JRDG Company Special – Concentra 1
1996-2001
Retail price in 1998 in the Netherlands 7.260 euro
The Concentra is Jeff Rowland’s very first integrated amplifier. More or less a one-box version of the Synergy 2 preamp and model 2 poweramp. Put more precisely, the power supply was taken from the Model 2 Amplifier and combined with an output section that resembles that of the model 10 and model 112 power amp. There is no official info on the matter of output stage but from looking at the pictures it seems that the LM3886 integrated amplification circuits have been used instead of bipolar transistors. This integrated has created quite a stir in high-end circles. It had a modest 100 watts of power but just like all Rowland amps, it was much more powerful than these figures would lead you to believe.
All Concentras have a balance control which makes sense because they contain a version of the Synergy preamp inside. Using the remote control, the balance will work but this just is not indicated on the front panel. To reset the balance, press “Mute” for a couple of seconds.
The early Concentras had no possibility of putting it into standby or “sleep”. It would always consume a quite large amount of power unless you pulled the plug but that would lead to a long startup time every time you plugged it back in. The Concentra 1 can be identified by its red display. There is an option to upgrade early Concentra units with a “standby” mode that allows the unit to run cool and lower power consumption when not in use. The standby mode is then engaged by pressing the “mute” switch after which the power transistors shut off and the unit consumes only a few watts. However, the original Concentra cannot be upgraded to Series II status.
It can be fitted with optionally available high-quality internal phono preamp modules for 884 euro, as can be seen below.
The inside of the Concentra 1 is mostly lifted from the model 2 power supply but the power output devices are not bipolar. Instead, the output stage is apparently built using LM3886 integrated amplification circuits. You can tell by counting the pins: 11 instead of 3 as is usual for bipolar transistors. This looks like these were taken from the Model 112 or 10 power amp which both appeared later. Would the Concentra therefore actually be their forebear?
Problem Solving
Coherence, Synergy, Concentra, and Concerto IR Remote Control lock-up
The remote controls for the above-listed products have an internal capacitor that can cause the microprocessor to lock when the battery has been nearly drained. This problem will continue even after a fresh battery has been installed. This capacitor allows the remote to continue to function even after the battery has become very weak. The solution to this problem is simple: remove the new battery and allow the remote to stand overnight with no battery installed. Once the battery is reinstalled in the morning, the remote should function properly again.
Complete lock-up
It can happen that the Concentra locks up when you operate many buttons at the same time and also adjust the volume. All you need to do is unplug the power cord, wait for 10 seconds and reconnect. If you reconnect too quickly, the Concentra may not work. The same is true if you swap the power cable or change the position in the extension block. As a rule of thumb: always wait 10 seconds before reconnecting the power.
Concentra 1 Features
Three balanced XLR inputs per channel plus three unbalanced (RCA) inputs per channel.
Preamp Out in both balanced XLR output and unbalanced (RCA) outputs per channel.
Tape input and output jacks allow tape recording from any source and monitoring of tape recorder output.
Rear panel handles assist moving and transport of unit.
Chassis and all chassis components, precision machined from 6061 aluminum plate, reduce distortion resulting from mechanical resonance and thermal instabilities.
All operational functions under microprocessor control. Within five seconds of any function selected, the microprocessor reverts to a nonclocking “sleep” mode which eliminates any possibility of digital noise contamination.
Non-multiplexed, zero electrical noise generating numerical display indicates volume level over entire range of 99.5 decibels.
‘Display off after five seconds’ option available for non-intrusive, low light listening environments.
Dual range volume control allows large volume level changes when knob is rotated abruptly, yet permits precise small volume level changes when knob is rotated slowly.
Optional plug-in phono cards (installed internally) convert Line Input 1 to high performance phono inputs. Four gain and input loading options standard for moving magnet and moving coil cartridge types.
Full electronic and thermal protection modes guard against output overloads and short circuits.
