RGR (Grodinksy Research) Model 5 amplifier

Discussion in 'Solid State' started by cdfac, Oct 22, 2012.

  1. cdfac

    cdfac AK Subscriber Subscriber

    Anyone ever serviced or rebuilt one of these? I'm taking a nice one in trade and plan to give it a work-over (hopefully just new caps). Would appreciate any tips or things to look out for, but I know it might be a long shot as these weren't terribly common. I know that there is no S.M. or schematic readily available.

  2. Robie

    Robie Live it or live with it. Subscriber

    AK Member JohnVF has one and thinks very highly of it as I recall. He had the matching preamp as well.
  3. 240sx4u

    240sx4u AK Subscriber Subscriber

    Bob, that's definitely Johns amp. :)
  4. JohnVF

    JohnVF Banned

    I should take cleaner pictures if they're going public :). Yep, that's my amp. For a few more days anyway...it's been quite the workhorse here over the last 5 years.
  5. 240sx4u

    240sx4u AK Subscriber Subscriber

    The apogee contraption tipped me off.
  6. cdfac

    cdfac AK Subscriber Subscriber

    not a bad pic at all, John! gives me a good idea what i'm working with. if you want, though, you can delete the pic from your folder and it will just disappear -- i suppose i could have gotten clearance first!

    at any rate, i'm excited, the internet chatter on this guy is all positive. i'm hoping it will sound something like a Yamaha M-4, but with more oomph in the bass on difficult loads and somewhat better dynamics in general. definitely going to miss the Accuphase, though! someday, i'd really like to track down a P-266 amp, which is a bit of an upgrade on the amp section in the E-303X.
  7. 2chanman

    2chanman Well-Known Member

    cdfac: I own one of the RGR model 5 amplifiers, along with the matching preamplifier. If the amplifier is working presently, I strongly advise you to avoid getting into it, as you are sure to regret doing so. This amplifier is excruciatingly difficult to work on. First, there is absolutely NO service information or support available. There are NO component designations on the circuit boards. Each amplifier circuit board was individually tweaked by the manufacturer's technicians. In other words, they are NOT identical to each other. MAJOR chassis disassembly is required to get at the soldered side of the circuit boards as they are totally inaccessible without doing so. The output stage is merely Quasi-Complementary (NO PNP output transistors) and clips assymmetrically when over driven. Individual transistors in some instances are soldered to each other's leads, rather than being individually mounted on the circuit boards.
    Incredibly, the thermal contact between the output transistor heat sink and the bias transistor is through pieces of DUCT TAPE wrapped around the bias transistor collector tab resting against the heat sink! Offset adjustment is ridiculously sensitive. I have never seen or worked on such a shoddy design as the RGR model 5 in my entire 59 year career as an electronics technician.

    In spite of these major shortcomings, this is a very good sounding amplifier. Keeping it operational, however, can be a major hassle. Mine has failed 4 times.
    The matching preamplifier is built to a higher standard of quality than the amplifier, but is an unimpressive performer sonically.
  8. cdfac

    cdfac AK Subscriber Subscriber

    yay, a ringing endorsement! :banana: ;)

    well, someone's got to dig in, or something will fail before too long (already close to 30 years old now). i doubt you'd have had much fun in my Accuphase either, even with your vastly greater experience. no SM or schematic or parts values there, major disassembly, and much tighter quarters. but perserverance pays off, as you know. i'm not sure how many years John has had this one, but i don't think he's had any issues yet, so i'm thinking this one got built on a Tuesday! yeah, the duct tape is a little scary (i think i might be able to see some in this photo).*

    if you can offer any other tips, either about parts or disassembly, i'd love to hear them. from what i can tell only by looking at the photos, the rear board (protection and whatnot?) should fold down pretty easily once the screws are removed. the main boards have plastic holders and a couple screws, and they also look like they will fold down, since all of the wiring seems to have slack (something sorely lacking in my/John's Accuphase). removing the main caps first should give the boards more room to flop down, and if i don't have to remove them or the heatsink completely to get enough access to the PCB bottom, then i'm a very happy guy.

    EDIT 10/31: Upon inspecting the amp at my place yesterday, I don't see any duct tape, and IMHO the assembly is actually very good in this amp.

    Last edited: Oct 31, 2012
  9. 2chanman

    2chanman Well-Known Member


    All of the failures in my model 5 were semiconductors. I have replaced only one capacitor, and it failed because one of the silicon rectifiers in the power supply shorted and applied raw AC to it. I don't believe in wholesale "recapping" of electronic gear. It is one of the silliest misconceptions extant in audio. I have seen far more equipment ruined or seriously damaged than "saved" by "recapping". More often than not, new problems are introduced by the procedure.

