Power Supply Upgrades for tuner component

[RonaldP]

I have been modifying a tuner starting a few years back which include fast recovery rectifier diodes, total recap and alignment. Yesterday I decided to triple the capacitance from 35v 3300uf to 40v 10,000uf for the main filter capacitors off the transformer as I seen some info of other preforming this modification and I was never happy with the tuner as it was clean back lacked dynamics. There modification also had a 0.01uf Poly Bypass capacitor which I tried to see effect by clipping on when on bench but decided to hold off adding now.
Since I was changing the original design I decide to put a oscilloscope on the I/O of the power supply board. Apparently the power supply design changed from the design I had and on research there are 3 iterations my tuner which I bough a DVD in a effort to get the exact one I have. Apparently the specification I have showed 6600uf of capacitance (2 3300uf parallel with different voltages 25/35v). Also my transformer voltages were off slightly high 21vac measured 20.5vac rms and 6.3vac measured 6.8vac rms. The DC rails were not balanced at the newly added 10,000uf caps one was 27.2v DC the other was 29.0v DC. The scope said there was 2 volts ripple but I had to trust the peak to peak measurement as I was not sure how to zoom in on ripple.
The sound after 24 hrs on variac and couple hours of listening showed a great improvement in air sound and highs sounded good but bass was flabby and loose and mids sounded a bit tinny.
My questions are
What should I be looking for in a good functioning power supply? (Why different voltages at caps I increased value of?)
What can I do to improve the mids and bass? (Poly Bypass caps on newly added 10,000uf cap?)
Since the specifications changed in the power supply it was either due to cost or sound quality or both. I have been told its all in the power supply many many times when it comes to high end equipment.
If needed I can added the tuner model number but hate to put information out there that is not vaild as I'm learning so though I would start the topic on a general approach to such matters that applies to all equipment.

 

[ChrisMarantz]

I'm going to assume that you are working on a Receiver and not a Tuner - since tuners do not have amplifiers built-in.

The Brand and Model are not irrelevant pieces of information when modifications are the topic of discussion. What one person may consider to be "high end equipment" may be another persons "dog of the day".

Also, you may be trying to reinvent a wheel that that already been improved on by may others, without knowing what you're working on we are all just guessing here - Chris

 

[I LIKE MUSIC]

Increasing power supply filter capacitance can be somewhat of a can of worms in technical terms, in terms of perceived sound quality and opinions.

Here is a thread where I posted some basic information about power supply operation in terms of what is called, in technical terms, power supply load step response.

There are no free lunches. The parts that come before the power supply filter capacitors have a limit. It is not necessarily always true that just throwing a lot of additional filter capacitance will improve performance.

One of the first issues may be the large increase in turn on inrush current (the current that is required to charge the capacitors at turn on). This can be a strain on the parts that come before the power supply capacitors such as the power switch, power transformer and power supply diodes.

In simple terms there, is no basic rule of thumb that applies at all times for the change in perceived sound quality when modifying a power supply. What works for one person on a certain piece of gear may not necessarily work for another person with a different piece of gear.

 

[RonaldP]

OK I'm working on a Accuphase T100 tuner.
The tuner is known for a tube like sound and just upping the capacitance of just two capacitors as I said others have done appears to given the tuner a much more tube like sound with vigor. I still need to review I LIKE MUSIC thread (Thanks). I was thinking will lowering ESR by using bypass may decrease transformer voltages and increase currents ever so slightly and give a even fuller sound. I don't know I'm open for discussion.

 

[I LIKE MUSIC]

To be clear, I am not trying to be the capacitor upgrade police. I am not against a little DIY modification experimentation.

I am just sharing some basic power supply information.

This may be going a little too deep down the rabbit hole, but if I am looking for particular sound quality, I would if it had not already been done, be su re that the alignment is spot on, especially the output of the RF mixer section that supplies the 10.7 MHz RF signal to the IF chain. IIRC the IF chain in this tuner uses ceramic filters. I would want the output of the RF mixer section centered on the overall RF response of the IF chain. Then I would want to be sure that both sections of the FM detector (tuning the detector so it is centered on the 10.7 MHz RF signal and the correct distortion adjustment).

To be totally honest, my very, very, very slight (HA) OCDness has taken me down more rabbit holes than I care to admit, more like Journey to the Center of the Earth. .

BTW, since the power supply in this tuner is regulated, there are other parts in the regulator circuit one could investigate if they are interested in modifying the performance of the power supply. Then there are components in the analog audio chain that comes after the FM detector.

There is even an audio output coupling capacitor that could be experimented with. You know brand X vs. brand Y, vs. brand Z. To be clear it is not my intent to turn this thread into a do different capacitors have different audio signatures thread.

BTW, did I mention that I may be only very, very, very slightly OCD about my audio hobby?.

Do what, within reason (additional stress and so on caused by modifications) that makes the music sound good to you.

After all it, is all about the .

 

[RonaldP]

I LIKE MUSIC => Well the comments so far I will reread many times to assure I get every detail and see exactly what you mean. Like I said I had the tuner aligned already and was provided a spec sheet that indicated distortion was down and separation was up. It did sound clean but lifeless too! (New capacitors gave life back but hoping to land at that clean with air tube sound). I'm not ready to mess with FM tuner alignment tweaks but often thought myself that I bet they could make a difference if one had passion to go slow adjust and listen iterations.
I read through your other post and it just a general information how things work but no real info in how to I will say tune such things and experiment for yourself. As like I said many times I like what I hear so far with the new capacitors and that's what its all about for sure! The tuner output appears to have higher gain (Preamp volume near at zero even going out of adjustable T100 outputs at say 80%) now but don't quote me. I did not analysis ever step I did I just basically decided to got after the pair of caps and was pleasantly surprised so far and would have to say it been the biggest impact in right direction I have done to this tuner to date. I did purchase the new caps from Part Connection that were described as power supply caps and think the previous ones that were a eBay purchased Elena and may have not been the real deal.
Sorry for a lack of direction but I was hoping to learn more and may when I ready about your rabbit hole experiments as I can not find much info on such things.

