tag:blogger.com,1999:blog-2663163979779760684.post2976569176584691254..comments2024-03-18T14:33:16.252-04:00Comments on DIY Audio Electronics from Zynsonix.com: The Norman Koren Dynaco PAS PreampHiGHFLYiN9 @ Zynsonixhttp://www.blogger.com/profile/07267488633313702661noreply@blogger.comBlogger12125tag:blogger.com,1999:blog-2663163979779760684.post-75586820732215754672020-09-11T07:31:07.139-04:002020-09-11T07:31:07.139-04:00why schematic diagram not part value?????I want to...why schematic diagram not part value?????I want to learn and compare with dynaco pas-3.Thank youHybrid Tube Amplifierhttps://www.blogger.com/profile/00598823108712508351noreply@blogger.comtag:blogger.com,1999:blog-2663163979779760684.post-76111479288903581582017-02-18T23:22:31.187-05:002017-02-18T23:22:31.187-05:00That's a tough one Terry. I actually moved thi...That's a tough one Terry. I actually moved this build to another system for phono duty and ended up removing the added capacitors and adding an additional xformer to handle the needy demands of the rectifier tube. I found the heaters were too demanding for one over-rated PA211 and I would have channel imbalance in certain circumstances. You could check with Geek at Classic Valve to see if he still has boards but he's getting out of the space FYI. HiGHFLYiN9 @ Zynsonixhttps://www.blogger.com/profile/07267488633313702661noreply@blogger.comtag:blogger.com,1999:blog-2663163979779760684.post-84448098778551884222017-02-18T18:39:02.403-05:002017-02-18T18:39:02.403-05:00Wish I'd heard about the ClassicValve boards b...Wish I'd heard about the ClassicValve boards before I started this project, but I went ahead and did everything from scratch.<br /> <br />I've constructed a version of the Koren PAS preamp (2001 version)in a brand new (not PAS) chassis. It comprises the phono preamp and "purist" line preamp. The filaments of the tubes are powered by a separate external transformer (25V, 2A), feeding 3 parallel 25V DC heater circuits via a stabilized supply (317-based). The negative rail of the filament supply is lifted by about 70V ref. to chassis to which it is decoupled with a large cap. An original PAS transformer (PA211) supplies the B+ thru an LR8/TIP50 stabilized supply (which appears to be clean on a scope). Wiring is on turret boards and there is a star ground.<br /><br />The preamp seems to be operating fine (all voltages are correct) but I'm getting audible tube rush at the output of the line amp. I've tried different tubes but they change things very little. Other blogs I've read report that the preamp is very quiet, so something must be wrong. Perhaps there is some RF instability, so I will try raising C3M up to 15pF, but I can't go any higher w/o compromising the HF response too much. At the moment I have C3M at 10pF and C3C at 15pF. Any other ideas?<br /><br />I don't need all the 10X gain, so I will try the mod suggested above of splitting R6C (probably 39k & 82k, with the latter in parallel with a 5uF capacitor). This should reduce the gain to about 3 and also lower the output noise, and I'm oping that the increased feedback doesn't create instability. Pity about the extra capacitor, however, as Norman worked so hard to eliminate caps as much as possible. We need a SPICE wizard to rework the circuit for lower gain! I might eventually try substituting a 12AU7 in for TU4, but I'm not sure that my design skills would succeed in not screwing up the rest of the circuit. I think that the PA211 would just about cope with about 2 x 2mA extra current as it's not powering the filaments.<br /><br />I'm very appreciative to have found this blog (but wish I'd found it sooner....)<br /><br /><br /><br /><br />Anonymoushttps://www.blogger.com/profile/02296722439947444346noreply@blogger.comtag:blogger.com,1999:blog-2663163979779760684.post-50114808889055705702014-02-22T23:35:28.346-05:002014-02-22T23:35:28.346-05:00After some system changes I'm currently using ...After some system changes I'm currently using the unit as a phono pre-amp. I returned the gain to the original settings with the 120K resistors for now, but left the cap/resistor board in the unit if I end up switching it back to pre-amp duty at some point in the future. This unit is really a great value, the sound quality is very impressive. Thanks again Gregg for making the PCBs and directions available. HiGHFLYiN9 @ Zynsonixhttps://www.blogger.com/profile/07267488633313702661noreply@blogger.comtag:blogger.com,1999:blog-2663163979779760684.post-73308415022204867402014-02-22T07:54:18.953-05:002014-02-22T07:54:18.953-05:00Thanks for the review!
