Tinkering with the office rig.....

heiney9

Finally found one of these worth purchasing (completed w/higher end parts). I've had the opportunity a few times only to pass (pun intended ) after looking at the workmanship or price or in one instance paid only to be refunded after the amp developed a problem right before shipping.




These are DIY amplifiers and are only as good as the builder's skills. I bought a pair to build my own mono's, but I really wanted to hear one for myself and being the impatient type as well as this being the "upgraded" version; I decided to get one already assembled before I build my own.

This has the rare smps filter since these run on 24V 5A Meanwell branded switching power supplies. 8-10 wpc while dissipating 35 watts per channel in heat, single ended Class A. very simple circuit.

This has larger and better sounding Nichicon KG (Gold Tune series) output coupling caps a few other caps have been replaced with hybrid aluminum polymer caps. A few resistor value replacements allow slightly higher power (couple watts or so). Basically the "Tungsten Audio" upgrades approved by NP himself.




I did have to make a repair on this ACA amp. The smps board (purple board) was not secured inside the chassis and during shipping one of power leads broke off. I had to re-solder and I was able to do it without disassembly. The seller was so apologetic even offered to pay to have it fixed at a repair shop. The fix was simple, but access was a ****.

I've also been running a Schitt Gjallahorn -10wpc discrete power amp. Nice little amp, but the ACA amp does almost everything better. Gjallahorn seems to have a bit deeper soundstage. The dynamic swing is much better with the Pass ACA. Bass is superd. Still evaluating as the Pass ACA is only a few days here.





I also finally came across a couple older Keces pieces that are superb despite their age. HA-171 which is a headphone/pre amp with 2 gain settings. And a DA-152 USB dac/pre/headphone amp. I still have a DA-151 USB dac that I've raved about for the last 10 years. Now that I have the DA-152, essentially the DA-151 and pre-amp in one, I'll let the DA-151 go. These use the older BB PCM-2702 chipset.







I'm rolling discrete op amps in place of many single channel LME 49710 I/C's in the (2) Keces units. I've had some of the New Class D op-amps sitting here idle for a few years and just bought some Burson V6's and a new Burson hybrid op-amp. They change the sound pretty convincingly. I use some of the same discrete op-amps in both my Eastern Electric DAC's.



I may use one of these as a pre-amp or I may move them along. Still evaluating. Maybe get a simple tube pre-amp. Not sure yet.

The R200's and RT25i's are still the main speakers. Starting the RT25i crossover upgrade this week. I'll post in a separate thread.

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F1nut

Brock is having fun

heiney9

F1nut wrote: »

Brock is having fun

Yes, I am. Except one of the volume pots has started having issues. I'll turn it and I hear severe crackling and the sound diminishes until I've stopped on a position then the sound comes back. This happens moving left or right.

Before the recent crackling and drop out I thought I was hearing very mild distortion. This confirms my ears. (I should always rely on my ears, they rarely fail me.) I thought perhaps it was because the discrete op-amps needed to break in.

I was also thinking perhaps putting (5) discrete op-amps in at once was starving the power supply or over working the regulators and causing distortion. I removed 3 of the 5 and put the stock I/C's back in, no change. So it's got to be the volume pot. Keces overbuilds the power supplies.

The brand is TOCOS (Tokyo Cosmos Electric Co.). It's a fairly expensive volume pot for the price point back in the day.

Besides, the usual places, Mouser and Digikey where would I be able to find this exact part? I can barely make out the model # on the back w/o removing it. RV 30YG 20S ????. I know the 30 means 30mm?

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treitz3

Have you tried electrical contact cleaner on the volume pot yet? It may just have enough oxidation to cause an intermittent contact, while turning the knob. This usually clears up any issues, even with very old gear. If it is readily accessible, try putting DeOxit Gold on the connections to help keep the contact area(s) clean.

Tom

heiney9

Tom, I have not, yet. Trying to see if I can find a point on the pot besides the shaft. This went from mostly working to extremely not working. This unit probably 15-20 years old. I have read a few things on a couple of the headphone BB's, these wear out.

I did see some comments from the manufacturer back in the day that said the pots in these units were Korean made and they were having a zero failure rate. He said their cost at the time (I'm assuming wholesale) was $24. Which for a unit that retailed for $399 is a bit of money for one part. The unit I have could've seen a lot if use. Next step is DeOxit to see if that helps.

Bothe HA-171 and DA-152 use the same pot. So if all else fails and the DA-152 is my preference I will just take the one out of the HA-171.

Once I try some DeOxit I'll report back.

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pitdogg2

Fader lube would be better than either deoxit or deoxit gold. Believe it or not the deoxit gold has less cleaning properties than red deoxit.
Fader lube is made especially for slides and radial volume pots

treitz3

You do have a very valid point. Knowing him, I figured he already had the aforementioned on hand, and it works in a pinch (provided the pot is reasonably accessible.

Tom

pitdogg2

It does Tom, but if he needs to order 😁

heiney9

treitz3 wrote: »

You do have a very valid point. Knowing him, I figured he already had the aforementioned on hand, and it works in a pinch (provided the pot is reasonably accessible.

