HI!
I'm pretty green at DIY, but have completed a ground up scratch build of a highly modified ST70 amp using ALL new parts. I now want to build up my Main System!
For the pre i'm going with Coffedj's 12B4 once he has the chokes and power supply ready to go. While waiting i'd like to research the power amps. I've done some reading here, but haven't come up with a schematic yet.
What I want is your basic PP Ultra or E linear class AB 4 power tube (KT88?) Mono blocks! Around 100W per block would be nice! I want something at least equal to the better commercial offerings in sound quality. If I can't equal them, i'd rather buy new. Any schematics floating around her fit the bill? Did I pick the right topology for higher powered block?
I mainly see alot of lower powered amps being built.
I'm pretty green at DIY, but have completed a ground up scratch build of a highly modified ST70 amp using ALL new parts. I now want to build up my Main System!
For the pre i'm going with Coffedj's 12B4 once he has the chokes and power supply ready to go. While waiting i'd like to research the power amps. I've done some reading here, but haven't come up with a schematic yet.
What I want is your basic PP Ultra or E linear class AB 4 power tube (KT88?) Mono blocks! Around 100W per block would be nice! I want something at least equal to the better commercial offerings in sound quality. If I can't equal them, i'd rather buy new. Any schematics floating around her fit the bill? Did I pick the right topology for higher powered block?
I mainly see alot of lower powered amps being built.
If you are green to DIY, and green to tube amp building, a scratch built 100 watt amp is very ambitious, and the chance of failure of disappointment high. Such an amp is going to be expensive, and if it does not perform up to your desires you will feel like you have wasted a bunch of money for nothing. As well as the 'traps for young players' with these builds, there is also the danger with the high voltages involved. First question though, why do you need 100 watts? Every watt in a tube amp adds to the cost and weight of the project. I moved from a 50 watt chip amp to a 7 watt tube amp and enjoyed the experience! I do have reasonably efficient speakers though.
I would describe the music you listen to and the type and efficiency of your speakers and you will get some advice here on what a realistic power level would be for the amp. As a tube amp tends to clip much more benignly than a solid state amp, you require much less headroom with the power, hence the advice that tube watts are more powerful than solid state watts.
Good luck with the quest, you will find plenty of friendly helpful advice here!
Regards,
Chris
I would describe the music you listen to and the type and efficiency of your speakers and you will get some advice here on what a realistic power level would be for the amp. As a tube amp tends to clip much more benignly than a solid state amp, you require much less headroom with the power, hence the advice that tube watts are more powerful than solid state watts.
Good luck with the quest, you will find plenty of friendly helpful advice here!
Regards,
Chris
I listen to mostly classic rock, but do have of interests as well. The goal is to have the option to drive many speaker types up to the difficult Maggie MGM! I'm green, but i found the ST70 build not to bad. I do have a nice solder station, and fluke, as well as a new scope, and freq generator for trouble shooting. A low powered SET is something i'd like to do for fun later, but for the main system I really had High powered monos in mind. For the price I see even used monos going for on Audiogon, it would seem that DIY would be much cheaper, even with quality parts. This would not be a budget build. However, I would like to be well below the cost of even used commercial offerings. The main requirement would be at least equaling the quality of these commercial amps. If thats not possible than i'd never be happy!
TM,
The BALLSY PSU in a McShaned Cit. 2 allows you to get 60 WPC continuously and more than 120 WPC instantaneously out of a PP pair of KT88s. PSU quality is step 1 in executing any good project.
In spite of their hunger for power, "Maggies" are tube friendly, thanks to a reasonably flat impedance curve.
As the owner of a "Duece", the only speakers I would not connect are big Thiels, with their NASTY dips down to 1 Ω. IMO, a superior PP KT88 design, as opposed to a PPP design, is all you need.
There is no doubt in my mind that you can get better performance out of a DIY project, rather than spending the cash on something like ARC, CJ, etc.
The BALLSY PSU in a McShaned Cit. 2 allows you to get 60 WPC continuously and more than 120 WPC instantaneously out of a PP pair of KT88s. PSU quality is step 1 in executing any good project.
In spite of their hunger for power, "Maggies" are tube friendly, thanks to a reasonably flat impedance curve.
