ijedouglas wrote: ↑Fri Jul 16, 2021 2:36 pm
What is the measured value of your V2 snubbers?
280pF and 290pF
Dials look good. My OD level is normally higher...around 5-6 and my master is lower... Around 3-4. I see your mid switch is off, I normally engage that with SC and mostly with HB too.
I didn't get a good listen to the clips as I'm traveling but was the HB better?
ijedouglas wrote: ↑Fri Jul 16, 2021 6:46 pm
Dials look good. My OD level is normally higher...around 5-6 and my master is lower... Around 3-4. I see your mid switch is off, I normally engage that with SC and mostly with HB too.
I didn't get a good listen to the clips as I'm traveling but was the HB better?
I was also traveling last weekend and didn't see your post. I believe I should turn up pre-amp vol a bit, as well as switch on mid to match your dials, since I'm using a standard 10% audio taper. If I'm not mistaken, the equivalent to 5 in your dial (half dial) would be 7 in my Alpha pot. It would probably be easier if I put the correct pot but I couldn't find a 1M 30% taper pot. The only one I could find was the CTS 250K 30% taper.
My HB didn't give a better sound, but it is positioned at the bridge and it is a specially bright pickup. That didn't help. I believe I should test again with a different HB.
I tested replacing the JJ 6L6GT with a TAD 6L6WGC pair. It improved the sound by taming the high end slightly. I'll keep testing.
ijedouglas wrote: ↑Mon Jul 19, 2021 3:31 pm
Were you able to try Gils tweak with replacing the 150K OD2 out with a 180K?
It's on my list. I'll test that this week.
Another thing I already tested was to increase the 2.7k resistor between B2 and B3 to get closer to the preamp plate voltages specified in Tony Albany's layout, but that didn't make much difference.
ijedouglas wrote: ↑Mon Jul 19, 2021 3:31 pm
What speaker/s are you using?
I'm currently using a Weber Signature 12" alnico. Next week I'll try with a borrowed Celestion Vintage 30.
Last edited by xpc1000 on Mon Jul 19, 2021 6:31 pm, edited 1 time in total.
Vintage 30 will take off some high end which can be nice with the right amp. I use a V30 in a 1x12 Dumble cab with my Bluesmaster for that 'Rock' tone on this particular release. That was a '78 Les paul deluxe on bridge pickup.
norburybrook wrote: ↑Mon Jul 19, 2021 5:53 pm
Vintage 30 will take off some high end which can be nice with the right amp. I use a V30 in a 1x12 Dumble cab with my Bluesmaster for that 'Rock' tone on this particular release. That was a '78 Les paul deluxe on bridge pickup.
I finally replaced 150k at OD2 by 180k as recommended by Gil. After this change and together with the previous change on the power tubes I did (JJ 6L6GT replaced by TAD 6L6WGC) things have improved. I can say that the OD channel is not anymore bright! Thanks, Gil!
I also have ordered a CTS 1M Audio J taper so I'll have my pre-amp vol with the correct taper.
What I couldn't solve yet is the problem with lows sounding fuzzy on OD channel when pre-amp vol is >=5 and drive >=6 on the dial. I'll make some verifications today with the scope and report back.
Pre-amp vol: 7 (equivalent to 5 on a 30% audio taper)
Mid switch on
Drive: 6
Ratio: 4
Master: 1
I input a 25 mV (rms) sine wave of 82 Hz to trace the point where I was having the problem. I found that the signal was normal until the V2b grid. At the V2b plate, the signal was distorted the way it would be expected, but right after the coupling cap (0,005 uF) the wafeform totally changed.
In the attached image, probe 1 (below) is connected to V2b plate and probe 2 (on top) right after the 5nF coupling cap. I'll try to replace this cap just in case it is leaking.
You do not have the required permissions to view the files attached to this post.
Your scope results look pretty normal to me. I think what you're looking at is the effect of the cap and following resistor/pot on the low end. In square waves this is a way to see if you've got a bass boost or cut. When a square wave slopes like your yellow trace, you've got a bass cut. This is in line with what you'd expect from a 4n7 cap followed by a 250k load. You've got a high pass with a 135Hz -3dB point.
I replaced the coupling cap by a new one and the result was exactly the same as before. I also unsoldered one leg of the 0.02 uF cap at the input of the PI and same result. Only when I disconnected the 100k ratio pot things changed. When I tested without the pot, the impedance to ground was 1M (the input impedance of my PC scope) and the waveforms at both sides of the coupling cap were practically identical. Next thing I did was to try the same test, but with a 250k pot. Things improved, as can be seen in the attached image.
I then tryied with the strato and the fuzzy sound has almost disappeared. My first impression was positive, although I remember Gil mentioned he was not in favour of using 250k pots in the overdrive section. I'm not sure what would be the drawbacks.
You do not have the required permissions to view the files attached to this post.
rootz wrote: ↑Wed Jul 21, 2021 8:06 pm
And I'm interested to hear where you bought that 1meg J-taper pot! I can find them, but for unreasonable prices, or at Jelle with high shipping costs.
rootz wrote: ↑Wed Jul 21, 2021 8:04 pm
Your scope results look pretty normal to me. I think what you're looking at is the effect of the cap and following resistor/pot on the low end. In square waves this is a way to see if you've got a bass boost or cut. When a square wave slopes like your yellow trace, you've got a bass cut. This is in line with what you'd expect from a 4n7 cap followed by a 250k load. You've got a high pass with a 135Hz -3dB point.
Thanks for the clarification. After the change, I increased that load by replacing the original 100k pot by a 250k and the result was not only more bass response, but I also noticed that the lows were sounding less fuzzy and the overdrive tone was different in general. Not sure the reason.
xpc1000 wrote: ↑Wed Jul 21, 2021 8:39 pm
My first impression was positive, although I remember Gil mentioned he was not in favour of using 250k pots in the overdrive section. I'm not sure what would be the drawbacks.
One of the drawbacks being a 250k will add too much bass giving you the very problem you have? A fuzzy saw-toothed sounding low end Sounds like you want to decrease the low end content.
BTW.Are those metal film's you have on the plates on V1 V2?
Tony
" The psychics on my bench is the same as Dumble'"
Sounds like you want to decrease the low end content.