Questions about my next tube amp project, 18 watt design.

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Re: Questions about my next tube amp project, 18 watt design.

Post by Bieworm »

I think you should adjust your opinion on 18 watts and reverb...
https://www.dropbox.com/s/0n81wlamgt5mr ... e.m4a?dl=0
And tremolo for that matter ...

Also... that's a pretty expensive kit for what you get. I paid 150€ less for my first kit and that one included the chassis and tubes. I only had to build a cab and buy a speaker.. ok , it were hammond transformers and jj tubes but still.

That layout is pretty full of flaws ...certainly on grounding area

This site has far better documents for a build, built over and over without all the hassle of unwanted noise and such.

Check the tremolo TMB reverb ... that is an epic amp of which I have built 3 units in the past year. I can't stop building it..

Seriously, you'd better start reading the threads here and then decide...
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Re: Questions about my next tube amp project, 18 watt design.

Post by Bieworm »

Watch it.. the reverb takes 2 triodes. I don't know of any reverb with only 1 triode... then you'll need mosfets too.
The 36W you heard is nearly identical to my 18W.
Here it is:
https://www.dropbox.com/s/mmgt5y0wo4efb ... 6.m4a?dl=0
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Re: Questions about my next tube amp project, 18 watt design.

Post by JMPGuitars »

Raezzordaze wrote:
Wed 04/21/21 3:04 pm
Oh, I'm not getting the kit. I'll be sourcing all the parts myself and making the chassis from sheet stainless. I'm sorry if I didn't make that clear. I just wanted to make sure I had the schematic correct and that the changes I made were feasible. I won't be using the layout either. The only thing I cared about was the component values, gain/tone stack/master volume layout, stuff like that.

Also, that clip you linked was a 36 watt design. Most of the 18 watters I've heard with reverb didn't sound nearly that good. And tremolo just isn't an effect that interests me. I understand it's great for certain types of music and atmospheres, it's just on the rare times I might want it it'd be better off using a pedal. If I could get the reverb to sound that good, however, that'd definitely be a great use for that 4th triode!
Take a look in the downloads section: viewforum.php?f=25

All kinds of project versions there, 18W and 36W. Choose what you like.

Thanks,
Josh
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Re: Questions about my next tube amp project, 18 watt design.

Post by zaphod_phil »

I advise against the negative feedback. It will make your amp sound dull by comparison. The lack of NFB is one of the key magic ingredients of the Marshall 18W sound,as with the Vox AC30 and AC15.
You can use the extra triode to add in another gain stage (perhaps with a JCM800-style 10k cathode resistor), which should be cool. :mrgreen:
Raezzordaze wrote:
Wed 04/21/21 12:47 pm
So I decided my next project is going to be an 18 watt marshall clone. After looking over all the various designs out there I decided to use the Triode Electronics TMB design here. There was no schematic, so I used the layout here to transcribe one on my own. Here is that schematic. I got rid of the normal/clean channel, added a 4/8/16 ohm selector 3 way switch, and a negative feedback loop with a 4 way selectable feedback switch (off, 50k ohm, 100k ohm and 200k ohm.)

What I want to ask is:

1) Is my transcription accurate in the bits I didn't remove/add?

2) Does that feedback loop look ok? I know I might have to fiddle with the resistance values to make it worthwhile I just want to make sure the general connections are proper where I take the feedback signal from and where I'm adding it back in are ok.

3) What about the bass/treble pot connections in the tone stack? I am seeing all kinds of different ones and I'm not sure what is what there? I know the schematic isn't the same as the layout and I have seen a schematic that looks similar to the layout (the Trinity 18 watt TMB here has that style tone stack) but it just didn't look right to me, especially considering the 2204/2203 is connected the way my transcribed schematic is. Am I missing something? Is there a reason not to connect the bottom of the treble pot to the top AND wiper of the bass pot and just connect it to the wiper of the bass pot and that .022 mf cap?

4) I have a whole unused triode. That makes me sad. :( I was thinking of adding reverb but after hearing some samples of reverb on other 18 watt clones I was like, naaaaa. Could I use it for maybe another gain stage or would that be too much? I guess I could always add the clean channel back in and drop the signal back into the regular signal flow right before the tone stack (the junction of R7, C3 and cathode of V2A? (Sorry about the valve labelling on the schematic, I couldn't change the included valve symbol labels.) Also thought about maybe adding tremolo but I'm even less excited about that idea than the reverb tbh.

Anyway, thanks for any help!
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Re: Questions about my next tube amp project, 18 watt design.

Post by TriodeLuvr »

If you want it to sound like a Marshall, forget the NFB. No switch, no pot, nada. It's a total waste of time and effort. The problem with NFB in a guitar amp is A) it attempts to correct for the same distortion that you want to introduce, and B) it causes more abrupt breakup in the driver and output stages. That's the opposite of what Marshall was trying to accomplish with the gain structure and tonal contouring in these amps. The Marshall concept is to have breakup begin early and progress gradually. I don't claim to be a guitar amp expert, but I have run most of the Marshall 2104 circuitry through a SPICE simulator, and there are many subtleties to the design that are easily undone with hasty modifications.

