Robert Grodinsky Research Pre & Power Amp info?

I have the opportunity to get my hands on a RGR Model 5 power amp and a pair of preamps (don't know what model yet) for a very good price...
Googling doesn't turn up much info on these at all.
Anyone have any experience with these amps or RGR equipment in general?

John
 
Member
Joined 2004
Paid Member
thejohn:

Sorry for the late response; I only just found your post. The RGR Model 4 preamplifier was the first high end preamp I purchased. It was very highly regarded by The Absolute Sound in the early 1980s, back when TAS was still credible (and only just beginning to accept advertising). The RGR Model 5 amp was also a TAS favorite, but was too expensive for me at the time (I purchased an Amber Series 70 amp instead). The RGR gear were very well designed and exceptional sounding, but quality control was a little spotty. Resoldering every solder pad was a one-time tweak that, at least in my case, worked wonders. I enjoyed my RGR 4 for about 7 years, until replacing it with a Rowland Coherence. The Rowland was the far superior preamplifier, but the RGR was the better bang for the buck.

If you're still in the market, and the Model 5 amp and Model 4 preamp are still available, you might consider making the investment and then trying your hand at some simple upgrades.

Regards,
Scott
 
Hi Scott,

I was beginning to think nobody else ever had these things, there's so little reference to them on the net.

I ended up getting two Model 4 preamps and a Model 5 power amp along with some other bits and pieces (like a Carver CD player and 3 Sugden A51's) practicaly for free!

One preamp is in original condition and working 100%, the other has been seriously butchered by the previous owner - nearly every componet has been changed - badly!
The power amp is working but has also be badly worked on by someone - the power supply caps are outside the amp, hanging on leads!

Interestingly, this lot came with a set of original schematics for the preamp in an envelope from RGR. Unfortunately none for the power amp!

For now I'm using the working preamp as is, the broken one is in my pile of future projects and the power amp I'm just going to neaten up the bad work done previously and put it to good use too.

Do you know anything about the design / topology of the power amp? Anything out of the ordinary / interesting about it?

If anyone happens to know of a schematic for the power amp I would love to get my hands on one!

Thanks again,

John
 
Member
Joined 2004
Paid Member
thejohn:

Unfortunately, I have nothing left from the RGR Model 4; whatever documentation I had was included when the preamp was sold. The Model 5 amp was a mystery to me -- 100 watts into 8 ohms, sounded terrific (remember, this was the early 1980s) but beyond that I know nothing. However, Robert Grodinsky is alive and well, living outside Chicago, Illinois. He's probably in his late 70s, but the word is he remains active. You might try contacting him directly -- he may be willing to provide some advice (schematics, perhaps).

I'd be curious to hear about the results of your efforts. That Model 4 preamp really was a wonderful little beast (with far superior sonics to the competition in its price range, which included the Apt Holman, Amber, Adcom, Supraphon and PS Audio preamps).

Good luck!

Regards,
Scott
 
I have a RGR Model 4, as well. I can also confirm that it's a very nice little preamp. Unforunately, I am missing one of the rectangular buttons on the face of mine. If you should decide to part out the hacked up preamp, I'd surely be interested in one of the buttons.
 
Model five

I got a Model Five of RGR and is a really wonderful amp.
It arrive badly tweaked. I beguin to recover in the following steps.
Change RCA and speaker lugs with Cardas.
Changed BIG caps with 22.000 uF computer grade of CDE.
Changed hook up wire with 16 AWG 19 strands copper silver threads
(19).
Bypass BIG caps with 470 uF (Nichicon low impedance)+0.47 uF+0.01 uF (polypropilen in oil)
Result the best amp I have ( Classe 175, ML Nº29,Threshold S250 , Threshold SA3, Nakamichi PA7, Forte 4a) all of they with new caps.

Is incredible the sound, sweet, ultradefined, dynamic, with a defined and extended soundstage. A really refined and realistic sound
 
Google turned up this bit of info:

An externally hosted image should be here but it was not working when we last tested it.

