Desinging my very first tube amp...
I am in the infant stages of designing a tube amp. Since this is going to be a first for me, I am going to be designing a single monoblock. If all goes well, I'll just build a second matching monoblock.
I'm not sure about much of it yet, as in if it's going to be SE or P/P and Tube or SS rectification. Heck, I'm not even too sure on what I'm going to use as output tubes yet!
I do know that I'm going to use a low MU tube for the driver stage, most likely a 12AU7 or 6SN7. I'll probably go with the 6SN7 because of the beefiness of it. If I go with a tube rectifier, it will probably be a 5U4G.
As for the output tubes, I have entertained the idea of everything from a single 6AS7 in P/P (naturally), to a bank of 6 - EL84's to a single or pair of 45's to even things like a single 211, 811 or 845 tube.
At one point, I was even thinking about running a single 6AS7 in stereo mode and run both channels off of each side of it for some nice SE power.
Please keep in mind that I am doing this project on a pretty tight budget and want to keep cost as low as possible.
BTW, I've got some questions if anyone feels up to giving some free advise...
1) So what do you all think?
2) Any suggestions on tube or SS rectification?
3) A single, pair, quad or even a bank of output tubes?
4) Who do you all use and/or recommend for PSU and output trannies? (Hammond, Parts Express, etc, etc...)
5) Any other good, reliable and inexpensive places to shop for various parts?
Thanks in advance!!!
I am in the infant stages of designing a tube amp. Since this is going to be a first for me, I am going to be designing a single monoblock. If all goes well, I'll just build a second matching monoblock.
I'm not sure about much of it yet, as in if it's going to be SE or P/P and Tube or SS rectification. Heck, I'm not even too sure on what I'm going to use as output tubes yet!
I do know that I'm going to use a low MU tube for the driver stage, most likely a 12AU7 or 6SN7. I'll probably go with the 6SN7 because of the beefiness of it. If I go with a tube rectifier, it will probably be a 5U4G.
As for the output tubes, I have entertained the idea of everything from a single 6AS7 in P/P (naturally), to a bank of 6 - EL84's to a single or pair of 45's to even things like a single 211, 811 or 845 tube.
At one point, I was even thinking about running a single 6AS7 in stereo mode and run both channels off of each side of it for some nice SE power.
Please keep in mind that I am doing this project on a pretty tight budget and want to keep cost as low as possible.
BTW, I've got some questions if anyone feels up to giving some free advise...
1) So what do you all think?
2) Any suggestions on tube or SS rectification?
3) A single, pair, quad or even a bank of output tubes?
4) Who do you all use and/or recommend for PSU and output trannies? (Hammond, Parts Express, etc, etc...)
5) Any other good, reliable and inexpensive places to shop for various parts?
Thanks in advance!!!
The following suggestions are my own opinions in good faith. Not everyone will agree but that's OK.
1) So what do you all think?
I'd avoid designing for difficult tubes. Since you're starting from scratch, you may as well avoid tubes with poor linearity like 6AS7 and 12AU7. 6SN7 is fine, though, as is its nine-pin miniature equivalent 6FQ7. Some of the OP tubes you mention require high voltages, which can make power supply design more tricky and (of course) can be more dangerous to use.
You need to decide what speakers you're going to use and what you expect in terms of sound character and power. The SE/PP decision hinges on this.
Don't skimp on the power supply. It's as important as the rest of the amp. Use a choke, preferably in a choke-input filter if your power tranny has enough voltage. You'll get better smoothing and regulation.
It's best to avoid OTL, IMHO. It's a topology that seems unnatural, terribly inefficient and potentially dangerous to me but YMMV.
2) Any suggestions on tube or SS rectification?
SS is a less expensive way to go but I don't think it really matters, as long as you get what you need from it. For example, if you plan on a PP output stage that is in a class other than Class A, you'll need good regulation and SS rectification will help. Avoid the old noisy SS diode types like 1N4007, there are better choices. If you plan on Class A (PP or SE), then regulation isn't so critical and you may prefer tube rectification, which is reputed to sound better than SS.