 

[RonaldP]

I just got the schematics for my power supply today so answers can have more focus and some more questions arise too.

Should I try shunting all the 5 larger caps in power supply below with 1/10th film as stated below by a designer?
(I replaced the 3300uf/35v with 10,000uf,40v already)
Any recommendations on type or different size then 1/10 for bypass?
Any other things I should check or dial in like resistive values, tolerance to voltage test points or noise on line?
Will these tweaks effect alignment?


"Over the years it became apparent that changes to the power supply had unexpected benefits to the quality of music’s reproduction. The first I ever heard about power supplies affecting sound quality was in early 1974 when it was suggested that placing a small 1/10th of a microfarad capacitor in parallel with a large electrolytic capacitor made an immediate improvement to sound quality. Transients were quicker, the music more open and alive—as if a veil had been removed from the speakers.

This first technique, known as bypassing, is still in use today. Look at any one of our circuit boards and you’ll note that every single electrolytic on the board has been bypassed with a small capacitor—the type and size chosen for the specific circuit application. Bypass capacitors improve the high-frequency performance of their more sluggish electrolytic mates. Bypassing is but the tip of the power supply iceberg."

 

[avionic]

 

[merlynski]

me too

 

[RonaldP]

OK What does the Popcorn mean? I get the feeling this type of stuff is guarded information. The comments from I Like Music are just to general or advanced for me to act upon.

Cheers!

 

[merlynski]

Sitting back watching the movie, eating popcorn . If you want to Watch a thread you either have to select 'Watch Thread' or post in the thread. Those of us who want to take the lazy way to lurk and watch just post popcorn. I am interested in watching for the learning experience, but had nothing substantive to post . . .

 

[NAD80]

Have some tuners myself to play with. Watching here for ideas to improve the sound of mine. Want to see how this turns out.

 

[RonaldP]

I found 2 Qty 2SA661 PNP and 2 Qty 2SCA1166 NPN transistors in the power supply which were stated to be notorious for being noisy so they were replaced with updated NTE290A/NTE289A. I also bypassed the 10,000 uF with 0.2uF Poly Capacitors. I also reflowed all the solder joints on the power supply board. I only checked power supply with scope for general operation and from memory I seen no difference in noise levels, most voltages were the same or slightly higher (Early Morning measurements). On initial try out with in 30 seconds I was impressed. Sure not all stations sound perfect but I think I have made a improvement here.

 

[ChrisMarantz]

I found 2 Qty 2SA661 PNP and 2 Qty 2SCA1166 NPN transistors in the power supply which were stated to be notorious for being noisy so they were replaced with updated NTE290A/NTE289A.

The problem here is that the NTE transistors are of unknown quality. NTE typically sources their components from all sorts of vendors, they do not manufacturer anything themselves. Because of this, you never really know what you're buying - the NTE's that you used could actually be the same transistors that you removed. - Chris

 

[KentTeffeteller]

OK I'm working on a Accuphase T100 tuner.
The tuner is known for a tube like sound and just upping the capacitance of just two capacitors as I said others have done appears to given the tuner a much more tube like sound with vigor. I still need to review I LIKE MUSIC thread (Thanks). I was thinking will lowering ESR by using bypass may decrease transformer voltages and increase currents ever so slightly and give a even fuller sound. I don't know I'm open for discussion.

Send it to Accuphase. Get it repaired properly.

 

[ConradH]

Adding small film caps across larger electrolytics is based on arguments that sound perfectly sensible, until you do the math and/or measure some real parts. Then it all falls apart. IMO, the perceived results are often due to expectation bias than anything else. Now, there's a case for small bypass caps, but across larger electrolytics is usually the least effective place to put them. If you're going after RF junk from diode bridges, put them there. If you're going after local HF bypassing, put them as close to the circuit as possible.

Different power supply voltages usually come from either having different loads on both sides, or transformers that aren't truly balanced. It doesn't usually matter, but that depends on the circuit. Remember tracking regulators? Almost nobody uses them anymore because they rarely accomplished anything.

 

[RonaldP]

Send it to Accuphase. Get it repaired properly.

Its not obviously broke and been aligned by a local technician who stated it was improved based on data after he was done. So not sure its worth sending across the country and risk breaking and paying a small fortune to shipping if nothing obvious is wrong. I'm just wondering if It could be better. I'm not happy with the performance. Its just not as good as CD always when I think it should be.

 

[KentTeffeteller]

Ever thought it might be the station's audio quality? Many stations have very dynamically compressed and limited audio. Try it on a NPR or college station and see if the sound is better.

 

[avionic]

I'm not happy with the performance.

What type of antenna are you using?

 

[RonaldP]

I have a roof top large rotor with yagi that is less then 5 year old. I added a TV tuner attenuator and adjust the signal from 5 to 4 and noticed the multipath drops to less then 1 when I do so this year.

I have had the tuner for 5 years after some tuner rolling. I kept this one based on the dynamics of sound.

The NPR or college stations do sound better at night. I have a very revealing system. which consists of LP, Cassette Tape, Music DVD, and CD and in my opinion those sources sound perfect every time.
I have a music server and tuner that disappoint more then please.