Disclaimer
Everyone keep in mind that I have made this look deceptively simple and easy. It is not. I have developed a group of methods for doing this. My first one took considerably longer and had me pulling my hair out. After three or four you get the hang of it. I was also fortunate to have a design from someone who knew what he was doing. I have built other things of Gabe's and trust him. Be very careful of the design you choose unless you know how to troubleshoot. Also, be very careful around lethal voltages as well as some dangerous shop tools. Always use safety glasses and hearing protection.
Having said all that, do not get frustrated and give up, be patient and remember help is only a new thread away.
I will answer questions and post more about the sound of this amp as it burns in.
Everyone keep in mind that I have made this look deceptively simple and easy. It is not. I have developed a group of methods for doing this. My first one took considerably longer and had me pulling my hair out. After three or four you get the hang of it. I was also fortunate to have a design from someone who knew what he was doing. I have built other things of Gabe's and trust him. Be very careful of the design you choose unless you know how to troubleshoot. Also, be very careful around lethal voltages as well as some dangerous shop tools. Always use safety glasses and hearing protection.
Having said all that, do not get frustrated and give up, be patient and remember help is only a new thread away.
I will answer questions and post more about the sound of this amp as it burns in.
Great going, looks far better than my unfinished SRPP 6B4 SET 
I have been mucking around with the circuit a little, I now use DC on the filaments to get rid of all the hum, and I have inserted a little negative feedback (not too much, there isn't enough gain) which made little difference, but seemed to improve the bass a bit. I wish I had a scope!
With regards to the high frequencies, after a few days they had definitely improved. It's all there now, much to my relief.
Next thing I will try is increasing plate dissipation on the Sovtek 6B4, up to 25W or so. Anyone tried fixed bias on a SET?
~h~
I have been mucking around with the circuit a little, I now use DC on the filaments to get rid of all the hum, and I have inserted a little negative feedback (not too much, there isn't enough gain) which made little difference, but seemed to improve the bass a bit. I wish I had a scope!
With regards to the high frequencies, after a few days they had definitely improved. It's all there now, much to my relief.
Next thing I will try is increasing plate dissipation on the Sovtek 6B4, up to 25W or so. Anyone tried fixed bias on a SET?
~h~
Why Gabe, don't tell me you didn't know it would work. Oh man, that could have been a huge waste of time...I could have been a failure in front of the whole forumn...
How could you do that to me Gabe... I knew it would work and it doesn't sound bad at all with the 125's. I left out the blocking cap at the input though. I think I should have put a resistor in it's place though as my preamp can drive it well into audible distortion and very loud output.
Shifty:
Thanks, I'm sure when you get done mucking about you'll dress her up a bit. I followed your thread on that amp earlier. Glad to see your still working with it. I will probably let this one burn in for a bit before I make any changes. I've been listening to a 6Bq5 pp for a while now and my ears are picking up a huge difference. My bass is excellent though it's probably due to my TL's. They really put out good tight bass, and get pretty low as well. I can't wait for the high's to catch up.
The 125ESE's will get you going with SET. After that you can always move up to better. I probably only have 300.00 in this amp. To me that's pretty cheap for SET.
How could you do that to me Gabe... I knew it would work and it doesn't sound bad at all with the 125's. I left out the blocking cap at the input though. I think I should have put a resistor in it's place though as my preamp can drive it well into audible distortion and very loud output.Shifty:
Thanks, I'm sure when you get done mucking about you'll dress her up a bit. I followed your thread on that amp earlier. Glad to see your still working with it. I will probably let this one burn in for a bit before I make any changes. I've been listening to a 6Bq5 pp for a while now and my ears are picking up a huge difference. My bass is excellent though it's probably due to my TL's. They really put out good tight bass, and get pretty low as well. I can't wait for the high's to catch up.
The 125ESE's will get you going with SET. After that you can always move up to better. I probably only have 300.00 in this amp. To me that's pretty cheap for SET.
Well.... I did say I worked on the concept but hadn't had the chance to actually make one.
As some other designs I had done, I knew it would work, but how well is always a mystery... and a pleasant to ecstatic surprise. Hence why I wouldn't use a program like Spice. Where's the fun in knowing how a circuit will work before building it and trying?
I love the smell of burnt circuits in the morning!
Thanks for having the confidence in me.
Enjoy!
Gabe
As some other designs I had done, I knew it would work, but how well is always a mystery... and a pleasant to ecstatic surprise. Hence why I wouldn't use a program like Spice. Where's the fun in knowing how a circuit will work before building it and trying?
I love the smell of burnt circuits in the morning!
Thanks for having the confidence in me.
Enjoy!
Gabe
I've been running it all day while I build on the 6L6 push pull. It is really starting to smooth out really nice now. It is an en excellent amp with extremely high detail. I can just imagine it with some good iron. I can really see what the hype about SET is all about now. Looking at some of the other 2A3 designs I had no doubt it would work. Why the 12AX7 though, why not the 6EU7 or a 6SL7 driver? Just curious. I built the amp with the filaments set up just like the plan and get absolutely no noise what so ever out of my speakers. I havn't done any measurements though. Thanks again Gabe!!!!!!!!!!!!!!!!
