pot should work too. (And of course the Volume pot.) The mid switch works, it cut around 150-200Hz. - I can see in the frequency any change acting the trimmer after Q2. -The other trimpot set the bias, or something else? Its setting is crucial to get a right amount of the signal. - The Bass switch doesn't do anything, though small cap between the transistor and the 9v (for example replacing the 220uF) actually cut bass. - I have to say that the frequency response is almost flat with a linear Treble pot, while a log cut highs at noon. The Treble pot I guess attenuate or emphasizes the high frequency well, but doesn't roll off. Maybe it's ok, I don't know, but this sounds a bit strange to me, sometime. We could add a 1k resistor in line to the signal before the 10pF cap, and change this cap in something bigger like a 470pF, for example, getting a high filter.
I'm trusting of the emulation software, but what I'll saying could be difference in the real world.
Anyway, if we consider the value of a cap in parallel with the 1k I can see how much big can be the value to not cut bass. We could use even a 47uF without cut any useful low end, I suppose. It will roll off just the lowest frequency. A 10uF give a more drastic cut, but the peak is still around 80hZ. A 4.7uF could give better result. All these values should be tested by ear. A 470nF cut a lot, it seems to me: 20db under 200Hz.
If in the schematic/layout we swap the 220uF and the 470nF, the trick could work ok. Replacing the 220uF with a 100uF could be still ok. And, last thing, if the 470nF cut too much, a 4.7uF could sound ok.
Demo of the original: https://www.youtube.com/watch?v=aeZWEwRb8RA
Of course the one we have is not the definitive schematic and I have to say that, at this point, there's something different (or wrong), indeed. Anyway, just to talk, the Mid switch, the one add the 4.7nF to the 12nF boost between 100-300Hz. This could be ok, the mid boosted seems to me not so drastic, and low-mid style, the switch adds body to the sound. Other thing, the bass switch is 3-way, and it doesn't cut too much bass.
Are the 2.2uf caps non-polarized?
ReplyDeleteYes, they are, I'll add it to the notes.
DeleteProgress Report:I'm getting signal through. The output is below unity at the moment. The trim pot in the top right doesn't seem to have any effect. The gain pot drastically drops the volume when backing off the gain.
ReplyDeleteI've tried the 15k resistor at D-2 and E-2 since I wasn't sure with that big 220uf convering the area.
Cool! Thanks for tackling this. I will triple check everything in a couple of days when things is getting less busy here. Which trannies do you have in there?
DeleteAnd yes, 15k should be connected to 2E.
DeleteI used low leakage Russian GT313a PNP Ge trannies and then for kicks, I tried some Si 2n3906. Oddly enough (if I remember correctly), when I was trying 2D and 2E for the 15k, when I had it set in 2D, the bass switch seemed to have a more drastic effect .
DeleteThe non-working switch could be something to do with the software, maybe. Anyway, changing the type of the transistors (I can't use russians but just those the software has) the roll off affair has changed. It could be ok just like that.
DeleteBut, the Bass Switch adds the 470nF in parallel to the 220uF, right? How much difference could do add just 0.470uF to 220uF? Am I missing something?
DeleteI didn't work on this layout, but I have fun to emulate the circuits, so I try this one looking at the schematic I found.
ReplyDelete- The gain pot should work too. (And of course the Volume pot.) The mid switch works, it cut around 150-200Hz.
- I can see in the frequency any change acting the trimmer after Q2.
-The other trimpot set the bias, or something else? Its setting is crucial to get a right amount of the signal.
- The Bass switch doesn't do anything, though small cap between the transistor and the 9v (for example replacing the 220uF) actually cut bass.
- I have to say that the frequency response is almost flat with a linear Treble pot, while a log cut highs at noon.
The Treble pot I guess attenuate or emphasizes the high frequency well, but doesn't roll off. Maybe it's ok, I don't know, but this sounds a bit strange to me, sometime.
We could add a 1k resistor in line to the signal before the 10pF cap, and change this cap in something bigger like a 470pF, for example, getting a high filter.
My guess is that there is a bug in the schematic. It makes more sense to have 470nF and 220uf swapped?
DeleteI'm trusting of the emulation software, but what I'll saying could be difference in the real world.
DeleteAnyway, if we consider the value of a cap in parallel with the 1k I can see how much big can be the value to not cut bass. We could use even a 47uF without cut any useful low end, I suppose. It will roll off just the lowest frequency.
A 10uF give a more drastic cut, but the peak is still around 80hZ. A 4.7uF could give better result.
All these values should be tested by ear.
A 470nF cut a lot, it seems to me: 20db under 200Hz.
If in the schematic/layout we swap the 220uF and the 470nF, the trick could work ok. Replacing the 220uF with a 100uF could be still ok. And, last thing, if the 470nF cut too much, a 4.7uF could sound ok.
Demo of the original:
https://www.youtube.com/watch?v=aeZWEwRb8RA
Of course the one we have is not the definitive schematic and I have to say that, at this point, there's something different (or wrong), indeed.
Anyway, just to talk, the Mid switch, the one add the 4.7nF to the 12nF boost between 100-300Hz. This could be ok, the mid boosted seems to me not so drastic, and low-mid style, the switch adds body to the sound.
Other thing, the bass switch is 3-way, and it doesn't cut too much bass.
This comment has been removed by the author.
ReplyDeletehello everyone and congratulations for the beautiful site, has this layout been corrected?
ReplyDelete