Tube Rectified Tube Amplifier on UPS/Power Conditioner

[Guest davidness]

I have a Bob Latino ST-120 that I've had some problems with the amp blowing rectifier tubes. I went through about 12 in the past year. Various brands, types, from new to vintage.

I'm having Bob thoroughly go through the amp, but before he's had a chance to diagnose the problem, he mentioned that he's seen problems with tube rectified tube amps like his and the Dynaco's when used on a UPS.

The UPS I have is a big one, a 5-U APC SU2200XL.

I would think that using a UPS would only HELP, in that it would serve to condition the power before hitting the tube amp's rectifier circuit. Plus, the UPS serves to provide even power to the tube amp during momentary power outages, which prevents the problem that the internal capacitors have with 'short cycling' of the power. (I was told to never turn the amp back on immediately after turning it off, but rather wait 30-45 seconds, for this very reason). The UPS solves that problem.

Has anyone else heard not to plug their tube amp into a UPS?

[mark1101]

I had the same amp for a year or so and it performed pretty well. I ended up selling it. I never used it with a UPS or other power conditioner and I only blew maybe 2-3 rectifiers. Bob always recommended the solid state rectifiers to me but I was too scared to use them as they supposedly start up fast and could possibly stress other components. I just didn't want to take a chance. But he was convinced they were good and didn't sag on bass notes like a tube recitifer. Maybe you ought to try one of those. There is probably nothing wrong with your amp. The new production rectifiers are pretty cheap. I used to use Sovtech because they were cheap to replace. If you have one of those UPS units on a PC in your house and are running the software that comes with them you can check the log for voltage evernts and also simply read your wall voltage. Have you checked that out?

[Guest " "]

It's more than a voltage regulation issue. you might think you are getting stable line voltages, but you are not getting a true sine wave and your are probally not getting a consistent frequency i.e. 60hz. I would not put any amp on a UPS. What do we think we are getting out of this. UPS's are to provide voltage during a system shut down senerio in data computing operations. UPS's have poor voltage output in terms of what the sine wave looks like. Very little isolation between associated receptacles occurs and there is very little reduction of the noise floor, but in fact, higher incidences of line noise associated with the DC to AC circuits inside the unit. Put that UPS on a computer and connect the serial port to management software. For you audio gear, all you need is voltage regulation and the best approach is an autoformer based solution such as those offered by furman or even monster. Cleaning up line noise or associated outlet surges and noise is done best by the use of isolation transformers, blanced power transformers, and 2nd and 3rd stage filtering. Some units provide exclusive features in one area and other units for even another. A monster AVS 2000 provides 2000 watts of line regulation using a giant autoformer. Its partner the Monster HTP7000 provides isloation of two outlets thru the use of 2 balanced power transformers, as wells a 2nd and 3rd stage filtering tuned to frequencies unique to video, digital, analog, line levels, power amp levels, etc.

[kevinmi]

I have a Latino ST120 that I built a little over a year ago. I blew up my first tube rectifier within a week of startup. I followed Bob's recommendation and bought the Weber Copper cap solid state rectifier. It worked better than the tube rectifier as far as ease of biasing the tubes, and is a lot quieter than those cheap rectifier tubes. The Weber that Bob recommends for the ST-120 is much stouter than a single rectifier tube. Weber calls it a 2X (double) rectifier. Also, the Weber has a slowed start-up, so you needn't worry about blowing up your tubes. I recently took out the Weber and replaced it with a new JJ tube rectifier to see if I was missing some "tube magic", and all I got was more noise and a fear I was going to blow up a tube every time I turned on the amp. The Weber rules in this particular amp, IMHO.

[sunnysal]

I have heard that ST120's are hard on rectifiers and I fully back the advice on getting an uprated rectifier would be a good idea. I have had bad luck running my tube amps on votage regulators and UPS's, all my failures have occured when connnected to those, I cannot be sure they were to blame but since I have disconnected my tube amps form those I have not had a single failure. T

[Guest davidness]

Thanks for all of the input.

In addition to all of the tube rectifiers I've gone through, I've also gone through at least one of the Weber Copper Cap (Solid State) WZ34 rectifiers (GZ34/5AR4 replacement). I know I have at least one more WZ34, and also two more of the 'double-strength' WZ68's, which I wasn't told about until more recently, which is what Bob now recommends. Bob has started going through my amp, and has found some bad soldier joints in key components, so there might have been more going on than just the UPS causing my rectifier problems. A couple of capacitors actually fell off the board during shipment!?! (not my soldier work, btw).

I'll know more in a few days.

Once it's been 'refurbished' by Bob, the use of the solid-state Weber WZ68 and getting the amp off of the UPS sounds like it should make for a much more reliable configuration.

[Bob Latino]

Above is what the inside of David's amp looked like when it got to me. One coupling capacitor had popped out completely, another was just hanging on by one connection and the other two were loose. I checked on the history of this amp and it was built with the stock coupling capacitors. The customer (who was I believe the second owner of the amp) later requested a set of Russian PIO capacitors from me and installed them himself. Unfortunately he didn't do a very good soldering job. Most of the capacitor connections appear to be cold solder connections without enough heat applied. I believe this was the problem with David's amp. Each one of those Russian PIO caps looks at +275 VDC on the inside terminal and about -55 (negative 55) VDC on the outside connection. This is a voltage swing of about 350 volts. I can't be sure but possibly after the board heated up, one (or a number of) solder connections went in and out of contact causing a 350 volt voltage spike which could take out the rectifier and/or an output tube. Just to be safe I put in a matched set of four new Russian PIO caps. The last Email that I got from you David was that the amp had been running fine since it was returned to you.

Bob Latino

[Guest davidness]

Yes, since Bob securely installed replacement Russian PIO caps, the amp has been perfect. I wish I had discovered the problem a year earlier and saved the lives of those 12 rectifiers! I swear, I had been inside the amp many times and didn't notice the bad solder joints. It took the gorilla handling of UPS to knock them loose making the problem obvious to see. The amp now sounds freakin' awesome, and seems rock solid with no more problems.


I really want to publicly thank Bob and commend him on the great value of the Latino VTA ST-120, and for his help in repairing my amp.

While all this was going on, and before I knew my problem would be resolved by Bob, I came across a chance to buy a NOSValves VRD45ST that I just couldn't resist. The VRD is an amp that costs over twice as much as the ST-120, but the difference between the two, sound quality wise, is much closer than you'd think (sorry Craig. Your amp is beautifully designed & made, no doubt). I'm still rolling tubes and conducting a thorough shootout to see which one stays, but it is saying a LOT of the Latino ST-120 to see it wasn't a slam dunk and the comparison is as close as it is.

If you need a great sounding amp that is also a great value, look no further than one of Bob's amps. Better yet, buy the kit and build it yourself (just do a good job of soldering and it'll turn out fine).


BTW, Bob's default choice of tubes, the NOS Mullard CV4024's (12AT7) and the Valve Art KT88's are, in my opinion, the best sounding tube compliment on this amp. I've rolled a lot of alternate tubes, and have come back to these as my favorites.

[Guest davidness]

PS: Bob, welcome to the Klipsch Forum! There are a lot of your customers that hang out here.