3) A single, pair, quad or even a bank of output tubes?
My preference for a first design would always be PP, using one pair of OP tubes per channel. Parallel tubes need to be balanced carefully, to avoid one tube hogging the current. PP is easier to design and build, in terms of achieving success. I realise SE seems simpler, at least in terms of the number of parts involved, but it's more of a challenge to get it working well.
4) Who do you all use and/or recommend for PSU and output trannies? (Hammond, Parts Express, etc, etc...)
Lundahl trannies and chokes seem to be quite reasonably priced, compared with other top-qualilty iron. They're not cheap, though. Hammond are less expensive and are probably OK for power tranny and smoothing choke but I don't know about their OP trannies. For the power tranny, I'd plan to have some spare capacity, in terms of available current, so it doesn't run hot.
5) Any other good, reliable and inexpensive places to shop for various parts?
Can't help here.
1) So what do you all think?
I'd avoid designing for difficult tubes. Since you're starting from scratch, you may as well avoid tubes with poor linearity like 6AS7 and 12AU7. 6SN7 is fine, though, as is its nine-pin miniature equivalent 6FQ7. Some of the OP tubes you mention require high voltages, which can make power supply design more tricky and (of course) can be more dangerous to use.
You need to decide what speakers you're going to use and what you expect in terms of sound character and power. The SE/PP decision hinges on this.
Don't skimp on the power supply. It's as important as the rest of the amp. Use a choke, preferably in a choke-input filter if your power tranny has enough voltage. You'll get better smoothing and regulation.
It's best to avoid OTL, IMHO. It's a topology that seems unnatural, terribly inefficient and potentially dangerous to me but YMMV.
2) Any suggestions on tube or SS rectification?
SS is a less expensive way to go but I don't think it really matters, as long as you get what you need from it. For example, if you plan on a PP output stage that is in a class other than Class A, you'll need good regulation and SS rectification will help. Avoid the old noisy SS diode types like 1N4007, there are better choices. If you plan on Class A (PP or SE), then regulation isn't so critical and you may prefer tube rectification, which is reputed to sound better than SS.
3) A single, pair, quad or even a bank of output tubes?
My preference for a first design would always be PP, using one pair of OP tubes per channel. Parallel tubes need to be balanced carefully, to avoid one tube hogging the current. PP is easier to design and build, in terms of achieving success. I realise SE seems simpler, at least in terms of the number of parts involved, but it's more of a challenge to get it working well.
4) Who do you all use and/or recommend for PSU and output trannies? (Hammond, Parts Express, etc, etc...)
Lundahl trannies and chokes seem to be quite reasonably priced, compared with other top-qualilty iron. They're not cheap, though. Hammond are less expensive and are probably OK for power tranny and smoothing choke but I don't know about their OP trannies. For the power tranny, I'd plan to have some spare capacity, in terms of available current, so it doesn't run hot.
5) Any other good, reliable and inexpensive places to shop for various parts?
Can't help here.
ray_moth said:
Great bang for the buck. Edcorusa.com has about the same Hammond quality for 1/2 the price
Of those tubes listed, 6SN7 or as Ray said, 6FQ7. The rest will put you over budget or be out of your skill since this is your first amp, or in the case of the 6AS7, not the best for linearity.
What power do you want? If you have efficient speakers, a simple SE could be the way to go.
Hi ray_moth!
Thanks for the input.
I failed to mention this before, but my father will be doing the majority of the building (a.k.a. - ALL of the building) as he's been building tube amps and crystal radios out of cigar boxes and old cookie tins since he was 8 years old!!!
In fact, he was just telling me the other day that back in the late 60's or very early 70's (before I was born) that he built from scratch his own design integrated amp using something like a pair of 6L6G output tubes per channel in PP which was good for around 35wpc. Tube rectified of course, and it had 3 inputs for tuner, reel-to-reel and phono with RIAA built in. And all of the other details of that amp that he told me about, it was like reading the description of a modern tube amp in Stereophile Mag or something!