If you haven't read "How the Marshall Plexi, 2204 and JCM800 Amplifiers Work" at Rob Robinette's site, now is the time! :)

Jack
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Re: Questions about my next tube amp project, 18 watt design.

Post by Bieworm »

My philosophy on the 18 watt is: less is more.. so a NFB loop is obsolete and only a possible source of noise and such. Admitted I need reverb and tremolo + TMB tone stack ... so less is more is kinda bypassed in a sence ;)
I have built 3 tremolo TMB amps. One 18W without reverb, one 18W with reverb and recently a 36W with reverb (which will be my main amp from now on, no doubt).. if I'm honest, the one without reverb sounds a little better than the ones with reverb. It's much more 3D sounding with a glassy plexi like bell kind of whiff.. the ones with reverb don't sound that good, even with the reverb knob on zero..
listen to this.. this is a sound clip without any knob adjustments.. only lighter and heavier string attack:
https://www.dropbox.com/s/k4rlwdg0c64a9 ... 2.m4a?dl=0
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Re: Questions about my next tube amp project, 18 watt design.

Post by TriodeLuvr »

Bieworm wrote:
Thu 04/22/21 1:13 am
the ones with reverb don't sound that good, even with the reverb knob on zero..
Why is that? Are there other differences beside the presence of reverb circuitry? Was something significant changed in the signal path to accommodate reverb? Just curious.

Jack
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Re: Questions about my next tube amp project, 18 watt design.

Post by Bieworm »

TriodeLuvr wrote:
Thu 04/22/21 10:58 am
Bieworm wrote:
Thu 04/22/21 1:13 am
the ones with reverb don't sound that good, even with the reverb knob on zero..
Why is that? Are there other differences beside the presence of reverb circuitry? Was something significant changed in the signal path to accommodate reverb? Just curious.

Jack
You know Jack... I would be an awful librarian. I'm not consistent in documentation of tweaks and changes. I recall fiddling with the bias of V2.. vaguely 😄.. I'm pretty sure the dropping resistor at the filter caps is slightly higher in value too..
And I might have used different brands of components..so the BS I wrote is probably not supported by anything. And the combo cab is the type with top panel control whilst the others are the frontpanel type.
Truth is they all sound pretty awesome. And the one without any noise is the last one, the 36W with Josh’s PCB.
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Re: Questions about my next tube amp project, 18 watt design.

Post by TriodeLuvr »

I understand. Results aren't always as "scientific" as we might like. At least your amps all sound good! :D
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Re: Questions about my next tube amp project, 18 watt design.

Post by Bieworm »

They do indeed.. thanks to Josh though
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Re: Questions about my next tube amp project, 18 watt design.

Post by zaphod_phil »

TriodeLuvr wrote:
Thu 04/22/21 10:58 am
Bieworm wrote:
Thu 04/22/21 1:13 am
the ones with reverb don't sound that good, even with the reverb knob on zero..
Why is that? Are there other differences beside the presence of reverb circuitry? Was something significant changed in the signal path to accommodate reverb? Just curious.

Jack
Yes, the signal path becomes different when you insert a reverb stage :evil:
I've always said that with the Marshall 18W's natural chime, you don't really need reverb.
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Re: Questions about my next tube amp project, 18 watt design.

Post by JMPGuitars »

zaphod_phil wrote:
Thu 04/22/21 2:35 pm
Yes, the signal path becomes different when you insert a reverb stage :evil:
I've always said that with the Marshall 18W's natural chime, you don't really need reverb.
The signal path with my circuit is the same either way on the first half of the PI. The reverb comes back in the second half of the PI. Bieworm's differences in his circuits are based on his component and speaker and cab choices...and as he said, they all sound good.

But to the point, you're right; reverb isn't needed. But it sure is fun to have! 😉😉
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Re: Questions about my next tube amp project, 18 watt design.

Post by Bieworm »

JMPGuitars wrote:
Thu 04/22/21 2:48 pm
zaphod_phil wrote:
Thu 04/22/21 2:35 pm
Yes, the signal path becomes different when you insert a reverb stage :evil:
I've always said that with the Marshall 18W's natural chime, you don't really need reverb.
The signal path with my circuit is the same either way on the first half of the PI. The reverb comes back in the second half of the PI. Bieworm's differences in his circuits are based on his component and speaker and cab choices...and as he said, they all sound good.

But to the point, you're right; reverb isn't needed. But it sure is fun to have! 😉😉
Unfortunately.. I need it. But I can surely enjoy a dry tremolo TMB tone. I love the woody sound with those "real bells" that f#nders are supposed to have 😄😄😄.. Phil is absolutely right!
That said... I installed an emi reignmaker today, not really expecting anything special. But frankly...dang!!! this is a nice speaker. When my son's exams are finished I will post a clip. And that attenuator is really worthwile.. very pleasantly surprised.
image-22-04-2021_19-23-53-58.jpg
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Re: Questions about my next tube amp project, 18 watt design.

