Deacy Amp (?)

[Killer Queen]

Aha! The link to martin pitcher's site!
http://homepage.mac.com/martinpitcher
Thanks to the chap who posted that over at the BrianMayworld forums.
There's one or two sound samples of his home-made deacy on the site. (Presumably based on the same schematic that he gave me.)

[Manolo Dudes]

Friends, Killer_Queen has granted www.pisotones.com to host this file for all of you:

Deacy

Hope you enjoy it and thanks to Killer_Queen and Martin Pitcher.

[vanessa]

What kind of transformers are these?

[mbello]

What kind of transformers are these?

Yes, anyone knows about this data? or any primary/secondary impedance?
Thanks so much.

[12afael]

the speaker is 5.3 ohm???
they are a couple of rare value 3-3ohm , 5-6k, 2-2k are 3.3, 5.6k, 2.2k?

if someone have a couple of small radioshack audio transformer could test if they works. if we have luck they have the same impedance .

if the power is 0.45watt. and the output of a pick up is 100mV I think is very easy to overdrive this amp.

[Manolo Dudes]

I think it's not "5.3 ohms" but:

L.S.3 ohms

that is... Loud Speaker 3 ohms 

[Killer Queen]

There's some more info over here if anyone wants to look:
http://www.voxamps.co.uk/downloads/VBM1_E1.pdf
At the back of the manual, in the `Technical talk` section, it says a few quite interesting things.

As already mentioned in DETAILS at the beginning of this manual, the original amplifier itself dates back to a Mullard circuit that was published when transistors first became vailable as a consumer product, and was probably “rescued” from a car radio, as it is built on a commercial printed circuit board. The amp features the total amount of four germanium transistors â€" two for the preamp and driver stage, and two for the push-pull output stage. The circuit also has an inter-stage driver transformer (between the driver transistor and the pushpull pair) and also an output transformer from the output stage into the speaker. When connected to a 9 Volt lantern battery the amp produces a massive 0.45 Watts output.
The amp circuit-board was mounted into a 1960’s contemporary bookshelf HiFi speaker cabinet, of quite small proportions (England’s bookshelves were not very big at the time!), and contains a small woofer loudspeaker and a cone tweeter that is coupled through a capacitor. Due to the speaker technology of the time (and having been played for many years by Brian) it has a relatively mellow sound when compared to today’s hi-tech, hi-fidelity speaker systems. As it happens, said mellowness is actually quite complementary when the original Deacy is used in conjunction with Brian’s homemade guitar and Treble Booster. Due to the very low input impedance (12kOhms) of the amp John Deacon salvaged from a pile of rubbish (remember, in all probability it was originally designed for use in a car radio), it is actually not very useable when a guitar is plugged directly into it. This is because guitar pickups need to see a much higher impedance in order to do their job properly. Hence the use of Brian’s homemade Booster pedal was vitally important, not only in terms of tone but also in terms of the overall compatibility of the signal path.

It also mentions that the speakers used are no longer available.

[Vsat]

That schematic is  the same one shown on Fig.4, page 171 of the 1961 Mullard manual.
The transformers are identified in the text as Colne 06005 (for T1) and Colne 06006 for T2.
The equivalent Hammond transformers are listed in the back of the manual as 57318 and 57319.
Maybe someone has an old Hammond catalog that lists the specs?

Text also states that this amp is the same as the one shown in Fig.13, page 160, (but with the preamp added).
Fig.13 has some further transformer info:
T1 is 3.5:1+1, Rp < 130 ohms, each half of the tapped secondary has Rs < 40 ohms.

T2 is 3.1+3.1:1, each half of the split primary has Rp < 1 ohm, Rs < 0.2 ohm.
Speaker is 3 ohms.
The OC81D driver and OC81 matched pair were supplied as a set by Mullard.
Cheers, Mike

[mbello]

Thanks for the info.
The transformer that connects oc81d, it's a driver transformer? Maybe an old spica driver transformer will do that work!

[Vsat]

T1 functions as the driver transformer,  probably a safe  guess is that it was sold as a driver transformer(?). Wonder if this thing is all that different from those little one-watt germanium amplifier boards that Radio Shack used to sell in the 70's?
Mike

[Ivana]

Thanks a lot all of you! 
Sorry for my offline - I was in a tour...
Now I will try this scheme in my perfboard witn my old different russian germanium transistors! 

[christiancm]

Hello everybody,

I agree with JimRayden, the clean channel was great and the second channel is very fizzy, but with a cabinet and a another "treble booster", that changes all ! (please, visit my website for more informations: http://www.ccm.fb.bz ).

This Deacy project is very interesting, but for the moment i don't find the transformers and the OC81D.

Christian.

[Ge_Whiz]

The transformers are probably something like these old 'Eagle' standbys, the LT44 and LT700:

http://www.maplin.co.uk/Search.aspx?criteria=eagle%20LT700&doy=18m10&source=15

One is a driver transformer, the other output. Can't remember which off hand, and Maplin can't be bothered to say, but the answer is surely only a Google away.

[coxy46]

The specifications for the maplin transformers are as follows....
Type No. Application Primary Secondary 
  impedance impedance 
LT44 Min TR LT44 Driver 20k&ohm; 1k&ohm;CT 
LT700 Min TR LT700 Output 1·2k&ohm;CT 3·2&ohm; 

Hope this helps, look forward to hearing if anyone has built one/building one, and seeing if the schematic works and with which transformers.

[Skizzo]

I don't have understand..... 
Whati is the value of T1 and T2!?
And where I can find the transistors OC81 and OC81D!?
TNX

[Penguin]

after doing a little reading i wonder if one of the old fender interstagetransformer would work for this circuit.  i have one if anyone wants it. i have not use for it.

ed

[Ivana]

I have test this scheme yesterday. With different russian transistors and transformers. With the treble booster in front of it. Sound is good, but very depends from:
- transistor's gain.
- value of the first input resistor (i remove the cap - I have it in a booster).
- value of general feedback resistor. I remove it.
- transformers and its parameters!

"T1 is 3.5:1+1, Rp < 130 ohms, each half of the tapped secondary has Rs < 40 ohms.
T2 is 3.1+3.1:1, each half of the split primary has Rp < 1 ohm, Rs < 0.2 ohm."
is not agree with
"LT44 Min TR LT44 Driver 20k&ohm; 1k&ohm;CT 
LT700 Min TR LT700 Output 1·2k&ohm;CT 3·2&ohm"
what is true?

[coxy46]

Ivana,
  I only posted the spec of the maplin transformers as Ge_Whiz  was asking what spec they were. I doubt that they are what is needed though as the figures are a lot different to that stated in the mullard manual.
Be interested to hear any sound samples of your deacy.

[christiancm]

hello everybody,

I contacted many manufacturers of transformers.

Unfortunately, none did not answer favorably.

For the moment, I have not solution.

Christian.

[Ge_Whiz]

"T1 is 3.5:1+1, Rp < 130 ohms, each half of the tapped secondary has Rs < 40 ohms.
T2 is 3.1+3.1:1, each half of the split primary has Rp < 1 ohm, Rs < 0.2 ohm."
is not agree with
"LT44 Min TR LT44 Driver 20k&ohm; 1k&ohm;CT 
LT700 Min TR LT700 Output 1·2k&ohm;CT 3·2&ohm"
what is true?

It looks to me like Rp and Rs are DC resistances, whereas the specs for LT44 and LT700 are impedances - very different beasts.