alzinski

I would have to agree with him. For blokes that can't seem to get rid og ground loops in their setups an audio isolation transformer can galvancally isolate equipment and put an end to pesky hum issues. Quality ones are expensive.

Any active preamp can only add noise and distortion. When you say "fly past" I am guessing you like a little coloration since you are using a 300b line stage. For people that want purity and have low Z out sources along with high Z input power amps a resistive divider and a source selection switch is all you need provided your not trying to run long cables.

You are a top bloke! Cheers!! I was looking at your VRD amps, they look nice. I typically procure vintage pieces which I see you restore. It's nice to see folks keeping the oldies going.

I did read and that's why I added the "or not" part of the sentence. There was clear disdain for the product from your corner and I wasn't sure if it was aimed at the marketing or the actual product. Thank you for clarifying it's the marketing you dislike.

Wow shots have been fired look out!! Nosvalves should have the right to voice his opinion on whether or not he thinks the amp is a POS or not, even if at the poor OP's expense. The OP should be happy with his purchase regardless of what others think, and to be honest it seems there is only one person pooping on the amp so that should tell us something. Maynard clearly has touched a nerve with one of his comments but I don't know enough to see the harm in his statements, again I defend free speech. However I am glad a moderator has stepped in to get this thread back on track as I am very interested in the amp and not anyones home business or ramblings about the way our current tech production has ended up. Trust me, I hate the fact that almost everything is made in China, or more specifically assembled in China. A lot of high quality components going into things actually come from Japan or Germany et cetera. Products are designed in the states or Europe and all the parts are sent from various places around the globe to China to be assembled. We here in the US seem to just consume. Good thing I still use equipment from back before color TV!! Made in the good old USA!! I think I will hook up some Fairchild 255a's tonight This may be a long shot but I can't be the only one that likes amp porn here, I would love to see the inside of the amp to see the craftsmenship and parts selection. If the OP can find it in his heart and the time to open her up it would be much appreciated. It sure is a beautiful looking piece of gear.

I completely agree in that it is a tip of the hat marketing tactic of which I have no problem with. You are not going to build a Corvette these days the same as you did in the fifties right? But it's still called a Corvette. On the other hand there are too many copy cat clone builders out there that recycle old circuits or worse, steal them from competitors. The former I see it all the time, same Fender amp circuits called something different without a mention of their lineage, same old Dynaco circuits but in a different box. Boring and unoriginal.

Test tones are -12db. Jim's figures are correct for figuring max power. (into 8 ohms) 12db is 4x 5*4=20 20*.7=14 14^2=196 Divide 196 by whatever load you like 196/5=39 39 watts or 25 watts for 8 ohms et cetera

So much confusion in here I reckon these blokes will never get this sorted out properly. I don't konw how much more laymen it can get. 1) Listen to music 2) Play test tone 3) Measure. The calculated result already accounts for max headroom as digital can only go to 0db. If it hasn't sunk in yet it never will. Purchase a megawatt arc welding amp and close thread, end of discussion.

I am certanly not criticizing anyone for liking what they like. A lot of the vintage gear I like was built with extremely poor components but had nice iron, decent circuits, and well executed layouts. The latter is more of my gripe with certain amps. The Moondog 2A3 amp circuit particulary isn't terrible at all and I can attest to the cascading 6SN7 triodes driving a 2A3 to be a beautiful combination. Staying well below grid current all is well, everyting behaves and the amp does it's job just fine. But with a 2 watt amp it is easy to get over zealous and turn the volume up to where you may encounter some blocking distortion and depending on variables within the circuit it could take a while to recover and stabilize, this will effect the sound. This isn't an opinion it is fact. Does the amp need direct coupling to sound good? Not at all. It is my opinion that low powered amps can benefit from it as a precautionary measure because they often run near max output. In a power supply filter where no signal is present (C1/C2) only see 120Hz. The cap reactance will be much larger at this frequency regardless of ESR which is in series and sums with the reactance i.e. When the reactance is 132 ohms (10uF at 120Hz) the impedance difference between film and electrlytic is moot. Now with higher frequencies where reactance drops the ESR can begin to dominate. This isn't opnion, it's fact. I figure since he may be going through the amps in the near future and possibly buying new caps or fixing things up I can express my opinion on the matter and he can weigh them at his own accord. It is just as easy for him to say as he did, I like the amp the way it is and I don't want to change them but thank you for input. Which is fine and I am no way offended. Somebody on the other hand may have done the opposite and say, let me try using this here as suggested, it will only cost me a couple bucks extra and a little bit of soldering time (some people like soldering). Then they listen, they either notice a difference or don't, the latter no worries either way and the former if results are good it's a benefit, if it's a negative improvement then it only take a little more time to undo. I was not suggesting the current owner go ahead and do major modifications, maybe some cap choice and value changes at most. Whether the original designer is offended that I said to DC couple things? Not sure, I doubt it, different ways to skin a cat they say. Layout Layout Layout. What I don't budge on is layout. So we have a good circuit that sounds good and is well recieved. My bone to pick would be mainly with component choice and layout. Engineering is tradeoffs. I like p2p a lot but large film caps just hanging on by their leads randomly placed is a recipe for disaster, and may be part of why he is having issues. Fourth owner and the amp is being shipped around and vibrated, something may have come loose and made a bad connection. I guess I just see a lot of audio related gear with huge film caps shoe horned in places where they don't belong. I can see in some places where the signal is present like as a cathode bypass or C3, but other places like in the power supply it's of no real benefit sonically. I would love to see sombody be able to audibly discern the difference between a film or lytic' cap in C1 position. Or, I am all ears if someone can explain to me why a film cap in this position is of any use. If you are worried about RF you can bypass the lytic' with a small film cap. At the end of the day I think it's a great excersise to discuss these technical matters openly. Nothing is better for progress than peer reviews and nobody has to act upon what is discussed if they don't think it has any merit. Thanks for listening to this old bugger. I love audio gear and discussing how they work. No offense intended.

