First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by JMPGuitars »

Daviedawg wrote:
Wed 04/08/20 2:23 am
Looking forward to that Josh. My 18 watt is ss rectified and every once in a while this little thought worm gets going suggesting a valve rectifier. So it will be really of great value. All my recently built amps have valve rectifiers even my valve reverb unit. So the 18 watt is an oddity here.

Dd
Ignore the worm (or eat it if it's from a tequila bottle). You'll hear the video when I post it. There's plenty of sag from the power transformers, which is maybe why the lack of a sag resistor isn't as noticeable. I dunno, you can be the judge when you see the video. ;)
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by Yamariv »

Cool thanks! So why is it called a Lite? Is it missing something or is it just a name for an 18 Watt TMB? This version would have more gain than the stock 18 Watt right? :D
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by JMPGuitars »

Yamariv wrote:
Wed 04/08/20 11:21 am
Cool thanks! So why is it called a Lite? Is it missing something or is it just a name for an 18 Watt TMB? This version would have more gain than the stock 18 Watt right? :D
I believe he called it the superlite because it has only 4 tubes with a lot going on. I dunno, I could be wrong, ask ZP. ;) The Lite series was named lite because they are single channel versions of the classic 18W. They usually have 5 tubes with the rectifier.

With a cascaded preamp tube, the preamp has more gain, and can have overall more gain. It's very tweakable though depending on how you use the gain and volume knobs. You benefit from both preamp and power amp gain.

BTW- I'm going to post a small change to the layout, to move the preamp decoupling cap closer to the preamp cathode resistor/cap. I'll probably have that up later today.

EDIT: The new layout is up.

Thanks,
Josh
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by zaphod_phil »

Yamariv wrote:
Wed 04/08/20 11:21 am
Cool thanks! So why is it called a Lite? Is it missing something or is it just a name for an 18 Watt TMB? This version would have more gain than the stock 18 Watt right? :D
It’s called Lite or SuperLite because it’s a single-channel version, which is simpler and uses less tubes than a Classic 18W or TMB amp. Based on that philosophy, it’s not supposed to have a tube rectifier. UF4007 rectifiers with a sag resistor will do exactly the same job. So it only needs a total of 4 valves. And yes, it has plenty of gain available! :mrgreen:
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by Yamariv »

Just thought I'd update you guys, the amp is finally fixed and working as it should. I ended up totally rewiring the amp and converted it to a TMB circuit that was recommended here :D

The more I played the original amp I found it had an odd sounding wooshy distortion to it, hard to explain unless you heard it, add in the hum and I figured the TMB design would cure that.

When I played the new TMB it sounded horrible, the clean channel was super distorted in the same wooshy sound as before, something was definitely not right and I still had the low hum. Since I had already changed literally everything in the amp, I started to wonder if the output transformer could be failing..Some forum posts I found online seem to describe similar sounds to a failing output transformer. I was using an old Hammond Organ OT so I figured why not order one and try it, had nothing to loose.

Well, that was the problem all along!! Hum is gone, all channels sound great, wooshy distortion is long gone!! :D The amp is one of the quietest I have at idle, forgot it was on the other day! I've also finally heard the sound the 18 Watt is supposed to make..finally it's done!

Just thought I'd pass the fix along in case it can help someone else with a faulty OT. Thanks for all your help guys!
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by JMPGuitars »

Bieworm wrote:
Mon 04/06/20 2:46 am
NOTE: the gridvoltage on V2 were probably aroudn 50V..I didn't know any better back then, so I measured on DC instead of AC ;)
All tube voltages are measured in DC, except the AC voltage going to the rectifier tube. In the case of the EZ81, that's Pins 1 and 7. Everything else on the tubes is DCV.

Daviedawg wrote:
Wed 04/08/20 2:23 am
Looking forward to that Josh. My 18 watt is ss rectified and every once in a while this little thought worm gets going suggesting a valve rectifier. So it will be really of great value. All my recently built amps have valve rectifiers even my valve reverb unit. So the 18 watt is an oddity here.
I don't know if you saw the thread, but I posted my demo: viewtopic.php?f=4&t=25615

Yamariv wrote:
Fri 05/22/20 9:25 am
Well, that was the problem all along!! Hum is gone, all channels sound great, wooshy distortion is long gone!! :D The amp is one of the quietest I have at idle, forgot it was on the other day! I've also finally heard the sound the 18 Watt is supposed to make..finally it's done!

Just thought I'd pass the fix along in case it can help someone else with a faulty OT. Thanks for all your help guys!
Glad you sorted it out! Would you say the "wooshy" distortion had an almost phaser-like effect to it?

