Monkeymatic NDS

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xtian
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Re: Monkeymatic NDS

Post by xtian »

Thanks, guys. Bias pot closeups attached. Attached to chassis with Bondic (magic, UV-curing plastic). Yes, pot is electrically isolated from chassis.

Going balls out to finish the amp today.
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xtian
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Re: Monkeymatic NDS

Post by xtian »

Finished. No issues. Dead silent at idle.

Sounds GREAT at bedroom level. Does exactly what I want with the volume gained and the master down low--that is, nice preamp harmonic distortion and warmth.

Left out the bright cap (on the volume control) entirely. Not needed--plenty bright.

Have not had a chance to rattle windows yet. Can't wait to put it thru it's paces when the house is empty.
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cbass
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Re: Monkeymatic NDS

Post by cbass »

Vury nice
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ampmike
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Success

Post by ampmike »

Awesome,Have a blast today!!!!!Thanks for sharing the build!!!
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Leo_Gnardo
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Re: Monkeymatic NDS

Post by Leo_Gnardo »

Oh my so neat & pretty, makes my eyes hurt, I'll never be able to catch up...

"Like" the big SG resistors, I guess you don't believe they should be used as fuses. Never did much like that idea myself. Awaiting the test at full volume report, should be scrumptious!
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xtian
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Re: Monkeymatic NDS

Post by xtian »

Wow, yeah, amp sings at high volume. Was getting 440v on plates at 50 watts clean output. Too damn hot! This is meant to be my stage amp, and to get slightly hairy at low volume.

So I put in Aiken's MOSFET/Zener voltage dropper. Now I have 385v on plates, biased at 65%, putting 36 watts clean into 8 ohms. This helped increase the preamp distortion a bit at lower volume.

BUT, I'm only getting a tiny amount of distortion from V1b. With Volume dimed, I'm just getting a slightly rounded sine wave on the scope--exactly what I'm aiming for, just need more of it. This whole exercise was launched because the clean channel of the D'Lite I built is so awesome. Maybe I'll up V1a's Ck to 25uF to boost the volume--extra bass won't be a problem.

When the volume AND master are way up, I'm getting a lot of distortion from the PI. Then the amp sounds like a JTM45. Rockin!
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xtian
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Re: Monkeymatic NDS

Post by xtian »

The 22uF bypass on V1a didn't make much diff, but upping the 10K bass-to-ground resistor to 27K made a world of betterment. A bit more gain, and a lot better tone.

You know, I put a variable tone-stack lift in my 6G6B, and that's an awesome front-panel control.
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M Fowler
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Re: Monkeymatic NDS

Post by M Fowler »

That 150k slope resistor allows a lot mids I would decrease that for better tone.

Mark
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xtian
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Re: Monkeymatic NDS

Post by xtian »

M Fowler wrote:That 150k slope resistor allows a lot mids I would decrease that for better tone.

Mark
Thx, Mark. 120k? 100k?
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deeder
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Re: Monkeymatic NDS

Post by deeder »

I'm not a 'thousands posts guy', but you're doing what I'm looking after, so many thanks xtian to share your design and building :idea:
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xtian
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Re: Monkeymatic NDS

Post by xtian »

Cheers, deeder!

Here's a note about grounding schemes. I have tried very hard to have a silent amp at idle, starting with the placement of the OT and PT (I use the headphone trick to make sure I minimize hum). Then I try to incorporate best practices in grounding the high-current reservoir caps and power tube screen supply at one point on the chassis near the PT, and all other grounds routed to a point near the input jack.

I also like neat layouts, so any time I can eliminate a long wire run in favor of a more convenient grounding point, I do that. In my layout, you can see one long ground wire from one of the radial caps on the board back to the ground point near the PT. Just to check if this was necessary, I moved the ground to the copper bus on the turret board--yup, that introduced pre-amp hum. So the long wire stays.
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Leo_Gnardo
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Re: Monkeymatic NDS

Post by Leo_Gnardo »

xtian wrote:
M Fowler wrote:That 150k slope resistor allows a lot mids I would decrease that for better tone.

Mark
Thx, Mark. 120k? 100k?
Sunn put in a "contour" pot, you could do it with a pot or switch. Lower values tip the spectrum toward darker tones, higher = brighter. Some favorite Marshalls all the way down at 33K, still plenty bright for me, but lets bottom & low mids thru for a good chunky tone. With a pot or switch you can decide at gig or recording time.
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Smokebreak
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Re: Monkeymatic NDS

Post by Smokebreak »

I think you are in a good position to go ahead and try the different D style Rp and Rk arrangements, as well as the 4 or 6 tonestacks. It looks look you used high plates and a skyliner TS. For instance, for me, this arrangement can sound a bit sterile, or crystalline, but of course that's some folks' bread and butter. I prefer low plates and a "classic" stack, which is probably most like the Fender stack, but with mids. This arrangement is the most "Fendery" to me, which is my vibe.
Good description here of the various stacks here
http://ampgarage.com/forum/viewtopic.ph ... 4&start=30

If you wanna get more umph outta the preamp, seperate the bass pot from the treble pot via large resistors, and slap a 1200-2000p across the treble cap. These can be separate functions or on a dpdt for a whallup. PAB and Mid boost.
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xtian
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Re: Monkeymatic NDS

Post by xtian »

Awesome advice. Will be playing with the tone stack.

As for the high-plate values, I think they're awesome, if they have anything to do with the amount of compression I'm getting. I kept looking sharply at my pedals to make sure my compressor wasn't on! The amp makes my humbuckers sound awesome for David Gilmour style singing leads. Do you think the high plates contribute to that?
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Smokebreak
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Re: Monkeymatic NDS

Post by Smokebreak »

xtian wrote: amount of compression I'm getting. Do you think the high plates contribute to that?
I'm not exactly sure. I think with all else the same, higher Rp values will increase gain and compression, comparatively, but IIRC the plates are increased, but so are the Rk, so I think the high plate stages are roughly biased the same as a typical 100k/1K5 stage. Something like that. Hopefully someone else will chime in on that.
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