captainbeefheart

Depends on how you use your speakers, if you have flea or low powered amps and listen to your speakers conservatively I am sure you can get away with using the crossover with the K-77. They have to write this warning because of worst case scenario, which actually happens quite frequently where someone runs a high powered amplifier full bore to fill a dance hall or large room party etc... If this is you then I also recommend only using these crossovers with an upgraded tweeter that can handle the power. So the answer to which speakers can use this is it depends on the tweeter in either LaScala, Klipschorn, or Belle speakers OR if you do not push your speakers hard and use low powered amps (less than 10 watts I would think) your fine with just the K-77 in either of these three speakers. I prefer the AA networks in my LaScala's personally but some people like the A/4500, it's subjective.

Wow that is just fantastic! I am so happy you got one too. If you need the service manual for it I can email it to you. My unit didn't work when I got also and I forget what it was but it was something really stupid like the preamp to power amp jumpers or something, I just remember it was a real easy fix except for the cabinet I had to refinish. Yes it is vaneer on the cabinet but looks really nice. Fabulous unit for the price, you will be happy when you get inside and have a look at the guts.

The S-7100a definitely does not have output transformers which will make repairs much easier in the future if one of the output transistors decide to die. I doubt I will have any issues since I went through the whole amp when I got it and made sure to set bias where there is not crossover distortion and harmonic distortion was under the rating of .25% @ 2v across an 8 ohm load. Some guys like to go and crank up the bias for more Class A operation and that's when you run into issues. I just dug out the service manual for the S-7100a and the confusion about output power might be because of the way they rated the amplifier. At 1kHz into 8 ohms it is rated at 22 watts which is more than the S-7100. So yes the later S-7100a version is more powerful but they then go and rate it for only 14 watts into 8 ohms @ 20Hz-20kHz and 18 watts 40Hz-20kHz. There are no transformers in the signal path so that can't be the issue with low frequency de-rating, it must have higher distortion at low frequencies so the de-rate the power to get good distortion figures. When I finish up unpacking all my audio stuff I plan to pop it back on the test bench and take distortion reading at different frequencies. Since I am no longer into vintage tube amplifiers I am getting rid of all my tubes I will never use. I rigorously test any devices I sell, especially tubes that will go into hifi equipment. I do not just pop into a transconductance tester and call it a day, I prefer to use a mocked up real circuit with a real load and match gain and distortion specs and obviously only sell low noise/microphonic tubes. That way there the end user can confidently install the tubes and have close matching gain and distortion figures for each channel. The vast majority of vendors do not take this amount of care into your gear, they just sell you tubes and hope for the best but being an engineer I know not all tubes will be the same and so I take the extra time, I and I mean it is a lot of time to make sure someone gets the best possible outcome from their purchase, not a roll of the dice. You can easily get these Sherwood amps for under $100 and they match very well with efficient Klipsch speakers, I have gotten more compliments from the sound of this Sherwood and RF-7 combo than using much more expensive receivers and power amps. We played cards with another couple last night where my friend once managed many bands along the North Shore and he was blown away with the setup, he was like a little kid asking to play his favorite songs. Something about some of these older SS amps that don't quite measure great on paper but just sound so life like, almost like a good tube amp really. My plan was to go through it and refinish the wood cabinet and pass it along to a friend that is in need of a good amplifier but the wife and myself ended up putting it in the keeper column. It was hideous when I first got it, someone spray painted a fake aluminum color on the veneered wood cabinet!! A quick strip and a very light sanding then a couple coats of tung-oil finish and it looks gorgeous again. Highly underrated amplifiers even though they are very well built internally and sound amazing. My guess, it hasn't enough power for the majority of people with power hungry speakers out there. Their loss.

Great Album!! I had it spinning on the TT and figured the album cover would make a nice backdrop for taking pictures of tubes I plan to sell. If you are not interested in the tubes at least you get a nice under-boob glimpse.

I got two matched quads of authentic vintage Mullard "XF2" EL34 Double O O getter pentode's for sale. PM to discuss price Thanks

I think it is because the economy has gone to shite because I have a beautiful pair of oiled birch LaScala's in mint shape for sale asking only $2,000 which I thought they would sell quick at that price but it has been like 2 months now and all I have got was BS offers for $1,000, some guy offered me $500!!! I had to ask if he was serious and he was dead serious thinking I would let em go for $500. Nope sorry keep it moving buddy LOL Good luck with sale

Sorry guys I have been inundated with messages to respond to. Far more interest than I ever imagined for tubes. I guess they have gotten pretty rare looking at the market for pricing them recently. I want anyone to fully understand that I am not your average fleabay tube vendor that knows nothing about tubes. I cringe everytime I see "tubes test at %80" or some rubbish like that. You have to be aware that tubes DO NOT have a linear lifespan you can relate to a % percentage, it's impossible. Tubes for the most part stay at their gm for their whole life and once emissions start to drop off at the very end of their life gm will start to decrease. A good tube will be around 20% +/- it's average transconductance. So for a 12AX7 that's roughly 1300uMhos to 1900uMhos transconductance values where 1600uMhos is average. I test all tubes in circuit for transconductance AND gain AND distortion. I also test for noise the same way Brent Jesse does which is in a real circuit hooked up to an oscilloscope and speakers. So it isn't just the tube you are paying for, it is the hours and hours of time I spend to weed through and only use or sell top tier tubes which is why they are worth every penny as you know it will be a great tube(s) that will perform excellent for many years to come.