Thanks,
Josh
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by Yamariv »

Yes, that's a great way to describe it actually!! The clean channel after the TMB mod sounded horrible, not clean at all and very bad sounding distortion, never heard anything like that before

Was actually just playing my TMB with my Junior which has the hottest pickup I own. Sounds friggen glorious!! Nice crisp and clear tones, very saggy vintagey distortion that you'd expect from a 60's design. Love it!
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by Yamariv »

Just saw your video link and checked it out, sounds awesome! Very smart to put the switch on the front! I never use my standby so I should have done that! lol

I did do a solid state witch at the back but going to solid state brings me to 400vdc which makes me a bit nervous to run the amp that high. At least the option is there. Also did a Mojotone effects loop and a tone cut knob to load her up with all the options incase I ever want to gig it :D
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by JMPGuitars »

Yamariv wrote:
Fri 05/22/20 12:25 pm
Yes, that's a great way to describe it actually!! The clean channel after the TMB mod sounded horrible, not clean at all and very bad sounding distortion, never heard anything like that before
Yuck. I think I'm in the same boat. I've done a million things to chase the problem with a build (all the while thinking it's the OT), but I chased other things down because it isn't usually the OT that's the answer.

I think I'm gonna swap out the OT and see if it's cured.
Yamariv wrote:
Fri 05/22/20 12:35 pm
Just saw your video link and checked it out, sounds awesome! Very smart to put the switch on the front! I never use my standby so I should have done that! lol

I did do a solid state witch at the back but going to solid state brings me to 400vdc which makes me a bit nervous to run the amp that high. At least the option is there. Also did a Mojotone effects loop and a tone cut knob to load her up with all the options incase I ever want to gig it :D
Thanks! Get yourself some 5W zeners, and run some in series to get the B+ voltages where you want them. I have both the amps in that video with two different strings of zener diodes each to adjust the B+ lines to where they are. Keep in mind that doing this puts the zeners before the first filter cap (actually before the standby switch), so they won't drop their rated value.

Thanks,
Josh
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by Yamariv »

I'm a bit confused, you have an amp that is doing the Phazer sound? You're thinking it's the OT or something else?

Ahh Zeneers, I may have to do that next time I have it open then, thanks! My rectified B+ is a tad high at 355 but I'm fine with that. Just flipping over to the 1N1007 diodes I put in bumps that to 400v! Eeek! Is there a way to just drop the Diode part of the B+? I'm guessing put them inline after the switch I put in to toggle back and forth? If I ran it at 400v and had some robust EL84's in there, could I actually run it like that safely?

I'm not too worried about using the solid state diodes though as I have other amps to do the tighter sound. I love the way the TMB sounds vintagey with the tube rectification!
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by JMPGuitars »

Yamariv wrote:
Fri 05/22/20 1:05 pm
I'm a bit confused, you have an amp that is doing the Phazer sound? You're thinking it's the OT or something else?
Yes, I do. I first thought it was the OT, but tried cures for every other possible cause first. Now that they've basically been eliminated, I'm going to swap the OT.
Yamariv wrote: Ahh Zeneers, I may have to do that next time I have it open then, thanks! My rectified B+ is a tad high at 355 but I'm fine with that. Just flipping over to the 1N1007 diodes I put in bumps that to 400v! Eeek! Is there a way to just drop the Diode part of the B+? I'm guessing put them inline after the switch I put in to toggle back and forth? If I ran it at 400v and had some robust EL84's in there, could I actually run it like that safely?

I'm not too worried about using the solid state diodes though as I have other amps to do the tighter sound. I love the way the TMB sounds vintagey with the tube rectification!
First, switch the diodes for the rectifier to UF4007 when you have it opened up. 1N4007 are not as good, and prone to be noisier.

The way I have it is that each rectifier has their own zener diode strings between each rectifier and the standby/rectifier switch. How you describe it is probably fine, I'm assuming because it's slightly vague. ;)

If you want to know what your tubes can handle, look at the datasheets. They'll tell you everything you need to know about what the tubes can handle. That said, the 345VDC goal is based on the sound and feel of the amp, not the limits of the tubes.

Even with diodes there's still sag from the PT. I don't think my demo sounds stiff at all, and there's no sag resistors in either of those amp models in my demo.

Thanks,
Josh
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by Yamariv »

Very cool, good to know about the different diodes, thanks! Wouldn't take much to swap them at all so might as well give it a whirl down the road.

Your demo didn't sound tight at all actually, I was quite impressed! :)

As for tubes, I have some Russian 6N14n in all the different configurations. The EV version seems to be able to handle 500v so that may be a good option!
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by JMPGuitars »

Yamariv wrote:
Fri 05/22/20 1:25 pm
Your demo didn't sound tight at all actually, I was quite impressed! :)

As for tubes, I have some Russian 6N14n in all the different configurations. The EV version seems to be able to handle 500v so that may be a good option!
Thanks. ;)

I've been wanting to try out some 7189A tubes myself.
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by Bieworm »

Yuck. I think I'm in the same boat. I've done a million things to chase the problem with a build (all the while thinking it's the OT), but I chased other things down because it isn't usually the OT that's the answer. 

I think I'm gonna swap out the OT and see if it's cured.

