PT for A15mk2???

distorted_frequency

The PT is 220/240v correct, is there a 120v tap or do i need a different PT? if i put a 120v PT in what other considerations do i need to take into account?

thanks,

Rob

polifemo

Zitat von distorted_frequency;234151

The PT is 220/240v correct, is there a 120v tap or do i need a different PT? if i put a 120v PT in what other considerations do i need to take into account?
thanks,
Rob

Regardless if you can use the PT or not, getting another one would be a really good idea.
The PT that comes with the kit delivers such low voltages which prevents this amp - that actually is quite nice if modded a bit - from sounding at its best.

A friend of mine has built a 2x6V6 amp that totally destroys the Madamp...
He is running his powertubes at about 450V whilst I´m running my 6V6´s at about 280V as this is the MAXIMUM (!) voltage that this PT can deliver. (A friend of mine who is a professional ampmaker runs the 6V6´s in one of his models at 490V)

Running the Madamp at such low voltages reduces headroom, clarity, dynamics and output volume. (When my friend start playing his amp, the Madamp can´t be heard...)

Get yourself a new PT - that delivers "normal" voltages and your amp will be soo much better!

ps As I´m quite pleased with the A15Mk2 - it´s heavily modded and has a totally redesigned tubedriven (both send/return) FX loop - I might convert it to a 2XEL34 amp instead by getting new transformers and changing some caps.
Will give me a usable amp at giggin´levels. ds

MAD

PT with higher voltages

Hi Rob,

if you use another PT with higher voltages, please be aware that you need to change some parts (filter caps, bias etc.)

Regards,
Martin

distorted_frequency

Zitat von MAD;234238

Hi Rob,
if you use another PT with higher voltages, please be aware that you need to change some parts (filter caps, bias etc.)
Regards,
Martin

how do i figure out what parts and what values? i wanted to use this: http://www.torresengineering.com/hammedlevpow.html transformer. also if i change what fuse value do i need? the reason i was asking is because where i am located we use 120v

thanks

eBernd

Hi

if you will use this PT you have to change the rectifier (from bridge to two diode rectifier):

Be shure to change the bias of the power tubes with the higher plate voltage - otherwise you will blow the tubes...

The higher voltage will affect C28, 29, 26, 17, 10, 8...
Eventually you have to fit R48, 36, 29, 10 to get the right voltages in the preamp...

You see a lot of work is coming up to you...;D

Bernd

distorted_frequency

I don't think I'm ready to be modding an amp if I've never even built one. Before I get in over my head, i guess i should ask: does the PT has a 120v tap? Or does the PT have a split primary that uses two 120v windings in series to get 220v?

if not what are the specs on the PT so i can locate a identical one in 120v? is it the one on your site: 230-0-230 6.3V @ 4A

I don't think I'm ready to be modding an amp if I've never even built one.

edit: i think i may have found a better choice here:http://www.hammondmfg.com/260.htm the 260E

eBernd

Hi

the PT datas in the kit are

Vpri = 230 V no tap
Vsec1 = 230 V/0,12 A
Vsec2 = 20 V/0,12 A (needed for bias voltage)
Vsec3 = 6,3 V/4 A (2,2 A needed for A15)

But why don't you put this question directly to Klaus of the MusikDing shop?

Bernd

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