OD pedal?
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Re: OD pedal?
Josh,
Attached is a sound file. No guitar input and turning up volume pots. First Normal channel then TMB. TMB side is noisier. Can't tell if I'm hearing a slight high pitched ringing?
Attached is a sound file. No guitar input and turning up volume pots. First Normal channel then TMB. TMB side is noisier. Can't tell if I'm hearing a slight high pitched ringing?
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Re: OD pedal?
Here a few samples with guitar into TMB channel. Low output bedroom level. And with JJ EL 84s. One without pedals, then with a tube screamer and a second one with an OCD. The OCD doesn't sound quite as bad as it did at first, but it still has a harsh bluntness to my ears. Maybe that is the way it should sound through my amp?
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Re: OD pedal?
Just watched the soldering technique video. Wow! I had not idea I was so far off. Surprised my the two amps I built work as well as they do. I'm going to re-wire them. Is it best to use stranded wire?
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Re: OD pedal?
For the most part I use 20AWG pre-tinned stranded wire. If you can find good pre-tinned & bonded wire, even better.
I use 18AWG pre-tinned stranded wire only for the mains, IEC ground, and PT power switch. I use pre-tinned 18AWG solid core for the ground buss. Some people go heavier for the buss wire.
The noise I heard in the demos sounds fairly consistent with your build photos. But the tone was a little off. It could be the JJ EL84s, the speaker, or something else causing that. I'm not a fan of JJ EL84s. I would use them as the "test tubes" for your rebuild, and then replace them with better tubes when you're past all the troubleshooting and doing your final tweaking.
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Re: OD pedal?
Thanks again. I'm encouraged that the amp sounded a little better today after making a few of the changes suggested. I'll follow up after I rebuild.
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Re: OD pedal?
Josh,
I rewired my amp and it seems much better. Voltage chart attached. Sounds good, less noise, but seems to have more bass than before. I used a 1000uf cathode bias cap with a 150ohm cathode resistor on the power tubes. I'm going to try a 2200uf and 180ohm combination to see how that does. Any thoughts on my voltages. See anything that looks off?
I rewired my amp and it seems much better. Voltage chart attached. Sounds good, less noise, but seems to have more bass than before. I used a 1000uf cathode bias cap with a 150ohm cathode resistor on the power tubes. I'm going to try a 2200uf and 180ohm combination to see how that does. Any thoughts on my voltages. See anything that looks off?
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Re: OD pedal?
You've got a few things going on there. But first...
Your voltages, including your B+ are too low. Pin 3 of the rectifier is your B+. Do you have a different rectifier you can test? It doesn't make sense for you to be only getting 334VDC at pin 3 with pins 1 and 7 VAC so high.
Also fill the bottom box on the sheet. Those numbers are important too. A and B are the two halves of the first filter can, A being the higher voltage where the standby switch connects to the cap. C is the point on the board that feeds the PI plate resistors. You can just measure that at the point where the PI plate resistors usually share a turret.
B+ ideally should be 345VDC +/- 5V. Under 340VDC usually sounds muddier, with lower headroom.
Oh yeah, definitely go up to 180R and 2200uF on the cathode. You're currently biased too hot.
Thanks,
Josh
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Re: OD pedal?
Try a SS rectifier?
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Re: OD pedal?
No I don't have another rectifier tube. What I'm using is an old stock German made ez-81. Perhaps I need to get a new one. I need to replace the JJ EL-84s anyway.
Just noticed it does sound a little dull. That nice crispy top end that it had previously is not there.
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Re: OD pedal?
There is something wrong on your chart .. A is right after the rectifier and B is after the filter cap. I think you swapped your values...sruffinc wrote: ↑Mon 06/01/20 2:00 pmTMB_Voltage_Test_Chart - 6.1.20.pdf
Added the ABC readings to the chart.
No I don't have another rectifier tube. What I'm using is an old stock German made ez-81. Perhaps I need to get a new one. I need to replace the JJ EL-84s anyway.
Just noticed it does sound a little dull. That nice crispy top end that it had previously is not there.
Trying a solid state rectifier is easy. Just a couple of 1N4007 diodes and perhaps a 100R resistor ... at least then you're sure your voltages are more in the right ballpark
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Re: OD pedal?
JJ EZ81 tubes have been fine, and not expensive. Get a couple. I think your old stock is too old.sruffinc wrote: ↑Mon 06/01/20 2:00 pmTMB_Voltage_Test_Chart - 6.1.20.pdf
Added the ABC readings to the chart.
No I don't have another rectifier tube. What I'm using is an old stock German made ez-81. Perhaps I need to get a new one. I need to replace the JJ EL-84s anyway.
Just noticed it does sound a little dull. That nice crispy top end that it had previously is not there.
Bieworm is correct, your voltages don't make sense. If you don't have a dropping resistor or zener diode between Pin 3 of the rectifier, and "A" (the first filter cap), then the voltage should be exactly the same. There's a resistor between A and B, so B should be lower than A.
