Hello,
I am new here, but not new to building tube amplifiers. I have build 6 guitar amps of various difficulty. So have pretty decent experience in wiring, PSU design, gain stages design, grounding, etc. Pretty good at theory as well. Of course not all of this applies to Hi-Fi, specifically dealing with distortion, which to some extent is quite desirable in guitar amps.
Now I decided to build Hi-Fi tube amplifier, but my knowledge of the subject is quite limited (for example what are best amplifiers people pray for).
Also I am a bit confused in figuring out the difference between power amps, preamps and integrated amps. Integrated amplifiers are easier - they are combination of preamp and power amp. However when it comes to power amps, I am confused. I've seen power amps that actually accept line level signal. Can I connect my CD player to them? What is the role of the preamp then (I know that some may have phono preamp, in this case I understand what its role is - amplify phono output level to line level)?
Now what I want to build:
20-30 watts Push-Pull class AB (maybe class A, anyway on low levels even class AB will work as class A). Most likely EL34 tubes, but honestly my knowledge of the tubes used in Hi-Fi is limited. By 30 watts I mean 30 watts with minimum distortion. Not a total power it can deliver.
I am going to listen mostly vinyl records (I will use separate phono preamp) in a medium sized room, and not very loud. I would even say on low or moderate levels. Say not more than 100db.
I use Klipsch RF-82II with sensitivity 98dB @ 2.83V / 1m
Please recommend what would be the best amp to build.
Thanks,
Alex
I am new here, but not new to building tube amplifiers. I have build 6 guitar amps of various difficulty. So have pretty decent experience in wiring, PSU design, gain stages design, grounding, etc. Pretty good at theory as well. Of course not all of this applies to Hi-Fi, specifically dealing with distortion, which to some extent is quite desirable in guitar amps.
Now I decided to build Hi-Fi tube amplifier, but my knowledge of the subject is quite limited (for example what are best amplifiers people pray for).
Also I am a bit confused in figuring out the difference between power amps, preamps and integrated amps. Integrated amplifiers are easier - they are combination of preamp and power amp. However when it comes to power amps, I am confused. I've seen power amps that actually accept line level signal. Can I connect my CD player to them? What is the role of the preamp then (I know that some may have phono preamp, in this case I understand what its role is - amplify phono output level to line level)?
Now what I want to build:
20-30 watts Push-Pull class AB (maybe class A, anyway on low levels even class AB will work as class A). Most likely EL34 tubes, but honestly my knowledge of the tubes used in Hi-Fi is limited. By 30 watts I mean 30 watts with minimum distortion. Not a total power it can deliver.
I am going to listen mostly vinyl records (I will use separate phono preamp) in a medium sized room, and not very loud. I would even say on low or moderate levels. Say not more than 100db.
I use Klipsch RF-82II with sensitivity 98dB @ 2.83V / 1m
Please recommend what would be the best amp to build.
Thanks,
Alex
Hello Alex,
With those speakers, you will run out of the room with 30W power and most likely have the volume pot always at low-level.
I would consider a Tubelab SSE, or a Baby Huey EL34, or an engineer amp from Pete Millett. All 3 come with PCB you can buy, what is left is collecting the components, building a case and assembling the amp. BH and Eng-amp are push-pull, SSE is single-ended. Eng-amp uses TV tubes and Pete has developed derivatives monoblocks with more power. No personal experience with them, but I have built 2 eng amps, one with Edcor transformers and the other one with Toroidy. Both amps are wonderful and would rock your Klipsch ! Toroidy is perfect for european builders. Quality, fast, good service (I'm not affiliated). No idea about shipping overseas, ask them.
As for the preamp, depends on your sources. The minimum you need is some sort of volume control between your source (CD player) and your power amp. If you only have one source, a volume pot or better a stepped attenuator will do the job. If you have more sources, you can add an input selector. You need to check impedances, but modern sources can usually drive modern amplifiers (except smartphones are crap sources). If you need a phono preamp, build it separately, it has its own challenges that are better kept away.
