Brian May's Deacy Amp secrets revealed  [traced]

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Post by analogguru »

almost exactly with having basically the same topology as Vanessa's schematic, but using the type of transistors you've described.
The topology is from the 50´s , similar to Vanessas schematic and used until the 70´s.
It was full of nice Toshiba 2SA... type germanium transistors and I got about 10 usable ones out of it.
In the power-amp would have been used 2SB...trannies
I guess I'll have to repopulate the power amp section of the board with some AC128s and see what happens.
You also would need the driver-stage....normaly there is (different to vanessa schematic) a feedback from the secondary of the output transformer to the emitter of the driver stage.

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Post by vanessa »

Hmmm...

I've never investigated the cassette angle, because I had not read that quote you posted (thank you!).

I have read quotes saying he thought it to be a car radio. The schematic I provided was handed down to me from someone who was given it from the gent that had a look see into the original . I have the gents name somewhere (possibly that Pete Malandrone? I know it to be the "other guy" because one wanted to look into it to build a clone for May (Greg Fryer?) and then sell clones and the other was not in business to clone and it was him who provided the schematic).

The closest radio I could find to all the info I had was the Roberts R200/R300. It has an identical output section as the one in the schematic, 9V, and is really quite small and could fit easily into a small home speaker cabinet.
I'm pretty sure that the schematic he provided (I posted) was to show the circuit layout not specifically the transistors. There's many transistors that can be subbed in this circuit. It's a very common power section and was used in just about all the transistor radios from the late 50's to early 60's. I've seen all sorts of transistors subbed into this circuit. Including AC128's like you'll find in some of the vintage Roberts R200/R300's (depends on the year).

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Post by soulsonic »

Yes, you are correct; a pair of 2SB56 are used for the output.

No feedback from the output though - I'm sure of that.

Very, very close to Vanessa's schematic.

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Post by vanessa »

soulsonic wrote: I guess I'll have to repopulate the power amp section of the board with some AC128s and see what happens.
I'm pretty sure that you could use many different transistors in there without any major change in tone. It would be more important to have a match pair and a higher gain (you might even use lower gain si's in there and not notice a difference in tone. VOX did on their reissue Deacy) in that PP output section. I could be wrong but I think the trademark sound of the amp is from the overloading of the transformers.

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Post by soulsonic »

Is there any substantial difference between these transformers and the crappy little "42TMxxx" Xicon ones Mouser sells... It's seems like this would be pretty easy to recreate... the only difficult to source part is potentially the transistors, since I've been pulling my hair out lately trying to get decent germaniums.

Little bit OT: seriously, about germaniums; I really love AC128s, but almost all the ones I've gotten lately have been crap... low gains - around 30 to 50 hFE... and when they do have a decent gain, they have ridiculous leakage. One of the ones I tested from the last lot I got had an hFE of 130 - but a leakage of 1mA!
Is there a decent source for germaniums any more? I'd love to get more of these 2SA and 2SB Toshiba ones, but I have yet to find a decent source. I'm sick of eBay's BS, and there's no way I'm going to pay someone $10 to $14 for a pair of transistors that may not even be tested. It's really annoying... I'm very close to totally "quitting" germaniums.

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Post by analogguru »

I could be wrong but I think the trademark sound of the amp is from the overloading of the transformers.
One of the standard mystifications spreaded around the use of audio-transformers, but not really true.

To "transform" a (huge amount) of AC-voltage you need an iron- or Ferrite-core. The lower the frequency, the bigger the core most be.
For this reason (old) submarines didn´t use 50 Hz or 60Hz, they used 5kHz to reduce the weight caused by the necessary iron.

If the iron is not enough and can´t handle the current it will be "saturated".

