Guitar Gear Forum

Right off the bat. Might be that this thread´ll stretch a bit as far as time. Got WAY to much to do ATM but..i still find that it´s a good call starting this thread.
Bear with me.

So. Bouyer ST series amps. French made,and stems from the -50´s as far as i´ve understood. Have seen these up for grabs on the various Euro e-bays more time then i care to remember,simply haven´t picked one up. Until now.
As french designs they ARE different. Make no mistake,however...good different. Take my word for this,to the point where i´d say what we´ve got here is a forgotten treasure-as far as guitar use.

ST series could be had in a variety of power levels. From the 20 all the way up to a quad of 6L6´s run at various voltages. What´s more,they´re DIRT cheap. The one in the pic there,picked two of them up-one for a friend,ran me like 160 Euros for the pair incl freight.

Apart from the in this case twin 6L6´s they´re rectified via a GZ-34/5AR4 and in turn sports a number of EF-86´s and an ECC-83.



They cater for various impedances outbound. Something set right there,at the one shortside wall.



As i got home after some well deserved RnR a number of amps were waiting for me,incl these two Bouyer amps. Took to taking them apart and checking them out...

So. 30 watts out of the pair of 6L6´s? Not exactly leaning on them is it? Now...notice that "power meter" there on the faceplate. Keep that one in mind...



Ok. So old PA amps. All well and dandy i guess. Much like their German made cousins the ST´s use symbols rather then text explaining what does what as far as inputs.



Seing my past with cars i have to go on record and say that the ST series amps are neat builds by ANY measure. More than can be said for French cars..i´ll tell you that much! Nah,these are well designed and layout amps,no two ways about it. Mark how "roomy" and spacious the chassis is. Overkill...
Please also note the mega difference in size between the powertransformer and output transformer.
Yep. Preamp and PI is PCB based. Not bad for an amp this age!



Uhu. The PCB. Sport all in all three EF-86´s and an ECC-83/12AX7. Put to good use i´d say. The small signal pentodes are all hooked up as triodes tho . French. Different is the name of the game here but...please read on.



Still a neat build...in fact,my hat´s off even. See that small transformer low and right in the pic? Uhu...these amps use an interstage transformer for PI. French. Different.



Powertubes. There´s what´s known as a zobel network in there to,i suppose,combat high freq oscillation. As for the need for that TODAY...is a whole different ballgame. None the less,well executed and performed. That small electrolythic capacitor across the powertubes cathode resistor should always be replaced. This particular one was dead as a doornail.



Uhu. The small interstage transformer. Does what it should i´d say!



The flipside of the PCB. As you can see it seems it was used for more than just the ST-30.



This in turn then the mains fuse. A setup we´ve run into before...where the fuse and voltage selector are one.

Hooooooooooooooooooooowever....i at the top there asked you to stay tuned. Well...hint one,this piece sports a downright plethora of primary taps rendering that it within reason can be run anywhere in the world. But...there´s WAY more to it than that.





Did i mention it´s French? Make no mistake..
Well. These amps were thought of as PA or Cinema amps right. Notice that there dial with the skull on it. By switching the dial next to it you opt for different taps. Most likely to me able to alter voltage between the amp and a projector at the time but the truth of the matter is that within reason...?
Kevin O Connor eat your heart out cause RIGHT THERE you´ve got sorts of a powerscaling setup. Of COURSE the tubes are gonna take a beating from it,but no matter that the dial in the pic lets you alter B+ voltage between approx 360VDC to 500VDC with modern day n era ECC wall voltage.
How´s that for size!



The flipside of the PT then,and its various taps. Notice the two unused ones on the secondary side? Well,that hands us approx 25VAC,in other words taps for fixed bias need be. (Amp is cathode bias stock)

So?
Yadda yadda,what´s so fantastic about it?

Well. Tell you what. From time to time there´s talk of bang for the buck here on GAB and...well,motherload. That simple. Motherload.
If you´re in the market for a dirt cheap amp that´ll cater to your basic rocknroll needs,this is it. Hands down.

What you need to do is a few things. First up check that the stock main smoothing caps are still alive and if not,replace. If in doubt,just replace.
Then you add a 1/4" jack inbound...and one outbound,for the speakers.
That´s it.

Turn the thing on,dime the SOB and stand back. This thing sounds even -80´s metal right off the bat as is. Turn it a tad down and you´re in bluesrock heaven. No BS.
This thing delivers there´s no tomorrow,as is. You don´t have to alter squat to make it run with the pack. It´ll even cater to soaring lead tones as is. Just use the volume knob on your guitar.

It´s to the point where i´ll go on record and state that one of these picked up at 50 Euros...there´s nothing out there that´ll touch it. No BS. This thing RAWKS right outta the hole.

