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Recommend tube amp to build
Recommend tube amp to build
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Old 2nd February 2019, 06:40 AM   #1
guitarist1977 is offline guitarist1977
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Default Recommend tube amp to build

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
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Old 2nd February 2019, 07:10 AM   #2
cbueche is online now cbueche  Switzerland
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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

Last edited by cbueche; 2nd February 2019 at 07:27 AM. Reason: Ience with them yet.
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Old 2nd February 2019, 07:24 AM   #3
guitarist1977 is offline guitarist1977
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Thanks. You are right. With these speakers I don’t need that much power.

Now I wonder should I consider single ended design?

Alex
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Old 2nd February 2019, 08:28 AM   #4
cbueche is online now cbueche  Switzerland
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Quote:
Originally Posted by guitarist1977 View Post
Thanks. You are right. With these speakers I donít need that much power.
Now I wonder should I consider single ended design?
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.

tlsse.jpg

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.

Last edited by cbueche; 2nd February 2019 at 08:31 AM.
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Old 2nd February 2019, 09:06 AM   #5
OrbitalLex is offline OrbitalLex  United States
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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.
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Old 2nd February 2019, 10:57 AM   #6
Eli Duttman is online now Eli Duttman  United States
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Quote:
I use Klipsch RF-82II with sensitivity 98dB @ 2.83V / 1m
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.
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Old 2nd February 2019, 11:25 AM   #7
BJosephs is offline BJosephs  United States
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If you buy good parts and keep things simple (and follow verified designs) it will be hard to end up unhappy. I use a 5W single ended amp with 88db speakers and it’s fine for me.
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Old 2nd February 2019, 12:22 PM   #8
Schmitz77 is offline Schmitz77  Germany
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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.
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Old 2nd February 2019, 01:12 PM   #9
cbueche is online now cbueche  Switzerland
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Quote:
Originally Posted by Schmitz77 View Post
Never build anything based on a PCB!...
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.
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Old 2nd February 2019, 01:56 PM   #10
pblix is offline pblix  United States
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Damn the PCBs! Full speed ahead!
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