Melos GK-1+1 Preamp ... second call

[lorne]

Some years ago I asked if anyone was running the Melos GK-1+1 tube preamp ... or was familiar with these rare, idiosyncratic, preamps. A couple of guys came on board, and there were a few inquiries as well. I'm hoping some more fans have joined the few.

IMHO, the GK is a PITA, but you gotta love them for their amazing sound! I rebuilt and slightly modded the outboard PS. It runs so hot that I added a fairly large computer fan to keep it from boiling itself to death. WHWRRRRRR!! Many of them must have cooked-off and died by now! Some cement R's literally char the stock board! And according to some professional advice, I added a much huger heat sink to one device and devised some for others that originally had none.

Trolling through the web revealed no more info or comment on this unit than it did 3-5 years ago! That's a rare event in the annals of the exponential expansion of cyber space! I'm considering recapping the main board. And because ALL the documentation for all or nearly all Melos gear vanished years ago, we survivors need all the help and networking we can devise. Repair and rebuilding Melos gear can be a challenge. There are some parts such as some small diodes for which I simply cannot work up any data or specs. A pro would likely know what to use or substitute from just experience with familiar or similar circuits. I'm considering once again rebuilding the PS board — this time using point-to-point wiring.

Cheers ... Lorne

 

[chinacave]

Melos GK-1 Preamp

Well.... to resurrect an old thread -

I just bought one of these at the recent Mass October Franken-fest, and get the impression that while well regarded, these are not blessed with much information available.

It looks well-made, and having an outboard PS speaks of some certain attention to design and quality.

If anyone (Lorne?) has found anything, please pass it on! Like a schematic???

I gather that Melos was a pretty cottage industry outfit. The serial number is on a Dymo sticker (the crank telephone to the cellphone P-touch), Hot-melt glue is a prominent structure, and the vent holes in the PS were done quickly and free-hand on a drill press.

Pretty much all I have found via google is a pissing match over who had a hand in its design.

This one works, but has four small caps disconnected (lifted at one end) They are C20 A & B and C21 A & B. There is what looks like a HV delay relay on the main circuit board, and especially puzzling, a 1f cap that looks like the ones used to hold the time and pre-set settings on a radio - but on a tube pre-amp???!!

Again a schematic would really help.

Pix soon!

 

[lorne]

Hi chinacave:

OUT OF PRACTICE:
First off, I gotta say that I have not been doing much with audio recently. I have my files and projects stacked up after some brutal culling when we moved house a year ago. (OUCH!) I had to get more physically active once again — for reasons of health. And so instead of vintage audio, I took up vintage racing bicycles — rebuilding them and riding them for exercise. The forum men and women in that sphere are really great people — just like on AK! So much to be fascinated in — so little time.

So I am a bit out of touch, but here is what I have stuck in memory.

MELOS:

You are not way off the mark in describing Melos as a cottage industry. But, it was not quite that. Yes, it was a tad eccentric, yet as far as I can tell, they had a bunch of very competent people working who were galactic distance away from being just human robots with soldering pencils.

And we are really talking about the days before the computer was a standard office instrument. I have hand-written letters from the Melos founder that were handed on to me by the original owners of the amp.

A MANUAL — of sorts

I never did manage to find schematics for the GK-1 Melos. The documentation the defunct company left behind (presumably with the brokers) was auctioned off and was never heard of again — AFAIK. I remember thinking that I should leap in and bid. But my salary in those days was pretty low, and I had a failure of both imagination and courage.

Some time after Melos collapsed, some ex-employees put a service center together — somewhere in the Southwest I think. They serviced orphaned Melos gear for some time and then they too vanished. I remember reading that these technicians were restoring gear from memory. They too had no documentation but for the notes that they made as they did things.

Perhaps needless to say, a schematic was not provided with the sale of these things. There was a photocopy of a typed manual that described DIP switch settings for cartridge loading. Confused the hell outta me but I think I finally learned how to use it.

