[Folsom]

"
I should have better clarified my question. Can i run both the Sure TPA 3116 "&" the Magic Sound Buffer 6N3 x 2 + 6Z4 Tube Preamp off the
ASTRON RS-7A


Sure TPA 3116 Specs
http://store.sure-electronics.com/aa-ab32178

Power wise you'll be fine. It's plenty of current. But the preamp runs on higher voltage I think, so it may not work.

[rhing]

I've mentioned before that a friend who had built a pair of 300B mono blocks was so impressed with my modified Yuan Jing TPA3116 blue amp, he bought it from me. Even though I sold him my amp, I kept my upgraded Astron RS-12A, which I bought for $20 through craigslist. My friend ended up going to the nearest Ham Radio Outlet to purchase a new Astron RS-12A. When he hooked it up to the YJ amp, he was so disappointed in the sound. He said the sound was flat, lifeless and lacked any sizeable soundstage. I went over to his house and brought my Astron RS-12A for comparison. When we hooked my PSU up to his YJ amp and system, we could tell within 5 seconds that there was a significant improvement in sound.

We opened up his Astron RS-12A, and I was shocked to see this little 18,000uF/25V CDE electrolytic cap inside. Granted this cap has similar capacitance to the Kemet (formerly Rifa) PEH200 cap in my Astron RS-12A, the ESR is triple what the Kemet cap is specified at.



My friend said he was going to take the power supply back to the Ham Radio Outlet and get a refund. I made him an offer he couldn't refuse--I'd swap my upgraded Astron for his brand new stock Astron. He didn't hesitate at that at all, and I left his home with the new Astron. When I got home, I connected it to my system, and sure enough, the sound was flat, dull and lifeless. Everything measured as I could best determine. I switched from the stock 3x18AWG power cord to a heavier 3x12AWG power cord, and the sound improved, but I could still tell something was missing.



I set off on placing an order with Mouser for new caps:

• C1................................Nichicon UKZ1H102MHM, 1,000uF/50V
• C4................................Panasonic EEU-FM1E101, 100uF/25V
• C5................................Kemet PEH200MJ5220MB2, 22,000/63V
• C6................................Panasonic EEA-FC1E220, 22uF/25V
• C101.............................Panasonic EEU-FM1C222, 2,200/16V

I had to drill a 1/2" diameter hole in the bottom of my chassis to accommodate the M12 threaded stud on  the base of the large Kemet electrolytic cap. I secured this in place with an M12 Nylon locking nut. The Nichicon Muse cap is pretty large too. I wired everything back up, and the power supply looks a lot different now. Since the regulator board was raised to a position with a little clearance under the chassis top, I stuck a sheet of Teflon over the board to avoid shorting with the metal cabinet.





After allowing the power supply to burn in with a test CD in repeat mode over the course of two days, it was time to listen to some music. This is what I expected--a large, deep soundstage with punchy, articulate bass, very good separation of instruments and vocals and a greater sense of transparency. This was music.

If you have a stock Astron power supply and you know how to work safely with AC mains power, you owe it to yourself to upgrade the caps.

[randytsuch]

Rhing
Is your modded Astron better than the one you traded to your friend?

I have a couple Astrons, but I'm using them to power my music PC.

And is there a reason why you used a 63V cap?  (versus a lower voltage one)  I didn't think the big cap in my astron is 63V.

Randy

[Folsom]

D1, D2, and D5 look like they could be replaced with MSR860G for lower noise in the voltage regulating control.

The bridge can be replaced with this bad boy.

While you're at it... those mods would take it up quiet a bit, since most diodes in any equipment sold are just RF amplifiers.

I could come up with some other fun modifications, perhaps. There's limits to the amount of room inside of it, and the high amperage isn't friendly for some modifications. Those are just part replacement modifications. There are other diodes but they're zeners, current limiters, etc, and there just isn't anything to be done with them.

I used this service manual to look up parts, notice it has several of them and it's the second schematic. It appears over the years they've only changed a little bit of parts like capacitors (to crap, ha).

[rhing]

Rhing
Is your modded Astron better than the one you traded to your friend?

I have a couple Astrons, but I'm using them to power my music PC.

And is there a reason why you used a 63V cap?  (versus a lower voltage one)  I didn't think the big cap in my astron is 63V.

Randy

I haven't had a chance to directly compare the two power supplies. Based on memory, these are very similar, and all I can say is that the cap upgrades are definitely worthwhile. I like this unit as it already has the IEC inlet installed, so I can use a good power cord. OzarkTom mentioned the Reality Cables power cord. Right now, I have a Kimber Kable 3x12AWG power cord in there now. I know, I know--not C&C. But man it sounds so good right now.