Post by JMPGuitars »

Raezzordaze wrote:
Thu 04/22/21 6:22 pm
Oh, and JMP, I did check out yalls designs, as well as the the TRex on mhuss.com, and the Trinity design, the one from Mojotone, the original Marshall 18 watt, Train Wreck, etc. None of them really had everything I wanted (single channel with single input, TMB, gain and master volume) so I went with the closest thing and changed it up a bit.

Edit: BTW, that EF86 18 watter really piqued my interest. How does that sound compared to the original Marshall 18 watt?
You sound like what you want is the Superlite TMB. It's a great amp, designed by Zaphod_Phil. I put up new versions of the docs recently. It can be double or single input.

The EF86 18Watter is awesome, and it still has the Marshall sound, but also touches on the Vox sound. Check out the Superlite TMB instead, and don't worry so much about arbitrary things like the tube count.

Thanks,
Josh
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Re: Questions about my next tube amp project, 18 watt design.

Post by TriodeLuvr »

zaphod_phil wrote:
Thu 04/22/21 2:35 pm

Yes, the signal path becomes different when you insert a reverb stage
The reverb stage in mine isn't inserted, it's in parallel with signal path resistance already present. When the pots are at minimum, it's electrically non-existent.

Jack
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Re: Questions about my next tube amp project, 18 watt design.

Post by TriodeLuvr »

JMPGuitars wrote:
Thu 04/22/21 7:34 pm
The EF86 18Watter is awesome, and it still has the Marshall sound, but also touches on the Vox sound.
I'm a BIG fan of the EF86, but I'm surprised by its following for musical instrument amps. It's one of the lowest distortion small-signal pentodes ever made. Perhaps it's tendency toward microphonics at mV signal levels is a contributor to the unique sound.

Jack
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Re: Questions about my next tube amp project, 18 watt design.

Post by JMPGuitars »

TriodeLuvr wrote:
Thu 04/22/21 9:43 pm
zaphod_phil wrote:
Thu 04/22/21 2:35 pm

Yes, the signal path becomes different when you insert a reverb stage
The reverb stage in mine isn't inserted, it's in parallel with signal path resistance already present. When the pots are at minimum, it's electrically non-existent.

Jack
That's essentially the idea with mine as well. With the reverb pot off, the PI cap is grounded as it would be in an 18W style single-channel amp. Since that's a known, the difference in sounds for Bieworm's amps, are obviously the different components/cabs/speakers being used.

TriodeLuvr wrote:
Thu 04/22/21 9:56 pm
JMPGuitars wrote:
Thu 04/22/21 7:34 pm
The EF86 18Watter is awesome, and it still has the Marshall sound, but also touches on the Vox sound.
I'm a BIG fan of the EF86, but I'm surprised by its following for musical instrument amps. It's one of the lowest distortion small-signal pentodes ever made. Perhaps it's tendency toward microphonics at mV signal levels is a contributor to the unique sound.

Jack
The EF86 can produce very nice distortion in the preamp, but the tendency is to find the lowest microphonic samples of the tube. If you take a look at the sample of my "EF86 Xtra" circuit, it's actually fairly high gain (with a parallel 12AX7 following it). That said, I may want to try building a HiFi version with them eventually, I know they're quite popular for that.

Thanks,
Josh
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Re: Questions about my next tube amp project, 18 watt design.

Post by JMPGuitars »

Raezzordaze wrote:
Fri 04/23/21 7:05 am
JMPGuitars wrote:
Thu 04/22/21 7:34 pm
You sound like what you want is the Superlite TMB. It's a great amp, designed by Zaphod_Phil. I put up new versions of the docs recently. It can be double or single input.
That does look almost exactly like what I want! The only thing I think I might change is the diode rectifier to an EZ81. How well does that amp break up? I'm not exactly looking for heavy metal gain, but something that can do Angus AND Malcolm reasonably well. :twisted:
You can do that with the EZ81, or you can make it switchable between the two. Build it, you'll love it. It has a great range of dirt, and the break up is delicious.

Thanks,
Josh
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Re: Questions about my next tube amp project, 18 watt design.

Post by Bieworm »

IME that EZ81 adds nothing beneficial to these amps . The only time I could hear it was there was when it cr@pped out on me, crackling and popping. It took me 3 nights of troubleshooting before I traced it back to the rectifier. It was a new build with all new tubes, so of course I searched for the issue in the circuit.
I'm never using those again.

And... every single tube-o-phile needs only 1 guess on what brand it was 😉😉😉
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Re: Questions about my next tube amp project, 18 watt design.

Post by JMPGuitars »

Bieworm wrote:
Fri 04/23/21 8:51 am
IME that EZ81 adds nothing beneficial to these amps . The only time I could hear it was there was when it cr@pped out on me, crackling and popping. It took me 3 nights of troubleshooting before I traced it back to the rectifier. It was a new build with all new tubes, so of course I searched for the issue in the circuit.
I'm never using those again.

And... every single tube-o-phile needs only 1 guess on what brand it was 😉😉😉
That's why I suggest making it switchable. You can test for your own ears/fingers whether or not you prefer the tube rec...and even if you do, it's nice to have a backup if the tube fails.
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