A nice attenuator is the frontpanel module from John Broskie, collects an input selector and attenuator in a single module, and can be ordered with resistors. If you are located in Europe, I have a remaining engineer amp PCB, pristine condition. Pm if interested.
- FrontPanel
- Tubelab SSE Board | Tubelab
- DCPP Amp
- EL34 Baby Huey Amplifier
Charles
With those speakers, you will run out of the room with 30W power and most likely have the volume pot always at low-level.
I would consider a Tubelab SSE, or a Baby Huey EL34, or an engineer amp from Pete Millett. All 3 come with PCB you can buy, what is left is collecting the components, building a case and assembling the amp. BH and Eng-amp are push-pull, SSE is single-ended. Eng-amp uses TV tubes and Pete has developed derivatives monoblocks with more power. No personal experience with them, but I have built 2 eng amps, one with Edcor transformers and the other one with Toroidy. Both amps are wonderful and would rock your Klipsch ! Toroidy is perfect for european builders. Quality, fast, good service (I'm not affiliated). No idea about shipping overseas, ask them.
As for the preamp, depends on your sources. The minimum you need is some sort of volume control between your source (CD player) and your power amp. If you only have one source, a volume pot or better a stepped attenuator will do the job. If you have more sources, you can add an input selector. You need to check impedances, but modern sources can usually drive modern amplifiers (except smartphones are crap sources). If you need a phono preamp, build it separately, it has its own challenges that are better kept away.
A nice attenuator is the frontpanel module from John Broskie, collects an input selector and attenuator in a single module, and can be ordered with resistors. If you are located in Europe, I have a remaining engineer amp PCB, pristine condition. Pm if interested.
- FrontPanel
- Tubelab SSE Board | Tubelab
- DCPP Amp
- EL34 Baby Huey Amplifier
Charles
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Remember the perceived power is logarithmic, so with your high-SPL speakers, a 10W single-ended like the SSE will most likely suffice. It needs only 2 power tubes instead of 4 for push-pull, but the OPTs might end up costing more depending what you buy. You can go for cheap Edcors, or sky-rocket with high-end iron. I initially wanted to go for the ultimate stuff (Monolith Magnetics) but that will have to wait for some cash.
Right now I'm building one using expensive Electra-Print 5K OPTs (got a deal on them) and a Hammond 374BX (Switzerland, 230V) as power transformer. I have another SSE in the queue using all 3 transformers from Ogonowski.eu. Leszek has good credits from other people and attractive prices, 6 weeks delivery, I'm expecting mine within a few weeks so no personal experience yet.
soon to be tested SSE, with EL34, Hammond & Electra-Print, PSU choke and motor-run cap. Yep, the wires are long, but that's only a functional test.
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A few more for your consideration. I have built both of these. I prefer the EL84 amp for it's simplicity and surprisingly good tone. The other is quite good and flexible. For your power requirements, the EL84 amp would give you in the neighborhood of 10-15 very loud watts.
Attachments
Power is of minimal concern. Scan the archives for my posts regarding Paul Joppa's 102 dB. rule. Unfortunately, the spec. sheet omits an impedance curve. Substantial dips in that curve require that claimed 98 dB. sensitivity be derated to 95 dB., due to treating them as having a 4 Ω impedance. Let's assume modest dips and the "true" impedance is 6 Ω. The 5 or so WPC SE "12" W. multi-grid power O/P types will be sufficient. Such an amp can built at a modest $ outlay and still exhibit solid performance. That's what I suggest your initial effort be. You can move on to expensive, no NFB, SE, DHT, amps at a later date, should the urge occur.
"Wade" through this lengthy thread. The tweaked console amp settled on is (IMO) "exactly what the Dr. ordered". Oddly enough, I mentioned that the amp would be good enough for use with Klipsch "Heritage" speakers.
Never build anything based on a PCB!