So you see, I won't be totally in the dark doing this project. On the other hand, I still need to ask these questions because I want to get the proper parts and because my father isn't up to date on the most current "hi-fi" amplifier designs.
This is why I was thinking of a more advanced amp design. We've been talking about this for the last month or so and I'm really impressed with some of the stuff he's come up with so far for this amp. It's pretty much like anything I can think up, he can build it! I'm kind of just there for the "gathering of information" and for designing the layout and visual design of the amp. The final circuit design and build is totally up to him.
Again, thanks for the input so far and I look forward to getting some more soon from other members as well! I'm really looking forward to getting things rolling.
BTW, his website is in my Sig below.
Thanks for the input.
I failed to mention this before, but my father will be doing the majority of the building (a.k.a. - ALL of the building) as he's been building tube amps and crystal radios out of cigar boxes and old cookie tins since he was 8 years old!!!
In fact, he was just telling me the other day that back in the late 60's or very early 70's (before I was born) that he built from scratch his own design integrated amp using something like a pair of 6L6G output tubes per channel in PP which was good for around 35wpc. Tube rectified of course, and it had 3 inputs for tuner, reel-to-reel and phono with RIAA built in. And all of the other details of that amp that he told me about, it was like reading the description of a modern tube amp in Stereophile Mag or something!
So you see, I won't be totally in the dark doing this project. On the other hand, I still need to ask these questions because I want to get the proper parts and because my father isn't up to date on the most current "hi-fi" amplifier designs.
This is why I was thinking of a more advanced amp design. We've been talking about this for the last month or so and I'm really impressed with some of the stuff he's come up with so far for this amp. It's pretty much like anything I can think up, he can build it! I'm kind of just there for the "gathering of information" and for designing the layout and visual design of the amp. The final circuit design and build is totally up to him.
Again, thanks for the input so far and I look forward to getting some more soon from other members as well! I'm really looking forward to getting things rolling.
BTW, his website is in my Sig below.
Darn it, I keep forgetting things! LOL
As for output and the speakers being used...
This amp(s) will be used on speakers ranging from my brother's 92dB 1w/1m Infinity's to my 106dB 1w/1m Altec 511B/902-8B combo on my Klipsch Cornwalls (99dB). They are actively crossed over and bi-amped, but I could build a simple 2-way passive network for them, that much I CAN do.
But I'll be trying this amp on a wide selection of speakers over time, so I'm guessing at least 10 watts or so. One of the reasons I was looking at those 845 tubes is because they are good for a solid 20 watts each, if not more!
As for output and the speakers being used...
This amp(s) will be used on speakers ranging from my brother's 92dB 1w/1m Infinity's to my 106dB 1w/1m Altec 511B/902-8B combo on my Klipsch Cornwalls (99dB). They are actively crossed over and bi-amped, but I could build a simple 2-way passive network for them, that much I CAN do.
But I'll be trying this amp on a wide selection of speakers over time, so I'm guessing at least 10 watts or so. One of the reasons I was looking at those 845 tubes is because they are good for a solid 20 watts each, if not more!
BTW, here are a few pics of my father's handy work. He built this shortwave radio about a year ago for one of the guys on the Klipsch forum, all from scratch and with no schematic to go by... Well, except for the one thought up in his head at the time.
As you can see, he is quite capable!
As you can see, he is quite capable!
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Chops,
PP "12" W. multigrid O/P tubes switch selectable between triode and ultralinear modes should be fine for the speaker range you mentioned. If the nominal impedance of your brother's Infinitys is 4 Ohms, they might be problematic. If the impedance curve has significant dips below 4 Ohms, a tube amp may not be able to control the voice coils (too small a damping factor).
