Alembic F2B! (PCB and Layout)

Tube or solid-state, this section goes to eleven!
smoib
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Post by smoib »

If there is anyone out there who wants to try and build an F2B preamp with the Gilmour mods of an extra tube and different cap for me to put in a 1ru enclosure, I would be willing to pay for their work. If the extra tube bit is too hard, I would settle for just someone who can make up the kit for me (without the box) so I can mount it here.

I have the ability to mount it but I don't have the ability or knowledge to make it from scratch. Contact me any way you want and we can work out a price.

Brendan

SPeter
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Post by SPeter »

moltenmetalburn wrote:PCB pdf hosted here for all to download, enjoy!

http://www.redhillmetal.com/uploads/Alembic%20PCB.pdf

thanks again douglas! :applause:
Hi all,
The link doesn't work!
Could someone be so kind to send me the PCB pdf file!
My Email address:
peterdavidoff@hotmail.com
Thanks in advance!
:)

SPeter
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Post by SPeter »

Sorry I did it -right click-save link as!
Thanks!
Regards,
Peter
:)

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MarcoMike
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Post by MarcoMike »

Hi, I was comparing the original schematic posted by Boris with the other one you can find online (I found it on diyaudio, but it traced it being from moosapotamus)

the mids pot is 10k in one case and 250k in the other one...

what do you guys think about it? I tried to simulate it with Duncan's TSC, and I think I like the 250k version better... it seems more versatile and definetly with less attenuation...

Barcode
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Post by Barcode »

I really want to build this, but the pdf link doesn't work. I even tried the right click "Save as" option, and downloaded it, but it says the file can't be opened. Anyone have this that they could repost/attach?

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MarcoMike
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Post by MarcoMike »

just google it, you will find several schematics just searching for alembic f2b without the word schematic :D
the original version is the one with a 10k pot as mids control

twires
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Post by twires »

Can you say Fender Showman???
Thats what Jack & Phil favored at the time, so naturally thats what Alembic cloned.
Thank Leo!!!!
Output impedance is too high for most Solid State power amps and it sounds flat seeing less than half a meg. Add another twin triode wired as a cathode follower and then it really opens up! Voltage doubler power supply is a bit wimpy too...
If you play bass, Be sure to use Big coupleing caps on the outputs!!!

jay42
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Post by jay42 »

I don't like to preach, but the original voltage doubler circuit has issues. To put it simply, it polarizes the transformer. You can dig around TubeCad if you want the scoop. This is what I did for a single channel power supply. Notice that it uses the same number of diodes and capacitors...just rearranged.

re: the PF modifications are an extra 12ax7 wired as cathode followers on both outputs. The F2-B can drive a 50 or 100W tube amp just fine, but isn't up to long cable runs or your basic QSC PLX power amp at 1000 to 2000 watts bridged. The cathode follower helps with swing and current. You can substitute an IRF820 mosfet with no loss of personal integrity.

I believe the other mod(s) were cap swaps to roll off the low end earlier. It's the sort of thing any given player may or may not want done.
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f2b_power_s.JPG

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Jarno
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my favorite amplifier: Accuphase E-308 (no money for it, yet)
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Post by Jarno »

twires wrote:Can you say Fender Showman???
Thats what Jack & Phil favored at the time, so naturally thats what Alembic cloned.
Thank Leo!!!!
Output impedance is too high for most Solid State power amps and it sounds flat seeing less than half a meg. Add another twin triode wired as a cathode follower and then it really opens up! Voltage doubler power supply is a bit wimpy too...
If you play bass, Be sure to use Big coupleing caps on the outputs!!!
Alembic is pretty open to this, they used to customise Dual Showmans back in the day, to use them with McIntosh power amps. At one point in time they started to build them themselves. They are also pretty clear about the fact that the output impedance is pretty high. David Gilmour apparently had his unit adapted with an extra tube stage to lower the output impedance (and allow for longer cable runs to be used).
"It crackles....., but that's ok"

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Post by mganzer »

Hi guys;
Anyone have the files to re-upload?
many thanks

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Post by rbstep »

Give me an e-mail address and I can email them to you....

stephersonr@live.com

ron

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CrniDamir
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tictac
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Post by tictac »

I found this buried in some of my audio files stuff....

TT
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F2B original.jpg

phatt
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Post by phatt »

Anyone else see the mistake on the tone stack? :hmmm:
Phil.

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deltafred
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Post by deltafred »

phatt wrote:Anyone else see the mistake on the tone stack? :hmmm:
Phil.

Well spotted Phil.
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Post by tictac »

Yea, I saw the slope resistor miswiring but I thought it was cool they made a mistake on a "factory" schematic. The top circuit has the correct wiring anyhow...

So I guess nobody really wanted this schematic... :hmmm:

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deltafred
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Post by deltafred »

tictac wrote:YSo I guess nobody really wanted this schematic... :hmmm:
I forgot to hit the Thanks button. :oops:

I'm very interested as I am looking to build a (valve) bass preamp but it will have to have a cathode follower as I need to drive a low impedance amp with it.

I am looking at using a modified Weber AB200 preamp http://taweber.powweb.com/store/ab200_schem.jpg

It is currently on my bread board but other jobs keep stopping my making any progress.
Politics is the art of so plucking the goose as to obtain the most feathers with the least squawking. - R.G. 2011
Jeez, she's an ugly bastard, she makes my socks hurt. I hope it's no ones missus here. - Ice-9 2012

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