In addition to getting new tubes, I would also highlighter verify your build.
Solid state rectifiers are cool, but UF4007 is superior to 1N4007. They're better/faster diodes with less noise. The SS rectifier should have 4 of the diodes either way.
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Re: OD pedal?
I'll try all of that. If I can't get it on this try I may have to admit defeat and turn it over to a pro. I'm getting tired of spinning my wheels. I do appreciate all of the help.
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Re: OD pedal?
Patience, soldier!!! Don't give up on it yet...
We'll get this fixed, don't sweat
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Re: OD pedal?
What do you mean by less noise? What kind of noise?JMPGuitars wrote: ↑Mon 06/01/20 3:53 pmJJ EZ81 tubes have been fine, and not expensive. Get a couple. I think your old stock is too old.sruffinc wrote: ↑Mon 06/01/20 2:00 pmTMB_Voltage_Test_Chart - 6.1.20.pdf
Added the ABC readings to the chart.
No I don't have another rectifier tube. What I'm using is an old stock German made ez-81. Perhaps I need to get a new one. I need to replace the JJ EL-84s anyway.
Just noticed it does sound a little dull. That nice crispy top end that it had previously is not there.
Bieworm is correct, your voltages don't make sense. If you don't have a dropping resistor or zener diode between Pin 3 of the rectifier, and "A" (the first filter cap), then the voltage should be exactly the same. There's a resistor between A and B, so B should be lower than A.
In addition to getting new tubes, I would also highlighter verify your build.
Solid state rectifiers are cool, but UF4007 is superior to 1N4007. They're better/faster diodes with less noise. The SS rectifier should have 4 of the diodes either way.
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"THIS should be played at high volume..preferably in a residential area"
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Re: OD pedal?
Diodes can be noisy (usually buzz when it happens), 1N4007 is noisier than UF4007. I don't think it matters enough to swap out old ones for another (assuming no problems), but when building anything new, I'd go with the UF4007.
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Re: OD pedal?
Any reason to avoid 1N5408s? Cost about the same and heftier...
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Re: OD pedal?
Ok, rewired the amp and put in a new JJ EZ-81 and new Tung-Sol EL-84s. Preamp tubes are the same JJs. Voltage chart attached.
Numbers look better. B+ is up to 340. V4 and V5 bias looks good at 12. Some of the voltages on V1 and V2 look a little off. Cause for concern?
Attaching sound file also.
No hum, so all grounds seem good. Some hiss, but not enough to bother me. I started with no signal then went through normal channel lo and hi, then tmb channel, lo and hi. It seems I have a bad MV pot. I had trouble with it going in, so I think that is why it is cutting out as I rotate it around the dial. I'll replace that as soon as I can get a new one ordered.
Sounds decent. Have 50uf caps in the inputs, so maybe too much bass. Treble/highs sound kinda thin, but I'm only running volume at 2. Maybe this is just EL84s?
If I keep MV low and crank volume up to 6-8 it gets some distortion, but not a lot. I would need to run some pedals to get a sound I like at this volume. Not sure if this is normal? I don't know what to expect I guess. I've listened to some youtube videos of similar builds/amps and I don't know if mine sounds the same or not. Variances in volume and recording techniques have some factor. I'm not sure I like the amp as much as my tweed princeton for cleans. With a tube screamer I like it better for Marshall rock tones.
Thoughts, suggestions?
Numbers look better. B+ is up to 340. V4 and V5 bias looks good at 12. Some of the voltages on V1 and V2 look a little off. Cause for concern?
Attaching sound file also.
No hum, so all grounds seem good. Some hiss, but not enough to bother me. I started with no signal then went through normal channel lo and hi, then tmb channel, lo and hi. It seems I have a bad MV pot. I had trouble with it going in, so I think that is why it is cutting out as I rotate it around the dial. I'll replace that as soon as I can get a new one ordered.
Sounds decent. Have 50uf caps in the inputs, so maybe too much bass. Treble/highs sound kinda thin, but I'm only running volume at 2. Maybe this is just EL84s?
If I keep MV low and crank volume up to 6-8 it gets some distortion, but not a lot. I would need to run some pedals to get a sound I like at this volume. Not sure if this is normal? I don't know what to expect I guess. I've listened to some youtube videos of similar builds/amps and I don't know if mine sounds the same or not. Variances in volume and recording techniques have some factor. I'm not sure I like the amp as much as my tweed princeton for cleans. With a tube screamer I like it better for Marshall rock tones.
Thoughts, suggestions?
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Re: OD pedal?
The plate voltages on your PI are too low. You should get them to spec. That would make a huge difference.
I think the resistor between B and C (rated 8.2K normally) is off. Maybe wrong resistor? Did you put something else there? If not, I would try lowering it to 4.7k and measure the voltages again
I think the resistor between B and C (rated 8.2K normally) is off. Maybe wrong resistor? Did you put something else there? If not, I would try lowering it to 4.7k and measure the voltages again
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