That I AM gonna tear into it is just cause i´m a moron and can´t ever leave well enough alone,but that´s a whole different matter isn´t it.?
Those of ya into it for bang for the buck as far as rocknroll tho,look no further.
This really is it.

Digging the sound and the looks of this one! Id totally rock that, even with the french history of.. er.. reliability or lack thereof.

An interstage transformer for PI ? It the interstage transformer meant to do more than just boost the output signal to the speakers?

ajaxlepinski wrote:An interstage transformer for PI ? It the interstage transformer meant to do more than just boost the output signal to the speakers?

Some designs use PI transformers, usually high power or HIFI stuff.
http://www.hammondmfg.com/124.htm

Never had the pleasure myself though and I doubt I ever will

Hey! Never say never!
Interstage transformer PI amps are around..no two ways about that. True though that they are rarely used as guitaramps.
Buuut...look at the old Fender PS series for instance.

Ontopic of interstage transformer amps i´ve visited that before,Geloso used it frequently back in the day,and TBH it´s a setup that ain´t sans merit.
What it normally brings is a rather..."different" clarity when under distortion i believe it´s rare to run into otherwise.
Huh?
Yeah well,my previous experiences on the matter is that such amps are often harder to play as their practical presentation is different. In short amps so equipped are not for the novice player.

ajaxlepinski wrote:An interstage transformer for PI ? It the interstage transformer meant to do more than just boost the output signal to the speakers?

We normally see the phaseshift needed for a push/pull config amp handled by a tube. What´s done here instead,give it a few secs afterthought,is that we use a single end transformer to the same avail.

This brings a few things.
First up the secondary side gets a more..."natural" split in as much that we can tailor what goes on to a great extent. With a tube there really is no such thing as a completely balanced phaseinverter. Ain´t gonna happen. If a tube driven PI is used we can get to see balance at one volume/gain level just to see that balance go out the window at another. In fact,this is more the norm than anything.

This raises the reasonable Q if we at all WANT a balanced phaseinverter,and oftentime this is NOT the case when talking guitar amps. Just take a look at the schematic for a Dumble for instance,with its plate load trimmer and what not.

Using an interstage transformer though we get to tailor that whole deal way different. In essence we can tailor the transformer itself to carry properties a tube have a hard time handling.
Can a transformer be pushed into distortion?
Of course it can. This is oftentime a matter of saturing the core of the transformer and when this happens some REALLY interesting phenomena come into effect.
But..let´s leave it at that for the moment.

A transformer will have a different "eta" (efficiency) than a tube in the application. I guess that´s simple for all to understand.
We can opt to handle this in several ways,but ONE fact remains and that is that said transformer HAS to have some sort of driver and this driver is often...*drumroll*...a tube.

Now. To push signal through a transformer is something way different then for instance plot how load has an effect on a tube PI. Output impedance of a tube is often rather high as most such PIs are plate driven. That,in this instance,brings that the signal is easy to "kill". Lower output impedance in turn..quite the opposite.
Well,one advantage of a transformer is that we can basically tailor said transformer to any impedance we see fit and this WILL have a rather dramatic effect on powertube behavior as we start to push things.

Ok.
So does this mean that the transformer is not only about the transformer itself but about its driver tube too?
Yes. Yes it does. We see many different setups basically all over the map when using interstage transformers,and they all work. Just work different.

In the case of Gelosos so equipped for instance it is very common for this tube to be a 6V6. A tube that carries properties we surely can use ONE of being that it can push currents small signal tubes do not.
In the case of this Bouyer a small signal pentode is used,just setup as a triode by hooking its screen grid and plate as one.
Current vs amplitude then? Yes. Which is the better? Well,u tell me.

Ok?
So? What´s the better choice? Answer to that is...it is not. Using a given transformer with a given driver tube is simply something arrived on by choice of output properties.
That choice in turn is made by the designer.

From a practical POW though let it be known that interstage transformer PI amps DO carry a different behavior than their tube such counterpart.
Like stated above the x-former amps will be more "honest" in what they reproduce. Some players like that and take to it,others do not.
I guess it to an extent though could be summed up as "crap in=crap out".

Fascinating stuff!!! Thanks for the explanation.

What are the names of the European "ebays" that you're lookin at?

I'm interested!

Italian and German e-bay.
In turn Dutch "marktplaats"
French "Leboncoin" too.
Then there´s the Belgian 2ememain.be
And so on...

In the second to last picture, the one with the lighting bolt (I assume that means power)....the knob shows a sine wave at one end of travel, and I can't tell what's at the beginning...What does the sine wave mean? the other symbol?

Are there other brands I should look at?

Can you tell me what French or Italian words that I could put in the ebay/etc. search field?

[video]https://youtu.be/gvr1-HudkFk[/video]

that dirts up in a mean-assed way. i dig it! dispenses of any kind of tube softness, that's for sure

long standing member wrote:In the second to last picture, the one with the lighting bolt (I assume that means power)....the knob shows a sine wave at one end of travel, and I can't tell what's at the beginning...What does the sine wave mean? the other symbol?