The PCB was invented to avoid high skilled trained staff which costs a lot. With PCB, automation came into production and the goal was to solder and equip the PCB automatically with the parts. It was that kind of cost cutting, that would make mass production possible for low consumer priced gear.
PCB based amps do not sound excellent, always watch for the best and thats purely handwired. But most audio-fools are not able to build hardwired, because that needs special attention to details.
Look at old WE gear, old Marantz or Fisher amps, thats the way to go. Those classics are worthy today, the other ones are worthless and will never become classics. No one will speak about something like a Baby Huye in 30 years from now.
Look at the Mullard 20 Watt and the whole Mullard book. They showed in detail how to build an excellent amp thats worth the money invested. You can change the first input stage to triode because that amp has lots of gain.
But don't change the parts to ultra modern ones, that will change the whole sound character of the amp. Try to get NOS parts or used old parts if you want to build something first class.
The PCB was invented to avoid high skilled trained staff which costs a lot. With PCB, automation came into production and the goal was to solder and equip the PCB automatically with the parts. It was that kind of cost cutting, that would make mass production possible for low consumer priced gear.
PCB based amps do not sound excellent, always watch for the best and thats purely handwired. But most audio-fools are not able to build hardwired, because that needs special attention to details.
Look at old WE gear, old Marantz or Fisher amps, thats the way to go. Those classics are worthy today, the other ones are worthless and will never become classics. No one will speak about something like a Baby Huye in 30 years from now.
Look at the Mullard 20 Watt and the whole Mullard book. They showed in detail how to build an excellent amp thats worth the money invested. You can change the first input stage to triode because that amp has lots of gain.
But don't change the parts to ultra modern ones, that will change the whole sound character of the amp. Try to get NOS parts or used old parts if you want to build something first class.
Dear Schmitz77, with all due respect, a first-time builder is more likely to succeed using a proven design and a PCB.
In regards to components, I think some modernity is welcome. E.g. CCS are easier to build using solid-state than tubes, and perform better than resistors. So I would be more nuanced. Look for example at the ripple filter used by Pete Millet in his DCPP. Of course you can use a choke, but the small circuit around Q2 is elegant and efficient.
It's true that most early vintage PC boards were junk. The phenolic based stuff will absorb moisture, de-laminate, and become brittle with age and heat. Unfortunately phenolic is still used in ultra cheap stuff. (Brown paper based laminate).
For most of my 41 year engineering career at Motorola I designed PC boards for "mission critical" (someone's life depends on it working) two way radios for police, fire and military applications. I spent a few years designing cell phones where noisy digital, RF, and audio must coexist on a 50 X 100 mm PC board containing 500+ parts, without interaction. NONE of these devices could EXIST without a complex multi-layer PC board.
These techniques and materials can be used to design a modern tube HiFi amp that sounds every bit as good as a hand wired amp. Where the PCB design shines is in it's REPEATABILITY. If the design is done properly, every amp built with the same components WILL sound IDENTICAL.
This is exactly my point. I started building tube guitar amps in the 60's. Sometimes two identical amps sounded different, some hummed, and maybe one would oscillate.
I started making PCB based tube and solid state amp designs in the 70's, but by the late 90's I couldn't make them fast enough. I shared my schematics, (still on the web site) but hand built versions didn't always work as intended due to differences in component layout.
I started making PCB designs for my amps, and they all worked....If you put the right parts in the right holes, it WILL WORK, and sound good. Do I still do hand built PTP? Yes, for a one-off. For two or more, I make a PCB.
I don't know the baby Huey, but it has been around for some time. My TSE design uses a high Gm triode (WE417 / 5842) to drive a 45, 2A3 or 300B. How many threads have been written discussing how to kill oscillations in the 5842?
The TSE design has been around for over 15 years. The final PCB design was done 14 years ago. It has become a "modern classic" and several hundred have been built.....how many people complain about the sound quality or oscillation?
Will it be around in 30 more years? I doubt it, because I would be 96 years old and probably not still here. After 15 years it IS being retired, Why?
