OD pedal?

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sruffinc
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OD pedal?

Post by sruffinc »

Some OD pedals do not play nice with my 18 watt tmb. Any boost, Mad Professor Sweet Honey Overdrive and Keeley Red Dirt Germanium all sound good and I love the amp. However, I've tried Fulltone OCD, Keeley 1962 and Catalinbread Dirty Little Secret and they all sound bad. It's like they hit the amp too hard and produce a hard clipped sound. Not what I expected.

Is that just something I have to accept? Some pedals work with certain rigs and some don't? And is there an easy explanation why some pedals work with my amp this way?

I've tried upping the 500uf cap to a 1000uf cap but don't hear any difference. Just makes everything slightly harder sounding.
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Re: OD pedal?

Post by JMPGuitars »

Between this post and your other one, it seems to me that maybe something is out of spec in your build. Post your voltages using the appropriate chart from the download section.

You may also need to consider the Paul Ruby Mod if you're getting the wrong kind of distortion. The new Superlite TMB docs include the mod so you can see how it's done.

Thanks,
Josh
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Re: OD pedal?

Post by sruffinc »

Voltage chart attached. It does look different that it did before I started messing around with the wiring.
TMB_Voltage_Test_Chart - 4.21.20.pdf
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Re: OD pedal?

Post by Bieworm »

Looks like there is some work on those voltages...
The PI values should be closer to spec than that. Pin 2 and 7 should be AC measurements. Looks like you dus them on DC.
What are the heater voltage values?
One very important thing I learned is that hou have to build very clean and precise wire layout. Heater wires twisted...
My tmb tremolo has a huge difference in sound and noise between the first sloopt build and the new clean build...with the exact component values.
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Re: OD pedal?

Post by sruffinc »

Your right, I did DC. Attaching revised chart and photos of my chassis.
TMB_Voltage_Test_Chart - 4.21.20 - rev 1.pdf
IMG_2331.JPG
IMG_2330.JPG
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Re: OD pedal?

Post by crgfrench »

That Mallory 0.01uF coupling cap (second Mallory from the left) looks like it got cooked when you were soldering the grid leak resistors or ground wire right next to it. Also the high side turret of that cap looks like it's not soldered properly (the one going to pin 1 plate of V2). Finally, the PI coupling cap at the grid leak on the far right (the last yellow Mallory on the right side) appears as though its valve-side lead could come in contact with the board mounting screw underneath it. Oh, also it looks like there's a dangling white ground wire off the bus by the single input jack?
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Re: OD pedal?

Post by crgfrench »

Bieworm wrote:
Tue 04/21/20 3:31 pm
My tmb tremolo has a huge difference in sound and noise between the first sloopt build and the new clean build.
That looks very nice. Just curious why you use JB caps -- on paper (datasheet), the Mallory 150 series seems to have superior specs, have you found these sound better?
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Re: OD pedal?

Post by Bieworm »

crgfrench wrote:
Tue 04/21/20 7:20 pm
Bieworm wrote:
Tue 04/21/20 3:31 pm
My tmb tremolo has a huge difference in sound and noise between the first sloopt build and the new clean build.
That looks very nice. Just curious why you use JB caps -- on paper (datasheet), the Mallory 150 series seems to have superior specs, have you found these sound better?
For the money the JB caps are fine . The difference in sound is neglectable IMHO..
+ there are lot of stories about some expensive stuff being relabled cheap stuff.. (thank you, forgers from the far east) ;)
I think the JB are just fine. I've had other stuff that was clearly crap. The wires not running in the center...immediatly breaking off. I am very pleasantly surprised by the JB's..good stuff
I learned not to buy any more stuff from shops that also sell really cheap things. My last buy was from jukebox-revival.nl ... they only sell quality. The times before I bought from tubetown.de .. good prices, but they sell a lot of generic things. I really regretted the turrets I bought there. They were practically unsolderable. Think I overheated a lot of components while doing that..so I had some crazy persistant noises I couldn't get rid of.
Last edited by Bieworm on Wed 04/22/20 12:41 am, edited 5 times in total.
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Re: OD pedal?

Post by Bieworm »

sruffinc wrote:
Tue 04/21/20 4:01 pm
Your right, I did DC. Attaching revised chart and photos of my chassis.

TMB_Voltage_Test_Chart - 4.21.20 - rev 1.pdf
IMG_2331.JPG
IMG_2330.JPG
On offense man.. but that amp must be very noisy. You should try to get all connections as tight as possible. That ground bus floating in the air worries me. It is a very important principle to get your grounds fixed as firmly as possible.
I advise you to rewire the heaters to a very firm twisted coherent strain. I learned from Josh it's better to put the resistors and caps from the pots on the board. Floating wires and components can behave like antennas. Not to mention the possibility to break connections while transporting the amp.
Believe me..it CAN be done. I've been there too...and thanks to the tips and advice here on 18Watt I moved on to better building capabilities...I'm very proud of my last build
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Re: OD pedal?

Post by sruffinc »

Thanks for the tips. Actually my amp is really quiet, but someday when I have the time I'll try rewiring....again. I've done it too many times to count and I really wish I could just play the damn thing. :-)
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Re: OD pedal?

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sruffinc wrote:
Wed 04/22/20 8:55 am
Thanks for the tips. Actually my amp is really quiet, but someday when I have the time I'll try rewiring....again. I've done it too many times to count and I really wish I could just play the damn thing. :-)
I know the feeling.. been there. Will always be tweaking, so I built 2 ;)
The 2nd one..the TMB tremolo is beyond WOW sounding!!! Very advisable
I won't be tweaking that one. It's perfect!