If you restrict the small signal circuitry to 'SN7 family tubes, you will wind up using Williamson topology. While "tried and true", Williamson amps have more than their share of phase shifts. REALLY good (COSTLY) O/P trafos are a must. OTOH, if you are open minded about the small signal tubes, I suggest you peruse the "El Cheapo" Project thread. "El Cheapo" is exactly the sort of low cost/solid performance project you seem interested in. If you build an "El Cheapo" with DynaClone Z565 O/P trafos, you will be pleased.
-----------------------------------------------------------------------------------
Daddy's work is SUPERB. You can rest easy about the end result.
edit: added remark about father's work
PP "12" W. multigrid O/P tubes switch selectable between triode and ultralinear modes should be fine for the speaker range you mentioned. If the nominal impedance of your brother's Infinitys is 4 Ohms, they might be problematic. If the impedance curve has significant dips below 4 Ohms, a tube amp may not be able to control the voice coils (too small a damping factor).
If you restrict the small signal circuitry to 'SN7 family tubes, you will wind up using Williamson topology. While "tried and true", Williamson amps have more than their share of phase shifts. REALLY good (COSTLY) O/P trafos are a must. OTOH, if you are open minded about the small signal tubes, I suggest you peruse the "El Cheapo" Project thread. "El Cheapo" is exactly the sort of low cost/solid performance project you seem interested in. If you build an "El Cheapo" with DynaClone Z565 O/P trafos, you will be pleased.
-----------------------------------------------------------------------------------
Daddy's work is SUPERB. You can rest easy about the end result.
edit: added remark about father's work
Eli Duttman said:Chops,
PP "12" W. multigrid O/P tubes switch selectable between triode and ultralinear modes should be fine for the speaker range you mentioned. If the nominal impedance of your brother's Infinitys is 4 Ohms, they might be problematic. If the impedance curve has significant dips below 4 Ohms, a tube amp may not be able to control the voice coils (too small a damping factor).
If you restrict the small signal circuitry to 'SN7 family tubes, you will wind up using Williamson topology. While "tried and true", Williamson amps have more than their share of phase shifts. REALLY good (COSTLY) O/P trafos are a must. OTOH, if you are open minded about the small signal tubes, I suggest you peruse the "El Cheapo" Project thread. "El Cheapo" is exactly the sort of low cost/solid performance project you seem interested in. If you build an "El Cheapo" with DynaClone Z565 O/P trafos, you will be pleased.
-----------------------------------------------------------------------------------
Daddy's work is SUPERB. You can rest easy about the end result.
edit: added remark about father's work
Hi Eli,
Thanks for the complement on my dad's work. Everyone has always been impressed with his work. In fact, his last job right before he retired a couple months ago was desinging pipe organs for Foley-Baker, Inc up there in CT, and he was also the one updating and rewiring all of the organ consoles to include anything from a full restore to incorporating a MIDI interface.
Way back when, when he was just a kid in the army (late '60s), he was the one teaching the electronics classes (the instructor realised that my father knew more than him and left the teaching to him!!) and was in charge of the Signal Corps maintaining and opertating everything to keep communications up and running while in France and Vietnam.
******
Anywho... My brother's Infinitys are 8 ohms, so that shouldn't be a problem there. My Altec topend is 8 ohms as well, however the Klipsch K33-E woofer is 4 ohms, but is still an easy load to drive, even with flea-powered 2A3 amps.
I am planning on building a custom bass bin dedicated to the Altec 511B/902-8B's which will incorporate 2x 15" drivers of about 98 - 101dB each per driver. So I can have up to 101 - 107dB 1w/1m bass bins (if not more) somewhere between 4, 8 or 16 ohms depending on what drivers I go with. Also, I'm not sure if I'll be going sealed, ported or even Open Baffle with the bass bin. Since those 15's have to reach up to 600Hz or so, the OB design would help with the midrange.
So what would you recommend going with other than 6SN7's? I want to use a low MU tube just keep noise and such at a minimum, plus I feel they give a warmer, smoother, even cleaner sound. Would a 12AU7 be a better choice?