The design is sound, the parts have gone extinct. Even the company that made the filament regulator has gone extinct, Sharp has been swallowed by Foxconn.
The current generation PCB for the TSE has been sold for 14 years. People still want it, so it is being redesigned to use a current regulator chip, and a list of requests by current users is being accommodated. Will it last another 14 years? Will I still be selling boards at 80 years old? Will this forum still exist?
The previously mentioned SSE is a Simple Single Ended design that uses a CCS loaded 12AT7 to drive a KT88, 6550, EL34, or 6L6GC. Again it's been around for over 12 years, several hundred have been built, and it is well liked. The first few WERE hand wired. The schematic is on the web site. It now uses a PC board, but is simple enough such that it can be hand built using Point To Point wiring, and indeed a few have been built that way. There was ONE builder who made one using point to point wiring then complained about hum. When I asked him to post pictures so that we could help, he refused.....
Of course anyone is free to build whatever they like however they see fit, but blanket statements saying that ALL PC board based amps are bad and will sound bad just don't fly today. IF the board is PROPERLY designed and MADE in the first place, it will work good and sound the same as all of the others like it.
Of course, transformer and component choices DO influence the sound quality, but that is a different story where entire books have been written.
He wrote that he had build guitar tube amps already, so he may be a newby, but not to tube amps.
CCS is a technique established first with the advanced transistor designs, when I remember correctly. It was then adopted by the tube audio community to implement in their late 1970s improved tube audio circuits, because some amateur DIY had learned from the advanced transistor circuits.
I was pointing the classic tube audio designs up to the mid 1960s. To my knowledge, there are no classic designs that use this technique, may it be implemented with tubes or transistors in tube audio circuits. But I may be wrong, please correct.
P. S. Even the very best PCB designs sound flat against the same circuits build hard wired three dimensional and with exact wiring and soldering, seen in the best professional amps (mostly military grade or Klangfilm etc.) At least for me, I prefer free hard wired amps and will never implement any PCB where its not abolutely necessary.
P.P.S. No body is talking about the 1980s tube amp designs any longer, its only a very small group of amp schemes that made it to a classic. They are all from the big and famous companies. Not much surprise, they had the very best engineers than.
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Some power tube circuits parts such as transformers and inductors are not suitable for PCB mount. A bit of point to point wiring is needed anyway. When the circuit is very simple, such as many old designs, a full point-to-point wiring is a good option despite the shortcomings. Guitarist1977 stated that it has experience in wiring, so I would not rule out a point to point build. A recreation of a classic Mullard design, as example, could be built point to point with ease. The real question is the amount of support that the original poster needs. There is no doubt that it will be far more likely to get it by selecting a design that is actively supported by the posters on this forum, and most of them are based on a PCB for the obvious reasons listed by Tubelab.
To get back to the first post questions about the best tubes to use, I would say that the most critical and usually most expensive part of a Hi-Fi power tube amp is the output transformer. If cost/performance ratio is important, I would start by checking the cost and availability of the transformers and comparing it to the total build budget, then select a suitable design. According to my findings, the cost/performance "golden spot" today is a push-pull of 6L6 - EL34 or KT88.
To get back to the first post questions about the best tubes to use, I would say that the most critical and usually most expensive part of a Hi-Fi power tube amp is the output transformer. If cost/performance ratio is important, I would start by checking the cost and availability of the transformers and comparing it to the total build budget, then select a suitable design. According to my findings, the cost/performance "golden spot" today is a push-pull of 6L6 - EL34 or KT88.
I was wondering at want point discussion about PCB vs hand wired will start. 
I don’t mind either. My guitar amps are all hand wired, but mostly for convinience to modify them. But in guitar amps I suppose it is different, I swap components quite often to get best distortion / overdrive out of the circuit.
PCB is absolutely fine, though I like esthetics of good hand wired amps.