High current preamp outputs (balanced XLR and unbalanced RCA) allow simultaneous driving of external power amplifiers for subwoofers, vertical bi-amping, etc.
All inputs are transformer-coupled to provide maximum immunity from RF contamination and system ground loops and enhance compatibility with a wide variety of interconnected components.
Speaker outputs are fully balanced to provide maximum sonic performance and immunity from RF contamination due to high output common mode noise rejection.
Optical encoder type volume control maintains quiet, trouble-free performance and accuracy over entire lifetime of product. þ Six-function hand-held IR remote control.
Concentra 1 Specifications
Output Power Continuous RMS Watts
@ 8 ohms 100 watts
@ 4 ohms150 watts
Bandwidth
0.5 Hz to 160 kHz, -3 dB
Slew Rate
30 volts per microsecond
THD and Noise
Less than 0.06% at rated power
Damping Factor
60, 20 Hz to 20 kHz, 8 ohms
Output Current
16 amps continuous, 28 amps peak
Gain Structure
Preamplifier Section 14 dB
Amplifier Section26 dB
Volume Control Range
99.5 dB
Volume Control Resolution
0.5 dB ±0.05 dB over entire range
Input Impedance
36k ohm
Common Mode Rejection Ratio
Greater than 60 dB, 20 Hz to 20 kHz
Power Consumption
100 watts idle; 550 watts maximum
Inputs
Balanced Line3 per channel (XLR)
Unbalanced Line3 per channel (RCA)
Record1 per channel (RCA)
Unbalanced Phono (optional)1 per channel (RCA)
Outputs
Balanced Pre Out1 per channel (XLR)
Unbalanced Pre Out1 per channel (RCA)
Record1 per channel (RCA)
Speaker1 pair binding posts per channel
Dimensions
17.5 in (W) x 14.35 in (D) x 5.75 in (H) 44.5 cm (W) x 36.2 cm (D) x 14.6 cm (H)
Weight
50 lbs (23 kg)
More Jeff Rowland
Jeff Rowland Company Special Main Page
Jeff Rowland Company Special Integrated Amplifiers
What a wonderful site!
Thank you for detailed information on such an old amplifier.
A week ago, a friendly dealer lend me Concentra I to listen to while my amplifier is being repaired. I am shocked how beautiful it sounds after more than 25 years… Time to start searching for a new amplifier. Do you have any information on serviceability of these? After all, it has been 20 years and some parts may need replacing. It would be a shame if modern replacements are not of the same quality as original. Also, are there any comparisons between Concentra I and Gryphon Callisto 2100 ? Kind regards,
Hi Steven, nice to hear you are enjoying my JRDG pages!
Unlike some Rowland amps such as the model 2 and model 6, there are no encapsulated components inside the Concentra so servicing should not be an issue. The only thing to look out for are the two coke-can-sized capacitors inside the original Concentra 1. When replacing is needed, they should have the exact same size and circumference. The Concentra 2 has regular capacitors that should be easy to replace when needed. Nothing lasts forever but JRDG amplifiers seem to go on and on and on…
Thank you 🙂 Time to start hunting for one 🙂
Hello everyone. It is possible to purchase such an amplifier for $ 3000. A good price for it? I want to connect it to my JBL speakers.
Although prices seem to be rising currently, I would say that 3000 is too much for the Concentra 1. It used to be available for less. Also, the 1 is getting quite old by now. I would aim for the Concentra 2 which should be available for only a little more.
Unfortunately, in the entire secondary market of Russia, only one copy of such an amplifier is offered. Christian, do you think there might be any hidden problems with him?
Another important question for me, how does he play at a very low volume? You will have to buy remotely, so you won’t be able to listen to it.
Thank you.
There are rarely problems with Jeff Rowland amplifiers and the C1 should be highly reliable. However, we’re talking about a 20-25-year old amplifier here. The amp sounds transparent and well-resolved at any volume level but you have to like or want its relaxed and sweet overall delivery.