So the hypothesis of overloading the transformers maybe true for low-frequencies like bass, but not for normal guitar-frequencies, where the iron is enough not to get saturated....
Yes, you are correct; a pair of 2SB56 are used for the output.
No feedback from the output though - I'm sure of that.
Very, very close to Vanessa's schematic.
But there should also be a small disc (NTC) or diode near on of the output trannies for temperature compensation (not shown in vanessas schematic)
I really love AC128s, but almost all the ones I've gotten lately have been crap... low gains - around 30 to 50 hFE...
Where is the problem ? AC 128 have been (only) constructed for the pupose of power-output stages like this. And there you don´need more hfe. FuzzFace etc is not a typical application for this transistor, it´s a misuse....
Is there any substantial difference between these transformers and the crappy little "42TMxxx" Xicon ones Mouser sells...
No.... these transformers were made exactly for this application, you only have to choose the right one for the desired outputpower and transistors used.

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Post by grolschie »

I love the sound of Brian's gat on the earliest Queen albums (I, II, Sheer Heart Attack, ADATR, ANATO, etc) but hated the processed overly chorused tone in the 80's. Actually their music was way better back early on too IMHO. The Game was the beginning of the end for me, and Hot Space was the end for me - although I still bought their albums. By then Freddies vocals also not the same anymore. [smilie=a_damnit.gif] I'd be stoked to get close to that early Queen sound.

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Post by vanessa »

soulsonic wrote:Is there any substantial difference between these transformers and the crappy little "42TMxxx" Xicon ones Mouser sells... It's seems like this would be pretty easy to recreate... the only difficult to source part is potentially the transistors, since I've been pulling my hair out lately trying to get decent germaniums.
The first transformer (T1) is a 3.5:2, you could use a 3k:3k coupling transformers that has R of about 250 ohms per side. If I remember Mouser carried something like that last I checked.

T2 is 3.1+3.1:1. This is the hard one to find. You would have to find someone to wind you one of these at about a 2W rating. It is the reason I got to digging deeper than just that schematic and the transformer specs. I wanted to know the exact model of radio because I wanted to gut it for the transformers.
Most of the radios (RCA, Japanese) with the same circuit can be had on ebay for less than $10 (shipping included). No need to have someone wind you one for $30+.
soulsonic wrote: Little bit OT: seriously, about germaniums; I really love AC128s, but almost all the ones I've gotten lately have been crap... low gains - around 30 to 50 hFE... and when they do have a decent gain, they have ridiculous leakage. One of the ones I tested from the last lot I got had an hFE of 130 - but a leakage of 1mA!
Is there a decent source for germaniums any more? I'd love to get more of these 2SA and 2SB Toshiba ones, but I have yet to find a decent source. I'm sick of eBay's BS, and there's no way I'm going to pay someone $10 to $14 for a pair of transistors that may not even be tested. It's really annoying... I'm very close to totally "quitting" germaniums.
I don't think the big deal with the circuit lies in the transistors (this is not a distortion circuit). It's design is to be a clean power amp to boost the output of the signal of a radio. It may have some effect when pushed hard by a Rangemaster cranked on 10, but I really think a lot of the tone comes from the transformers being pushed by the Rangemaster into saturation, and I'll add the speaker (size of, make, etc) and it's enclosure.

If you were plaining on putting together a PCB and do it from scratch I would recommend maybe putting in some of those Russian Ge's and experimenting. Get some low leakage all around, and match a higher hfe pair for the output section. You could also go Si and use a lower gain (or if you prefer higher gain) matched set for the output pair. Maybe 2N3906's.

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Post by Torchy »

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Post by bajaman »

Hey Torchy - thanks for posting the Pig nose schem :wink:
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Post by Avatar »

Hi there,

but what's about the Vox Brian May Special Edition Amp? Does anyone have the schematics for this one?
It was sold for some time two or three years ago for about 150EUR.

There was a treble booster and a 6,5" speaker built in - I think, it was called YBM.

Best regards,
Hannes

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Post by celadine »

I'm very close to totally "quitting" germaniums.
You probably know this, but Small Bear has plenty of different geraniums, pre-tested for acceptable leakage, and sorted for gain. I got 3 a couple of weeks ago, all were fine.

