Organ amp project

[sweet]

I was wandering if these amps make good projects. I am a beginner in building so I want to work with something that is already there to get my "Feet Wet".
This came out of an Organ. The only thing I know is that it came from an Allen organ dual input single output and uses 6550 output tubes. I am assuming this would be mono and I would need two to make it a stereo and a preamp.
can anyone help me out here.
Thanks Steve

[EC8010]

It might well be quite a good amplifier. Since organs deliberately produce full power sine waves at low frequencies, the output transformer is probably quite good at LF. It might not be so good at HF. Finding another organ amplifier to make a stereo pair will be hard. Still,it would make an excellent learning project.

[DigitalJunkie]

Or maybe it could make a nice subwoofer amp. (if indeed the LF response is suitable.) P-P 6550's should make a fair amount of power.

[sweet]

I do believe this amp is 90 watts.

[Enzo]

Allen organs tend to be upscale and very high quality. Overbuilt things even. Though they make home units, their main business is in church sound systems. That should be a pretty nice hunk of gear there. Don't know just how hifi it is, but it should be well built.

[audiousername]

As stated before, some organ amps can have problems with high frequencies. Paul Cambie has written an article here about his resotration of an organ amp, and he found the open loop gain down 3dB at 5kHz.

[sweet]

Originally posted by audiousername
As stated before, some organ amps can have problems with high frequencies. Paul Cambie has written an article here about his resotration of an organ amp, and he found the open loop gain down 3dB at 5kHz.

Interesting read, what it has done for me is raise my level of excitement. This is what I've been wanting to do since I got bite by the tube bug. I'm not an electrical engineer so I want to learn how to build one and what better way than to learn by modifiying a well built amp but not quite up to par. I will have to get the schematics. From reading in this forum I am assuming that at 90 watts this must be other than a class "A" and that means distortion. Am I correct? If this is true, will I be able to compensate or couold it be turned into a class "A".
Thanks in advance for everyones help and recommendations.
Thanks Steve

[Stocker]

Class A
per se
will not always
make your day!



but it will
keep you warm
in winter.

Seriously, if it's got the frequency extension the amplifier on the linked page has after modification... have a listen, see if you like it. Save a few hundred dollars on electricity.

[Original Burnedfingers]

I picked up (4)Wurlitzer organ amps. Two gave they lives for other projects and two are living happily ever after. They do not suffer from high frequency loss and have a very nice low end. They use a 6SN7 as input and driver, driving a pair of 6L6GC's with a 5U4 rectumfier tube.

[rcavictim]

I have a matched pair of unmolested vintage Northern Electric P-P 6L6 monoblock amps with 5U4 rectifier. I understand that they came out of a church organ installation. They have an input Z of about 12K and need a bit of drive as the mu-metal shielded input transformer is the phase splitter output tube driver xfmer. I was able to drive them adequately with my stock Mitsubishi SS stereo preamp and was very, very impressed with the HI-Fi sound quality. I was considering making a stereo preamp which could take normal SE line input, provide a volume control and pass a low-Z drive signal to each amp's input xfmer. I was thinking a single 6SN7 for each channel to provide a bit of voltage gain and cathode follower to drive the cable run. These amps have huge 25Hz power xfmers which barely get warm and use a PSU choke (way oversized, a good thing, for 60 Hz service). This is a good someday project. I was planning to dress them nicely in hardwood bases.