AHUM.
Hi,
6EU7 is a low noise version of the 12AX7A and obsolete, it only runs from a 6.3 heater supply.
6SL7, kind of a grand-daddy of the 12AT7A but in octal basing and although it exists in in a 12.6 V heater incarnation the 6V one is more popular...quite likely because people stop looking at the databooks once they find a usable type for the task at hand and most output tubes uses 6.3V heaters...
Pick up your 12SL7s now guys, the writing's on the wall already.
Cheers,
Hi,
6EU7 is a low noise version of the 12AX7A and obsolete, it only runs from a 6.3 heater supply.
6SL7, kind of a grand-daddy of the 12AT7A but in octal basing and although it exists in in a 12.6 V heater incarnation the 6V one is more popular...quite likely because people stop looking at the databooks once they find a usable type for the task at hand and most output tubes uses 6.3V heaters...
Pick up your 12SL7s now guys, the writing's on the wall already.
Cheers,
6EU7, 12AX7, 6SL7...
I'll let you boys argue over those. Sovtek still makes them all and doubt that they will stop on your say so.
As for why the 12AX7? Because there are more 12AX7 die hard fans than any other. But you could sub for either of the above.
BTW Frank, the 6SL7 has more in common with the 12AX7 than AT7. the 12AT7 has up to 10 mA of plate current capability. It also has a medium mu, something like 40. The SL7 has a mu of 80, a 2-3 mA max plate current, and a similar plate resistance to the AX7.
Glad it sounds better to you. I just finished two 2A3 based amps for customers. One is the Afterglows, and one the Sun Audio. The customer for the Sun wanted to use 45's. I liked the sound, but preferred the 2A3's. The Afterglows are very nice, and not yet broken in.
Over all... I prefer the 300B solely for the power. Otherwise the 2A3 seems very close.
Gabe
I'll let you boys argue over those. Sovtek still makes them all and doubt that they will stop on your say so.
As for why the 12AX7? Because there are more 12AX7 die hard fans than any other. But you could sub for either of the above.
BTW Frank, the 6SL7 has more in common with the 12AX7 than AT7. the 12AT7 has up to 10 mA of plate current capability. It also has a medium mu, something like 40. The SL7 has a mu of 80, a 2-3 mA max plate current, and a similar plate resistance to the AX7.
Glad it sounds better to you. I just finished two 2A3 based amps for customers. One is the Afterglows, and one the Sun Audio. The customer for the Sun wanted to use 45's. I liked the sound, but preferred the 2A3's. The Afterglows are very nice, and not yet broken in.
Over all... I prefer the 300B solely for the power. Otherwise the 2A3 seems very close.
Gabe
It would seem to be very easy to pop a 300B together just like this one. This is starting to get fun as I understand more and more about it. One day I might be a hot shot tube design guru like some others around here. At least I don't have any preconcieved notions about it. Ignorance is bliss
Perhaps I will juice this one up a bit.
Perhaps I will juice this one up a bit.
OK, OK GET technical if you want to!
Oh, the AY7 is 40. Sorry. Well, for the technical folks, µ of 44 actually.
But there are more differences between the AT7 and the SL7 than the SL7 and the AX7.
As for the 300b, it also sound very natural. Most natural tube I have ever heard. Power being hand in hand with it.
Smile!
Gabe
Oh, the AY7 is 40. Sorry. Well, for the technical folks, µ of 44 actually.
But there are more differences between the AT7 and the SL7 than the SL7 and the AX7.
As for the 300b, it also sound very natural. Most natural tube I have ever heard. Power being hand in hand with it.
Smile!
Gabe
Weeeellll... there's something about kilovoltages that frizzles my hair.
Been zapped by 13 kV once or twice... big dummy me. Working on old TVs with the power ON. Touched the anode cap of the horiz output once (I think about 1 or 2 kV). And the output of the tripler another. That was only about 7 kV.
OTOH, I did hear a transmitter tube amp once. Very live sounding. I was deeply impressed and moved to tears by the emotion of the music and sound combination. Very nicely done.
Here are a few pics of that get together. On one is a pic of some transmitter tube job all lit up.
http://www.home.earthlink.net/~oswaldsmill
Gabe
Been zapped by 13 kV once or twice... big dummy me. Working on old TVs with the power ON. Touched the anode cap of the horiz output once (I think about 1 or 2 kV). And the output of the tripler another. That was only about 7 kV.
OTOH, I did hear a transmitter tube amp once. Very live sounding. I was deeply impressed and moved to tears by the emotion of the music and sound combination. Very nicely done.
Here are a few pics of that get together. On one is a pic of some transmitter tube job all lit up.
http://www.home.earthlink.net/~oswaldsmill
Gabe
The trick is it's either right, or not right. It's yes or no, there's no in between. Your cuts and angles are correct or wrong, and no amount of fudging or wood putty will make up for a wrong cut.arnoldc said:nice woodwork! i hope i have the skill and equipment to make one like that
To summarize the Waterboy's biggest fan "YOU CAN DOO IT"
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