looking for very good SE output transformer

Over at diyaudio that has been a popular OPT for the tubelab SE amp along with the bigger CX version. Some use the 5K primary for less distortion at the expense of a little loss in output power. I would go for the GX for sure as it has had really positive reviews in that it sounds better to some than the CX. Price is nice too!

George Anderson of tubelab.com has a form @ diyaudio & you can look at a schematics for his affordable PCB's of his SE & SET amps. From what people say it, you might really like it! He was let go from Motorola a few yrs back and I think he want to get back to work, so maybe you two can talk & maybe you'll learn a lot about tube Hi FI !

For high end SE or SET George has used Electraprint a US maker that is popular for SE ones on the Forums. You are looking at about $150 ea. but depends on Wattage and Ma you will be running at , but may be more what your looking for and expect! Some have Golden Ears and it sounds like you will appreciate the higher quality ones!

Are you saying higher primary resistance than for max output power lower distortion? I have the other thread on this subject. If you have knowledge on this, please join in. I read it the opposite way that you use lower primary impedance to get lower distortion. I have no idea which is the right way. Please help.

For this particular SE amp, I am just trying to see whether I can salvage the kit amp as I spent $250 and it's a total garbage. Before I dump it, I just wonder whether I can spend like $100 to make it at least acceptable. I don't think my speakers are efficient enough, so I don't expect a lot. Just wonder any way to at least improve it a little. My money is going to be on the push pull tube amp as in the other thread where I am willing to spend the money. PP is going to be more in line with my speakers.

Thanks

Alan
 
That's what I've read on the forums over the years and George Anderson (Tubelab) says he prefers it for lower distortion, though at the expense of a little power! There may be some situations or tubes where it's not good however, but on many SE or SET amps it seems to be a fact. We aren't talking about a big impedance change either!

Some PP amp designs benefit using say 10K primary over 6K on lower power ones and for the higher power PP you want for KT-88 type tubes close to 5K would be nice and not a big change! Dynaco used 4.3K on their med & high power ST-70 & Mark III. Many high end vintage 50-70W /CH used lower like 3.5K to win the power wars! They were however using the best wound OPT's so distortion wasn't an issue.

Perhaps someone else can pipe in! There are issues on GNFB to consider also and many opinions also. Some say to have none and others use some. Depends on the Output Transformers also!

As for the Edcors on that cheap SE amp I'm sure they will be somewhat better, but

PS. Watch for some good second hand fairly efficient speakers for best results!

The circuit may benefit from a little SS CCS like George has done too!

Read the Fisher forum on AK how Dave Gillespie has really improved the lower power amps with his EFB mod which is a little SS to help the tubes on PP. He started the Mod for the Dynaco ST-35/ SCA-35 for output tube life and sonics. People asked about other amps!

Another thing I may be wrong about , but I think it's harder to do nice sounding big amp in SE or PP unless you spend fairly big $. The circuit may be more complex too due to more stages required etc.
 
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Hi Shadowdog

How should I address you? I don't know your name.

I went to Tubelab but there is no contact information that I can write to him. I really want to find out the answer and hopefully why.

I am a true believer of mixing SS and tube which ever can do the job better. I am still studying tubes, it's going to be a little while before I am ready to talk design. I am just trying to take it all in. So far, sounds like OPT is the most important thing in the amp, everything else are secondary. I look at a few schematic, circuit seems to be very primitive and basic.

I am planning to build the first amp on wood board to make it very easy to change and modify. I am planning to start out with the most basic and conventional design using all tubes in the signal chain. I want to listen to an all tube amp first, then I am going to open up to every other possibilities. I already identify a higher voltage opamp that has reasonable THD spec. I already thinking about using opamp as input stage and even can be used as phase splitter stage as it can drive +/-40V or so.

