Need some help with a valve amp guys :)

[thepsy3ntist]

Hey everyone im new to this site and the world of valve amplifiers. Iv worked in modern electronics for a few years and have aquired a slight obsession with owning a decent vintage sounding amp so iv just bought a valve amplifier off ebay that came out of a Hammond E 100 as a project to recase and make in to a small peice of art i think it uses 2 6V6's in the output stage from what i can see on the picture as its not arived yet. just wondered if anyone knew anything about these amps as i can find very little online or if anyone had a good schmatic for me to build a good vintage sounding amp from the parts in this amp any info would be of great help eg estimated wattage, thanks guys

heres a picture

[Chuck H]

I don't have personal experience with that amp. But the tube compliment is good for a guitar amp and the transformers should be great... They're Hammond.

Along with any circuit changes you make, you can count on replacing every electrolytic cap in the amp. If you have access to a tube tester you could test the tubes it ships with to minimize replacements.

Unless you have your heart set on a particular amp you can probably get by with minimal circuit changes and skip a major rework. Many of those amps sound good for guitar as they come.

I found some schematics here. Your specific model may be on the amp when you recieve it. Then you can download the schem.

Hammond E 100-series schematics

Chuck

[thepsy3ntist]

Thanks Chuck thats what i wanted to hear.

I dont have my heart set on any specific design I just want to learn about valves and rescue what is someone elses vintage junk from the scrap yard and gain myself a beauty of an amp

I cant wait to get stuck in to this project. Thanks for the advice on the electrolytics (makes sense) and Thanks for hunting the schematics down.

You have any idea what the power output of this amp maybe from the Valves used?

[Chuck H]

It's hard to say exactly what the wattage will be. I can't look at a schem because the site doesn't seem to be working today but based on the 2x6v6 tubes probably fifteen to eighteen watts or so.

You have what appears to be an enormous power transformer, a very large output transformer and a third transformer that could be a choke or possibly a reverb drive transformer. I'm guessing it's a reverb transformer. So you may need to get a spring tank and you'll have reverb on this model Also, the amp may have been hooked to a field coil speaker in it's original console. That would mean some work in the power supply. But nothing too tricky. These old organ amps make excellent guitar amps.

It's hard to make out the exact tube compliment but it looks like a pair of 6v6's, a rectifier tube and a bunch of 9 pin noval sockets. I doubt you'll be using all the preamp tubes. Maybe four if you have a reverb and decide to use it.

I'll know more when the schematic site gets back up.

The only trouble I ever have with these sorts of builds is, if I'm making drastic changes to the circuit and I change the layout I end up with a bunch of unused holes in an odd shaped chassis. Aesthetically unpleasant if your the festideous type. If your handy with cutting holes in metal you always have the option of raping the console unit for parts (trannies, sockets, pots, tubes, etc.) and start from scratch. But IMHE it's easiest to make a cabinet and faceplate for the existing chassis and just don't look at the extra holes in the back.

Chuck

[tubeswell]

just wondered if ... anyone had a good schmatic for me to build a good vintage sounding amp from the parts in this amp

Try one or more of these places for vintage amp schematics. The Hoffman site is full of other handy stuff. Merlin b's Valve Wizard site is a pretty good introduction to tube gueetar amps too

The Fender Amp Field Guide

Schematic Heaven. Where All Good Amp & Effect Designs Await Resurrection...

http://www.el34world.com/charts/Diagrams.htm

How to design valve guitar amplifiers

[thepsy3ntist]

Thanks guys. fifteen to eighteen watts is reasonable for my first valve amp project recon

Iv just bought another amp that uses 4 ECL82 valves in the output stage, an ECC83 and a EZ81 rectifier. All valves are vintage Mullards but it looks in bad way lol Seems to be addictive this valve amp stuff looks to have substantial transformers tho but to be quite honest i have no idea on the output this will have. Ahh well good times and lots to learn

Thanks again guys. finally found somewhere that people know what they are on about

[Chuck H]

Hey,

I just looked at an E100 schem and that third transformer with the two tubes next to it IS a reverb transformer. But it's a push pull transformer. The reverb has it's own power amp!!! This can be very cool if your into overdrive tones because you can drive the reverb pan with the dry signal power amp output, and then send the pan output to the reverb amp. No garbled reverb for you. If you've never heard one like this, it's the best pan reverb you can have. It requires it's own speaker. But it's worth it.

