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Hi guys,
I want to build the 15W spitfire. What kind of Transformarotors can I pick?
Because of of comming from europe think the Hammond 125 E and a 300-0.300 should be good..
The choke .... how much mH?

Kars6ten

Welcome to the forum!

The PT would be fine at 300 [a bit hi but OK]. OT, not a fan of Hammonds but it would work as would an 18 watt OT, and the choke can be be 3-10 mh, 100 ma. Take a look at the Lightning schematic in the forum. They're very close and the specs are on the drawing.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I used Hammond 158M choke 10mH 195Ohm, 100mA
Novarria 280V-0-280V power transformer

Hammond 125E output

Works fine, I'm happy with the hammonds, but if you'r not
on a tight budget go for the more expensive output transformers.

Yeah, espen built a killer Spitfire. check out:

viewtopic.php?t=674&postdays=0&postorder=asc&start=40

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Thanks for answering so quick.
Ok, I will put a better OT. What do you think about the VOX® AC 15 Reissue?
This one is for 2 x EL84 class A. Can I take this one? Asking because of the spitfires class AB.

Karsten

On the Lightning, Matchless used a transformer that was 4K on the primary not 8K as you would think. I'm not 100% on the Spitfire but I'd check on the AC15 to see what the impedance was anyway.

But, an 8K will work fine and I'd think the AC15 RI would be good too.

Espen, what did you set the impedance of your transformer to?

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Spitfire is 4K primary, and thats what I used in my amp. With a 4Ohm
and 8Ohm output.

Just an hour ago I've been mismatching the output impedances to test
how it changes the sound. Connected 8Ohm speaker to the 4Ohm output
(this changes primary to 8K, increases voltage on the transformer, but
still within safe limits)

With the 8K primary it kind of loses a tiny bit of 'sparkle' on highs
when playing clean(due to the lower voltage on the output tubes?).
Distortion sound is more 'Marshall' (not so bright) and I think it sounds
pretty good for Led Zep at high volumes.

I also tried some TAD premium 12ax7, and man they sound amazing,
totally got rid of the high freq. 'fizzle' I had when using Electro Harmonix
12ax7.


I also think VOX® AC 15 Reissue transformer would be good.

Hi Espen,
Read your finishing thread and I'm very impressed. Ordered the TA from Italy as well. And will take the OT from Hammond.
Your schematic of the spitfire is very good. I will build the spitfire with the help of your schematic. Do you have a bill of material? I want to build the spitfire in a hammond case. Builded my Madamp in a 440mm case. Think the spitfire can be dropped in a smaller one.

Here's a foto of my M15


Karsten

Thats a nice M15

Uploaded parts list to web page:
http://home.online.no/~eber-ha/TubeAMP/PartsV4_V1.1.xls
And the voltage chart:
http://home.online.no/~eber-ha/TubeAMP/ ... report.txt

The final version of the schematic is 1.2 which you will find here:
http://home.online.no/~eber-ha/TubeAMP/amp_build/

The schematic is based on the Spitfire, if you want to build an exact
copy, then search the web for the Spitfire schematics.
But there are only three things I changed from the original Spitfire:
-lower value Phase Inverter cathode resistor 1.2K to 820 ohm
-EL84 cathode resistor 120 ohm to 150 ohm
-added the CUT control

Hi Espen,
Do you really need 2 Watt resistors everywhere?
Looking in the list of materials you are using 2 DPST mini toggles (bright and tone bypass), one DPDT and a SPST.
Following the schematic I only need two SPST for tone and bright, a DPST (heavy) for power and a SPST (heavy) for the bypass. I'm not sur if I'm right. Can you help me with this one?


Karsten

You only need 2 Watt res. for the power supply RC filter (the two
22K'ones) And maybe for the 'Line out' 22K and 3.3K.
The 100 ohm EL84 screen resistors 1 Watt or higher.
I bought 1000 2 Watt resistors so thats what I use everywhere.


Two SPST for tone and bright is correct, I just put in two DPDT mini
toggles in case I wanted to use the switch for an additional function
in the future. The power switch should be DPST and the bypass SPST
as you pointed out.

There is an error in the parts list for the power switch SW1001
it says 'Toggle switch, DPDT, metal' it should be
'Toggle switch, DPST, metal'