Anybody know about Bogen Tube Amps?

I just got a bogen K10 for free - tested it - works 100%. I notice there is a socketed transformer for the mic input, and that the input goes directly into a 6AU6. Then there is the a phono input, and it goes on to some EQ presets and the amp stage which consists of 2 6AQ5 tubes.

Any chance this will be useful as a mic pre? It would probably be easy to pinch the output before that final stage. The tubes are all american in there - nothing too special, but I do have a nice amperex 12AX7 that has been looking for a home.

Another thing I notice about this guy is that the mic input is reversed - ie, the input is male not female. Was that common for these amps? Seems weird to me.

In the old days mic inputs were often a male XLR; this was before they discovered the mic cable could be extended if a male and female were used on the cable and a female XLR for the mic input.

I wouldn't get to excited about using this as any kind of high quality mic preamp. Bogen gear was generally designed for cheap paging amp applications, not studio quality audio. The transformers were often anything but close to flat across the audio band.

Call Sid Harman. He used to work for Bogen. I'm sure he would be delighted to converse with you.

(insert here sound of brush clearance chipper in action...)

[quote author="BYacey"]Bogen gear was generally designed for cheap paging amp applications, not studio quality audio.[/quote]
But Bogen also made high quality equipment, so it could be either. But with 6AQ5 outputs perhaps it isn't in this case...

Best regards,

Mikkel C. Simonsen

ok, thats not the most inspiring set of posts, but it gives me a sense of what this thing is good for. Maybe its just destined to get sold on ebay to a harmonica player or something - or talkback overkill.

I've got a Bogen amp I use as a mic pre. It sounds great on a guitar amp with a shure 315 ribbon. Flat, schmat. It sounds cool.
I'm pretty sure you saw it when you were here. It's not the same as what you have-- it has two 12ax7s (GE and Telefunken). My advice is try it out and use your ears. I'm sure it'll be useful for something.

> the input goes directly into a 6AU6.

Input overload is on the order of 30mV. Most modern recording work runs MUCH hotter.

> It would probably be easy to pinch the output before that final stage.

No. Everything inside is 100K impedance.

Run a guitar direct to the input tube grid and hang a speaker off the end. These bogen power stages were respectable; their mike stages were totally low-buck and barely adequate for school announce systems.

I used to have a Bogen, it used a some kind of AU7 and two 6GW8's. Anyways, it was not that useful for mic inputs, but as an electric guitar amp, it was pretty raunchy with all the knobs on '10'. The output tube plates glow a pretty bright orange when you're doing this, so tube life might be a tad short....

I have never seen any Bogen gear that would be classed as "Professional or Semi pro" equipment. Bogen is and has been generally paging, 25V / 70V used for background music or institutional paging. Not many professional audio facilities boast of using Bogen for recording or live sound. That isn't to say that you couldn't modify a tube model to provide decent audio performance. As I mentioned, the transformers are generally lowest of low quality, so replacing with a decent transformer (if required for your application) is a good starting point. The Bogen transistor stuff I wouldn't even bother looking at.

I guess in a nutshell, you might be further ahead to build the stages you need from scratch than trying to modify something into what it was never meant to be.

Look at it this way; somebody gave you a tough chassis, some sockets and a power transformer for free. Put in some new filter caps and build something you like. Maybe even a guitar amp, which would let you use the output iron.

Peace,
Paul

Paul is right. You can't go too far wrong with the power supply and chassis, but I would question if the output trnasformer would have enough "beef" for a guitar amp application. These were typically meant to have a frequency response of 100 to 15K.

> I would question if the output trnasformer would have enough "beef" for a guitar amp application. These were typically meant to have a frequency response of 100 to 15K.

Even the low-price Bogens were flat better than 50-15KC, and all the push-pull tubers had power bandwidth down to 50Hz or lower. In fact some of the Bogen PA amps may be "too good" for guitar-amp.

Have a look at a K10:



That output iron is not really smaller, per watt, than my Fisher 20W/ch amp, which is a kick-butt HiFi and mighty darn heavy.

I suspect a Fender push-pull 10 Watt (if there were one) would have half as much iron.

And dig the crazy 500Ω output! This bad boy could drive a passive EQ hard enough to melt the chokes!

BTW: the "phono" input is almost certainly not for a magnetic cartridge, but the old ceramic needles. It is in fact a line input, but with extra-high impedance.

That's not a bad 20 w.

I used a 6CA7 version for a guitar amp but the pwr transformer started smoking. Then it shorted out. I launched it over the frat house balcony (it stunk to high heaven, I think they used refinery sludge as varnish) and grabbed the ol Fender out of the trunk.

I don't think the Bogen liked the times 10 preamp that was stock in the B.C Rich Seagulls back then!

You are talking Old, old Bogen. I stand somewhat corrected. The stuff I have had experience with was the Bogen / Lear-Siegler stuff. Nothing to really write home about. Today's Bogen, even less to talk about.

[quote author="BYacey"]I have never seen any Bogen gear that would be classed as "Professional or Semi pro" equipment. Bogen is and has been generally paging, 25V / 70V used for background music or institutional paging.[/quote]
Bogen also made high-quality hifi amps if you didn't know. Not pro audio, but still a lot better than paging and background music...

Best regards,

Mikkel C. Simonsen