Model 1 Modules
Mr Rowland has new modules available now. You could upgrade. I think Stereophile did a follow-up on the new modules.
Since he’s selling some as upgrades, he may have some old, working modules if you’re trying to save some money. I know mine were working when he replaced them.
Jeff
Mr Rowland has new modules available now. You could upgrade. I think Stereophile did a follow-up on the new modules.
Since he’s selling some as upgrades, he may have some old, working modules if you’re trying to save some money. I know mine were working when he replaced them.
Jeff
@willie-aspen
it would be nice if it were all true!
I'd like to understand if you are referring to the availability of the power amplifier model 1 driver modules.
The problem is that I don't live in the States but in Italy and I don't want to send the power amplifier at Colorado or entrust it to the assistance of the national importer but I prefer to do the work myself.
I know that Mr. Rowland intervenes very little in the forum for this I need precise information on the availability of the 2 driver modules.
Thanks.
it would be nice if it were all true!
I'd like to understand if you are referring to the availability of the power amplifier model 1 driver modules.
The problem is that I don't live in the States but in Italy and I don't want to send the power amplifier at Colorado or entrust it to the assistance of the national importer but I prefer to do the work myself.
I know that Mr. Rowland intervenes very little in the forum for this I need precise information on the availability of the 2 driver modules.
Thanks.
Model 1 Modules
I think it cost $450 for the upgrade of both modules. I was able to drop it off at the factory since I live close by.
To make sure we are talking about the same thing, here's a picture of the Model 1 and I've circled the modules I'm talking about.
I think it cost $450 for the upgrade of both modules. I was able to drop it off at the factory since I live close by.
To make sure we are talking about the same thing, here's a picture of the Model 1 and I've circled the modules I'm talking about.
Attachments
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Could you please do a simple check on your model?
Could you measure the temperature of both channels measured on the heatsinks in several points of the same?
I can't find an owner who currently owns this power amp.
Many thanks.
After a long search, Mr. Jeff Rowland has now found the circuit diagrams of the modules and kindly sent them to me as a PDF.
After study the topology it is completely clear to me that the not potted line-level replacement modules with the AD746 cannot provide the same sound quality resp. sonic character than the genuine discrete modules.
From the genuine potted line-level modules I note, that the version for inverted mode sounds even a bit better than the non inverted mode.
I carried out the comparison by a listening test in a non symmetrical operating mode (power amp with cinch/RCA input) at a Aleph 4 from Pass Labs.
The reason therefore also explains the circuit topology:
The inverted line level module consist of only one inverted voltage gain stage (folded cascode consist of two single cascode configuration) which is buffered by a BjT Sziklai-Darlington.
Basically the (very favored by me) configuration of Fig. 5.5 under
Memory Distortion Philosophies - Part 5 : Circuits, continued
The non inverted line (and even the phono high gain) module consist of two cascoded inverted gain stages with subsequent buffering also by a BjT Sziklai-Darlington. This provide a more pronounced (colored) sonic signature.
The low-level phono (input) module from series I use two jFETs in a parallel mode for lower noise and an additional buffer stage for reducing the influence at the first gain stage's output for equalizer (RIAA) parts.
The low-level phono (input) module (version for low voltage supply in series II) consist also of a folded cascode, which is buffered by National Semiconductors's LM6321N.
In contrast to the inverting line modules, however, these are individual jFET transistors (working in parallel mode) and not two single cascode configuration.
Due the present offset servo units and the absense of a differential amp input (LTP) the clone of the circuit with today's available parts isn't a great challenge.
For the N-CH jFET 2SK147 I will use a BF256 and a 2N4401 or BC550C resp. BC560C in jFET/BjT darlington or Sziklai-darlington configuration.
The same for the P-CH jFET 2SJ72 - here maybe the J175 from onsemi together with the same BjT small signal transistors.
The using of genuine jFET's from TOS (e. g. by purchase of NOS parts) isn't a good idea, because here is the risk of changing of the TO-92 plastic material and consequently this could have influence of the parameters.
Due the high voltage of +/-49V for the series I modules 2N5401 and especially ROHM's 2SD786 needs a replace by high voltage versions.
The 2SD786 (ROHM) is special made for ultra low noise applications, but I don't think, the replace by an BF422 provide an unwanted audible effect, because it operates as cascode transistor in common base configuration.
I think, at whole this is a better solution as the use of integrated OP-AMPs - among others because I can determine the individual idle and reference current values.
However, due to possible errors in the component values so as a bad resolution copy, I don't want to upload the circuit diagrams here.
After study the topology it is completely clear to me that the not potted line-level replacement modules with the AD746 cannot provide the same sound quality resp. sonic character than the genuine discrete modules.
From the genuine potted line-level modules I note, that the version for inverted mode sounds even a bit better than the non inverted mode.
I carried out the comparison by a listening test in a non symmetrical operating mode (power amp with cinch/RCA input) at a Aleph 4 from Pass Labs.
The reason therefore also explains the circuit topology:
The inverted line level module consist of only one inverted voltage gain stage (folded cascode consist of two single cascode configuration) which is buffered by a BjT Sziklai-Darlington.