As the owner of a "Duece", the only speakers I would not connect are big Thiels, with their NASTY dips down to 1 Ω. IMO, a superior PP KT88 design, as opposed to a PPP design, is all you need. There is no doubt in my mind that you can get better performance out of a DIY project, rather than spending the cash on something like ARC, CJ, etc.
Now were cookin! If you think a deuce will drive the MGM's to decent levels, i'm in!
Now for the schematic? something that could trounce a Conrad Johnson would be nice, but it woulld have to be doable by a newbie. Any proven tested designs around that fit the bill? One that someone here with a pic of the p2p layout would be a plus!
One option may be to use the DIYtube Posiden replacement board for the Mark 2 amps. Perhaps follow that path but with mods and way uprated iron? I'd still want a Conrad / ARC killer!
Now for the schematic? something that could trounce a Conrad Johnson would be nice
, but it woulld have to be doable by a newbie. Any proven tested designs around that fit the bill? One that someone here with a pic of the p2p layout would be a plus!One option may be to use the DIYtube Posiden replacement board for the Mark 2 amps. Perhaps follow that path but with mods and way uprated iron? I'd still want a Conrad / ARC killer!
TubeMack said:
Very few diy projects can surpass in cost/quality used (<1/3 retail cost) commercial stuff. Once you factor in a presentable chasis and high quality components diy does not look so attractive. Not to mention quite unpredictable sonic results and close to zero resale value. Of course you may turn out lucky and end up with a Reference basher for peanuts but a more realistic scenario is fine tuning a prototype over many months and buying lots more components then you will actually use.
Or
As in my case, you may find that what you built sounds better then anything you've ever bought, for 1/2 to at cost... (plus the added fun of fine tuning, seriously). Take your time, do it right, and don't let the neigh sayers here keep you from building what you want. My only advice is to follow the good advice of the experienced builders that helps you accomplish your goal, keep one hand in the pocket when the amp is on, and find a good/complete schematic to work from, at least for the power section, the PSU can be knocked out with PSUD II and a bit of fiddling. All that being said, good luck and I look forward to seeing what you build.
Oh one more thing, find a good article on star grounding. I read lots of posts about ground issues causing hum and lots of DIY frustration people have spoken about, I've dealt with myself.
As in my case, you may find that what you built sounds better then anything you've ever bought, for 1/2 to at cost... (plus the added fun of fine tuning, seriously). Take your time, do it right, and don't let the neigh sayers here keep you from building what you want. My only advice is to follow the good advice of the experienced builders that helps you accomplish your goal, keep one hand in the pocket when the amp is on, and find a good/complete schematic to work from, at least for the power section, the PSU can be knocked out with PSUD II and a bit of fiddling. All that being said, good luck and I look forward to seeing what you build.
Oh one more thing, find a good article on star grounding. I read lots of posts about ground issues causing hum and lots of DIY frustration people have spoken about, I've dealt with myself.
TubeMack said:Now were cookin! If you think a deuce will drive the MGM's to decent levels, i'm in!
Now for the schematic? something that could trounce a Conrad Johnson would be nice
One option may be to use the DIYtube Posiden replacement board for the Mark 2 amps. Perhaps follow that path but with mods and way uprated iron? I'd still want a Conrad / ARC killer!
The H/K Citation II is a stereoblock and its complex, 3 nested NFB loop, topology is not (IMO) something a comparative beginner should tackle. OTOH, the "classic" topology of the Mullard 5-20 IS straight forward. A 6GK5 voltage amplifier and 10M45 CCS loaded tail 12AT7 LTP will provide plenty of gain for KT88 "finals" and the global NFB loop. Pay attention to PSU quality and don't cheap out on the O/P trafos. Better sounding and more durable than either CJ or ARC? I think so. Their primary (sole?) object is profit.
hey-Hey!!!,
I'd go for a 6AC7 E-Linear front end. B+ in the low 400's to drive PPP KT88 with a 3k a-a load. For output iron, Citation II iron, or Heathkit W6m( in either original or new Heyboer production ), would do quite well.
You'd be able to idle each tube at 80-90 mA if you keep to something like 420 Volts o the B+ to deliver ~80W or so. With a single pair of KT90 I get ~60W from my W6m. They're currently doing bass service in my bi-amp rig.
cheers,
Douglas
I'd go for a 6AC7 E-Linear front end. B+ in the low 400's to drive PPP KT88 with a 3k a-a load. For output iron, Citation II iron, or Heathkit W6m( in either original or new Heyboer production ), would do quite well.
