I have a Topping D90 and started out with a Schiit Modi 3+. The Schiit Modi 3+ was a step up from my Audiophile grade CD player from the early 2000's. I bought my DAC a while ago and these were great at the time. I bought the Topping for $450 used shipped which was a great deal at the time. Maybe a normal deal now-a-days. Really, the analoge part of the whole deal is what seems to make a huge difference. Decent power supply. The topping was a step up in clarity and worth the investment.
When you get to higher end sources, you tend to need a well setup listening room/space as well as good speakers. Then the differences become more appearant.
When you get to higher end sources, you tend to need a well setup listening room/space as well as good speakers. Then the differences become more appearant.
@Mikerodrig27
I’m really really enjoying the upgrades. I use the one preamp I placed Nichicon UKA electrolytics for my audio room, and with the 604 opamps was very happy with the result (Benz Micro SL MC, Thorens TD125 Mk2, SME V, Musical Surroundings Nova III feeding the preamp, ADCOM GFA 545 mk 2 into Ohm-Walsh 4 speakers), but…
How come you didn’t change out the input stage IC’s IC 205/206?
I’m considering doing this for fun, I’ve got extra opamps handy. Just a pain to unplug, open up and put in IC sockets for that stage.
Thanks in advance.
Norm
I’m really really enjoying the upgrades. I use the one preamp I placed Nichicon UKA electrolytics for my audio room, and with the 604 opamps was very happy with the result (Benz Micro SL MC, Thorens TD125 Mk2, SME V, Musical Surroundings Nova III feeding the preamp, ADCOM GFA 545 mk 2 into Ohm-Walsh 4 speakers), but…
How come you didn’t change out the input stage IC’s IC 205/206?
I’m considering doing this for fun, I’ve got extra opamps handy. Just a pain to unplug, open up and put in IC sockets for that stage.
Thanks in advance.
Norm
Honestly, I didn't think of it. Sounds like a fun idea. I am glad you are enjoying the preamp! Your setup with the Ohm-Walsh 4 speakers sounds like it would be pretty interesting to hear.
Be sure to use an old style Holco H4 for R213 (R214). They are dog bone shaped. The new ones currently for sale by TE are NOT the same quality or construction.
Use an OPA604 for best results for IC201 (IC202). It was always used in our 565 upgrades. The OPA134 is rather lackluster in sound quality.
Use an OPA604 for best results for IC201 (IC202). It was always used in our 565 upgrades. The OPA134 is rather lackluster in sound quality.
I liked the sound of the OPA604 a LOT.
I like the sound of the SPARKOS 3601 a lot BETTER. More open, stage recordings are more lifelike, more detail from recordings pops out in a good way.
Considering using the 3602’s for tape out.
The Sparkos 3601 is a bipolar input device. The ADCOM 565 uses FET input opamps for main amplification. You can usually replace a bjt device with an FET one but not necessarily the other way around.
Sorry, I'm late to the thread. I modded my 565 a few years ago. I have a few comments:
First of all, I don't believe that the power transformer is "underspecified" and I don't believe that replacing it will provide any improvement whatsoever. I will probably get some flack for that but that's my opinion.
Replacing all of the electrolytic caps is obviously a must for a 40 year old preamp. However, once I did that, I still wasn't happy with the sound.
I believe the weak spot is the line stage. The opamp with buffer in the feedback loop looks good on paper but never sounded right to me. I ended up replacing the opamps with LME49713 current-feedback opamps (metal can version). These are no longer manufactured but I was able to buy a few from a fellow diyAudio'er. This is not a plug-and-play replacement. It is fairly straightforward but you need to make some changes to the circuit, since these are current-feedback amplifiers and not standard general-purpose op-amps. You do not need the LT1010 buffers anymore, these can be removed and jumpered across on the PCB. The LME49713 can drive 100ma on its own so the external buffer doesn't provide any additional benefit, and would probably make the LME49713 unstable. Other things to note, the LME49713 has a max rail voltage of +/- 18V so you need to make sure the power supply is around 17.5. Also, it is necessary to add some resistance between the volume control wiper and the input of the 49713, or it will become a little VHF transmitter when the volume is at zero.