On your heater wiring... you use too thick wire to get it nicely twisted. I used 22AWG silicon covered wire. Easier and just as good
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Re: OD pedal?

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Thanks!
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Re: OD pedal?

Post by JMPGuitars »

Bieworm wrote:
Tue 04/21/20 3:31 pm
Looks like there is some work on those voltages...
The PI values should be closer to spec than that. Pin 2 and 7 should be AC measurements. Looks like you dus them on DC.
What are the heater voltage values?
One very important thing I learned is that hou have to build very clean and precise wire layout.
Pin 2 and 7 of the PI are DC voltages. The only AC voltages read on the tubes are from the HV going to the rectifier tube. That's pins 1 and 7 on an EZ81.

sruffinc wrote:
Tue 04/21/20 3:05 pm
Voltage chart attached. It does look different that it did before I started messing around with the wiring.
V1 is a little low, but okay.
V2 is a little low, and maybe okay, but has some bad solder connections visible.
V3 is also close enough.
V4 and V5 are mostly okay, but you can see from V5 pin2 that the solder connections on V5 are not as good as V4.
V6 looks good.

I'm going to be blunt and point out some things. This is for your benefit, not to pick on you. ;)

Your PI plates are a little low. If you look at the anode resistor for the PI on pin 1, you can see the solder connection is terrible. Most of the solder connections don't look very good. Please review the solder technique thread and watch the linked videos multiple times: viewtopic.php?f=4&t=25396

The quality of your solder connections will literally make or break your amp. I only reviewed one of your photos, and I've added some arrows to point out only some of the issues:
IMG_2330j.JPG

In that photo, if you look closely, you can see a number of problems (I didn't mark them all). Lots of components are burnt from the iron when you were soldering nearby things. Some have solder blobs on them. I pointed an arrow at the largest solder blob. If any of those blobs get loose, they will most likely short something out.

A lot of the wires in the amp also have been melted or burned by the iron for the same reason as above.

Some leads are too close or touching that shouldn't be.

In the solder technique videos they also discuss the correct length to strip your wires. This is a big issue in your build. Too close interferes with the solder connection and melts. Too far doesn't protect the wire. The tubing I pointed out on the cap going to the pot is not long enough to actually protect the lead from shorting out on the pot.

Another thing they point out is making mechanical connections before soldering. For example, your output impedance switch has no mechanical connection at all. Just a wire through a hole.

A lot of things are melted, or damaged from the iron. Before soldering something, look at it carefully. Look at what's around it, and see what's the best angle you can solder it from. Many of these issues can be avoided by doing things in the right order, from smallest to largest.

Personally, I always wire the sockets and the board first, before putting anything on the board. Then I install the resistors, from smallest to largest (diodes too, if applicable). Then the capacitors from smallest to largest, followed by the electrolytics last. This helps avoid damaging anything. In some cases where a component is joined with another I'm not soldering yet, I'll only solder the side that's independent first. Then when the second component is connected, I solder them at the same time.

Your heater wire is too thick. Use 20AWG or 22AWG, preferably pre-tinned and bonded. Much easier to work with.

If you would rather try and troubleshoot this first, that's fine. Troubleshooting is one of the best ways to learn. I wouldn't rewire your heaters until you rebuild the whole amp. In the meantime, I would zip tie all the heater wires so they're fairly tight together.

Bieworm is right that cleanliness is extremely important. It's not always resulting noise that's the issue. Sometimes things just don't work. Sometimes they work for a while, then die. Sometimes they start a fire...or if you're lucky just blow a fuse. I know most people get excited when building an amp, especially if it's one of their first builds. Finishing it feels awesome. But, it's better to take your time and go through everything meticulously so that when you are finished, you have a much better amp. Enjoy the journey.

If after experimenting with this build you decide to rebuild it, I would replace everything besides the chassis and transformers and start fresh. Take your time. Make sure everything looks as clean, straight, and as symmetrical as you can.

I also recommend using Kester "no clean" solder. That will resolve the issue with all the excess flux all over your build. In the meantime, clean that off. You can try carefully with a stiff brush and/or an electronics cleaner or alcohol. Be careful not to get any cleaner on any of the components.

Thanks,
Josh
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sruffinc
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Re: OD pedal?

Post by sruffinc »

Josh, thanks for the constructive advice. I'll keep working on my technique. It's gotten so much better than it was a few years ago, but being self-taught it's difficult to know how I'm doing. When I get this one in good order I think I'll try a new build and improve on my neatness from the beginning.

As I originally posted, the amp sounds pretty good on its own and with a tube screamer or light gain OD. I'll try to post some sound samples and see if anyone can identify the harshness I think I'm hearing with pedals like the OCD and DLS. Maybe it's just my ears.

I'm also going to look into some of the suggested online resources and dig back into a few of my amp books to try to understand what I'm actually doing other than just following a recipe.
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Re: OD pedal?

Post by JMPGuitars »

Sound samples could certainly help.

Fix those things I mentioned, but watch those soldering videos first. I still watch the solder videos every now and again to improve whenever/whatever I can.

One thing that I find odd- you changed your voltages to AC for pin 2 and 7 of the PI for the second chart? With no signal, those pins should read 0VAC. If you're getting 44VAC, there's something seriously wrong there. If it was 44mVAC, that's not so big a deal, I would assume it would drop to 0 if you left the probe there longer. If not, then it's still a little odd.

In your sound sample, please include what the amp sounds like when idle with the gain turned up. Turn some knobs too.

Thanks,
Josh
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