New build- Tweedle Dee-now with sound clips

[norburybrook]

Hi Marcus,

Excellent work! That looks really nice. How do you find the EV? Did you get a chance to play with the PI trimmer vs. Your Ear?

The EV just delivers what ever the amp can shove out, so good or bad it's loud and unforgiving. If you want some speaker breakup then it's better with my 2x12 alnico's and a bit softer. However I'm liking the EV, it's the last thing I'd have tried it with but I'm glad Aaron suggested it.



I'm not really getting the P.I thing yet. It's obviously subtle and when you're playing an amp loud your ears get fatigued so i'm going to have another go tomorrow.


I've got the amp with everything at 12 O'clock and ruuniing a strymon flint for verb/trem and I'm going through a pile of OD/boost pedals to see what works best. Klon, Bluesbreaker and a Red Snapper. I'm testing it with a standard telecaster at the moment.


I'm enjoying the difference from the Dumbles, it doesn't handle the bottom end as well when driven like most 'fender' amps but it's certainly got a 'sound'


When i get a cabinet made I'll post some clips asit will probabaly be burnt i by then


i think the 6V6's would make the amp more small gig friendly but it's a 1 minute swap to put them back in. I'm surprised how loud it is with the russian valves, they are a 6L6 so they would be i suppose.

M

[pompeiisneaks]

Marcus,

On mine, I just set it for perfectly balanced and left it. Your mileage may vary, but to me it seems to open up more at that point. When imbalanced you can get a bit more of the second harmonic, and that's what you try to balance out, If you have an FFT mode on your scope OR a signal analyzer, set it to FFT mode and try to find the second harmonic of the input signal and then dial it back and forth to optimize this second harmonic. That's the scientific approach anyway

~Phil

[norburybrook]

Phil, I don't have a scope [emoji3]


M

Sent from my Nexus 6 using Tapatalk

[pompeiisneaks]

then that won't be easy I do recall someone mentinoing to shoot for an imbalance of about 6VAC on the PI outputs, that may be a good way to do it, or to get it balanced, just input some sine wave at say 1kHz and measure the outputs in VAC and get them as close to identical as possible for a more balanced output.

~Phil

[martin manning]

Marcus, you can do like this: https://ampgarage.com/forum/viewtopic.p ... 78#p216778

[sluckey]

with a sine wave input, put your DMM across the PI coupling caps (on the power tube side) and adjust the trimmer to zero the measured AC voltage.

I don't think that's gonna work.

[martin manning]

Yes, reconsidered. Need to sum the signal voltages, or you can just measure and match VAC on each coupling cap output. DC volts across power tube cathodes as in the linked sticky is fine.

[pompeiisneaks]

with a sine wave input, put your DMM across the PI coupling caps (on the power tube side) and adjust the trimmer to zero the measured AC voltage.

I don't think that's gonna work.

Sorry badly worded, zero difference I meant to be nearly identical. So say one side was 23VAC the other should also be 23VAC! Doh!

~Phil

[guitarmike2107]

Adjusting the trimmer compensates for PI imbalance as well as the power tube imbalance, really needs a scope and signal generator. otherwise just use your ears. it will be very subtle.

Great info on the FFT with the scope, I never knew I could do that with my scope.. now I can! really wish I could get a day or so with someone that really knows how to use a scope.

[pompeiisneaks]

Yup pretty cool, not all of them can, and it's not super fast/real time often, but if you let it cook at a setting for a bit, it's pretty good. Interestingly I found several ways to get balance, first off both probes are on the output of each half of the PI. Set to the same scale etc.

1. set the second one inverted, and they should almost overlap, but as the PI adjustment is done you'll see them slowly merge over one another. Adjust to taste
2. keep them opposite, and then set the scope to math mode and do A+B so the 'differences' will be all that shows up, and adjust until they fully cancel out to 0
3. Set the second one inverted as before, and do math mode A-B and they should net close to 0 again, but adjusting can make it a single line.

Different ways to skin the cat. ;D

~Phil

[guitarmike2107]

Thanks Phil, will try and figure that all out when I get there

[M Fowler]

Marcus, very nice looking amp, congrats.

Mark

[67plexi]

Marcus, Looks great I gig with my 4 input D Deluxe nice and light easy carry.

Steve.

[norburybrook]

thanks guys. I'm building a head cab and speaker from left over 18mm(3/4) ply so it's suddenly not light anymore compared to a deluxe. However compared to a 100w Dumble it's still light.

I like the convenience of combo's but the flexibility of a head/cab is nice and also combo's can be bad for rattles etc in the studio so having a head you can place away from the speaker is a plus.

I'll finish the head cab later today as my tolex is arriving.

watch this space.



M

[norburybrook]

here we are then. I've been busy today

So I had some fun designing a head cab. I decided to go with a 50's retro look and did a few pencil drawings to get and idea then just went for it.

I think it's turned out pretty good. It's actually very light. I think I need to build a matching cab now though.

IMG_20180907_184259-01.jpeg

IMG_20180907_184238-01.jpeg

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Marcus