Are there other brands I should look at?

Can you tell me what French or Italian words that I could put in the ebay/etc. search field?

Yep. The skull and lightning bolt means power. As i state in the vid one can alter voltages within,within reason,by turning that 8 way dial. Sine wave in turn just means that it alters AC voltage.

When searching for a Bouyer...just type that i guess. I picked two of these up as a pair on German e-bay recently and had them delivered while i was abroad for a while rendering that in the clip i´ve basically just had them both on the bench to check that they´re not lethal or dangerous. That aside...zip. Nothing has been done.
Hence the scattering sound,which i presume is from oxides and so forth (nope..hasn´t even been cleaned out)

Yes. There are several amps that i at least find worthy to look for,these Bouyer amps just being one brand. Issue with that is that not all were created equal.
I mention the Italian made Geloso amps,and they indeed ARE of top shelf quality however "newer" such won´t really roar until you reset them to.
In other words them amps are beyond the scope of this post. The Gelosos to look for if what you´re after is a cool amp that´ll roar to hearts content are the Gelosos made in the -40s and -50s. As old PA amps they are rarely busted beyond belief and most of them have lived their lives at a rather leasurily pace in one place.
Thus most of them work to this day.

However. ANY old tube amplifier WILL need work. Ie; replacing electrolythic caps at a minimum. Some will require diagnose as far as the occasional shot resistor,occasional worn out tube socket,switch or whatever.
That though are jobs i believe most any able bodied man can perform and if not it is cheap enough to have done by someone like me.
As that rate though that "50-100 Euro amp" has turned into a 150 or 200 one..and that kind of defeats the general idea doesn´t it.
Replacing the main smoothing caps tho,especially so with these old and simple circuits,anyone can do that knows how to swing a soldering iron IMO.
It ain´t rocket science exactly,and if one is apt enough to handle that...them Bouyers up there are TRUE contenders for most bang for the buck out there-here in Europe that is.
There´s an absolute abundance of such amps around that can be picked up for a song and change. Just be aware of WHICH is worth scoping for. These Bouyers are IMO prime candidates.
Replace smoothing caps and smaller e-lytes in general (in short replace all such caps),check integrity of wiring in general and if a 3 prong mains wire isn´t installed already do so.
Then drill two holes. One for an input jack and one for a speaker out jack.
Done.

In the US you have amps like Stromberg,Bogen,DuKane and so forth that basically comes to the same means and end. Some of them will sound da bomb with only fresh capacitance tossed at ´em,some will not.

Racing wrote:Yep. The skull and lightning bolt means power. As i state in the vid one can alter voltages within,within reason,by turning that 8 way dial. Sine wave in turn just means that it alters AC voltage.

That is BEYOND crazy!! A built in Variac? So one could brown out the voltage, like EVH used to do? And that feature is built in?????????

SHEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIITTTTTT!!

I really want to get a new toy, i.e., an old amp I can work on/restore/convert to guitar use. So, yeah, I would do all the work myself, no problem.

In the video, did you kick in a distortion pedal? It DID get rather wicked suddenly!

And who the hell is "MAX" amplifiers?

And what the hell! Is that MAX cabinet a 6 x 12?

long standing member wrote:
That is BEYOND crazy!! A built in Variac? So one could brown out the voltage, like EVH used to do? And that feature is built in?????????

SHEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIITTTTTT!!

I really want to get a new toy, i.e., an old amp I can work on/restore/convert to guitar use. So, yeah, I would do all the work myself, no problem.

In the video, did you kick in a distortion pedal? It DID get rather wicked suddenly!

And who the hell is "MAX" amplifiers?

And what the hell! Is that MAX cabinet a 6 x 12?

Nope. All used is the volume knob of the guitar. Distortion is all amp. In general i use one pedal and that is a T-Rex delay. Only "add on" when going live is a Line6 G-50 wireless.

MAX 40,incl the speaker cab known as "MAX 40 Devil".
To my knowledge the only tubeamp made for instrument use to come out of Denmark. This in 1965. I mod the living crap out of them and add a tube powered loop,they sound rather pitiful for modern day n era rock stock,as i´m half Danish and it simply feels good to tout that rig along when i gig.
Stock the cab sports some REALLY old "modular" Celestion AlNiCo´s but they´re way fragile and worth like a million so those have been replaced.
Cab is a 312 and two of them are British made Greenbacks and the third one out,which is switchable at the back,is an Eminence Cannabis Rex.
In the clip it´s Greenbacks only.

Hello. I am not good at electronics but i love the sound of these. I have one, but get very low volume out of it? And i have a phillips el6411 that also sound great but is low too. If these are built for cinema volume then what am i missing???