[stehei]

Dear all,

I'm a newbie to this forum, at forehand, I'm from the netherlands,
so please excuse my poor language since I'm not a native English speaker.

1,5 years ago I was on the lookout for a tube preamp and found a
very unusual preamp of a brand I've never heard before of in the
Netherlands: Audio Reference. After some research we went to the second hand shop
where it was located, and found a preampt with an external power
supply, but could not get it to work. We bought the unit as is for
50 euro, and went home to investigate.

When we opened the unit it turned out we had mistaken the
volume and balance control since someone had changed the
pot-meters. But a lot more was changed. The amp was heavily
mutilated, changed, adapted, you pick the words. The attached
pictures show what was done to the amp.

However, it did work. And sounded rather good, for as far as we
could determine. But the external power supply got dangerously
hot, and when determining some voltages we got some very strange
readings.

We contacted roger at ram-labs, and he sent us the schematics,
wondering how anybody could destroy an amp this beautiful, and
after a while we went to work in restoring this amp.

We are almost done in getting the amp in the original state, on its
own power supply etc. But we have one problem we could use your
help. Not only the top, bot also the bottom was heavily modificated.
Signal paths have been cut, new one built etc.

My question is, is there anybody owning this amp who would be willing
top open his unit up and take a picture of how the print layout looks from
the bottom. This would help us tremendously in checking if all the
paths are back to original. Just to make sure,

Any help would be highly appreciated

The top


and what they did to the bottom


kind regards

stefan

[Goosepond]

Stefan,

I just sent you a PM.

Gene

[rbwalt]

it sort of looks like a MR. i use to have a RM5MK2. can you take a pic of the front and rear. roger's main boards were green.

[Goosepond]

I took pics of my RM-5 MkIII for Stefan and noticed how different mine looks from his. 

Gene

[Ericus Rex]

It's definitely an RM5 but most of the internal wiring has been altered and the phono section has been heavily 'modified'.  Also looks like the gain DIP switches have been nixed altogether.  My board was cream colored just like Stefan's.

You can also Google Image "Music reference RM5" and a couple of internal pics come up there too.

Best of luck with the rebuild!  It's a great sounding preamp...when not mutilated.

[rbwalt]

roger ever See's this he will no doubt poop in his pants. it is a later version. roger did away with the gain switches and i believe started hard wiring the jacks directly to the board. think there are really two choices now. see if roger has a board for it or put it out to the curb and get something else. the bloody thing is a mess!!!!!!!!!!!!!!!!!!! to bad.

yea a decent sounding Prue in its day.reliable as hell. never had a issue with mine except tubes from time to time and i did have to install the input jack support bracket for it. think i had mine for over 15 yrs and 11 or 12 for my RM9mk2.

[Goosepond]

Well, here is the pic of my RM-5 MkIII I sent to Stefan:



Gene

[rbwalt]

yep that be the one. yea my board might have been that color. i got rid of mine over 4 yrs ago. roger at MR got it and sold it right away.

what a hatchet job on the other one. so sad. well i hope he gets things sorted out.

brings back memories.

thanks.

[Ericus Rex]

Well, here is the pic of my RM-5 MkIII I sent to Stefan:



Gene

Yep, that's exactly what mine looked like too.  I sure hope Stefan can bring his back to spec.  $50 for it was a pretty great deal, even in such terrible shape.

[stehei]

Hello All,

thanks for the help and the moral support. Gene sent me great pictures we
can use for the rebuild. We started getting rid of the mess step by step, all
kind of parts were disconnected, etc, getting that into place again. The
external powersupply which bypassed the original is gone, including all
the changes that were made. It's a
lot of work, but with the schematics, the pictures and the experience of
my nephew (when he was 8 he already repaired color-tv's, no wonder he
became an engineer) I hope we can pull it of. Here is a snapshot at where
we are.



Any thoughts about the sound of the original pre-amp? Musical Reference is
a pretty unknown brand in Europe, in what kind of category can one rate it?

thanks all, warm regards

stefan

[rbwalt]

glad to hear that you are on the way to cleaning up a big mess. in its day it was a good pre. better than most with MR reliability. as far as sound quality it was good considering its price point. it was not the most dynamic nor open sounding pre i have heard. think it had a touch of grain to it. out of 10 i would give it today a 7.5. enjoyable and a bit relaxed with a decent soundstage.

when that pre came out it sold for 1250.00 here in the states. roger made a few changes to it but nothing earth shattering. all i can say is get it back to or as close to normal and let us know what you think. it has been over 10 yrs since it was in my system.

enjoy!

[Roger A. Modjeski]

Congratulations on the restoration.  When I see extensive mods like were done to this preamp by some unknown person I wonder why they just didn't build a preamp from scratch rather than make a mess of something that was carefully done. From the pictures of the restoration I am not able to see the 6 small cathode bypass capacitors that go with each tube (2 per tube). They sit very close to the tube itself. We built the preamp both ways and I prefer the cathode bypasses which are 1000 uF/6.3 volts, the value is not critical.

I note also a lot of polystyrene caps in the RIAA EQ area. Those need to be within 1% of the values listed on the schematic (0.23 and 0.68 uF) to make the EQ accurate which it is to 0.1 dB. We tested each unit for EQ accuracy before it left the factory and I test EQ on any preamp that comes here, which they rarely do even at the age of 30 years now. I have not found any that need to be "recapped". The Nichicon electrolytics I used have proven to be excellent sounding and extremely l long lived. I'm not sure caps made today will last as long.

As to the sound in its day and it's place in today's sound; if I were to make another 3 tube preamp there would be no changes in the circuitry. There aren't any changes to make.  The preamp has 3 simple and identical gain stages with passive RIAA between the two phono stages. Really, what better can one do with 3 tubes? Perhaps the RM-1 sounded better. It has the same architecture except that in the RM-1 there are 3 tubes per gain stage with feedback and a servo on each gain stage. When I built the RM-5 I decided to make each gain stage a single tube and thus reduce the price and complexity by more than a factor of 3.  I will say that whenever an RM-1 comes across my bench I am still amazed at what it can do. It just took a lot of parts to do it.

Today's preamps have different requirements. I am working on a new one that will have remote volume and input selection, balanced and unbalanced (single ended) outputs and 3 RCA and 1 XLR fully balanced inputs. It will of course have more tubes to do all that. It may be a year before that is available because the OTL amps are on my bench now and the RM-300 is coming along next.