I agree 100% about the output transformers, they are the most important part in the amp and is an area where you don't want to skimp. I am not in the amplifier business but knowing a thing or two about electronics and having heard hundreds of amps in my time I have an idea of what to do and what not to do, what works well and what doesn't work so well. I only offer advice from my life experiences, whether people listen or not is another thing. I am just trying to help you get your amp up and running. The 2A3 is a wonderful tube and it is indeed hard to make it sound bad.

To me it doesn't look like they are in series or in parallel. Follow the wires and do a continuity test to confirm but this is what I think is going on. C2 and C3 are supposed to be a multi section can cap but it's not in this amp. You can follow the wires to and from the choke. The white wire goes from C1 to the choke and the black wire returns from the choke to the board, that point on the board has a yellow wire going to C2 and R13 which goes over to C3. It then looks like a white wire above the board carries from C3 over to the orange wire of the output transformer. I don't want to sound harsh but this is a poor desing that uses expensive parts for no actual good reason. No need for poly caps in the power supply. This is a single ended amp and the output stage's signal goes through the power supply, specifically C3, it would be better to just use regular electrolytics throughout the power supply and just use a very large C value for C3 to keep the AC impedance low for all frequencies, 680uF works, it is 11 ohms at 20Hz where the 10uF 400v used in your amp is 800 ohms. There are two unused triodes that could have been put to good use, maybe a follower stage directly coupled to the 2A3. Maybe more open loop gain to use some global feedback. In the audio biz it appears people that don't understand good engineering practices tend to try and use expensive parts thinking it will be better, it's not, no substitute for sound engineering and proper use of components.

Why would they use two dual triode tubes and then only use one triode from each bottle? Strange..........

Why is there a resistor in the 5v winding serial to the rectifier heater? What value is it? Is it .40 ohms? That's going to drop your GZ37 heater voltage by over 1 volt. It's probably supposed to be R14 on the 6.3v winding?

Still using it? You are brave. You should check B+ voltage. You may have a L input filter instead of a C input now if that cap failed open giving you much lower supply voltage. Hard to believe that cap would fail open.................Maybe it originally failed short and gracefully destroyed itself open? Anyway it's safe to say go ahead and check voltages before replacing anything.

I agree with this. I don't see a poly cap failing so soon especially with a 350-0-350 transformer it will never see anything over 500v, actually factor in source resistance and a tube rectifier and it probably never sees anything close to that. One thing I am not sure of is the ripple current rating of them, maybe something you should look into. They don't specify in the datasheet but say this; "They have lower dielectric absorption factor, lower equivalent series resistance, lower inductance, higher resonant frequency, more linear impedance, lower dissipation factor, higher curr ent capacity, faster rise time, unrivalled handling of fast high current pulse, high temperature stability, excellent long term electrical and mechanical reliability and a better damped mechanical self resonance under dynamic signal conditions." Datasheet: http://www.wescomponents.com/datasheets/capacitor/solen/fastcap.pdf ***Make sure your rectifier isn't shorted from plate to cathode.***

You can't go past 0db. In your screen cap peak amplitude for channel 2 is -0.05db. For dynamic range 12db isn't enough but that's not what this test is about, he could have ran the test tone at -24db and change the maths around, either way it would tell you the same thing.

The zero global feedback SET amp I use has a better damping factor than the Manley Stingray II. I suggest you try that amp on your speakers before you buy it as it may not have enough control. I was worried my SET amp only had a damping factor of 8 but the La Scala's are under control with it. The Stingray says DF of 2.4.

Do you have the EQ set flat? Or do you have loudness setting on?