Tom

I have DeOxit. Not a very likely place to spray any. I went down the rabbit hole of trying to find a replacement. I'm going to pull the entire PCB the pot is attached to. That way I can see if there is a better lube point. Looking at photo's similar models, they are closed. Plus once I get the nut and washer off maybe there is a better lube point than just the shaft. Man, don't take that last sentence out of context

Luckily it's a single PCB with 3 connections. Easy to remove.



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F1nut

https://tocos.com/sales-locations

heiney9

KISS - Keep it simple stupid!

DeOxit seems to have fixed it (for now). I should know better. But I just got down the rabbit hole looking for a replacement.

BTW, I just let gravity do the job. No disassembly beyond removing the volume knob.

Back to swapping the remaining 3 discrete op-amps back in.

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VR3

Chatgpt is invaluable for finding substitution parts, just make sure you ask the right questions

treitz3

Man, I differ from you on that. AI and chatgpt is like a Chinese guy trying to splell Amerika. It gets the main things right sometimes but, it's still off the mark. Considerably at times.

Tom

heiney9

It's an op-amp issue. It seems to be with the Burson V6 Vivid's. I have heard they can be kind of power hogs. I know with my old Adcom DAC we had to add caps to the underside of the sockets of the OPA627's we swapped in to keep them happy.

If I goose the volume knob up or down the music signal goes weak and crackles until I settle on a stop position....then everything catches up. I have no idea how to calculate what cap size would be needed. For the Adcom it was small. I probably have a couple of those left over. Don't recall how they were wired. PIN #1 to ????

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heiney9

I have a pair of 120uF 25v Panasonic FC's left over from the Adcom build from 15 years ago.....these were the caps we put on the Op-amps.

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VR3

The trick to chatgpt is you have to have some knowledge base about what you are asking and confirm results

Ie, what is a drop in replacement for xyz volume pot?

What are the mechanical or electrical differences?

Will this require any circuit adjustments?

Is there a higher quality or military version available?

Can you find any issues with what you are telling me?

heiney9

This is the part of the Adcom mod I was referring to above. A local power reserve.

Remove the opamps and install the new opamps--careful attention to pin #1 orientation,,in the case of the dogs,,pin 1 corresponds with the "b" in browndog.The adcom opamps were marked with a notch of sorts denoting the pin #1.I would suggest installing the DIP 8 sockets, then you have the ability to roll opamps like tubes,if you prefer. Next you want to install 120uf/25 volt electrolytic caps to serve as local power supply reservoirs. the positive lead from the cap goes to pin 8(opamp) and the negative cap lead to pin 4.Then connect the remaining + and - leads on the caps,and tie them to ground.I ran a wire fron the caps which I mounted on the underside of the board to the ground of the power supply,which is easily distinguished.

I may need to do this. Although if I'm not fiddling with the volume knob. It sounds damn good.

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heiney9

The voltage regulator heat sink is definitely running a bit hotter. Nothing crazy, but def. warmer

It sounds excellent. So much more depth and bass is much better vs. the stock LME4910's

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treitz3

Running hotter or running at optimum temperature?

Tom

heiney9

treitz3 wrote: »

Running hotter or running at optimum temperature?

Tom

Running warmer than when the original op amps were in the unit. Probably within spec.

heiney9

Not leaving well enough alone I had to go back down the tube rabbit hole. I have been keeping an eye on various Schiit gear. The idea was to try and keep things simple by using a pre/dac. A compromise, but this is a secondary rig. I don't ask as much from it and I love finding inexpensive gear that gets the toes tapping and allows one to "see into" the music.

I decided on trying this.





With the AK4490 Delta Sigma dac.

It uses one 6SN7. The one (actually 2) tube I don't currently have or use in anything. Going down the rabbit hole. So far the few I have purchased, they seem to mirror my 6SL7 experiences. I have 6 - 6SN7's so far. They all sound different, for sure.

I also have to shout again - CABLES MATTER!! I had to switch back to my Signal cable I/C and Canare 4S11 speaker cables. The MIT Terminator 2 I/C and MIT AVt 3 speaker cables don't play nice with the Pass Amp Camp Amp. Very bright, too bright, IMO.

So far I am blown away with the Lyr3 and the Pass ACA. 8 wpc of pure bliss.

I need to get on building my pair. If one sounds this good, I can only imagine what a parallel mono pair sounds like.

This is so much fun now that I have a larger room to mess around with stuff.

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heiney9

The other nice thing about the Schiit Lyr 3 is you can bypass the dac section and use it as straight pre-amp. Utilizing another stand alone dac.

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invalid

heiney9 wrote: »

The other nice thing about the Schiit Lyr 3 is you can bypass the dac section and use it as straight pre-amp. Utilizing another stand alone dac.

H9

I take it that the preamp uses the 6sn7 tube for voltage gain and it has a transistor current gain stage.

heiney9

Most likely. Here's the press release with an explanation.

https://www.stereolifemagazine.com/news/item/1367-schiit-audio-lyr-3

I was mostly interested to get a bit of variation and not break the bank with buying pairs of tubes. Right now I don't own anything with the 6SN7 tube, only 6SL7 for octal tubes.

The tube definitely has influence but it's more for minor tweaking than full blown tube experience. I've acquired about 4 different 6SN7's so far ( a few more on the way) and they all have a different presentation.

Pretty much exactly what I was looking for and it's fun factor is up there too.

H9