Does anyone care to ask an amplifier designer a technical question? My door is open.

@grannyring  I have a technical question regarding a PP EL86 tube amp I am modifying. I would like to upgrade the power supply. The current power supply is very, very simple and while simplicity is good I think a more robust supply could help sound quality.

A couple of questions and these should also have application for many others here.

1) All filaments are AC heated! Not DC. No filtering, no rectifier....Love you hear your comments on this. Would converting to a CLC filter with possible voltage regulation be worth doing?

2) 5U4 rectifier Tube receives 350 VAC and post tube VDC of 476 with no load. The plate supply is a simple RC only. 100 ohm resistor followed by two 680uf electrolytic caps in series. This feeds the vintage Scott output trannys. If I wanted to add a choke where should it be placed and how do I determine the value correctly. Like to know how you would design the plate supply for this simple PP el84 amp.

I ask your opinion of SS voltage regulation on both filament and plate supplies. Is it something you regard as very important?

EL 86 is an interesting tube. I think of it as an EL84 with half the screen voltage so Ultralinear is generally out. What is the circuit like? Most people dont realize the screen supply is more important than the plate for hum. So how are the screens connected?

No need to DC heat power tube filaments, better not to. If you have hum in the front end DC heaters may fix that. 

The 5U4 is a good rectifier but does have a larger voltage drop than a cathode tube like a 5AR4. They put the 100 ohm resistor to reduce the plate peak current. Even a 5AR4 doesnt like to see more than 40 uF. All that information is on the data sheet. Tube rectifiers were useful in their day, I see no need for them now.

As to filtering, you really have only one cap and thus a fair amount of ripple. C L C filtering is the best and make the last C large so the bass can draw on it and not sag. There are lots of power supply emulator programs out there. Duncan Amps has a nice one. 

Regulation for filaments is easy so use a 3 terminal regulator for that. B+ regulation is difficult. Dont try to do too much too soon in the learning process.

@ieales  More than once I've rejuvenated a system by re-plugging ALL connectors, both internal and external.

YES, YES, YES.  Ive fixed so many things just doing that. Flat screen TVs, my Sony ES player many times, Its used up 6 of its 9 lives. 

Its sad how many components, expecially CD players end up on the scrap heap that could be fixed in 10 minutes. Dont forget the ribbon running to the laser head. That one needs the most attention. Use some logic. If the player cant read a CD go for that one. If some of the display is out or buttons dont work go for the one going to the front panel. Its really simple and you have nothing to lose. CD players cannot shock you. Do unplug them however. (I dont). 

When I open a unit with lots of those ribbon connectors inside I know it has limited life. All connectors oxidize. Oxides also form rectifiers in the signal chain and distortion.  

The old Polk Audio Cobra cables were a very high capacitance design, and caused some amps to become unstable.

@ramtubes. 

   It is very likely that what I’m hearing with this preamp vs passive thing is a less than perfect passive, against preamp distortions which “smooth” the sound. I’d like to know more about your suggested solution to this issue, but contact outside of this discussion is probably best.

   I do have technical questions regarding cabling and AC outlet use though! I’m not excited about super expensive cables (I’ve tried many with very little in the way of difference), but there are electrical differences (capacitance, inductance) in wire. Also, there are different metals and connectors used. What should one look for in terms of material (copper, silver, etc), and electrical properties (capacitance, etc) when choosing wire?
 
  Regarding AC outlet use, how does one best work out the unavoidable need to plug various components into a two outlet wall plate? I had an electrician run a dedicated 30A, 10AWG line to the duplex behind my system location to isolate the stereo components, and to provide enough amperage for the amplifier’s initial turn on draw (it was tripping the 20A breaker). I have seven components that need power. I plug my power amp into one of the outlets, and a “high end” six outlet power bar to the other outlet. Is there something special, and necessary about power strips for stereo components? If so, what does one look for when choosing between them?

@twoleftears  Technical question: Do certain electronic components, e.g. capacitors, need to "form" before they operate at their best?

Electrolytic caps do need to form and the form time is related to how long they have been off or stored. This is why smart tech bring up old equipment on a variac, to let the caps form. If power caps are just hit with full voltage they will draw DC leakage current as they form. If they get too hot in the process they explode. The process is regenerative so it goes very fast at the end. Many people destroy otherwise good caps by just turning things on for too long. 

If people want to know there is a lot to be said about these caps and I have studied them in depth. I made a current limited "former" that will prevent the overheating runaway. Sometimes old caps are better than what is being made now. I know because Ive tested them. 

It takes about a day to fully form a 10 year old cap. They often form to much higher voltage than the rating. The old man at Mallory explained it all to me.  In large quantities where we spec what we want, the voltage written on the cap is more often the voltage on the purchase order rather than what the cap was made for. 

For example we ordered 1000 pcs of 150 uf 315 volt caps at Beveridge. I tested them and found them good to over 500 volts, therefore I would say they could have been marked 450 but we ordered 315V. We got more than we paid for, but one has to TEST these things to know. 

He also told me that stored at cool temperatures 10 years takes only a month off the life of a cap. Basically nothing. Its all about the water inside staying inside. 

I am sad to report that modern caps from good makers are having other problems that prevent this kind of testing. Recently I found some good caps flashed over at slightly above rating because the edge margins on the paper had been reduced to shrink the cap's size. Now that is sad. 

My advice, heed this well, If you have old lytics that are working fine, DO NOT REPLACE THEM. The new ones may not last nearly as long. I have 30 year old caps in RM-9s that are doing just fine. I don't think modern caps are going to last 30 years. 

Oh, perhaps I forgot to mention, Im really into finding out why parts fail. One has to care to make long lasting equipment.