Yes, I know iron is NOT cheap and I do not want to skimp on that, especially not for the PSU. If the O/P trannies roll off around 30Hz or so, I won't worry too much about that as I doubt my bass bins will go much lower than that anyway, not to mention that I have my mains crossed over at 50Hz anyway to a push/pull sub. Although, I did see a trans on Hammond's site that did go down to 20Hz, I'm not sure on the price though.
Also, my father has a bunch of good sources on various parts and such, including trannies, so he might be able to get a good deal on something as well. Eventhough those sources are msotly tube radio based, a lot of the bigger old radios used some major quality iron. And talk about a large supply of 45 tubes!
I know the majority of cost for this project is going to be for iron. My father informed me of that early-on. Possibly the next biggest cost would be the O/P tube(s).
I would really like to go with something like a 211/845 tube, but my father hasn't had much if any experience with them. I like the idea of getting a solid 15-20 watts of SE power, but that might run into more money than I can spend right now. So with that in mind, I should keep my "wants/needs" in balance and go with smaller signal tubes as you mentioned. Have any in mind?
I'm assuming you're referring to the 12AQ5s as the O/P tubes. What really sucks is that I found seven 6BQ5s in my father's stash and all of them tested bad. The filament in one of them didn't even fire up! What a shame.
Chops,
The 12AU7 is INFERIOR to the 'SN7. Mu is the same (20); everywhere else, the 'U7 can't lift the 'SN7's jockstrap.
Stay away from transmitting triodes until you accumulate experience. 1 KV. B+ rails can get you killed!
There is MUCH to be said in favor of 2 stage amps, like "El Cheapo". Noise, hum, and phase shifts are reasonably easy to control. Also, "motorboating" is unlikely.
Yes, we were cost conscious in designing the "El Cheapo" PSU. However, the design is UNCOMPROMISED. A crappy PSU inevitably results in a crappy amp. We wanted something cost effective that works well. Add a little more money for good O/P "iron" and it works VERY well.
See if you can find a set of 4 6V6s in dad's stash. The 6V6 is perfect in "El Cheapo". The 12AQ5 is an inexpensive 6V6 "equivalent". Triode wired 6V6 family tubes are incredibly linear and they aint bad UL.
edit: removed schematic remark, as it's too big to upload
The 12AU7 is INFERIOR to the 'SN7. Mu is the same (20); everywhere else, the 'U7 can't lift the 'SN7's jockstrap.
Stay away from transmitting triodes until you accumulate experience. 1 KV. B+ rails can get you killed!
There is MUCH to be said in favor of 2 stage amps, like "El Cheapo". Noise, hum, and phase shifts are reasonably easy to control. Also, "motorboating" is unlikely.
Yes, we were cost conscious in designing the "El Cheapo" PSU. However, the design is UNCOMPROMISED. A crappy PSU inevitably results in a crappy amp. We wanted something cost effective that works well. Add a little more money for good O/P "iron" and it works VERY well.
See if you can find a set of 4 6V6s in dad's stash. The 6V6 is perfect in "El Cheapo". The 12AQ5 is an inexpensive 6V6 "equivalent". Triode wired 6V6 family tubes are incredibly linear and they aint bad UL.
edit: removed schematic remark, as it's too big to upload
Chops,
I would never disparage Eli's El Cheapo because it is an excellent design. I built one completely out of junk box parts because I had a nice Thordarson 6V6 Ultalinear output transformer and an old power transformer from a long defunct 6V6 P-P amp. I used full wave rectification instead of the voltage doubler because I prefer it and that's what the transformer was for. I was honestly amazed how good it sounded driving an 86 dB 1W/1M speaker (mono only).
