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Brightening tweed deluxe (DIY amp)

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9/28/1997 10:40 AM
Dion	Brightening tweed deluxe (DIY amp) Hi, I want to make my homemade tweed deluxe (5E3 circuit, DIY amp)more brighter? It sounds too brown to me. Should I adjust the caps in the tone control? Or decrease the value of the coupling caps after the first stage? Can anyone help me? Thanks, Dion

9/29/1997 11:43 PM

Hi Dion,
First thing .... are you using a screen resistor
on each of the 6V6's? If not stick about
500ohms in series with each screen lead to
the sockets to help limit the screen current.

Also see if this makes any difference in the
drive and tone of the driver....
change the anode 56K resistor on the driver
into a 57K5 resistor(56K + 1K5 = 57K5z). It
should help balance the driver a little bit.

I think a good thing to play around would be the
coupling caps. Try .022. My old man ears
really need about a 10:1 jump in cap values
to hear a big difference! I hope yours are
better.
How about putting about 47pF silver mica cap
across the top of the volunme control to the
wiper like a bright switch on a BF Twin?
Only solder it there. That should brighten it up
a bit too.
OK I just dug out a schematic for the Deluxe 5E3
and it looks like there IS a .02 cap on the 2nd
preamp to the driver section.
So.......
I wonder if you tried replacing the typical 25uF
cap on the common cathodes in the first preamp
with a much smaller value like .5uF?
Also on the 1st preamp section you could split
the cathodes apart and run seperate 1K5 resistors
on each half of the 12AY7 and have one with a
10uF to 25uF cap and the other with a .5uF cap.
Try a hotter tube in the front end too like a Ruby
7025 STR or a good NOS 12AX7. Then drop the .1uF
coupling caps to the tone / volume control to
.022uF or so. This might be pushing the limits of
stability so be prepared to insert a little series
resistance ahead of the second preamp stage.
I think I would also play around with the bypass
cap on the second pramp stage too.
Since it is a homebrew, did you build it with a
seperate tone circuit for each channel?
You could mess around a little with the tone
circuit and mess with that 500pF cap ...larger?
Post your results old man!
Hope this was not a bunch of hot air!
C U
Bruce

9/30/1997 2:58 AM

Hi Bruce,

Thank you for your reply.
I just finished the amp just two weeks ago. I just blueprinted the 5E3 schematic. So there aren't any screen resistors. Ill will try it.
i took 0.1% 56K resistors so I will add an 0.1% 1K5 resistor(I read in Weber's book that this would also help balance the driver).

I already had the 22nF in mind (next to 47nF). I didn't have the time yet to get those (polypropylene).
On my list was also the "bright-cap" after looking through my fender-schematics. I already used a mica cap for the 470pF cap in the tone control. They are hrad to get here in The Netherlands. It will take 2 to 3 weeks again to get 'm.

I haven't tried changing the preamp.
Oh well, there is already an Sovtek 12AX7 in it.
After you mentioned the decoupling cap on the cathode I thougt to myself: Oh yes! I gives the lows and mids an extra boost.

Lots of fun a DIY project.
I'm thinking of designing a guitar-amp with transmitting tubes (high voltages! Over 1KV).

I wasn't a bunch of hot air to me. I'm a student electronics. I think you have to wait a while for the results but I will post them. Thanks for the advice.

Dion

9/30/1997 11:42 PM

What kind of RF tubes are you considering?
Someone told me they can be rather glassy
sounding. I think thatis too broad of a
statement to carry much weight.
I have seen a few mentions here and there
about using old sweep tubes in some type of
simulated triode configuration.
I have quite a few RF tubes myself.
I saw an article not too long ago about using
a pair of 4-400's in push pull. Yikes!
I have a ton of these old 4X150 tetrodes
that I have been threatening to use to.
They are about 200 watts each at 2KV.
I was thinking of using one in class A
with reduced plate voltage and driving
it with a low power pentode.
It only takes about 1 to 2 watts on the grid
of one of these tubes to drive it full
output.
Good luck with all...
Bruce

10/1/1997 1:52 PM
Dion	I haven't really thought of what tubes to use . It's now merely an idea. With such projects I usually first start with where to get the transformers. Then the rest. Dion

10/9/1997 1:39 PM

Where to get parts in Holland

Hi,

being a Dutchman and hardcore solderhead too, I'd like to inform you where I did get my parts. For Transformers, tubes, high quality caps and pots you could contact FNS Tube Tech in Wageningen. This guy also builds custom transformers.
I usually mail-order HV polystyrene caps/elcos and 1W/1% metal film resistors at Conrad in Rotterdam. They are relatively cheap. I'm sorry, but I can't give you any phone numbers at the moment, because I'm in South-Africa for my study (electrical engineering).

Groeten, Niek

10/3/1997 6:39 AM

Re: Brightening tweed deluxe (DIY amp)

Try changing one of the coupling caps to 500pf. I'd try the triode without the tone circuit first to see if that helps. Which schematic did you copy? I have seen different schematics, some showing a .1 coupling cap on the driver tube pins 1 and 6 and others showing a .02. Play around with that one, although the first triode will give more controllable results. You might even try a pseudo "cut" control as found on AC30s. Let us know what you find.
James

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