    I think you would be wise to listen to the amplifier before you invest money and effort into it. You may not like the way it sounds. I would fuse any speaker systems you connect to it. Also, I would check the offset voltage at the output and let the amplifier run powered up for several hours with no load and check the heat sink fin temperatures periodically. They should stay close to ambient. Then hook speakers to it and give it a listen. If you have any specific questions, I will try to answer them.
    Good Luck!
  10. JohnVF

    JohnVF Banned

    Wow. or..Yikes?

    All I can say is that I've had this amp for nearly 5 years IIRC, and have never had a problem with it, except one of the RCA connectors came loose and it just needed tightened. Unlike most gear that I have, it was actually in use for a long time instead of just on the merrgy-go-round of gear here. I last ran it about a month ago, and it was again fine. If has been consistently a better sounding amp, at least with the preamps that I use, than most other solid state entries here, including a highly regarded Sony VFet amp that really doesn't hold a candle to it.

    I agree on the preamp. It's just a bad sounding unit. I think I used it maybe two evenings at most. I ran this with, at first, an Audire Legato and at times a Fisher 400, then most recently a Klyne 6L. A friend of mine knew Grodinsky and said he was always giving him grief about the preamp, and it was tweaked over the course of its run quite a bit, so one won't sound like another. The amp is much more highly regarded.

    Also, for those watching from the stands, this isn't a straight up trade...the accuphase is, of course, a far more valuable piece of gear. But the RGR, if you're not digging into it, is a fine sounding amp and a great deal for what they go for IMHO.
  11. KentTeffeteller

    KentTeffeteller Gimpus Stereophilus!

    Which gets to one of my pet peeves in high end audio. I refuse to purchase a major piece of equipment who's manufacturer refuses to publish service literature or sell spare parts to independent servicemen. I prefer gear meant to be serviceable and conservatively engineered with parts which are not highly stressed.
  12. JohnVF

    JohnVF Banned

    I buy gear that sounds good.
  13. cdfac

    cdfac AK Subscriber Subscriber

    with the ear John has, i have never doubted that it sounds great as-is. i'm excited to try this amp out. let's start there.

    frankly, i just enjoy doing full re-caps. it's a challenge (though not always too challenging), gives me a feeling of personal investment in the gear, and it's helped me polish my tech skills for when i really need them. and 95% of the time, i believe that the improvement is there, in varying degrees of course. i've never recapped something less than 25 years old. in older amps that run pretty warm, it's especially seems like a no-brainer. when i pulled the caps out of one of my Yamaha BX-1's, they were so dried out that they made a clear "tink" sound when i dropped them on the table.

    it's probably not too critical at this point for the RGR, which doesn't get hot from the sound of it, but if i can save myself or someone else real troubleshooting down the road by doing some preventative maintenance now that's pretty straightforward, and i can have some fun in the process, why not? if it looks like it's beyond my skills after all, i'll enjoy it as-is. the fact that there is no service manual is a bummer but not critical if the amp is still working. but let's leave the re-cap-or-not debate to the other 50+ threads that have already hashed it out.
  14. 2chanman

    2chanman Well-Known Member

    johnVF: The only price I've seen asked for a model five was from some outfit in Germany that was selling one for $1500. I consider that a laffer/laugher. Would you call that a "great deal"?
  15. cdfac

    cdfac AK Subscriber Subscriber

    i have seen one German site (audio-extasa) that lists the MSRP, which was about $1500 (in Germany, so you have to factor in duties and tariffs to compare to US MSRP). that being said, there is on guy on DIY Audio who said he liked his refurbed Model 5 better than several amps that sell in the $1500 used range.

    i'd like to avoid the issue of value, though, lest we end up in D&$. for my part, i feel like i'm getting a good deal. this thread was really intended only to be about the technical side of this amp.
  16. JohnVF

    JohnVF Banned

    I'm referring to what I bought mine for, and what I've seen another one sell for locally.
  17. kcroy

    kcroy New Member

    Hey - Hope it is ok if I tack onto this thread, since it seems to be a top hit on google searches for this amp.

    I recently picked up a RGR Model 5 amp and preamp. Did anyone ever discover a schematic?

    Mine came with a broken rocker switch ( stuck in the on position ). It fired up ok, but the protection circuit came on. Only way I know to reset it is to cycle it. Powering down doesn't seem to do the trick - either the rocker switch does something special in the OFF/RESET position, or the protection circuit is firing because of something internal to the amp.

    I've got a replacement rocker switch on the way, and opened the RGR Model 5 up. I was surprised, after reading comments, that it wasn't just a giant rats nest in there. Where is the duct tape I was expecting!


    I'm in the process of getting familiar with an oscilloscope - any tips on how to start debugging a protection circuit? Start with the audio input path and look for ...

    Any help appreciated!

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