Deacy Amp (?)

[PRR]

...3-watt would be the centre tap.....

No. 6W is the center-tap for the 1.5W winding.

[zbt]

...3-watt would be the centre tap.....

No. 6W is the center-tap for the 1.5W winding.

Yes Sir Paul, 6:4.5 I think.

@Sir Jim, what I mean is the speaker may be can use for deacy amp, the transformer could be for another class A amp.

Those line transformers are often well suited for class-A tube (which you already know) although I'm sure someone has done it with class-A transistor drive.

For tubes I have never made it, in theory from a book for class A, I've read it with transistor, in practice I haven't.
this attracts me because once made it in the form of a radio kit, like this HX108-2 7 Tube Radio Electronic DIY Kit, only locally made.

https://www.amazon.com/dp/B08C7WB8G7?ref_=cm_sw_r_cp_ud_dp_HV8DSE4TTFFXYD598A23

https://leap.tardate.com/radio/am/hx108-2/ another info in detail.

[anotherjim]

...3-watt would be the centre tap.....

No. 6W is the center-tap for the 1.5W winding.

Don't you need fewer turns to get power into the thing with a low voltage amp? I can see the 6W looks like half the total winding.

[PRR]

Don't you need fewer turns to get power into the thing with a low voltage amp? I can see the 6W looks like half the total winding.

This system these transformers are really made for is called "constant voltage". Often "70V". Does that help? Or do we need the chalkboard and a discussion of volts and watts?

[zbt]

from ref2

T2 (Output) Primary 140 ohm, Secondary 35 ohm
SP1 Speaker 3" x 5.5" PM 30-40 ohm

from ref5
T1 (Driver) Primary 2, Secondary 1

[Clint Eastwood]

from ref2

T2 (Output) Primary 140 ohm, Secondary 35 ohm
SP1 Speaker 3" x 5.5" PM 30-40 ohm

So the Deacy amp has an output impedance of 35 ohm, and what is the impedance of the woofer/tweeter combination in the original Deacy?

[zbt]

15 ohm, Elac  https://yonderbosk.wordpress.com/vintage-elac-speakers/

It doesn't match, is this what's causing the distortion?

[Clint Eastwood]

I think this plays a role in the sound of the amp. A lower speaker impedance means the amp is asked to deliver more current, so the output transformer will saturate sooner.

[zbt]

looking back at the schematic, for a deacy type output transformer the output signal is just to provide feedback.
If we omit feedback, than what use of primary windings, what if we place it with resistors?

I suspect that the problem is the two output transistors, maybe because the heat, make it out of sync.
Or maybe from the transformer driver windings, but I doubt it.

[Clint Eastwood]

Here is a link to an interesting thread about this output stage on DIYaudio: https://www.diyaudio.com/community/threads/wtf-push-pull-output-stage.330460/

[Clint Eastwood]

If we omit feedback, than what use of primary windings, what if we place it with resistors?

The AC resistance as seen by the output transistors would become (too?) low.

[mac]

I wonder how many turns the PR80 OT must have.

The minimun freq of a guitar is about 80hz.
And the OT primary impedance is Zp=140CT. The secondary 35 (140/35=4 --> 2:1 turn ratio)
From Z = w.L = 2.pi.f.u.N.N.A/L
N can be estimated.

But u ?? A/L ??

mac

[Clint Eastwood]

I wonder how many turns the PR80 OT must have.

Good question. Lots of formulas on the internet, but little practical information on output transformer design for transistor amps.
I found some info in an old Telefunken handbook. For a design using AC106 output transistors (a predecessor to the AC128), and a 5 ohm load, an EI42 transformer core is used. The primary has 168 windings of 0.32mm wire center tapped, the secondary 76 windings of 0.55mm wire.
The previous is for an OT with the speaker on secondary. But the PR80 has the speaker connected to taps on the primary, and the secondary is just for feedback. So I assume the secondary can be made from thin wire, there is hardly any current flowing,  and then you can make the primary wire thicker.  I suggest 180 windings ct with 0.5mm wire for the primary.  The DC resistance of the PR80 primary winding is 2-2.5-ct-2.5-2 , assuming the same wire for the whole primary this tells us where the taps should be: 40-50-ct-50-40.
For the secondary, the impedance ratio is 140:35, or 4:1, so the turns ratio is 2:1. So I suggest 180/2= 90 windings of 0.1mm wire.
To be clear, I have not tried this, just a guess as to what might work.

[mac]

For the secondary, the impedance ratio is 140:35, or 4:1, so the turns ratio is 2:1. So I suggest 180/2= 90 windings of 0.1mm wire.
To be clear, I have not tried this, just a guess as to what might work.

My first guess too, 40+50+ct+50+40 : 90

For the record,
My Crown CRC 530SW with silicon transistors, or my National RQ445 with Matsushitas GE sound pretty close to a Deacy.
Even the LT44/700 combo can sound really cool.

mac

[zbt]

Here is a link to an interesting thread about this output stage on DIYaudio: https://www.diyaudio.com/community/threads/wtf-push-pull-output-stage.330460/

One push too hard and the other not? make asymmetrical sine wave?

Also notice the power is not positive ground, would it be problem if using pnp?

This transformer is now hard to find 

[zbt]

Deacy factor

1. Amp
   - Feedback frequency
   - Mismatch output transistor
   
2. Speaker
   - Honk 600 - 650 Hz
   - We need Wolverine?

3. Cabinet
   -




For LHM0606 transformer

Black - Red 6W 164.6
Black - Blue 3W 236.4
Black - Yellow 1.5W 338.7

Yellow - Blue 1.5W 102.8
Yellow - Red 4.5W 174.7

Red - Blue 3W 72.2

Black - Red 164.6
Yellow - Red 174.7


mismatch 10.1 ohm, is it good? Can Red be centre tap





From radio kit

IT
Primary   29.8
Secondary    21.2 CT 21.2 -> 42.2

OT
Primary   2.7 CT 2.7 -> 4.9
Secondary   1.7

[Clint Eastwood]

You need to find out the turns ratio of the transformers to see if they would be suitable for a Deacy style amp. Connect an AC signal on one side, and measure what voltage appears on the other side.

[mac]

In this thread
https://groupdiy.com/threads/deacy-amp-transformers.78997/page-2#post-1011970
someone noticed that replicas have the secondary shorted. Negative feedback is removed and at the same time the gain is boosted because a previous emitter is AC bypassed fully by a big cap.

But shorting the secondary has to change things inside the core, possibly freq response...

Mac

[zbt]

You need to find out the turns ratio of the transformers to see if they would be suitable for a Deacy style amp. Connect an AC signal on one side, and measure what voltage appears on the other side.

using 12.69V

IT
P  12.69    S1 2.029
P  12.69    S2 2.022

S1 12.69    P  2.705
S2 12.69    P  2.600

OT
P1 12.69    S 0.939
P2 12.69    S 0.840

S  12.69    P1 0.986
S  12.69    P2 0.976



Speaker Transformer, is high voltage, as Master Paul said.

                     S 12.69                   
C     6W    0.642    85.4
C     3W    0.463    120.5
C     1.5W  0.338    168.6
1.5W  6W    0.648    83.4
1.5W  3W    1.082    48.48
3W    6W    1.454    21.20

[mac]

Who needs a rare african radio when lots of old radios are out there for a few bucks? 
Today I bought these two for USD 3. The bigger one was on every house in my country in the 60-70s.

https://postimg.cc/gallery/4x4ZbQ3

mac