Make sure you check the operating points of the valves. Those black molded capacitors are most likely used for AC coupling stages and in my experience they are extremely prone to failure and leak passing DC on to the next stage messing up bias and shifting operating points. The wiring and layout around the full wave voltage doubler looks terrible. It shouldn't cost much money to have someone etch you a PCB to tidy things up. It would make things much more reliable and look much more professional.

As you say most if not all amps are voltage drive. They have low output impedance and as the load impedance vairies so does the current. For a voltage source providing 8 volts into 8 ohms you will have 1 amp of current. The speaker will dip down at some frequencies to say 4 ohms this voltage source still puts out 8 volts but now it needs to deliver 8/4= 2 amps of current. I would go ahead and say that the top SS amps are not current driven. A current drive amp or also known as a transconductance amp is a whole different beast. Almost all of the speakers you encounter are designed for a voltage source and not a current source. A current source will have high output impedance, a perfect current source will have infinite output impedance. It will deliver a precise current and depending on the load the voltage will change. How does current influence a low watt tube amp? Your question is unclear to me. Maybe it's worded backwards? How does a low watt tube amp influence current? A low watt tube amp, especially a SET with zero global feedback (around the output transformer) can have in todays standards a relatively high output impedance, say 3 ohms. This is where the amps starts to somewhat behave like a current source. Say the device is delivering 10 volts at 100Hz and the impedance is 6 ohms at 100Hz you can view it as a potential divider. 6 / (6+3) = .66 and so .66*10 = 6.6v You will have 6.6v across delivered to the speaker and 3.4v is lost across the output impedance of the amplifier. Now say the impedance is 70 ohms at 2.5kHz, 70 / (70+3) = .95 and so .95*10 = 9.5v You will have 9.5v delivered to the speaker and only .5v is lost across the output impedance of the device. Remember you can have high and low output impedance amps with either tube or SS. Output impedance effects damping. Some speaker have better mechanical damping than others and so they don't require ultra low output impedance. But the majority of speakers out there assume a low output impedance and it's needed to dampen the back EMF created by the moving mass of the woofer. A lot of older amps had variable damping to cater to different speaker manufacturers. Today's speakers are different.

For the folks that haven't done the test the test tone files can be found on page 1 thanks to John Albright for graciously uploading them for us. I want to recap everyone that has done the test so far. I am posting the highest voltage from either test tone. Derrickdj1 - 2v Tube Fanatic - 1.4v Wirrunna - 1.8v alzinski - 1.8v Skibum - 1.5v Starting to see a trend here. For anyone wanting to know how this will relate to power, especially Klipsch speakers I will try and explain, hopefully others can help me. For the SS guys. Most SS amps are going to be close to an ideal voltage source. Derrick had some good questions I will also try and address later. Fundamentally a perfect voltage source has 0 output impedance and won't lose any power, it all goes into the load, voltage stays the same and depending on load only the current changes. In real life there will always be some output impedance but it's low enough to assume a voltage source. When we are doing these measurement tests with a low output impedance device we want to know how much power one needs. I would go ahead and say it's safe to assume that somewhere in the low frequency range you'll see a dip on an "8" ohm speaker go as low as 4 ohms. If you are using a SS amp and doing the calculations I would just go ahead and do the maths for a 4 ohm load to be on the safe side. Derrick has the highest voltage reading thus far at a whopping 2v, for a 4 ohm load he will need an 8 watt amplifier. Seriously that's it, and that's being generous. For the tube guys it gets a bit more complex. Most tube amps use an impedance matching transformer at the output. The speaker load actually reflects from the secondary back to the primary as the load for the output device/devices. It's a safe assumption that most tube amps can handle a 100% load mismatch so seeing a 4 ohm load (at particular low frequencies) when connected to the 8 ohm output tap isn't a big deal. So for the tube amps users no need to worry about the lumpy speaker impedance of Klipsch speakers, just do the calculation for the average impedance which is 8 ohms. So for Derrick and his 2v test tone reading he only needs a 4 watt tube amp. Hopefully I have this somewhat correct.

If you want to participate that would be the way to do it. I didn't measure my sub for the test.

If you measured 1.5v on the voltage test then you are looking at 2.25 watts into an 8 ohm load.

Yes I agree. Not all amps are created equal. Some can hang others can't. You sound like you have quite the collection.

My better half went out for brunch so I had some time to do some very loud listening on my La Scala's. With the volume to where it pretty much drove me out of the room, and where if I was cleaning the whole house I could hear it clearly from every room I measured 1.8v. There you have it, 1.8v and most likely 3.25w amp would do which would explain why I havne't found the need to use anything other than a 5 watt single ended tube amplfier. I did hook up some huge Scott 265a mono's a week ago and my ears were ringing after. I didn't kill any neighbors Maybe next time.