Separate power supply vs. single chassis

[seti]

Seti:

There a number of sources available -- them following off the top of my head contains some excellent information on vacuum tube audio electronics: the section a grounding among the best I have seen on-line.

http://www.aikenamps.com/index.php/white-papers

 

Thanks the part on grounding is what I have been looking for.

 

It seems separate power supplies is really the way to go especially for beginners even though I prefer to have everything in one chassis.

[Schu]

 

It seems separate power supplies is really the way to go especially for beginners...

 

 

 

[seti]

 

 

It seems separate power supplies is really the way to go especially for beginners...

 

 

 

 

 

LOL.... Haven't done that yet.... I have a tech comes by to help me with live measurements etc and to make sure I don't do anything stupid as well as learning good habits.

[erik2A3]

Separate power supplies MAY be the way to go -- but we can't help but recognize the fact that the majority of valve amps and preamps are not dual chassis designs - signal circuitry and PSU coexist on a common chassis; and in most instances coexist very well, not to mention quite silently.

Edited September 1, 2014 by erik2A3

[tube fanatic]

Thanks for the additional comments Erik, and also for yours Joe.  Using the two chassis approach really doesn't require any extra machining as the number of holes drilled, etc., is going to be virtually the same either way.  And from a cost standpoint, due to the smaller chassis sizes allowed by splitting out the p/s, the cost is not going to much different vs. going with the single chassis arrangement.  Regarding the opts, the only cost-viable option that I've found for enclosed types is to go with Edcor.  It's not a concern electrically, but I just can't stand that blue color that they use on the bells!  I've considered removing them and spraying them black, but that's more work than I want to do for this project!  I got away from using chokes once high value electrolytics became so inexpensive.  It's actually a lot less costly to use larger value caps than to bother with a choke (unless the application calls for the excellent regulation of a choke input filter- not the case here as the quiescent to maximum output current draw is only a few milliamps).  And, yes, I always use bleeders!  They are especially important in the full DC amps which have close to 3000 uf storing about 155V.  In my own amps I set the values fairly high as I don't care if it takes 10 minutes for a full discharge.  For those built for others, the value is much lower.

There are, so far, 4 designs perking and I anticipate that all will be built- 2 SETs, and 2 SEPs.  All will operate on identical power supplies and have fairly low power output (probably around 400 mw for the SETs, and double that for the SEPs).  The power won't be an issue as they will probably be used near-field, or at reasonable levels in a moderate to large rooms.  The speakers will all be Klipsch, of course!!!  One of the guys who is anxious to get going with one of them raised the point that with the separate p/s, if he gets a SET to start with, he can always get a SEP later on at much reduced cost since he already has the p/s for it.  Then, it's a simple matter to just plug in whichever he wants to enjoy.  He also said that it would be nice to be able to put the p/s out of the way and have a smaller amp chassis since he turns his equipment on and off from one master switch.  Lastly, he would like no design compromises (other than the power), so if the separate p/s offers even a small edge, he'd prefer that.  Those are good points too.  But, as you said Erik, it may be worth building one of the designs both ways to evaluate the true performance differences.  And I certainly agree that most tube amps are single chassis affairs and that it is not an issue!  Either way it will be fun.

I sure appreciate the input (no pun intended here either!) from everyone.  If any further comments are forthcoming they will certainly be welcome.

Maynard 

[seti]

Hadn't thought about the flexibility of reusing the power supply to test other circuits....

 

Hope you post pics as you go along.

[minermark]

If you have a say in splitting them, id say do it.

[erik2A3]

Hi, Maynard -

You're really right about extra chassis work -- I was just referring to the additional punches that will be needed for the connectors and umbilical you plan on using to connect the two chassis. If you are going to go the two chassis route, what I think I would consider (just thinking out loud here...) is single PSU and two monoblock amp chassis, or a total of four chassis with each amplifier beside its own power supply. But as you also mention, there are lots of options. Both possibilities could be on the table according to the needs/wishes of the end user. And I agree, lots of fun either way! So refreshing to see and read posts where enjoyment of the process is appreciated! I am assuming input/voltage gain stages with grid bias?

SETI: Quite honestly, my opinion regarding separate power supplies for first time builders is that it would be less desirable than a single chassis. Having both on the same chassis has the benefit of a much more straightforward build. There may be a reason for the fact that the vast majority of tube amps currently available are single chassis designs. It's just one of the advantages of real DIY amplifier design and construction -- no already-made circuit components being used and wiring is point-to-point. One can do as one chooses as long as all electrical requirements and safety precautions are accounted for and in place.

[tube fanatic]

Erik, you remember my preferred biasing method!  The SEPs will definitely use the grid-leak biased triode voltage amplifiers.  With the SETs, it will depend on where I decide to bias the power amplifier stage.  With a B supply of only 155V or so, the output voltage (at low distortion) of the triodes isn't huge.  So, I may get stuck having to go with a pentode in the front end.  I'll see what happens when I graph the load line and all of that stuff.  And SETI, I'll add to Erik's advice on the build by saying that your layout should try to keep the AC wiring from the power cord and on/off switch as far as possible from the voltage amplifier (i.e. driver) and input jack.  Also, be sure to tightly twist the leads from the power xfmr primary, all filament leads (if not using DC), and the wiring to the on/off switch.   If your layout allows the power xfmr to be located diagonally opposite the voltage amplifier tube that would be the best way to go (see my picture of the single chassis amp above).  If the voltage amplifier is a metal type it is of far less concern as the tube is self shielding.  

 

Maynard  

Edited September 1, 2014 by tube fanatic

[seti]

Thanks Eric and Maynard. Advice is much appreciated.

I've been studying all the DIY stereo amps I can find.

[DrWho]

Just an informal survey: would you prefer a single chassis amp to one with a separate power supply, or would it make no difference to you? Reasons for either view would be appreciated.

There's no question that isolating an amplifier's power supply to its own chassis, and locating it a distance away from the amp itself, results in a superior sounding unit. It has always been my preferred method. In spite of that, on occasion I'm asked to use a single chassis even if it results in a bit more noise, powerline grunge, and so on.

Looking forward to comments!

Maynard

If you take your separate amp and power supply, and then put them together into a really big box, then does count as a single chassis, or is the power supply still separate?

[Ski Bum]

Eric, is there anything particularly innovative about the Decware amp you mentioned? Dual supplies on a super tiny chassis, yet you report silent performance via sensitive speakers.