I suppose I need to adjust the initial requirements. I think 10-20 watts are going to be fine. Also it should not be nececerraly push pull and class AB. Single ended is good as well.
I have not mentioned the bandwidth. I would like to get to the at least 20hz - 20khz.
About the budget. I don’t have hard constraints, but would like to stay in $1000 +/- 200.
I briefly looked at the suggested amps and they look very nice. The one question I have is - volume control at the input. Wouldn’t it load the source too much at low level? Would it be better to have buffer before it?
I don’t mind either. My guitar amps are all hand wired, but mostly for convinience to modify them. But in guitar amps I suppose it is different, I swap components quite often to get best distortion / overdrive out of the circuit.
PCB is absolutely fine, though I like esthetics of good hand wired amps.
I suppose I need to adjust the initial requirements. I think 10-20 watts are going to be fine. Also it should not be nececerraly push pull and class AB. Single ended is good as well.
I have not mentioned the bandwidth. I would like to get to the at least 20hz - 20khz.
About the budget. I don’t have hard constraints, but would like to stay in $1000 +/- 200.
I briefly looked at the suggested amps and they look very nice. The one question I have is - volume control at the input. Wouldn’t it load the source too much at low level? Would it be better to have buffer before it?
Classic brands have adopted the printed circuit (PCB) as for example MC Intosh in their amplifiers to valves for quite some time and relatively new brands as Prima Luna only does in its secondary circuits as the Auto Bias.
I think the important thing here is that they should not be used in the power amplification sections, that is, in the output stages.
The high temperatures of the valve amplifiers wreak havoc on these weak conductor sheets, never comparable to a conventional cable. What we can check when we want to replace components in a PCB is a pain. If we apply the soldering iron for a little longer time than is strictly necessary (and it usually goes through the components with its wires bent at the back of the PCB) the printed circuits are raised!
If I would do a tube amplifier again, I would go through a circuit similar to the well-known Dynaco ST70. There is much in the network to internalize about it. The accessibility of the components is a big plus, who could copy an output stage of McIntosh transformer?
I think the important thing here is that they should not be used in the power amplification sections, that is, in the output stages.
The high temperatures of the valve amplifiers wreak havoc on these weak conductor sheets, never comparable to a conventional cable. What we can check when we want to replace components in a PCB is a pain. If we apply the soldering iron for a little longer time than is strictly necessary (and it usually goes through the components with its wires bent at the back of the PCB) the printed circuits are raised!
If I would do a tube amplifier again, I would go through a circuit similar to the well-known Dynaco ST70. There is much in the network to internalize about it. The accessibility of the components is a big plus, who could copy an output stage of McIntosh transformer?
Component availability is a point I forgot to mention, we build stuff that should last 20+ years, right ?
PP and SE OPTs can be ordered from multiple vendors and are not supposed to wear out anyway, but special tubes that are not in production anymore is a different story. As much as I like the sound of my 6JN6 TV tubes in Pete's amp, nobody build compactron tubes anymore. Another thread here pointed at the insanity of a pair of NOS WE 300B sold for 20'000US$. I'm happy to build amps based on EL34/KT88 knowing that a few manufacturers (JJ comes to mind) are able to provide quality parts and their replacement for sane pricing. Elrog looks nice as well, but no direct experience yet.
You may find further interesting ideas within your stated budget on the technical informations / schematics section of the lundahltransformers.com web site. Lundahl transformers have a good audiphile reputation. The easy to build EL34 SE 8W amplifier presented on that section had been popular at the time and is still a good design, on my opinion.
The PCB conversation reminds me of guys in the guitar world paying $200+ for a pair of 0.022uf 400v 1950's Sprague Bumblebee Oil Filled Capacitors for the tone pots of their dual humbucker Gibson Les Paul's & SG's because they can "hear" the difference....when what they "hear" is a cap that has drifted 25% in value. Anything can sound bad when done incorrectly. Anything can sound good when done correctly. But, hey....I am all too happy to continue selling Sprague BB's.
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