Also there was a simple, hand-drafted, plan-form diagram to show where the various tubes went. Melos installed tubes that were coated with something. An isotope? Here is where I have to consult buried, but neatly arranged files. Memory lapse ....

Also, Melos was very careful to point out in the quaintly typed doc that special French capacitors were very carefully selected.

WHAT YOU SAID ABOUT YOUR PS:

My power supply module came with nothing that looked hand done such as free hand drilling in the PS cooling provision. It came as a convincingly industrial production with a hardwired umbilical, power supply line to the amp. But, it was astonishingly under-engineered in terms of heat management. This was not a peculiar fault of my specific PS. When I showed some parts to the owner of a an electronics supply store that supplies the aviation and communications industry here, he went and got his calculator and then selected for me some heat sinks that dwarfed the originals. The PS module was cooking itself to death! The board was scorched and it was not a phenolic board!

So, from what you say, I do not think you have an original power supply. And if you do not have some flash caps in it, you must have someone"s rebuild remedy! (I did not use flash caps in my rebuild.)

In order to keep my new caps from rapidly deteriorating from heat, I installed a large fan — as mentioned in an older post above. Sometimes I forgot to engage the blower on start up, and I could smell stuff like glue and so on venting off gas. With the blower on, it runs like a charm — except for a bit of annoying noise that is fortunately not modulated.

My suggestion is to rebuild the PS on a big chassis. Use HUGE heat sinks. Use a couple of those little high-output but quiet fans that are available these days. Use some mesh screen to increase airflow. If there are small kids about they should never be allowed to get a hand inside this sucker. Elevate the diodes and resistors that heat up fiercely. DO point to point wiring. Do NOT use a board. Use caps that are rated for 105 or more. Don't even consider 85 degree types.

THE AMP ITSELF

This runs quite cool, although if it runs in a humid climate, some ventilation may still be a good thing. There are a number of electrolytic caps that should be replaced. And perhaps by now even a lot of the other types. ( I may be flamed for saying that — but that is my take on the subject.)

The switched gain controls that were used for gain and balance were a total PITA in this machine. Melos was very conscious of this, and replacements were supported by Melos Inc. My opinion ... the signal should be wired for optimum or flat. Perhaps balance could be attained by a passive attenuator box, but that introduces and whole other lists of possible "gremlins".

I am not gong to claim that this is the best preamp on the planet. But if you have one or encounter one needing a good home — then go for it. They are a very honest, open and true-to-life instrument. There is nothing of a bloated tubey sound. Some people might be convinced that they are listening to solid state. And they would be right because in its way it has a touch of the hybrid. — SS rectification for one thing. Depending on yer amp, you may never want another preamp. But you have to work hard to restore it and make it over so it will last another 30 or more years.

 

[chinacave]

Lorne -
Wow -

Thanks for the detailed reply!

I hope this thread might attract others with the Melos Pre-amps - there have to be more that just our two in existence....

Funny you should mention restoring & riding classic bikes - Here is a short photo saga of mine -

Wester Ross #023

Wester Ross Main site

Check out the video!

Again - Pix soon to kick-start this restoration / inquiry / historic documentation

 

[lorne]

I look forward to seeing all that comes out of your restoration — pics and all. Perhaps I should drag mine out and display my PS rebuild. I do plan to use the unit again in conjunction with a refurbished Dynaco ST-70.

Re: bikes — PM sent with my Email contact.

Cheers ... Lorne

 

[chinacave]

Melos GK1 Pre-amp

OK, so ONLY 10 months till I got to some pictures. Also have not listened to it at all since I checked that it worked when I bought it.

Lorne - there seem to be some differences between the one you describe & what I have found. But I see that this is a GK-1 and yours is a GK1+1. The PS IS point-to point, and there are 8 tubes rather than the 6 you noted in your post. They are all 6GK5's, Westinghouse brand, made in Japan, marked with a handsome star and the (?) date code of 92-12. I have not licked them yet to taste for uranium.