I forgot to say, now I have a Luxman L-550 All amplifier, it is a little difficult for him with the JBL S3100, but I like the character of the sound. I would like more low and high frequencies at the edges of the range. There is also a VTL ST-85 power amplifier, can you try using JR as a pre-amplifier? I read that he is good for this. Is the preliminary part also built on LM?
Thanks for your hard work, Christian.
I have heard a few Luxmans in other setups but have no personal experience with the L-550, sorry. Rowlands are known for having the power to drive more difficult speakers but the Concentra is not a power-house. If you want to play really loudly then perhaps another amplifier would be a better choice. Yes, the Concentra’s pre-out sounds great but then you could also opt for the Synergy 1 or the Concerto. The preamp is based around other OP-Amps than the LM3886 which are strictly for the power amp section. I would also add that most VTLs (within a reasonable price range of course), even those with a higher watt rating, are not more powerful than the Rowland, I’m afraid. Rowlands are all about refinement and I’m not sure if it will be “enough” different from the Luxman in terms of contour to satisfy your needs. Maybe I am reading you wrong, but if you crave more raw bass power and perhaps a spicier treble, then neither Luxman nor Rowland may not be the ideal brands for you. Perhaps Accuphase could be more fitting? Their low-end amplifiers can be a little clean nowadays but the Class-A designs are very nice. Older Accuphases tend to sound friendlier and more in line with the Rowland sound.
Christian, read your good reviews on PrimaLuna amplifiers, do you really think they are worthy? I am a little confused that they are made in China. Have you listened to their new Evolution line?
Hi Watson, the reality is that A LOT of equipment is made in China these days, including some of the most respected former USA high-end brands. The question is not if the country can produce quality gear. It comes down to the intention of the business owner. I stand by everything that I have written in the PrimaLuna reviews. Yes, better sound quality can be achieved, but it will also cost more. The build quality is much better than you could expect at the price.
Christian, thank you for the conversation. I still refused to buy the Concentra 1, for $ 3000, it’s still expensive for the old model. I think I’ll keep the VTL power amplifier for myself, and get a pre-amplifier for it. Have you ever used pre Aesthetics Calipso, Christian? There is an opportunity to buy for the same $ 3000. I didn’t find any Calipso reviews on your site. Could it be wrong that I am writing in this section of the site? I didn’t understand where you can communicate here. Thanks.
Hi Watson, I agree 3000 is too much for the Concentra. Alas, I have not heard Calipso, nor Aesthetics. There is no generic forum on HFA. The idea is that people select a review that touches on the subject they want to communicate about.
Good luck to you, and good sound! I really liked your site, I will use it.
Thanks!
I’ve just decided to sell my C1 to try something different, in the UK. Less than $3000 for sure.
Hello, Christian. Perhaps my choice will seem unusual to you… but I have acquired a new integral amplifier CODA CSib v3, the last latest revision. In our country, it is available for $5,800 from a dealer. In general, I like it, the only remark, the sound is a little dark, I would like more air at high frequencies. I think how this can be fixed.
How do you feel about Coda products? I didn’t find any reviews from you on this site.
Thank you.
Hi Watson, I have actually been very close to reviewing CODA and I’m sure they are very musical products, certainly at the price. Alas, due to circumstances, the Dutch distributor no longer carries the brand. Having read a few reviews and impressions, I also got the feeling that the sound would be a bit dark. Taming a bright-sounding system is probably easier than brightening a dark-sounding system. After all, ther treble that’s not there cannot be recreated. The best solution would be to match the speakers to the amp (use bright-sounding ones, ribbons, perhaps?) but if that is not possible then one trick to try is to use spikes, Ceraballs, Stillpoints, or other hard-coupling devices under certain components, low-capacity (“fast”) speaker cables or cables that are a little lean in the bass, thereby tilting the balance somewhat, move the speakers a little forward or change the toe-in, and, in general, avoid any accessories that are inherently slow-, or dark-sounding.