Basically the (very favored by me) configuration of Fig. 5.5 under
Memory Distortion Philosophies - Part 5 : Circuits, continued
The non inverted line (and even the phono high gain) module consist of two cascoded inverted gain stages with subsequent buffering also by a BjT Sziklai-Darlington. This provide a more pronounced (colored) sonic signature.
The low-level phono (input) module from series I use two jFETs in a parallel mode for lower noise and an additional buffer stage for reducing the influence at the first gain stage's output for equalizer (RIAA) parts.
The low-level phono (input) module (version for low voltage supply in series II) consist also of a folded cascode, which is buffered by National Semiconductors's LM6321N.
In contrast to the inverting line modules, however, these are individual jFET transistors (working in parallel mode) and not two single cascode configuration.
Due the present offset servo units and the absense of a differential amp input (LTP) the clone of the circuit with today's available parts isn't a great challenge.
For the N-CH jFET 2SK147 I will use a BF256 and a 2N4401 or BC550C resp. BC560C in jFET/BjT darlington or Sziklai-darlington configuration.
The same for the P-CH jFET 2SJ72 - here maybe the J175 from onsemi together with the same BjT small signal transistors.
The using of genuine jFET's from TOS (e. g. by purchase of NOS parts) isn't a good idea, because here is the risk of changing of the TO-92 plastic material and consequently this could have influence of the parameters.
Due the high voltage of +/-49V for the series I modules 2N5401 and especially ROHM's 2SD786 needs a replace by high voltage versions.
The 2SD786 (ROHM) is special made for ultra low noise applications, but I don't think, the replace by an BF422 provide an unwanted audible effect, because it operates as cascode transistor in common base configuration.
I think, at whole this is a better solution as the use of integrated OP-AMPs - among others because I can determine the individual idle and reference current values.
However, due to possible errors in the component values so as a bad resolution copy, I don't want to upload the circuit diagrams here.
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to avoid this there are suited approaches:
Fig. 4.3.2 under
Amplifiers & Impedance
with shorted R5 (Sziklai Darlington) - go also to fig. F1a under
Voltage Followers
Fig. 12 shows a normal darlington.
From this approach I haven't heard before:
https://www.ijareeie.com/upload/2014/september/20_Small_Signal.pdf
Another possibility would be to replace all jFETs with BjT parts and put on low Gm jFET input goggles for each module.
In all cases sonic character will be changed (that is fact), but not in the unwanted kind than by the use of integrated OP-AMP parts like AD746.
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in Fig. 10 under
https://www.onsemi.com/pub/Collateral/AN-6602.pdf
is show the simplified schematic of all modules working in the inverted mode.
https://www.onsemi.com/pub/Collateral/AN-6602.pdf
is show the simplified schematic of all modules working in the inverted mode.
post #94 unter
https://www.diyaudio.com/community/...surements-for-euvl.175040/page-5#post-6940400shows in the last attachment (pdf-file) a good approach for discrete modules
https://www.diyaudio.com/community/...surements-for-euvl.175040/page-5#post-6940400shows in the last attachment (pdf-file) a good approach for discrete modules
Hi Jeff, do you remember the characteristics of the original replaced capacitors?
Ferdinand
I have two pieces of Jeff Rowland Coherence one Series II, bougthed both used, and also bought for spare parts, a full set line level open modules and two potted invert modules directly form Jeff Rowland..
The one potted invert module i bought for spare with both two potted invert modules inside from the one paritcular piece of coherence, appears this kind of fault: after opperates around an hour or so (from cold situation-not standby) from the speaker hearded a realy strong sound, like a big knock, and automaticaly the power amp (Jeff Rowland model 5) turns to stanby mode, if i immediatelly reopen the amps, the channel were the fault module possitioned is mute, the other channel is operates O.K. After a sufficient period time for the fault module too cool down, the above syptomes rehappens It seems after a temperature a piece inside the potted module faults. I post this just for curiosity because of course this cannot be fixed.
The one potted invert module i bought for spare with both two potted invert modules inside from the one paritcular piece of coherence, appears this kind of fault: after opperates around an hour or so (from cold situation-not standby) from the speaker hearded a realy strong sound, like a big knock, and automaticaly the power amp (Jeff Rowland model 5) turns to stanby mode, if i immediatelly reopen the amps, the channel were the fault module possitioned is mute, the other channel is operates O.K. After a sufficient period time for the fault module too cool down, the above syptomes rehappens It seems after a temperature a piece inside the potted module faults. I post this just for curiosity because of course this cannot be fixed.
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tiefbassuebertr, the link does not seem to work... i.e. the link lets me se the AD825 and LM 49720 ... but then the next link is forbidden. 403 etc...
Basically, one have to perform the same steps as described under
https://www.diyaudio.com/community/...pair-crackling-popping-on-one-channel.358649/
if one don't want to create replacement boards with ICs
https://www.diyaudio.com/community/...pair-crackling-popping-on-one-channel.358649/
if one don't want to create replacement boards with ICs