You MIGHT be able to see in the pictures that the coupling caps are 4.0uf / 400v "Electrocube", the smaller silver caps are a mix of "Mial" and "Diel" brand, and the massive on-board filtering caps are standard-looking "Marcom" 750uf / 330v and strange to me PC-mount aluminum cans of 6.0 and 3.0 uf - possibly SCR brand -marked : / K200 MKP / 250v~DB / HPFNT 25-85deg. C / 4-85 (date?)

The green squat cap in the lower left hand of the first pix is a 1.0F (one Farad) 5.5v unit - which I thought was used mostly for power back-up for settings on memory chips - but there ain't no memory chips or apparent settings here to save....... So they must have been using it for... what? Armageddon filtering or one leg of the filament voltage? Surely something innovative....

Its an intriguing mix of what looks like careful layout, good parts, and to my untrained eye (but I have studied many pre-amp schematics, ) an unusual topology - the apparent heavy filtering and the many silver (RIAA? trimmer) caps. At the same time the build quality is really uneven, the pre amp itself seems well built, but the gloopy glue holding the caps in and the pilot light and the power supply cable bushing into the pre makes me think that at least this one was finished late at night to meet a shipping deadline.

All, as I mentioned, only slightly informed speculation.

I suppose that one of these days I'll fire it up and check the voltages, and then at least draw a schematic of the PS, and if I get ambitious, the Pre itself.

Lorne - anything you have that you could find would be very interesting!

Pre-amp -

Power supply-

Power supply 2 -

Check out the Dymo serial number tape - My Grandad had one of those crazy hand label-makers.

 

[WhiteSE]

why were they designed to run so hot?

 

[chinacave]

GK-1 Power supply cover

As I mentioned above, the power supply seems to be slapped together - see the photos in the previous post and the cover vent holes below! I mean, use a drill press at least, or clamp it down a bit better! Oy!

Not complaining, the unit works!

 

[slimpikkins]

Nice unit, i had a GK1+1 (so i was told but it was labeled just GK1) years ago. It had a wider power supply about as wide as the pre amp. Great sounding with the Perreaux 2150b I had at that time I wished I never sold it. I may have some left over papers from that amp on file but I think I gave them to the guy I sold it to. If I didn't you would be welcome to them. There was one for sale a couple weeks ago on one of the sites. I was tempted but resisted.
Jim

 

[jaymanaa]

Man, that's a whole lot of lytics on the preamp board. Something is up with this design and I'd love to see a schematic.

 

[chinacave]

Man, that's a whole lot of lytics on the preamp board. Something is up with this design and I'd love to see a schematic.

- you and me and Lorne in Japan both! / er.. triple.


Am I right to suspect that all them lytics are additional B+ filtering?

Slimpikkins - if you have ANY literature / data it would be way more than I have, I would gladly pay for postage / copying!
Any hints for tracing out a schematic and not going insane?

Thanks.

 

[lorne]

Something is up with this design and I'd love to see a schematic.

They are all gone. Vanished. All the Melos docs went up for auctions many years ago. I remember thinking that I should bid on them, even if the sum were to have been a silly amount. I was predicting their later value. Someone did obtain them, and the whole lot vanished. This is the storey told as well as I can remember it with as much if not imperfect info as I have ever had of the matter. Someone may redrw them — or has done. The originals are lost. But who knows. Perhaps they will re-surface one day.

 

[lorne]

WhiteSE:

why were they designed to run so hot?

Well the answer should be — in regards to my version of the PS — they were not designed to run hot. Rather, they were flubbed, badly engineered. And they ran searingly hot — hot enough to char the non-phenolic boards!

I replaced heat-sinks with ones hugely larger than the originals on the advice of a technician. And I equipped the beast with a large fan. In the winter, I could partially heat the room with the unit.

