Our Guitar Amp Project

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Lookin good and a great learning experience for your son.

I built a Twin clone myself that isn't quite the norm.
You can see it here and here.

I put 2 output trannys on mine as well but not for the same reasons as you. They don't run at the same time and I have them switched for different tube combos and types.

I don't really think you need anything other than a pair of 12's for a twin and mine has great bottom end and the top end sparkles. Just pick the right speakers.



:cool:
 
Thanks for looking amperex and Maxwedge!

We've been reading about and listening to a lot of amps and it seems he's looking more for a Marshall type sound. We'll probably close up the speaker box and might end up with Celestion speakers to get the tone he's looking for.

We both brought up Mesa-Boogie recently and I'll take a close look at those amps as we get further into it. They seem to offer flexibility, SS/tube rect, EL34 or 6L6, many overdrive options, etc. The tone stack and reverb look very much like Fender.

Nice job on your twin Maxwedge, very nice!

Pete B.
 
Interesting that the lower cost Jensen C12Q looks better suited to an open back cabinet based on its Thiele and Small parameters:
http://www.vintagespeaker.com/searc...&selectmain=Speaker&selectsub=12 inch speaker

Qts is 1.72 which on a relative basis will significantly boost the low end output at Fs = 84 Hz and help to compensate for the open baffle loss.

The more expensive, bigger magnet, C12N has a Q of .92 offering much less output at a slightly higher rolloff of Fs = 112 Hz.

The C12Q also has more Xmax = 1.5 mm as compared to the C12N Xmax = 1.0. The efficiency is significantly lower for the C12Q and it would make sense to use four of them to gain efficiency, power handling, and volume displacement in open back cabinets.

So these Jensens are by Recoton made in Italy, don't know how they compare to the originals. Anyone care to comment on reliability?

We're probably going to move to a closed or vented design anyway so the above consideration does not apply.

Seems the Alnico Celestion Blue is highly regarded, but the Weber copy also does well at half the price:
http://www.webervst.com/bt9908.htm

Anyone tried the Weber, or the Jensens?
 
Paul has been finding that to get the sound he wants, he'd need a distortion box, a chorus box, a Wah - which he has, and probably a few more boxes. He purchased the excellent Line 6 distortion box, and then learned about their amps. The excellent modelling available with presets at the turn of a dial make the amp perfect for what he wants. The Line 6 amps were on sale, and he got the 2-10 model which includes Celestion speakers, nice:
file.jpeg


It's good, the boxes and speakers could add up to more than the cost of this amp on sale. He will use the box we made as an extension cabinet when he has the money for speakers, and needs the extra output.

Pete B.
 
The Webers are here, build quality looks excellent.
VERY stiff suspension, I could believe that these need to be
broken in, given how stiff everything is.
Weber says to play music through them with the bass turned up, treble down so that there is some cone motion for a weekend, to break them in.

The cone seems to be very stiff with a strong drum like resonance
when tapped. Not saying this is bad, probably part of the tone, but it is very different from Hi Fi speakers.

Will measure T&S parameters when I get a chance.

Pete B.
 
I pointed out the differences in the much more expensive "pro" drivers from JBL and EV to Paul, and mentioned that I usually preferred many EV drivers over JBL.

A friend mentioned that Mesa Boogie used an EV driver in some of their equipment. Here is some data on the EVM12L:
http://www.srl.utu.fi/~tke/MesaBoogie/Loudspeaker/evm12L-eds.pdf

Paul did some research and found that Zakk Wylde had a custom "Black Label" version of the EVM12L make for him:
http://www.electrovoice.com/products/308.html

They look like they have too much magnet if that's possible, as the Qes is very low.

Pete B.
 
same

Hi PB2,
I took a look at your cabinet and it's nice I also agree that it's a bit of a shame having to hide that nice woodwork with tolex, even though tolex is cool (for Fender). Anyway I am guessing your son is more into rock (or metal) than southern or more traditional sounds, right? I think later on he'll find the difference in the overdriven tone of a push-pull tube power amp more crunchy and satisfying than a sound modelling amp such as the line 6. Probably more dynamic too. I made a Marshall copy (sort of) that has the preamp of a plexi, running only at 180V DC, and the power amplifier of an old EICO Cortina amplifier using Push-pull quasi-complementary (I think that's what it's called) power amplifier. It sounds OK.
In any case do you have pictures of the finished cabinet with the speaker, or it's too soon?

Rock on! (or whatever pleases ya!)
 
Hi,

Thanks for the comments. Yes, he's talking a lot about high gain, crunch and such, bands such as Tool, System of a Down, but also a lot of classic rock. He wants to work up to a half stack.

I'm looking at the Mesa Boogie Dual Rectifier which we might build as a preamp, with simplified mode switching.

I actually have an 807 Williamson Tube amp (Peerless/Altec output transformer) and new old stock 807s, so we might fix that up to start. Anyone know if this has any historical value?

I also have a Dynaco ST-70 that we might rebuild for him to use temporarily. I hear that Sunn used the Dynaco power amps designs, including Dyna transformers.

Pete B.
 
Weber T&S Parameters

Model: Weber Ceramic Sig 12F-B
Serial: #12790716
Cone Marking: 12781 4806
UNIT SAMPLE: PLB #1
UNIT DATE: April 2007
Condition: New Never Used

Effective cone diameter 25.4 cm measured
Delta Mass 15.75 grams (for measurement)
Fshift -19%
Fs 81.0 Hz
Vas 48.0 liters
Re 6.80 ohms
Qe .75
Qm 11.7
Mms 29.0 grams
no 3.28 %
SPLref 97.2 dB
Bl 11.6 T-m
Qts .70
Cms .133 mm/N

These parameters make a lot of sense. Celestion 12" drivers intended for lead
applications typically have a free air resonance of 75 to 85 Hz.

The Q for this driver is very close to a maximally flat design when used in a large
closed box, or an open box.

Vas is low indicating a stiff suspension, cone mass is on the light side for high
efficiency.

SPLref is 97.2 in the piston range pass band and taking into account midrange
lift, and upper midrange peaking this would probably compare to other drivers
marketed as 99 to 100 dB.

Pete B.
 
Weber T&S Parameters - After 4 hrs "break-in"

After 4 hrs break-in, small if any change beyond experimental repeatability:

Measurement date: 4/30/07
Model: Weber Ceramic Sig 12F-B
Serial: #12790716
Cone Marking: 12781 4806
UNIT SAMPLE: PLB #1
UNIT DATE: April 2007
Condition: 4 hrs on stereo bass up

Effective cone diameter = 25.4 cm measured
Delta M 15.75 grams
Fshift -20%
Fs 80.6 Hz
Vas 49.3 liters
Re 6.82 ohms
Qe .72
Qm 9.3
Mms 28.5 grams
no 3.45 %
SPLref 97.4 dB
Bl 11.7 T-m
Qts .67
Cms .137 mm/N
 
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