All those other 9 pin sockets are for the organ preamp and the percussion preamp. So it's basically two independant channels with an extra complete amp built in just for the reverb. How about one Marshall channel and one Fender channel in a solid wood cab using one 12" for the main amp and an 8" for the independant reverb? The whole thing would fit into a cab about the size of a Deluxe Reverb too. Lot's of options. I gotta find one of those.

Chuck

[thepsy3ntist]

Looks like i got myself a bargin here Is that the same as spring reverb? sorry if im all questions just new to this world lol lot more exciting than solid state anyway thats for sure.

Have you been looking at the schematics that you posted on here?

Looking forward to revamping this now Thanks for all your suggestions and advice. muchly appreciated

[thepsy3ntist]

Amp finally showed up today.. are Hammond 7591 the same as 6V6 valves? because thats whats in it at the minute. can see what you meant about the caps. most of them are cardboard like the inside of a toilet roll lol. Just need the schematics site to come back online now Think your right about keeping it in the same chasis. Im going to make a template up and cut a sheet of aluminium to fit over the transformers valves and caps to make it look smart then build a cab like u said chuck. Need to find out whats what on the connections now and get it fired up

[Chuck H]

Yes, it's a spring reverb. You'll need to get a reverb pan. A standard Fender type reverb is integral with the amps circuit. As if it were in an effects loop. When you push a Fender amp into over drive the reverb, and the dry signal, can become garbled because the phase inverter and power tubes are distorting everything together. But with your amp the reverb has it's own seperate power amplifier. That means you can drive the reverb pan (spring tank) with a voltage divider from the main amps power tubes and then re amplify the pan signal through it's own amplifier. Like I said before, you'll need a seperate speaker to do this. But it's a superior system that sounds much better.

7591 tubes were in the schem I saw too. IMHO they are a better tube for guitar amps than the 6V6. You can expect about 25 or 30 watts with a pair. There are current re-issues of that tube. Otherwise they are rare and expensive purchaced NOS. I don't know about the quality of the re-issue tubes. Worst case, if you decide against the 7591 tubes, you can rewire the sockets and bias circuit for a different, more common power tube.

One more note. If anyone following this thread can comment. The output transformer uses a center tapped SECONDARY?!? I haven't seen this arrangement before and I'm not sure why it's done this way or if this should be changed to idealize for a guitar amp.

Chuck

[techineer]

A 'center tapped' secondary on an output transformer may be used for the purpose of accommodating multiple values of speaker impedance.... a 4 ohm load would use half of the secondary, while an 8 ohm load would use the full secondary.

[Bruce / Mission Amps]

A 'center tapped' secondary on an output transformer may be used for the purpose of accommodating multiple values of speaker impedance.... a 4 ohm load would use half of the secondary, while an 8 ohm load would use the full secondary.

I don't think "Center Tapped' is really the correct description.
I didn't think the 4 to 8 ohm tap is in the center....
I'm not the magnetics guru here though so maybe someone with creds can verify this.

[techineer]

I don't think "Center Tapped' is really the correct description.
I didn't think the 4 to 8 ohm tap is in the center....
I'm not the magnetics guru here though so maybe someone with creds can verify this.

Agreed.... you'll note that I put 'center tapped' in single quotes. A better term would be multi-tapped secondary. However, in his case, I believe the 4 ohm tap would be in the center, so 'center tap' would also be applicable.

[Chuck H]

My bad for starting the discussion with the term 'center tapped'. But I am glad for the explaination. It's actually pretty obvious if I had considered it longer. And opens up some interesting possibilities should the need ever come up to run two different speaker loads simultaneously.

Chuck

[techineer]

And opens up some interesting possibilities should the need ever come up to run two different speaker loads simultaneously.

Chuck

You cannot run two different speaker loads simultaneously on a multi-tapped output transformer. It's either/or. You can put a 4 ohm load on the 4 ohm tap OR and 8 ohm load on the 8 ohm tap. Not both. (Or at least not without significantly reduced power output and distortion.)