Note well: Ian's version is an entirely different unit — as different as soup and nuts. I am very surprised.

When I get time, I hope to present pics and notes I made. As I have recorded earlier, I did rebuild my PS — almost entirely. The actual amp remains almost stock. It is packed away at the moment. I'd like to dig it out and play on this thread, but my workaday world is calling me to grind on making the Yen to pay the man.

Ian has offered an very interesting version that I was unaware of. And I am wondering if the PS was a redressed offering by the facility that opened up in the South West of the USA to service all the orphaned Melos equipment.. That facility is gone now, but back in the days it was staffed by some Melos employees who were left in a lurch when Melos failed. As stated earlier, no documents were available after they went to the receivers after bankruptcy — later to vanish after an auction. The new servicing/restoration company relied on the memories of former Melos people. I believe they produced informal drawings and notes that enabled them to work on circuits.

Cheers Melos fans and others ... hope to be back soon ... Lorne

 

[lorne]

chinacave:

As I mentioned above, the power supply seems to be slapped together - see the photos in the previous post and the cover vent holes below! I mean, use a drill press at least, or clamp it down a bit better! Oy

Yeah ... it makes me think that this did not come from the Melos factory. Besides my unit being totally different with two large squarish transformers on each end, it had a cover with neatly pressed out slots and a wrinkle paint finish. When I do dig it out and take some photos, you will be surprised at how different the to PS's are.

 

[chinacave]

Some possibly new info on Melos

Lorne - thanks again for updating - look forward to whatever you can find and might share!

Found a new company, made up of former Melos staff, who MIGHT be offering service & upgrades. I asked to be added to the contact list for this that they mention on the link below. Also would like (HA HA) a plexiglass faceplate for mine, as the one I bought is cracked:tears:


Melos Iteration - The Memory Player

 

[slimpikkins]

[QUOTE
Slimpikkins - if you have ANY literature / data it would be way more than I have, I would gladly pay for postage / copying!
Any hints for tracing out a schematic and not going insane?

Thanks.[/QUOTE]

Looked around today and no luck. I must have been diligent in giving all I had with the pre amp. Too bad there's not much info on Melos gear out there. Very nice sounding indeed, hope you can get it sorted out.
Jim

 

[chinacave]

Slimpikkins -

Hey thanks for checking!

I really appreciate it.

I did get a nice e-mail from Mark at the company noted above, he told me they would be offering upgrades / updates in about a year, and mentioned that he would be willing to offer tech support to product in the wild. He also mentioned that the GK-1 was one of, if not the first Melos product.

No faceplates, though!

 

[tubegear]

MELOS GK 1+1 PREAMP

I have a resistor that I am try to figure out its ohm's value. It looks like it could be 300 ohms or maybe 300k ohms. Is the larger brownish red one to the far right side of the power supply near the two diodes and where the transformer hooks up at the bottom right side of the board. Its in series with a smaller brownish red one.
These have no marking and when it burned all that is left is what looks like 3(0.
I found the style they are High voltage Bar Glass Glaze Film Resistors 3watt. Some kind of ceramic resistor. Pre amp has worked fine for years. It was still putting out sound but at a much lower gain. This resistor feeds the lower power transistor it is ice cool because of the open resistor that feeds it power.
Hope you can help.

THANKS

Craig

 

[lorne]

MELOS GK 1+1 PREAMP ... I have a resistor that I am try to figure out its ohm's value. SNIP>>>>>>>

My Melos is buried under piles and piles. But I'll try to find my notebook. I think that I made a parts list and some drawings. I replaced all the R's with much larger ones and I raised them off the board. Get get back to you later and if I forget, PM me. ... Lorne

 

[chinacave]

Hi Craig

I actually have mine playing in my system, so I can check my power supply in the next day or so- a picture of yours indicating the resistor in question would help. Also my power supply is a different versian than Lorne's, its point to point, not on a cuircut board