However, that being said, if your dad still has the schematic for that 6L6 amp he built, that might be a great place to start. You both would be supprised how little has actually changed in overall tube amp topology and maybe, with just a tweak here and there, it might be a great amp. 30 - 40 Watts would give you all the reserve power you would ever need with the speakers you mentioned and your dad might get a kick out of building almost the same amp he built in the '60s. The transformers have gotten somewhat better, the passive parts have gotten better, and now we can do things with transistors in support of tubes which they didn't used to be able to do.
Besides, I know for one that I would like to see you dad's design for the 6L6 amp and I'm sure others on this forum would too.
Also, if you haven't read it here about a thousand times (where's SY when you need him), buy Morgan Jones' book "Valve Amplifiers". It will GREATLY accelerate your learning curve on tube amps and if you are still living at home or you live near your dad, I bet he'd get a blast out of reading it too.
Ken
I would never disparage Eli's El Cheapo because it is an excellent design. I built one completely out of junk box parts because I had a nice Thordarson 6V6 Ultalinear output transformer and an old power transformer from a long defunct 6V6 P-P amp. I used full wave rectification instead of the voltage doubler because I prefer it and that's what the transformer was for. I was honestly amazed how good it sounded driving an 86 dB 1W/1M speaker (mono only).
However, that being said, if your dad still has the schematic for that 6L6 amp he built, that might be a great place to start. You both would be supprised how little has actually changed in overall tube amp topology and maybe, with just a tweak here and there, it might be a great amp. 30 - 40 Watts would give you all the reserve power you would ever need with the speakers you mentioned and your dad might get a kick out of building almost the same amp he built in the '60s. The transformers have gotten somewhat better, the passive parts have gotten better, and now we can do things with transistors in support of tubes which they didn't used to be able to do.
Besides, I know for one that I would like to see you dad's design for the 6L6 amp and I'm sure others on this forum would too.
Also, if you haven't read it here about a thousand times (where's SY when you need him), buy Morgan Jones' book "Valve Amplifiers". It will GREATLY accelerate your learning curve on tube amps and if you are still living at home or you live near your dad, I bet he'd get a blast out of reading it too.
Ken
Ken,
Thank you for the complement. What you did is totally in keeping with the "El Cheapo" ethic.
Obviously, there's more than 1 good way to construct a good B+ PSU. Using the "iron" available to max. advantage is a large part of the job. I followed in Stu Hegeman's footsteps, as that was the least costly way to have a high performance result, when buying all new parts.---------------------------------------------------------------------------------
Chops,
I agree with Ken. Please find a way to get dad's 6L6 design posted on this site. Yet better would have dad become an active member of this community.
After talking with my dad some more tonight, he corrected me about that amp he built years ago. It was NOT 6L6's, but rather 6V6's in PP. Also, it had seperate volume controls for each channel plus bass and treble tone controls. And the output was 30 watts per channel.
Oh yeah, and he also had a timed delay on there for the B+ so it wouldn't dump the full load on the... well, you guys know why.
At the time, he had a pair of Belle bookshelf speakers (which we still have!) that incorporate an 8" fullrange driver with a 3" cone tweeter with a single cap on the tweeter as the crossover, and in a ported solid wood enclosure with cane grills.
As for a schematic, I'll see if he can possibly draw one up in his spare time. Heck, I even told him before that it would be neat to reincarnate that amp. One day maybe, we'll see...
********
Eli,
Back to the amp design, I'm going to be reading up on your "El Cheapo" amp and discussing various things with my father about it.
When you're referring to "2 stage amps", I'm assuming you mean PP amps, right? And I don't know if he wants me dipping into his stash of tubes and goodies. Besides, he needs that stuff for his business. I don't want to take away from that. He does have plenty of them though, and metal 6L6's as well as I just tested 3 of them today, along with a bunch of other metal tubes. And I've got another box of them to go through tomorrow after work.
Hey, at least I'm learning how to use tube testers and what to look for. I now have several hours under my belt on both the Precision 915 Countertop and Sencore MU150 testers. In fact, in joking around today, he said to me, "Once you get good enough on those two, I may even let you use the Hickok 600A." LOL
wa4htz,
I believe my brother found an old picture or two of that amp my father built. I'll have to yack with him and see if he can find those pics again. If so, I can scan them and post them on here.