As for using the 63V cap, it has the proper screw terminal lead spacing. The lower voltage Kemet PEH200 cap has a 13mm screw terminal spacing, which would not fit this board. This 63V caps is the same cap that I installed in my old Astron. A possibly better alternative would be the Kemet (Rifa) PEH169 series caps. I also considered Kendeil caps from Italy. Quite a few Naim enthusiasts like both brands for their Naim power supplies.

D1, D2, and D5 look like they could be replaced with MSR860G for lower noise in the voltage regulating control.

The bridge can be replaced with this bad boy.

While you're at it... those mods would take it up quiet a bit, since most diodes in any equipment sold are just RF amplifiers.

I could come up with some other fun modifications, perhaps. There's limits to the amount of room inside of it, and the high amperage isn't friendly for some modifications. Those are just part replacement modifications. There are other diodes but they're zeners, current limiters, etc, and there just isn't anything to be done with them.

I used this service manual to look up parts, notice it has several of them and it's the second schematic. It appears over the years they've only changed a little bit of parts like capacitors (to crap, ha).

Thanks for the recommendations. I will have to try them after I have to chance to evaluate some mods to my Sure TPA3116 amp. For the moment, I'm back to enjoying my modified YJ blue amp with the CineMag transformers.

This new Astron unit came with a very clean copy of the schematic. I agree that the stock parts quality in my old unit were superior to what were in this new unit. In fact, I can say without a doubt that the parts upgrades with my old unit was less dramatic compared to the same upgrades made with the new unit. Oh well, I voided the warranty, but I'm enjoying the music. So is my buddy across the Bay.

[Odal3]

Interesting. So how old was your original unit? Is there a way to tell the mfg from the serial number? I have been looking to find a unit that is relative new but will now change it around and look for an older instead.

[Poultrygeist]

Interesting. So how old was your original unit? Is there a way to tell the mfg from the serial number? I have been looking to find a unit that is relative new but will now change it around and look for an older instead.

The older and IMO better units do not have an IEC.

[rhing]

Interesting. So how old was your original unit? Is there a way to tell the mfg from the serial number? I have been looking to find a unit that is relative new but will now change it around and look for an older instead.

Based on the components that were in my first, older unit, I estimate that it was at least 15 years old, possibly 20 years old. It had a large 2" diameter x 4" long Sangamo electrolytic filter cap and Elna electrolytic caps mounted on the regulator board. The serial no. was 9-11 digits long starting with "303." My current, newer unit has a serial number starting with "2014," so I assume it represents the year of manufacture.

As PG mentioned, the older units have a hard wired power cord. The newer units have an IEC inlet and a cheap detachable power cord.

If you look for older units, try to find one in good shape. Chances are you might not discover the history of usage. HAM radio operators put these power supplies through the paces more than a 90% efficient Class D amp ever would, so you might have to replace vital, aged components like electrolytic caps. Whether they are used much or not, electrolytic caps age with time.

Here is a good resource covering Astron power supplies:

http://www.repeater-builder.com/astron/astron-index.html

[OzarkTom]

Gregg at Reality Cables has cryo'd one of these Astrons, I will check with him and see if it made any difference. It would be interesting on getting one of these Astrons highly modified and then getting it cryo'd.

The new 9v stock unit that I bought made a huge difference in SQ on the Itube.

[randytsuch]

OK thanks for the info Rhing.

I'll look into it, but I have drilled out PWB's before, so for me it is an option to drill to use lower voltage (and cheaper) caps, if all the other specs are OK.  I'll have to check the specs when I get a chance.  This cap needs to be rated for a high ripple current.

I'm probably going to try this tweak
http://www.computeraudiophile.com/f10-music-servers/good-linear-power-supply-unit-s-computer-audiophile-pocket-server-music-player-wont-break-bank-17336/index12.html#post280401

Adding a damping RC circuit on the transformer secondary.  It's easy and cheap to try, and I need to go to Frys today anyway for a phone battery so I'll pick up the parts.

Randy

[rhing]

Here is the difference between the stock Cornell Dubilier SLP cap and the Kemet cap:

Cornell Dubilier SLP.......18,000uF/25V.......3.9A ripple current.....33mohms ESR

Kemet PEH200..............22,000uF/63V.......19A ripple current......10mohms ESR

[wushuliu]

Gregg at Reality Cables has cryo'd one of these Astrons, I will check with him and see if it made any difference. It would be interesting on getting one of these Astrons highly modified and then getting it cryo'd.

The new 9v stock unit that I bought made a huge difference in SQ on the Itube.

My gripe with cryo anything is that once something is cryo'd there's no going back. So if you don't care for the change (if any) then you're stuck with it.

[randytsuch]

Here is the difference between the stock Cornell Dubilier SLP cap and the Kemet cap:

Cornell Dubilier SLP.......18,000uF/25V.......3.9A ripple current.....33mohms ESR

Kemet PEH200..............22,000uF/63V.......19A ripple current......10mohms ESR

Thanks for looking that up

3.9a ripple?  Seems low.