The improvement over the stock line stage was not in any way subtle and I am extremely happy with the result. Basically it sounds as good as the LME49713 datasheet would lead you to expect.
The phono stage is pretty good as it is. I tried a few different opamps and the only ones that sounded better than the stock Linear Technology ones were LM49710's (essentially 1/2 of an LM4556, also discontinued).
First of all, I don't believe that the power transformer is "underspecified" and I don't believe that replacing it will provide any improvement whatsoever. I will probably get some flack for that but that's my opinion.
Replacing all of the electrolytic caps is obviously a must for a 40 year old preamp. However, once I did that, I still wasn't happy with the sound.
I believe the weak spot is the line stage. The opamp with buffer in the feedback loop looks good on paper but never sounded right to me. I ended up replacing the opamps with LME49713 current-feedback opamps (metal can version). These are no longer manufactured but I was able to buy a few from a fellow diyAudio'er. This is not a plug-and-play replacement. It is fairly straightforward but you need to make some changes to the circuit, since these are current-feedback amplifiers and not standard general-purpose op-amps. You do not need the LT1010 buffers anymore, these can be removed and jumpered across on the PCB. The LME49713 can drive 100ma on its own so the external buffer doesn't provide any additional benefit, and would probably make the LME49713 unstable. Other things to note, the LME49713 has a max rail voltage of +/- 18V so you need to make sure the power supply is around 17.5. Also, it is necessary to add some resistance between the volume control wiper and the input of the 49713, or it will become a little VHF transmitter when the volume is at zero.
The improvement over the stock line stage was not in any way subtle and I am extremely happy with the result. Basically it sounds as good as the LME49713 datasheet would lead you to expect.
The phono stage is pretty good as it is. I tried a few different opamps and the only ones that sounded better than the stock Linear Technology ones were LM49710's (essentially 1/2 of an LM4556, also discontinued).
LME49713 has been purged from the TexInstruments memory bank! They are available from Rochester if you want to purchase 100 of them. Datasheet is still on Mouser's website.
I think that the comment wrt to the trafo had to do with the additional burden of the Jung/Didden regulators used in Gary's article.
I think that the comment wrt to the trafo had to do with the additional burden of the Jung/Didden regulators used in Gary's article.
In the beginning of this thread, you insisted that replacing the power transformer was the best upgrade that one can do for this preamp!
When I upgraded my 565 I made a conscious decision not to do anything that would change the cosmetics of the unit. That includes external transformers, upgraded RCA jacks, etc. I wanted to keep the GFP-565 physically and functionally the same as a stock one so that someday when I'm tired of it I can give it to one of my kids or maybe another audio lover and have it be plug and play.
I read the Gary Galo articles before I worked on my preamp. Replace the power transformer with a larger external transformer. Replace the voltage regulators. Replace the RCA jacks, then replace all of the audio signal chain. Seems to me once you're done it's not really a GFP-565 anymore and you might as well have just built a preamp from scratch.
The power transformer is "correctly" specified. It is neither smaller nor larger than necessary. It is well shielded and fits inside the chassis.
These are just my opinions/biases. Feel free to do whatever you want with your own preamp!
I read the Gary Galo articles before I worked on my preamp. Replace the power transformer with a larger external transformer. Replace the voltage regulators. Replace the RCA jacks, then replace all of the audio signal chain. Seems to me once you're done it's not really a GFP-565 anymore and you might as well have just built a preamp from scratch.
The power transformer is "correctly" specified. It is neither smaller nor larger than necessary. It is well shielded and fits inside the chassis.
These are just my opinions/biases. Feel free to do whatever you want with your own preamp!