I have several Klipsch speakers, reference floor stands and bookshelf speakers are great and I do not find them too sharp. I would say my main system is my La Scala system, 2.1 with a self powered sub-woofer. The living room has the RF-7's currently mated to a vintage Sherwood S-7100A good for about 25 watts per channel. I really like the Sherwood receiver, really high build quality inside and it sounds great. Many people overlook these amps and you can scoop them up cheap. The wife doesn't like to fiddle with sources and what not, she mostly enjoys listening to WCRB classical station or the oldies stations on FM air waves which the Sherwood does in spades well. It is also connected to the TV via the AUX input where we can enjoy CD's, Bluray, etc.... I have much more modern and expensive receivers that I can hook up but we have been enjoying the Sherwood a lot lately so it is staying for a while. It pairs very well with the reference floor stands and is not "sharp" or "bright" at all. We have very tall ceilings in the living room fwiw, roughly 8,000 cubic foot area.

Yes similar to tantalum but the aluminum polymer types have lower ESR especially at frequency extremes low/high. Compared to regular aluminum electrolytics tantalum are more reliable, have better dissipation factor, and basically they are more stable and operate better over larger frequency and temperature range. Problem is they are more expensive so for power supplies we mainly stick to aluminum electrolytics, besides a little ESR in a power supply decouple cap is mostly beneficial to dampen LC resonance.

I am not missing anything, I said several times he built you different networks, that was my point. Yes, that is all I am saying. Your original post made a statement that I will quote: I was merely pointing out that it was the added inductors to the new networks, mainly the 500uH in the horn section that probably accounted for why you liked the new networks you had built. I am sorry if you took my comments as me being "arrogant", that was not my intention. My only intention was to point out that many people agree the added 500uH inductor to the horn section is an improvement with the A/4500 network. And, if you had your old networks you most likely would have liked them better if you added this inductor.

He actually added two inductors that were not originally in the A/4500 network, the 500uH in the mid-horn network and the 245uH inductor in the tweeter network. So comparing apples to oranges like I said since the built Deang network is completely different vs the original A/4500 network. Look at your board, the original A/4500 only has one inductor for the woofer and the autoformer for the mid-horn, your networks have 3 inductors and the autoformer.

Your original A/4500 crossovers do not have the 500uH inductors in the mid horn filter network which you have in the crossovers Deang made for you, so yes he did add a non-original component to the network so it is now a modified, non-original network. Get it? He didn't build you the exact same network, it is different because of the added inductor. Comparing apples to oranges since the actual circuit is different.

Might be a little off topic but I am curious about something. Has anyone tried using two low ESR dry type polymer electrolytics for crossovers? Mainly for the 13uF capacitor, you can place two 22uF back to back giving you a 11uF bipolar capacitor and then place a high quality 2.2uF film capacitor in parallel. This gives us the value of 13uF and still maintains low ESR. Price is less than $10 total for the 3 capacitors. Here is a datasheet for the type of capacitor I am talking about; https://content.kemet.com/datasheets/KEM_A4072_A759.pdf Since it is a dry type electrolytic they won't dry out over time

The added 500uH air core inductor in series with the mid horn driver Deang used on the A/4500 is most certainly the reason why you like his network over the previous versions that didn't have it. You could have just added it to the first a/4500 in your LaScalas and like you said you most likely would still have them today. It seems universal that the added inductor improves the A/4500 mid horn sound. Who knows, maybe the extra 200nF of capacitance in the tweeter filter is audible also.

More tubes I will never use again. When I had amps that needed a 12AU7 I preferred Amperex the best but harder to find. Made in Holland, Heerlen I much prefer the 6SN7 and 12AU7 are electrically identical in regard to tube properties; mu=gm*rp but the 6SN7 is much more linear and will yield less distortion. But someone with an amp already using 12AU7 these are going to be the best you can find I guarantee it. Message me if you can use them, thanks.

OH SIDE NOTE!! I found out the driver tube for the new Western Electric 91E amplifier is a 12AT7. I was a little unimpressed by this selection but I can see why they went with this selection; Relatively high mu, low rp and the ability to run some decent current through them and have them take it with their 2.5 watt plate dissipation rating, the 12AX7 is only rated for 1 watt for example. They are in current production and NOS variants are not through the roof expensive. Plenty of small power sections use a 12AT7, the famous Fender reverb circuit uses the 12AT7 with both sections in parallel as a single ended transformer coupled tank driver power amp, the tank input impedance is 8 ohms and the tube drives it just fine good for about 1 watt of power into the tank. Should be good driver for a 300b.

