#124 started

[martin manning]

PS I have bought balanced 12AX7's that we're pretty far from it!

[erwin_ve]

The positioning of the Orange drop outer foil had a very positive effect on the quietness when on idle. It also noticed it on my last build.
Glad you got it working! Congrats!

[norburybrook]

Thanks Erwin.

I had marked up a batch of caps but had to order some new ones as well for this build and couldn't be bothered to check so who knows which way round those ones are.

Anyway, the amp is more or less done. I shall let it break in over the next few weeks and make a cabinet. I'm thinking of making it slightly taller so I can fit my small form factor dumble-ator in as well. I'd have the controls at the back and slot it under the OT.

just a thought.


I'm not a fan of the aesthetics of the full size dumbleator at the front along the bottom of the cab like Ceriatone do it.

M

[rogb]

Glad you are up and running!
On the Vox brown, there is nothing more vile IMO, it ruins the look of any cab.
I tried it, waste of time and money. Couldn't bear looking at it.
You can get black from Banzai
https://www.banzaimusic.com/Vox-grill-c ... amond.html
After all that work, get the proper stuff

[norburybrook]

well here's the original #124 I think. I've got the tan suede, anyone know what grill cloth this is?


M

[larsvictor]

Maybe this ?
They say it´s original Fender. Not expensive.
For black vox there´s another supplier in Europe. Cheaper than Banzai.

[norburybrook]

Lars, thanks I'd seen that as I use Tube town a lot for parts, they're a great supplier.


I've just bought some black Vox cloth here


http://www.ebay.co.uk/itm/332064997139? ... EBIDX%3AIT


lets see when it arrives

I got the brown from taylor at amplified nation.


I can choose now which colour

Marcus

[norburybrook]

So, I've swapped the PI trimmer out for a 10k and that's a much better range.

I've also put a 220k instead of the 150k FET sim to get my voltages @180vDC V1 and 195 V2


Could someone explain why removing the 150k resistor put my voltages higher, but putting a smaller value resistor than the 150k resulted in a voltage drop? so I had to increase resistance to get higher plate voltages????



Marcus

[larsvictor]

This is simply ohm´s law.

B+5 =354VDC
With a 150k resistor to ground the current running through this resistor is: 354/150000 (I=V/R) = 2.36 mA

If you omitted the resistor totally minus 2.36mA current would pass every resistor in the string. With less current running through a resistor you will have less voltage drop across it (again ohm´s law!). For a 2.2k it would be less 5 VDC, for a 22k less 50 VDC and so on.

With a 220k as FET sim you also have less current through the string.

[norburybrook]

thanks Lars, I'd not taken into account the current element in the equation and was only looking at voltage and resistance.


I'm trying different pre amp valves at the moment

Marcus

[norburybrook]

Morning all.

Right, questions again.

Did some A-Bing with my #102 50w and the #124 seems a lot quieter with a less full sound unless I have the deep switch on.


Does the classic tone stack suck a lot of 'fullnes' for want of a better word out?


I have bourns audio pots on the master and Volume on the #124 that could be a difference in the taper.

I did a test though whereby I had both master volumes at 10 and the #102 waws loud even with the volume at 3 and I was getting power amp breakup.


on the #124 same setting it was as clan as a whistle and not nearly as loud.


Putting all the tone controls fully on and having the deep switch engaged seems to remedy the situation somewhat , hence my question about the tone stack.


Can I measure the volume pots resistance in circuit so I can set them the same to get a proper comparison?



marcus

[ToneMerc]

Morning all.

Right, questions again.

Did some A-Bing with my #102 50w and the #124 seems a lot quieter with a less full sound unless I have the deep switch on.


Does the classic tone stack suck a lot of 'fullnes' for want of a better word out?




on the #124 same setting it was as clan as a whistle and not nearly as loud.




marcus

On the surface 102 has more net gain at the front end and the Skyliner TS has more mids.

TM

[martin manning]

If you look at the values in the Classic stack you can see that it is likely to have more insertion loss than the Skyline, and indeed it does. Add the Deep network and you get even more loss.

[norburybrook]

Hmm.... I can turn the input volume to 10 and with a tele it's only just starting to break up a bit if I play hard. Seems like there's something sucking gain out early on to me if it won't crank at 10 on the volume. It's a nice clear sound just not what I was expecting.


M

[norburybrook]

If you look at the values in the Classic stack you can see that it is likely to have more insertion loss than the Skyline, and indeed it does. Add the Deep network and you get even more loss.

wow that's quite a difference bearing in mind +3db is twice as loud to our ears.

that's exactly what i'm hearing I would say. I seem to have more body and level with the deep switch in which seems to be the opposite of the graph which looks like is cuts lower mids when in. Also with the switch on the jazz setting there's really hardly any gain at all unless the deep switch is engaged, I doubt you could play above a drummer on the Jazz setting


Should I be able to turn the volume to 10 though and it still be cleanish with a single coil?