I will stick to my guns wrt the transformer, but horses for courses.
Going outboard allows you to use an Amveco with a bit better horsepower, and you can use the choke, and you can use the JD regulators. The JD regulators offer a very significant improvement -- I have to go from memory, but the Zout of the stock regulator circuit has impedance of 0.1 Ohm while the JD regulator is in low micro-Ohms...the PSRR of the JD regulator is at least 30dB better than the Darlington circuit shown in the service manual.
I did not cut up the tone controls etc as Galo did.
I have two GFP565, and the one with the outboarding sounds better.
Going outboard allows you to use an Amveco with a bit better horsepower, and you can use the choke, and you can use the JD regulators. The JD regulators offer a very significant improvement -- I have to go from memory, but the Zout of the stock regulator circuit has impedance of 0.1 Ohm while the JD regulator is in low micro-Ohms...the PSRR of the JD regulator is at least 30dB better than the Darlington circuit shown in the service manual.
I did not cut up the tone controls etc as Galo did.
I have two GFP565, and the one with the outboarding sounds better.
Can someone explain to me the purpose of upping C907 and C908 from 0.22uf to 1.0uf if I understand correctly? Thanks in advance.
Many higher serial numbered units have 1uF installed from the factory. The upgrade procedure reflects that change but specifies a higher quality polypropylene film. Even a .1uF would be ok in those positions.
Sorry to be so late answering this question! In case a user would like to install higher speed opamps, it is best to have local supply bypassing as close to the chip as possible. That is why the .1uF caps are added to the socket area.
So it might not affect the sound quality at all?
Then what are the purpose of these C907 and 908, sorry to ask, just try to learn here.
Very interesting thread and some great ideas. I am in the process of cleaning and updating this preamp and have some hopefully quick questions.
With regards to the resistor upgrades, it appears that most of the one-for-one changes are of the same resistance values (though there are a few 475 to 470 ohm changes). Are the OEM resistors of increased tolerance and thermal coefficient resistance? The PRP suggested resistors are 1%, but no TCR stated. The PRP data sheet indicates 25, 50 and 100 ppm/C. I'm cobbling together my BOM. Thanks, Jeffri
With regards to the resistor upgrades, it appears that most of the one-for-one changes are of the same resistance values (though there are a few 475 to 470 ohm changes). Are the OEM resistors of increased tolerance and thermal coefficient resistance? The PRP suggested resistors are 1%, but no TCR stated. The PRP data sheet indicates 25, 50 and 100 ppm/C. I'm cobbling together my BOM. Thanks, Jeffri
Good question, @Bowlrider.
Of course, when replacing decades-old components one would expect certain tolerances and features (like TCR) to have changed along with things like materials, size, etc.
I’m constantly amazed at how much smaller vastly superior capacitors have become over time with improved ripple, temperature and ESR figures depending on the application.
I’ve “updated” several 565 preamps but never considered changing any of the resistors for reasons you mention.
I did, however, replace the stock 4558 (?) opamps with 2134 (or 134’s) and am satisfied with the result.
I’ve also recently acquired a pair of APT-Holman preamps, one I had upgraded at Quirk Audio, the other I’m considering for the same treatment. Keeping one of the 565’s as a spare as I like the transparency of the APT-Holman preamps.
Of course, when replacing decades-old components one would expect certain tolerances and features (like TCR) to have changed along with things like materials, size, etc.
I’m constantly amazed at how much smaller vastly superior capacitors have become over time with improved ripple, temperature and ESR figures depending on the application.
I’ve “updated” several 565 preamps but never considered changing any of the resistors for reasons you mention.
I did, however, replace the stock 4558 (?) opamps with 2134 (or 134’s) and am satisfied with the result.
I’ve also recently acquired a pair of APT-Holman preamps, one I had upgraded at Quirk Audio, the other I’m considering for the same treatment. Keeping one of the 565’s as a spare as I like the transparency of the APT-Holman preamps.