BTW Eli,
Dad isn't one for forums, so unfortunately, I don't think he'll ever become a member, although I think it would and/or could help his business out. Oh well, that's parents for ya! LOL
Oh yeah, and he also had a timed delay on there for the B+ so it wouldn't dump the full load on the... well, you guys know why.
At the time, he had a pair of Belle bookshelf speakers (which we still have!) that incorporate an 8" fullrange driver with a 3" cone tweeter with a single cap on the tweeter as the crossover, and in a ported solid wood enclosure with cane grills.
As for a schematic, I'll see if he can possibly draw one up in his spare time. Heck, I even told him before that it would be neat to reincarnate that amp. One day maybe, we'll see...
********
Eli,
Back to the amp design, I'm going to be reading up on your "El Cheapo" amp and discussing various things with my father about it.
When you're referring to "2 stage amps", I'm assuming you mean PP amps, right? And I don't know if he wants me dipping into his stash of tubes and goodies. Besides, he needs that stuff for his business. I don't want to take away from that. He does have plenty of them though, and metal 6L6's as well as I just tested 3 of them today, along with a bunch of other metal tubes. And I've got another box of them to go through tomorrow after work.
Hey, at least I'm learning how to use tube testers and what to look for. I now have several hours under my belt on both the Precision 915 Countertop and Sencore MU150 testers. In fact, in joking around today, he said to me, "Once you get good enough on those two, I may even let you use the Hickok 600A." LOL
wa4htz,
I believe my brother found an old picture or two of that amp my father built. I'll have to yack with him and see if he can find those pics again. If so, I can scan them and post them on here.
BTW Eli,
Dad isn't one for forums, so unfortunately, I don't think he'll ever become a member, although I think it would and/or could help his business out. Oh well, that's parents for ya! LOL
A PP or SE amp can be two stage. It reffers to an amp with an input stage and an output stage. Ei driver and/or phase splitter followed by a power stage. For example you could have a 6SL7 differential pair proving phase splitting for a pair of push pull 6V6 power tubes on output. 6SL7s would give rather more gain than needed for hifi though. But they were just provided by way of example.
The 6V6s could be connected either triode, UL, or tetrode.
Edcor's 15watt output transformers are a great deal for this sort of amp.
Surplus industrial control transformers are one option for cheap heavy duty power iron. 120VAC on one side, and 2 240VAC coils on the other is typical. You would need a separate filament transformer.
PSUDII is very helpful in designing power supplies.
If your looking for more gain, you might try the 9 pin 6N1P, more gain still, but less grunt is the octal 6SL7. 12SN7s are 12V filament version on 6SN7s and may be cheaper.
Tone controls would probably mean the requirement of adding another stage to drive them.
The 6V6s could be connected either triode, UL, or tetrode.
Edcor's 15watt output transformers are a great deal for this sort of amp.
Surplus industrial control transformers are one option for cheap heavy duty power iron. 120VAC on one side, and 2 240VAC coils on the other is typical. You would need a separate filament transformer.
PSUDII is very helpful in designing power supplies.
If your looking for more gain, you might try the 9 pin 6N1P, more gain still, but less grunt is the octal 6SL7. 12SN7s are 12V filament version on 6SN7s and may be cheaper.
Tone controls would probably mean the requirement of adding another stage to drive them.
If You go with a single 6AS7G per channel do push pull, or if you have your heart set on Single ended, go cathode follower. You can only squeeze a little clean power out of those tubes with the conventional single ended, grounded cathode topology. Eventhough lo mu tubes (like the 6as7) take alot of drive voltage as cathode followers, they seem to sound better than high mu tubes as cathode followers.I had been thinking of doing a project like this myself to utilize the 6AS7's I have lying around.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.