--> not the tmb tremolo I hope?
My tmb tremolo has basically no clean, but the OD is far from ugly.. it gives a strange energy to my playing. I really enjoy it.. especially on my jazzmaster which has a 65 neck pickup and a p90 bridge. The neck pickup oozes very dirty crunch and the p90 screams ..but smooth and creamy screams
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by JMPGuitars »

Bieworm wrote:
Sat 05/23/20 4:55 am
--> not the tmb tremolo I hope?
My tmb tremolo has basically no clean, but the OD is far from ugly.. it gives a strange energy to my playing. I really enjoy it.. especially on my jazzmaster which has a 65 neck pickup and a p90 bridge. The neck pickup oozes very dirty crunch and the p90 screams ..but smooth and creamy screams
Not at all. I haven't started that build yet. I was going to be impatient and build it into a classic 18 watt chassis, but I changed my mind. I'm going to wait for Carey to make my new chassis for it. They're far superior.

Your Tremolo TMB sounds fantastic. I wouldn't worry about it. Do your treble bleed mods while you're waiting for my build. ;)
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by Bieworm »

JMPGuitars wrote:
Sat 05/23/20 7:12 am
Bieworm wrote:
Sat 05/23/20 4:55 am
--> not the tmb tremolo I hope?
My tmb tremolo has basically no clean, but the OD is far from ugly.. it gives a strange energy to my playing. I really enjoy it.. especially on my jazzmaster which has a 65 neck pickup and a p90 bridge. The neck pickup oozes very dirty crunch and the p90 screams ..but smooth and creamy screams
Not at all. I haven't started that build yet. I was going to be impatient and build it into a classic 18 watt chassis, but I changed my mind. I'm going to wait for Carey to make my new chassis for it. They're far superior.

Your Tremolo TMB sounds fantastic. I wouldn't worry about it. Do your treble bleed mods while you're waiting for my build. ;)
I have a strat with premium 250k cts pots. On that one the volume knob actually works without significant treble loss. It's pretty manageable OD-wise with that one. But it will stay an OD amp no matter what... I won't change the amp , no way! I like having that amount of it on the dial. It will loose its character when cleaned up I think. Now it's always some kind of nice nastiness lurking in a dark corner ;)
I bought another G12H30 real cheap (50$) .. the 70th anniversary UK made. The idea is to build an ext. cab to stack the amp upon. Closed back for extra oomph . And was thinking to put the speaker central bottom with 2 big holes left and right on top .. kind of detuned cab idea
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by JMPGuitars »

Bieworm wrote:
Sat 05/23/20 8:41 am
I have a strat with premium 250k cts pots. On that one the volume knob actually works without significant treble loss. It's pretty manageable OD-wise with that one. But it will stay an OD amp no matter what... I won't change the amp , no way! I like having that amount of it on the dial. It will loose its character when cleaned up I think. Now it's always some kind of nice nastiness lurking in a dark corner ;)
I bought another G12H30 real cheap (50$) .. the 70th anniversary UK made. The idea is to build an ext. cab to stack the amp upon. Closed back for extra oomph . And was thinking to put the speaker central bottom with 2 big holes left and right on top .. kind of detuned cab idea
If you're happy with it, that's all that matters.

With your cab, I strongly suggest making the back in 3 or 4 sections. That way you can leave it open back or closed back, without losing the support or protection.

Check out this post: http://www.roland.co.uk/blog/open-back- ... -back-amp/

The image there is the right idea, but I would make the middle section larger than the other two.

Thanks,
Josh
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by Bieworm »

JMPGuitars wrote:
Sat 05/23/20 9:06 am
Bieworm wrote:
Sat 05/23/20 8:41 am
I have a strat with premium 250k cts pots. On that one the volume knob actually works without significant treble loss. It's pretty manageable OD-wise with that one. But it will stay an OD amp no matter what... I won't change the amp , no way! I like having that amount of it on the dial. It will loose its character when cleaned up I think. Now it's always some kind of nice nastiness lurking in a dark corner ;)
I bought another G12H30 real cheap (50$) .. the 70th anniversary UK made. The idea is to build an ext. cab to stack the amp upon. Closed back for extra oomph . And was thinking to put the speaker central bottom with 2 big holes left and right on top .. kind of detuned cab idea
If you're happy with it, that's all that matters.

With your cab, I strongly suggest making the back in 3 or 4 sections. That way you can leave it open back or closed back, without losing the support or protection.

Check out this post: http://www.roland.co.uk/blog/open-back- ... -back-amp/

The image there is the right idea, but I would make the middle section larger than the other two.

Thanks,
Josh
Just wondering...in my combo there is a 16ohm g12h30, in the future cab too. When 2 speakers are connected ..1 in the first input and the 2nd in the 2nd input.. should I switch the impedance selector to 8 ohms?
It's parallel connection after all...
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by Yamariv »

Keep me posted on your results when you swap the OT on the one amp in question..Curious to see your results! 8)
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Re: First Test of 18 Watt build - Sounds great but has a steady loud hum - Help

Post by Bieworm »

I don't like replacing OT's as a solution...rather spend that money for an new OT in a new amp 😁
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