Everything on this board is...Thanks for the review!<br />Everything on this board is as Mr. Koren specified with no design<br />changes. The high gain we found to be useful when using low output MC<br />cartriges with an economical 1:8 or 1:12 step-up transformer from Edcor,<br />like the MX8cs or MX12cs. Would like to hear from someone that uses a<br />high-output MC, like a Denon DL-110 (1.6mV out) without a SUT.<br />Cheers,<br />Gregg<br />Classic Valve DesignGregghttp://www.classicvalve.ca/noreply@blogger.comtag:blogger.com,1999:blog-2663163979779760684.post-85941427172061953612014-01-26T14:31:09.725-05:002014-01-26T14:31:09.725-05:00Agreed, this is the best sounding pre-amp I own. T...Agreed, this is the best sounding pre-amp I own. The documentation at Classic Value states that this is a high gain design, and the owner of the site confirmed that his version had high gain as well, so I assume perhaps something changed with the conversion of the design to PCB. HiGHFLYiN9 @ Zynsonixhttps://www.blogger.com/profile/07267488633313702661noreply@blogger.comtag:blogger.com,1999:blog-2663163979779760684.post-43343693404122605402014-01-26T11:57:01.544-05:002014-01-26T11:57:01.544-05:00I have built Koren's PAS preamp using point to...I have built Koren's PAS preamp using point to point construction and had no problems with the gain of his design. I used all his component values without any changes. I used MOV4 remote volume and selector available on line in the 40 dollar range. Replacing his component values with something else just might remove the value of all his computer design efforts. I would encourage you to make sure your attenuator is connected properly since Kornens' gain is only 19 dB. The MOV4 has an IC amplifier but is not used until a 0dB level is selected. It has attenuation to -90 dB in 2 dB steps and works locally with a volume control or remotely and is completely passive until the 0 dB level is reached. It also has a digital display to show levels and inputs. It is manufactured by several different vendors, so this is not an advertisment. By the way, I have built over 30 different preamps and Mr. Kormens preamp is the best I have ever heard. Even though he did this work awhile ago, I believe this is reference quality.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-2663163979779760684.post-58209114410734961062012-02-28T02:22:53.026-05:002012-02-28T02:22:53.026-05:00Congratulations! This is outstanding work..
JPCongratulations! This is outstanding work..<br />JPAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-2663163979779760684.post-63390480699568485832011-12-18T15:04:57.696-05:002011-12-18T15:04:57.696-05:00I have personally seen the chassis and bezels at D...I have personally seen the chassis and bezels at Dynakit and the quality is first class. Now you can build a new PAS preamp without purchasing a donor preamp of unknown origins.Salhttp://dynaco-st70.comnoreply@blogger.comtag:blogger.com,1999:blog-2663163979779760684.post-88053565766210550082011-12-16T14:15:57.409-05:002011-12-16T14:15:57.409-05:00It's been quite a few months of waiting but it...It's been quite a few months of waiting but it was worth it, the PAS chassis from Dynakit Parts is out and is of very high quality. The build can now continue ;)HiGHFLYiN9 @ Zynsonixhttps://www.blogger.com/profile/07267488633313702661noreply@blogger.comtag:blogger.com,1999:blog-2663163979779760684.post-6874781471345283242011-09-02T11:23:15.440-04:002011-09-02T11:23:15.440-04:00As am I my friend. Kevin at DynaKit has spent a nu...As am I my friend. Kevin at DynaKit has spent a number of months getting a new production PAS chassis completed. I'm waiting for him to finish it up and this project will take off after that.HiGHFLYiN9 @ Zynsonixhttps://www.blogger.com/profile/07267488633313702661noreply@blogger.comtag:blogger.com,1999:blog-2663163979779760684.post-16134734718056206842011-09-02T04:36:20.237-04:002011-09-02T04:36:20.237-04:00waiting for more action.waiting for more action.Anonymousnoreply@blogger.com