Reußenzehn Guitar Preamp Mk.2

[ruepselrum]

Can anybody provide the schematic mentioned above, preferably the stereo version?

Thanks Sascha

[nickb]

Best to ask Herr Reußenzehn, I think.


But this creation of his is awesome!

[ruepselrum]

That's what I did at first but Herr Reußenzehn replied that the amp was out of production for about 30 years and he can't provide any information.

[nickb]

That's what I did at first but Herr Reußenzehn replied that the amp was out of production for about 30 years and he can't provide any information.

Schade. Well kudos to you for trying. Do you have any pictures, particularly the inside? I'm wondering how hard it might be to draw a schematic from looking at it.

Are you having a particular problem with it?

[ruepselrum]

I'll post some pictures during next week, gonna try to get some sharp ones!
If you have an eye for craftsmanship, you'll like it!
There are no particular issues with it. After some years of rest I had to replace the broken plastic footswich jack and probably I have to clean the tube sockets. Yesterday I played the preamp through my Marshall JCM800 2210 power amp, and it worked perfectly, no hum, no noise, no scratch.
...but the original idea for reactivating the preamp was to connect it to the power amp of a Peavey Bass Mark IV in order to have some sort of combined bass/guitar setup but this doesn't work at all. In any possible way of connection the two amps a big hum occurs. The guitar sounds weak and crappy, especially set to British channel. After all it 's better to connect the guitar straight into the bass amp.
As mentioned before everything is and sounds fine when connected to the Marshall power amp, epecially the California channel sounds way better than the Marshall's normal channel, therefore I was thinking about incorporating some values of the Reußenzehn into the 2210.
A schematic would be very handy to do so! Although I think it isn't too heavy to figure out and to draw, I would have appreciated if somebody else had done it before...

[Helmholtz]

Can anybody provide the schematic mentioned above, preferably the stereo version?

Thanks Sascha

Here R10.pdf

is a circuit dating from my shop days in the 80s. Model unknown.
Hope this helps somewhat.

[ruepselrum]

Thanks for the schematic!!!

Even though it's not exactly the same, it's a good starting point and I can concentrate on dfferences. Two o them I could find at first glance. The Mk. 2 has 4 12AX7 instead of 3 in the schematic and a common insert but the tone stack/controls look pretty much the same. I'll figure it out.

[ruepselrum]

Here are some pictures of the preamp.

[ruepselrum]

Recently I figured out the actual schematic of the Reußenzehn preamp and after 5-6 attempts of drawing I got a presentable version, which I want share.



I'd say nothing really new, one Fender-style channel and the other one Marshallesque with customized part values, but it sounds really good. Nothing to complain about.

There are only two things that I'm wondering about. The missing grid leak resistors of input tubes V1A/V2A and output tubes V1B/V3B and the shared cathode wiring (RC) of V1B/V3B.
What is it good for?

[nickb]

Well done on the drawing!


The assumption with the missing grid leaks is that the source ( guitar or FX loop return) has a DC path to ground. I think this is a really bad assumption. Pedals quite often are AC coupled both in and out.


There nothing wrong with the commoned cathodes so long at the bypass cap has a low impedance at all frequencies of interest. Especially as both sections have essentially the the same signal. Eve if the cap were to fail completely all that would happen is you'd loose some gain and get a bit of crosstalk between channels.

[ruepselrum]

To get it clear, is it advisable to install three grid leak resistors from jacks to ground? What about their values, mostly they are 1M, but after all some resistors in this unit seem to be a little smaller than usuall?
Could/should an anti hiss cap be inserted from grids to ground? I recently read something about it, but I'm not sure if it is really useful?

As for the shared cathode wiring, is it just as good as seperated cathodes but saves two components, soldering joints and space?

[nickb]

Well, it has been working for years so my inclination is to do as little as possible. Add 1M resistors across the two return jacks and the input jack and leave it at that. Yes, the commoned components are just for cost/space saving.

[ruepselrum]

I'll do that.

Thanks a lot!