10,000 Series Question

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jckid649
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10,000 Series Question

Post by jckid649 » Mon May 21, 2018 9:06 pm

I was wondering why the recommendation on the filter caps are all 50uf instead of the 32uf that was standard in most of the plexi's from '67. The video I've seen of George comparing the 10,000 series to an original Marshall compares it to a 1967. I just finished this build and I'm not sure I like how harsh it seems to sound. It seems to lack the airiness and harmonics of the one that George demoed in that video. I'm wondering if the one in that video has smaller filtering caps. I have read that the smaller cap values can make the amp smoother and softer, while the higher value caps make it tighter and faster. Is there a place I could start experimenting with these values that get me closer to the sound of the amp George was demoing in the video?

https://www.youtube.com/watch?v=oSv3RATOXjM&t=305s

Tazin
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Re: 10,000 Series Question

Post by Tazin » Tue May 22, 2018 10:39 am

The '67 10series with Dagnall Transformers (and some with the Drake 1203-80 & 1202-132 transformers) tend to use the following filtering:
Mains: two 100uF.
Screens: two 32uF-32uF (dual element)...Some also used two 100uF.
Phase Inverter: 32uF-16uF (dual element)...Some also used a single element 32uF.
Preamp: 32uF-32uF (dual element).

jckid649
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Re: 10,000 Series Question

Post by jckid649 » Fri May 25, 2018 12:23 am

Thanks. I'm probably gonna experiment with these values.

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neikeel
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Re: 10,000 Series Question

Post by neikeel » Fri May 25, 2018 5:43 pm

IMO the ones that make the difference are the preamp (dual 32uF is my choice) and the screens (32 x2 in series for 16uF)

Leave the mains at 50uF, I would experiment with PI last (either single 50 or both can halfs for 100uF (easy to do)
Neil

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Re: 10,000 Series Question

Post by jckid649 » Wed May 30, 2018 1:11 am

I changed the screens to 32/32 bridged and the preamp to 32/32. That seems to give it some good sag. I tried the 32/32 on the PI but the distortion seemed to kind of collapse into a murky mess at higher volumes so I switched back to the 50/50 there and that helped. It sounds good where it is but now it seems like the bass is a little flubby. I'm kind of not sure what to try here. Most of the consensus from what I have read is that changing the V1 cathode bypass cap from 330uf to 220uf is not going to make a noticeable difference unless it gets down to like 10uf. Thing is that the original '67 specs uses 330uf there. I did think if I did the split cathode it may help this but the '67 didn't do this so I don't want to veer too far of course of the original specs.

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neikeel
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Re: 10,000 Series Question

Post by neikeel » Thu May 31, 2018 7:28 am

Well actually the original uses 250uF 6v silver WIMA on v1 cathode.
A 25uF works well without losing flavour.
NFB is a place to experiment 27k/16ohm is stick and tightest.
Also consider the mixers 270k vs 470k and your choice of bypass cap.
I also suggest a 100pF cap on vol 1 pot.
You will find that the tightness feel of the amp will be a balance with the liquidity/squishiness of the guitar in your hand when going higher or lower with the screen filter cap values.
Turning mids and treble up and bass down (<2) and turning the volume up is traditional.
Neil

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