That's something I still don't quite get, tubes are very high distortion, but I notice the newer school of thoughts is trying to get more forward gain, then use GNFB to lower distortion and increase the damping factor. Then it's going to be more and more like SS amps!!! That's why Before going wild, I want to hear with my own ears, an all tube traditional amp with high quality OPT to set a standard first. Then experimenting with mix SS/tube technology. I am experienced in SS ( hell, that's all we have in the rest of the industry), so it will be a piece of cake to add in SS part like CCS and all.....That's what SS amp use all the time. Using MOSFET source follower rather than cathode follower will increase drive current to a different dimension. But that's for later.

Alan
 
Sorry I didn't say my name Alan as it's Randy!

I thought George did have an email address on his site to contact him to buy PCB's as he was still selling them recently. He may only respond on his Tubelab forum under Vendors @ diyaudio.com or under tubes on that forum.

There is another interesting EE over on the tube section by the name of Pete Millet that has also been selling PCB's on Ebay for yrs also. It's kind of funny (not for them as George is into building souped up amps with Pete's PCB's) as many of Pete's designs use out of production TV (mostly sweep type) tubes that can be had cheap (like a 1$ ea) till someone in Asia sees what they are doing on the forum & buys up all tubes!

Google Big Red Board or Engineer's Amplifier and you will also find his great & interesting web site with many tube books all free to read as Pete has scanned all he gets!
 
Hey studying the prior art is step two, after getting one's head around how tubes actually work. No sense studying something you don't understand. Like playing piano gotta build up chops first, Chopsticks precedes Beethoven for a reason. As for the classics look here:

http://www.triodeel.com/schindex.htm

Dave, have you heard a W6M? I haven't but that's certainly heathkit's masterpiece, would love to see one in the flesh some day. And Alan, it uses cathode followers and lots of trick negative feedback stuff, plus no tube rectifier.
I got a pair, they are beasts. Might be the largest PP outputs for kt88 amp although the Fisher 200 has some giant OPT. But that is because they are potted like the W6. Still impressive amps. I have not rebuilt mine. Still on the fence on what direction to take on that one.
 
I got a pair, they are beasts. Might be the largest PP outputs for kt88 amp although the Fisher 200 has some giant OPT. But that is because they are potted like the W6. Still impressive amps. I have not rebuilt mine. Still on the fence on what direction to take on that one.

Stock! They're a limited resource.
(climbs off soap box)

Seriously though, it shouldn't take too long to replace the capacitors and fire them up for a trial run. You could even J hook in some cheap film caps just to try them out.

Those Heathkits you have, the Lafayette 70 Watt amp, MC60s, some Altec models - how many other 1950s no compromise high power amps were there? It's definitely a rare and special breed.
 
You know when i first started into tubes, I was really inexperienced with audio and fell into the thinking that more tubes and higher power was they way to go. This culminated with my system consisting of Magnepan 3.6R speakers with MFA M75 amps and also a Roger Modjeski RM12 ? (PPP EL34). I was happy with that for about 4 years but still felt that there was something to the music that i was missing. It is then i started dabbling in SE amplifiers with more efficient speakers. Now i have Altec 19 and not a panel speaker in the house. LSS, i acquired the W6 in the "high power" days and never got around to rebuilding them. I got them "mothballed" so they are pretty safely stored.
 
I don't think Magnepan and tube amps go along. It's a panel speaker and low efficient. My friend has a pair of Magnepan, after he bought the Jolida 40W tube amp, he had to put that away in favor of a pair of more efficient, easier to drive speakers.

Problem is tube amp has very low damping factor, Speakers gone through quantum leap also, they designed with the availability of high damping factor, high power SS amps in mind, low efficient Martin Logan and Megnapan are two of those. You need big SS amp with high damping factor to bring out their glory. As I said, the SE kit I have sounded like crap with my speakers no matter how I modified it. it just doesn't cut it. I am sure I can buy a receiver less than $250 and kick the butt of that cheap SE amp.

Far as I concern, when I bought a pair of Heco in 1970 with soft dome tweeter, that was the best thing I even done, got away from horn tweeter. Never look back. Will never want to look at another pair of speakers with horns.
 