I am currently working on the model in LTSpice, the trick is the resistor values to get the best performance. With limited time to do this it may take me a few more days to find the time to go back and fine tune the circuit, after I will post the details for anyone wanting to try and build the circuit. It may even be fun to use a more standard, less expensive tube like say a triode wired EL34 tube which we will be able to at least double the power output. E.g. Anyone can build an inexpensive SET amp that puts out 10 watts per channel and uses inexpensive toroidal output transformers AC coupled. No DC current in the output transformer means we can get the inductance we need without the extra inter-winding capacitance and high leakage inductance. The output transformer can be a $15 Antek transformer and still get a very wide bandwidth. I think anyone wanting to get into SET amps would be thrilled at the prospect of a 10 watt output power and a price tag of ~$300 total depending on chassis selection. I prefer a steel chassis with a nice finish paint, two tone design with the transformer bells painted a complementary color to the chassis. My latest favorite color scheme are both BMW colors, a Metallic Blue for the Chassis with a complementary Mineral Metallic white. I purchased both these colors at NAPA mixed in a spray can, they have two cans per color, one is the metallic base and the other being the actual color. Then topped off with a nice clear coat. I spent $100 on just these paints alone and I have a lot left in the cans so my next several projects are going to be using these colors. My wife has an X5 with the MIneral Metallic white color which is where I got the inspiration, my good friend has the blue color on his M3. He painted his spare rims with the Mineral white Metallic color, the blue and white just looked so lovely together I made my mind up that was going to be my next color scheme for projects.

I am very shocked at the amount of interest in these tubes!!! Please be patient as I received MANY messages regarding these tubes and I will respond to everyone. Thanks

I have smooth plates in my phono preamp but both ribbed or smooth are great tubes for phono section. I have tried every tube under the sun and always go back to telefunken for my phono preamp, they are the best. What you want is ones screened for low noise and matched gain structures. I can match up a nice pair for you. I am a little overwhelmed, I just signed on to look at the forums and have over 10 messages in my inbox for these tubes!! I am going to respond to everyone in order, private message me and we can go over details.

Still unboxing things from our move and I am on to my audio stuff. We had to prioritize getting rid of a lot of other things to downsize before the move but now I need the awful task of figuring out what should stay and what should go for audio stuff. I only have one phono preamplifier that uses two 12AX7 tubes. Many moons ago lots of equipment used the 12AX7 and I always preferred European tubes, mainly Telefunken so I have the most of those. I also tinker and like to make amplifiers, I get the itch to make something every few years or so but I don't ever see myself making anything with a 12AX7 in it ever. I do like my phono preamp but I have far too many to be considered spares for an amp that might need new 12AX7 tubes every decade or two. I really dig that there are a lot of tube users on this platform so I figured I would throw it out there if anyone on here might be interested. I have about 25 that can go, planning to keep 15 or so for the future.

I think you meant to say make it a true parallel filter -- and get the tweeter leg in front of the 13uF. The 13uF doesn't touch the signal going to the tweeter, it and the mid-horn driver now appear in parallel with the whole tweeter and woofer circuits, like most crossovers. My theory is profit, why waste a high pass filter when it's already there, just add upon it with filters with a higher roll-off frequency.

Which is why a while back when radial electrolytics became the king of the hill where all the best caps are radial and axial took a back seat I made a universal board that takes advantage of increasing improvement in radial capacitors where they can be wired in series for high voltage ratings. I am surprised to see so many builders still using axial electrolytic capacitors, the choices are slim, ratings not so great, and the price is more than double!! Another wonderful rectifier is NOS Russian 5C3S which is similar to the 5U4G, the filament of the 5C3S looks amazing when powered up, much different vs the 5U4G.

This does allow one to use lower voltage rated power supply caps, basically rated to working voltages or slightly above. This simplifies the power supply because most common filter value electrolytics are under 500v. Tons of 350v even 450v choices, slims down quite a bit around 500v. With a 400v B+ and using an indirectly heated rectifier you can get away with one 450v cap, using SS rectifiers or directly heated tubes you end needing at least a 600v supply. BUT if the amp is ever turned on without power tubes you will get these voltages even with a 5AR4. I had universal power supply boards made up that can be configured a number of ways and it is setup for series caps with balance resistors. I use two 350v caps in series for most amps giving a 700v rating for worst case scenario no load condition. I can see why the 5AR4/GZ43 is more popular for Class AB amps as they have lower impedance vs the more common indirectly heated rectifier tubes like 5U4 or 5R4Y but I build Class A amps and so load stays consistent enough where you will not get any rectifier induced voltage drop compression with a higher impedance rectifier. I scored a ton of NOS NIB 5931 rectifier tubes a long time ago and have been using them pretty much exclusively because they just won't die, they are very rugged and robust, they seem to handle more capacitance without shortening their life. Two of my amps I have 100uF as the reservoir capacitor and it's been going on almost 20 years with the same 5931 in them.

That would only effect the woofer circuit, like if you wanted to cut less mids from the woofer not the other way around like you want. If you want less bass in the squawker try lowering the 13uF capacitor to a 10uF.

Which tube rectifier are you going with? I mostly use directly heated types and use the 5v winding center tap to feed B+ to the first filter. GZ34/5AR4 are overrated