[OzarkTom]

 (if any)

I hear you. I thought cryo was all bull also until this summer. Now I am a believer.

[rhing]

Thanks for looking that up

3.9a ripple?  Seems low.

That's what I thought when I looked up the specs after discovering this cap under the hood. The Kemet PEH200 and PEH169 series caps aren't cheap, but they have impressive specs and they work well in audio amplifier power supply applications.

I hear you. I thought cryo was all bull also until this summer. Now I am a believer.

I am a believer too to some extent. Cryogenic annealing is a legitimate material annealing process if the process is executed correctly. The big question is whether it produces audible improvements. It's been a mixed bag for me. With some vacuum tubes, it really makes a difference. It seems to make a difference with connectors and cables. Based on the science behind it, I doubt it has as much effect on less crystalline or amorphous materials like polymers (such as polymers in film capacitors) or dielectric insulators (such as Teflon or PVC wire and cable insulation).

As wushuliu said, if the results are worse with cryo, you are stuck with what you've got.

[Folsom]

For audio gear I would dampen the transformer from the primary side. Secondary snubbers aren't often appreciated by some pretty serious people on DIYaudio. Good idea, but the result isn't what you want.

[lacro]

Rhing,
 You have already given me some suggestions for a better cap to replace the big blue one in my SL-11A. I do have a question though: Would it be feasible to mount an even larger/better cap off the board in the open area shown in the pics below? I know keeping leads short is critical so this is probably a dumb idea. 

[rhing]

Rhing,
 You have already given me some suggestions for a better cap to replace the big blue one in my SL-11A. I do have a question though: Would it be feasible to mount an even larger/better cap off the board in the open area shown in the pics below? I know keeping leads short is critical so this is probably a dumb idea. 

One of the problems with selecting caps for most Astron power supplies is that the regulator board is mounted to the main filter cap, and the main filter cap is mounted to the chassis. In this arrangement, the filter cap body is the only thing keeping the regulator board mechanically fixed inside the chassis, so you must keep that in mind when selecting capacitors. Your best option is to find a slightly higher capacitance of 22,000uF with a low ESR and high ripple current. The snap-in type Panasonic TS-HA series seems to be the best option going through Mouser or Digikey. The Mundorf M-Lytic caps have impressive specs, but I do not have any experience with them.

http://www.partsconnexion.com/prod_pdf/mund_ag.pdf

The Astron "SL" series is shorter in height than the "RS" series, so you have fewer options for fitting capacitors inside them. When I looked for caps for my RS-12A, I used a 4" long paper tube to gauge the fit of a 100mm length screw terminal cap inside my power supply.

[lacro]

One of the problems with selecting caps for most Astron power supplies is that the regulator board is mounted to the main filter cap, and the main filter cap is mounted to the chassis. In this arrangement, the filter cap body is the only thing keeping the regulator board mechanically fixed inside the chassis, so you must keep that in mind when selecting capacitors. Your best option is to find a slightly higher capacitance of 22,000uF with a low ESR and high ripple current. The snap-in type Panasonic TS-HA series seems to be the best option going through Mouser or Digikey. The Mundorf M-Lytic caps have impressive specs, but I do not have any experience with them.

http://www.partsconnexion.com/prod_pdf/mund_ag.pdf

The Astron "SL" series is shorter in height than the "RS" series, so you have fewer options for fitting capacitors inside them. When I looked for caps for my RS-12A, I used a 4" long paper tube to gauge the fit of a 100mm length screw terminal cap inside my power supply.

I can mount the board without using the cap and it's bracket. There is a quite a bit of real estate between the IEC connector and the power switch to mount a larger cap. The big blue cap on my board is soldered on, not attached with screw terminals. If I were to mount the cap remotely off the board is that a bad idea because the leads would be longer going to the board? How critical is the lead length for these electrolytic caps?

[Folsom]

It acts more as a power reservoir, so having a little longer leads isn't going to be as noticeable as the performance gain from a substantially better capacitors. The decoupling of RF and what not is a job taken care of to a much larger degree by a few smaller capacitors, and capacitors in your load. Think of the distance the wires run to the load from the PSU, a very small run on this cap is going to be like having a slightly longer umbilical cord.

What you can however do is mount another small cap with leads that are very short directly to the pads. However I'm going to give you a little bit of a different recipe. Use a 1uf film, and the cheapest, crappiest, 300-400uf cap you can find. Solder them as short of leads possible right onto the pads, and then have the large one mounted off board.

You can even use a couple of these. 871-B32560J1105K

and maybe this will be a crappy enough capacitor 647-UVR1E331MPD1TD . If you have any cheap capacitors from a chinese product use one of those, some off-brand cap.