RGR Robert Grodinsky Research Model Five, Power Amplifier
Couple technical data:
Manufacturer: RGR, USA
RMS rated power: 2 x 360 watts into 2 ohms
2 x 200 watts into 4 ohms
2 x 100 watts into 8 ohms
THD (1 kHz): 0.04% at 4 ohms
Intermodulation 0.03% at 4 ohms
Performance bandwidth of: 0.04 Hz to 115 kHz at 4 ohms
Frequency: 0.08 Hz to 65 kHz - 1 dB
Outputs: 2 x speaker, screws
Protections: electronically: overload, DC: thermal
Special features: 19-inch casing with handles
Dimensions: 484 x 190 x 335 mm
Weight: 16.4 kg
Selling Price in Germany in 1984 was: 4400,- DM
 
I recently sold my RGR 5 and two 4's for the equivalent of arround US$600... Never thought it was posible to have too many amplifiers but it was time to cut down!

John
 

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Great preamp the RGR Model 4-2 is when working correctly

Hi Scott,

I was beginning to think nobody else ever had these things, there's so little reference to them on the net.

I ended up getting two Model 4 preamps and a Model 5 power amp along with some other bits and pieces (like a Carver CD player and 3 Sugden A51's) practicaly for free!

One preamp is in original condition and working 100%, the other has been seriously butchered by the previous owner - nearly every componet has been changed - badly!
The power amp is working but has also be badly worked on by someone - the power supply caps are outside the amp, hanging on leads!

Interestingly, this lot came with a set of original schematics for the preamp in an envelope from RGR. Unfortunately none for the power amp!

For now I'm using the working preamp as is, the broken one is in my pile of future projects and the power amp I'm just going to neaten up the bad work done previously and put it to good use too.

Do you know anything about the design / topology of the power amp? Anything out of the ordinary / interesting about it?

If anyone happens to know of a schematic for the power amp I would love to get my hands on one!

Thanks again,

John
High "thejohn" are you still our there somewhere? I read your old post and also have RGR model 4-2 pre amp. I'm VERY interested in the schematics and envelope you have for the preamp from Grodinsky... I would be willing to pay you to make me copies or scans for these as I love this pre amp but would like some of the other rare documentation that's out there. Thanks and Best Regards,

Bill aka the notfaded1
 
For what it's worth my new system I'm putting together are two Hafler DH-500 amps. The first one I'm in the process of doing the JFET CASCODE driver board swap. The RGR Model 4-2 preamp is stock and in good working order now. I'm trying to decide the best way to replace the RCA jacks on it in the back. The preamp has weird pairs of RCA jacks that are very close to each other in mounted pair groups that are a unit. I'm not sure larger full size RCA jacks two next to each other would fit in there very easily so it's an engineering design problem for me right now. In addition to the JFET CASCODE driver boards for the DH-500's I've ordered GBPC3508 BRIDGE RECT 1PHASE 800V 35A GBPC, 570-1057-ND (35 AMP Bridge Rectifier)
SL32 0R536 ICL 500 MOHM 20% 36A 31MM (New Inrush Limiter), and 2 565-3679-ND
E36D101LPC243UDA5M CAP ALUM 24000UF 100V SCREW (2 nice big 24000µF 100V Aluminum Electrolytic Capacitors Radial, Can - Screw Terminals). I'm going to reflow all the solder joints on the RGR Model 4-2 with my Metcal 5000 soldering station.

I've decided if I really like the new driver boards in the first DH-500 Hafler I'll do the second one then maybe add the bridge kits to them to make them both mono amps.

Bill aka notfaded1
 
Sorry only a part of model5's Schematics

thejohn:

Unfortunately, I have nothing left from the RGR Model 4; whatever documentation I had was included when the preamp was sold. The Model 5 amp was a mystery to me -- 100 watts into 8 ohms, sounded terrific (remember, this was the early 1980s) but beyond that I know nothing.





However, Robert Grodinsky is alive and well, living outside Chicago, Illinois. He's probably in his late 70s, but the word is he remains active. You might try contacting him directly -- he may be willing to provide some advice (schematics, perhaps).

I'd be curious to hear about the results of your efforts. That Model 4 preamp really was a wonderful little beast (with far superior sonics to the competition in its price range, which included the Apt Holman, Amber, Adcom, Supraphon and PS Audio preamps).

Good luck!

Regards,
Scott
 

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