Thanks Randy

One thing I notice, anything relate to audiophile are very expensive from Japan. I looked on ebay, when they sell stuff, they asked for ridiculous price. Even the same amp was asked two or three time the price than the same amp selling in US. These must be very expensive in Japan. I know, being from Hong Kong long time ago, car is not a big thing, most don't own a car, so they have to have other ways to spend money..........hifi. I remember they can get really fancy with their hifi system.
 
I don't think Magnepan and tube amps go along. It's a panel speaker and low efficient. My friend has a pair of Magnepan, after he bought the Jolida 40W tube amp, he had to put that away in favor of a pair of more efficient, easier to drive speakers.

Problem is tube amp has very low damping factor, Speakers gone through quantum leap also, they designed with the availability of high damping factor, high power SS amps in mind, low efficient Martin Logan and Megnapan are two of those. You need big SS amp with high damping factor to bring out their glory. As I said, the SE kit I have sounded like crap with my speakers no matter how I modified it. it just doesn't cut it. I am sure I can buy a receiver less than $250 and kick the butt of that cheap SE amp.

Far as I concern, when I bought a pair of Heco in 1970 with soft dome tweeter, that was the best thing I even done, got away from horn tweeter. Never look back. Will never want to look at another pair of speakers with horns.


Actually magnepan (old ones anyway) have a very smooth impedance curve, and are almost an ideal load for tube amps, since they aren't too sensitive to damping factor. The only bad thing is they need plenty of power, so enter the 6550/KT88. Probably your friend's amp just lacked the power.

The audio research plus magnepan system has been a high end match made in heaven for going on forty years already.
 
You know when i first started into tubes, I was really inexperienced with audio and fell into the thinking that more tubes and higher power was they way to go. This culminated with my system consisting of Magnepan 3.6R speakers with MFA M75 amps and also a Roger Modjeski RM12 ? (PPP EL34). I was happy with that for about 4 years but still felt that there was something to the music that i was missing. It is then i started dabbling in SE amplifiers with more efficient speakers. Now i have Altec 19 and not a panel speaker in the house. LSS, i acquired the W6 in the "high power" days and never got around to rebuilding them. I got them "mothballed" so they are pretty safely stored.

I hear you there, I used to have big mono amps and Magnepans, now I have 2A3s and La Scala.

Still think the W6 is cool though!
 
Actually magnepan (old ones anyway) have a very smooth impedance curve, and are almost an ideal load for tube amps, since they aren't too sensitive to damping factor. The only bad thing is they need plenty of power, so enter the 6550/KT88. Probably your friend's amp just lacked the power.

The audio research plus magnepan system has been a high end match made in heaven for going on forty years already.

This is just hear say, my friend has a 40W or 45W PP Jolida with two EL34 tubes. That should be plenty of power. He said it just doesn't work. I know Jolida use GNFB so the Damping factor should be on the high side of tube amps.
 
This is just hear say, my friend has a 40W or 45W PP Jolida with two EL34 tubes. That should be plenty of power. He said it just doesn't work. I know Jolida use GNFB so the Damping factor should be on the high side of tube amps.

40W is too low for magnepan speakers, you need more like 75W to really awake them.

Also Jolida is a Chinese amp, and although they get some positive reviews, I'm hesitant to trust the design before seeing measurements and hearing it for myself
 
Something in the neighbourhood of the ARC VT100 (those things sound great with electrostatics), is more suited for the application
+1 regarding those praised Chinese amps, I've heard some and I don't know why, but they were just 'meh', even with good speakers with smooth impedance load... Maybe the irons?

http://www.monolithmagnetics.com/
Pretty cool (and good looking) output transformers (just in case)
 
I have no idea how the Jolidas are, I only have my friend's opinion. He loves it. He just use another pair of speakers and put the Magnapan away. He said he's going to bring them over to try it on my amp.
 
See if you can convince him to bring the Jolida over, how it works with your speakers can give you very useful insight into how well your speakers will work with the tube amp you're building.
 
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