You'd be able to idle each tube at 80-90 mA if you keep to something like 420 Volts o the B+ to deliver ~80W or so. With a single pair of KT90 I get ~60W from my W6m. They're currently doing bass service in my bi-amp rig.
cheers,
Douglas
If you're looking at push/pull KT88 for about 60 watts a channel, the Dynaco Mark 3 deserves a mention. Reproduction power and output transformers are readily available which makes sourcing the big parts easy. Plenty of aftermarket driver circuits exist too, including one based on a modified version of the above mentioned classic Mullard topology.
If you haven't already got Morgan Jone's excellent "Valve Amplifiers" 3rd edition this should be on your short list. I would also recommend "Building Valve Amplifiers" from the same author, if nothing else these are very enlightening and entertaining reads - excellent birthday and Christmas presents. (That's how I got my latest copies.. )
I built a very limited number of PPP KT88/6550 amplifiers with Citation II iron (I was not the only one) commercially and I can only say that they were amongst the most thrilling amplifiers I have ever designed. (Clean and dynamic) The additional complexity was something of a nuisance, but the end result was worth it. They were not cheap, however compared to comparable amps they were a bargain and they've been reliable over 10yrs.
You should build what you want, if you have managed to build a ST-70 from scratch I think you can probably handle PPP. Take your time!
)I built a very limited number of PPP KT88/6550 amplifiers with Citation II iron (I was not the only one) commercially and I can only say that they were amongst the most thrilling amplifiers I have ever designed. (Clean and dynamic) The additional complexity was something of a nuisance, but the end result was worth it. They were not cheap, however compared to comparable amps they were a bargain and they've been reliable over 10yrs.
You should build what you want, if you have managed to build a ST-70 from scratch I think you can probably handle PPP. Take your time!
The Morgan Jones books mentioned above really are a "must have". As well, someone mentioned star grounding. I think reading this article is a "must" too: start grounding .
Good luck with the adventure!
Good luck with the adventure!
I do have Morgons book, and i'm sure it will be enlightening. But, If I design this myself, I surely won't end up with a world class amp on first try, or even a working amp....... I have limited space for multible amp storage. I'd like trying my hand at designing something like a SET later down the road. For this project I would need major hand holding, and an excellent proven design. Anybody game? Money won't be a issue (within reason). Custom Iron IS an option.
Buying used does tempt me, but I just went back over to Audiogon, and the things that I like are 4 or 5 grand! I guess even with the economy the way it is, people still are not givening these things away....
Buying used does tempt me, but I just went back over to Audiogon, and the things that I like are 4 or 5 grand! I guess even with the economy the way it is, people still are not givening these things away....
Morgan has two books. Valve Amplifiers is great theory about how they work and the design process. "Building Valve Amplifiers" is the companion book and looks at the construction techniques, component layout, wiring tips etc. If you are going to use a proven design in your own chassis, this book will be useful. Personally, I found the start grounding article above very useful. You really need to understand what is happening with the zero volt/ground currents if you are going to build a hum free amp.
Cheers,
Chris
Cheers,
Chris
Ty_Bower said:
Yeah I mentioned that Posiden board in a post above. As a matter of fact, i'm using the same basic Mullard LTP circuit in my ST 70 and it also came from DIYTUBE.
But, would this rank up there with the best? How about a MARK amp with a better PS, and Iron. I just don't know as I don't trade equipment as much as many here, so this would have to be "THE" amp for the long haul. It's got to be truely great!
BTW here my very first, and last DIY build. As i'm really proud of it, I always take an oppertunity to post a pic!!
An externally hosted image should be here but it was not working when we last tested it.
Assuming a good PSU and rational signal topology, the O/P "iron" makes or breaks the amp. Dyna style trafos (original or clone) are value champions, but they are not top shelf. No small part of the excellent performance found in the "Duece" is directly related to the fabulous Freed O/P trafos used. While it is very difficult to source that sort of bandwidth and power handling in combination today, you can come reasonably close. Plitron's PAT 4004-01 seems like a candidate.
For a "lifetime" project, buy the best "iron" your bank balance will tolerate.
For a "lifetime" project, buy the best "iron" your bank balance will tolerate.
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