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Post by soulsonic »

celadine wrote:
I'm very close to totally "quitting" germaniums.
You probably know this, but Small Bear has plenty of different geraniums, pre-tested for acceptable leakage, and sorted for gain. I got 3 a couple of weeks ago, all were fine.
I've bought from him before and those are fine if you're building one thing for yourself.... but they are WAY too expensive if you're needing a large quantity. At those prices, you may as well buy the NTE ones (which I've also had good luck with).

I'm thinking the various Russian ones are probably the best way to go. I've had very good luck with them so far. There seems to be plenty of them left on the market too. Seems like more variety too.

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Post by vanessa »

Avatar wrote:Hi there,

but what's about the Vox Brian May Special Edition Amp? Does anyone have the schematics for this one?
It was sold for some time two or three years ago for about 150EUR.

There was a treble booster and a 6,5" speaker built in - I think, it was called YBM.

Best regards,
Hannes
This amp is basically a Brian May boost > the schematic I provided (opamps subbed for transformers) > into a SS 10W amp.
Last edited by vanessa on 27 Aug 2007, 03:01, edited 1 time in total.

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Post by claus h »

vanessa wrote:
Avatar wrote:Hi there,

but what's about the Vox Brian May Special Edition Amp? Does anyone have the schematics for this one?
It was sold for some time two or three years ago for about 150EUR.

There was a treble booster and a 6,5" speaker built in - I think, it was called YBM.

Best regards,
Hannes
This amp is basically a Brian May boost > the schematic I provided > into a SS 10W amp.
Hey I got one of Vox Brian May Special Edition Amp I don't think it sounds that good :) But a fun little amp.. You can get very close to brian's sound with a treble booster schem found all over the web..

A small sample http://www.hottubes.dk/samples/QS192.mp3 Me >> Guitar >> Homebuild Treble booster >> POD in AC30 mode :) >> Marshall SLP power amp mod..

Later

Claus

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Post by grolschie »

What is your guitar Claus? What pups? Thanks in advance.

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Post by claus h »

grolschie wrote:What is your guitar Claus? What pups? Thanks in advance.
It's Ibanez S-series mahogany body with an Dimarzio Air Norton pickup I played with a coin to get that May sound :)

Later

Claus

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Post by vanessa »

claus h wrote: Hey I got one of Vox Brian May Special Edition Amp I don't think it sounds that good :) But a fun little amp.. You can get very close to brian's sound with a treble booster schem found all over the web..

A small sample http://www.hottubes.dk/samples/QS192.mp3 Me >> Guitar >> Homebuild Treble booster >> POD in AC30 mode :) >> Marshall SLP power amp mod..

Later

Claus
Hey Claus, There's already a Brian May Treble Boost (si) built into the amp in the very first stage (you can't miss it). Yes it's an ok amp. The add on SS 10W power amp is pretty cool as without it there's not a whole lot of output from this circuit. They should have had it where you could bypass it if you wanted.

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Post by claus h »

vanessa wrote:
claus h wrote: Hey I got one of Vox Brian May Special Edition Amp I don't think it sounds that good :) But a fun little amp.. You can get very close to brian's sound with a treble booster schem found all over the web..

A small sample http://www.hottubes.dk/samples/QS192.mp3 Me >> Guitar >> Homebuild Treble booster >> POD in AC30 mode :) >> Marshall SLP power amp mod..

Later

Claus
Hey Claus, There's already a Brian May Treble Boost (si) built into the amp in the very first stage (you can't miss it). Yes it's an ok amp. The add on SS 10W power amp is pretty cool as without it there's not a whole lot of output from this circuit. They should have had it where you could bypass it if you wanted.
Yes it has a treble booster build in but, I think my homemade one sounds better sorry :)

Later

Claus

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Post by grolschie »

claus h wrote:
grolschie wrote:What is your guitar Claus? What pups? Thanks in advance.
It's Ibanez S-series mahogany body with an Dimarzio Air Norton pickup I played with a coin to get that May sound :)

Later

Claus
Brilliant. Thanks. Neck or bridge? Coil split/tapped? So the coin is a massive factor in getting the sound? I tried once and found it very hard to play with a coin. :)

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