Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => MonAmour => Topic started by: Doc B. on November 08, 2019, 02:41:25 PM
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You asked for a 2A3 monoblocks kit like this a few months ago, and we have delivered!
https://bottlehead.com/product/mon-amour-2a3-monoblock-amps-kit/ (https://bottlehead.com/product/mon-amour-2a3-monoblock-amps-kit/)
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I'm surprised nobody has commented. Congratulations on your new babies! Twins no less. If I didn't just spring for a pair of Takatsuki TA-300Bs for my Paramounts, this would have been something to think about. Is this the first BH "mainstream" product to feature meters?
Gerry
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Is this the first BH "mainstream" product to feature meters?
Yes indeed, they are. The meters should give a pretty good indication of when the 300Bs are worn out, as well as confirm the current switch setting.
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Looking (drooling) at the in-depth info on the product page I see that even at the lower operating point the MonAmours put out an additional watt/channel (22%) over the StereomourII. Is this due to the use of the up-spec PCs and OTs, or are there other circuit changes that also play into the improved output?
(Voice in my head: "Back away from the order button, you already have more BH amps than sources.")
Karl
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It's a combination of a different operating point and the different iron that provide a bit more power compared to the Stereomour at the 50mA operating point. At 60mA, we are fully taking advantage of that beefy iron.
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Thanks Paul,
I missed the Something New thread.
With the transformer covers and plate finish they'll come out of the box looking as good as they'll no doubt sound.
Karl
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My order is in. I thought the Kaiju might be the last amplifier I'd need to to build, but I enjoy building the kits and have to do it just to see how it sounds with the Zu Soul Supremes. I don't have space for another system, so I may seriously think about selling the Kaiju to let someone else enjoy it once the MonAmours are built
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There will be some fun modifications available for this kit that just aren't doable with the Stereomour or the Kaiju. I have to order some bits and pieces that I don't have sitting around to evaluate these changes, but the flexibility offered by the simpler DC filament supply opens up some interesting choices.
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Bottlehead now has two amplifiers that put out 7-8 watts per channel: the Kaiju and the Mon Amour. For those of us who have been thinking about buying the Kaiju, is there a case to be made to buy the Mon Amour instead?
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It really depends on what you're looking for. The Kaiju eeks out a tiny bit more power, though certainly nothing you're going to notice. It's also a little bit quieter, but we have used noisier amplifiers on headphones before and not noticed that issue either, so that's not exactly a point in either favor.
The Kaiju is a bit less expensive but comes with lower quality parts. You could certainly upgrade those later on your own, and there is (barely) space to fit them in the amp. With the Kaiju, you will be married to the 300B output tube, which I don't think is a problem myself. I would say the Kaiju is a little easier to build overall. The form factor may also be more convenient for many, as it is a proper width to just take up one shelf on a stereo rack. The MonAmours are surprisingly large in comparison.
The MonAmours are a bit more expensive (we'll ignore the introductory sale thing) but offer film cathode bypass caps, some nicer coupling caps, and some nice cosmetic touches. The very deep low bass will be slightly better defined based on the altered operating point allowing us to use the full winding on the choke, but the Kaiju is already fantastic in this department. You will get the convenience of being able to use 2A3s right off the bat and the 2A3-40, which is really a 300B with its filament connected differently so it will run on 2.5V. I have been running the first pair for a few weeks now, and going from a Sovtek 2A3 to a JJ 2A3-40 and using the switch to adjust the current really does alter the amp from a 2A3 amp to a 300B amp sonically. There is also certainly the potential to modify the MonAmour to take 300Bs, and I hope to use the amp we built for the manual photo shoot on Sunday to perform these experiments.
I could definitely be happy with either amp, and I'm certainly satisfied having both around. My collection of 2A3s is far larger than my collection of 300Bs though, and some of those old stock 2A3s sound pretty nice. I also admit that I really like shrouds and meters. If cosmetics aren't much of a consideration and you're only ever going to run 300Bs, I'd stick with the Kaiju.
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Kaiju is a Stereo amp. It can be strapped to become a 16 watt (maybe really more like 18W) monoblock.
The bottom line here is whether you want a stereo amp or a monoblock amp.
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I'm happy to have ordered the new MonAmour while on the initial sale. Last Bottlehead kit was the original Foreplay 1 preamp which I actually still play from time to time.
Question... will the kit come with tubes or do I need to source?
Thanks
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We provide tubes with the kit, which are generally American old stock 5670s and Sovtek 2A3s.
-PB
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Great to hear, thanks!
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Hi Paul,
I finally ordered MonAmour.
Does the instruction/schematic ready to be downloaded yet?
Thanks
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I finally ordered MonAmour.
Does the instruction/schematic ready to be downloaded yet?
Awesome!
We shot the photos for the manual on the 10th, and the manual writing process usually takes some weeks, so it will be a little while longer before the manual is ready.
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Looks like a great kit and fun build. How are microphonics?
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Microphonics are visible on an oscilloscope, but not something I've been able to hear with any of the 5670 driven amps we have put out.
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Hi Paul
I notice that the parafeed caps is big (12uF !!) compare to usual 3-5uF.
If I want to substitute this, would 10uF sufficient? or should I go for 15uF? 12uF is rather hard to get.
Also what is the interstage coupling cap value?
I guess the 400V would be minimum rating for both coupling caps?
I'm in the mood for Christmas shopping here and already thinking of upgrade caps !!
Thank you very much
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The calculated value is 13.3uF, so 15uF is closer - but 10uF will work. The difference is unlikely to be audible, and if it is, it will be more a function of the speaker than the cap per se.
I do not recommend a voltage rating less than 600v for either cap. Interstage is 0.10uF.
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I am always impressed by how people know what to upgrade on an amp that no one except us guys here at Bottlehead have heard.
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Thanks Paul
Doc, I understand you have choose the components meticulously. I have no mean of disrespect in changing parts.
But I'm just want to build it in one go and don't want to de-solder and re-solder. Maybe the stock would already really good and I can't really hear the "upgrade". But its more for my peace of mind, fooling myself that I put "better" what ever component in and not wondering "what if".
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“What if†is what DIY is all about.
Jamie
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Being 2,800 miles away, I wasn't able to attend the MonAmour/Jager Listening Session on Friday. Would love to hear some feedback on how they were received.
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I am always impressed by how people know what to upgrade on an amp that no one except us guys here at Bottlehead have heard.
I’ve listened to Doc’s system more than many out there and can attest to the sound. The builds are stock and sound fantastic. Not once did we ever swap a component during a listening session. We moved speakers around plenty but the constant was always the outstanding sound from the quality stock builds.
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I learned to solder more than 40 years ago in a formal 2 year electronics class. My instructor taught us the importance of a solid mechanical connection prior to soldering. Whether I'm building a kit or a scratch build a little extra planning is prudent. With a kit build I'll build it stock but also think about what parts I might want to experiment with. Those components, coupling and parafeed caps for example, will just get tac soldered in place. That way it's super easy to try different components without the hassle of ripping mechanical joints apart. Then when you settle on something you like you can install it permanently.
I've been building Bottlehead kits for a long time. In the early years there were some areas where you could improve the quality of the components. Those little brown interstage caps an speco autoformers come to mind. But over the years Bottlehead has refined their designs. The prices of their kits have gone up a little but component quality has gone up a lot. I can't tell you how many times an "upgrade" that I thought would be better actually made the sound worse. But you wouldn't know that unless you built it stock first. My recommendation is to build it stock. Let it break in for a good hundred hours or more. Get familiar with the sound. Your journey might just end there. If you get the bug to experiment, go for it. Just take your time, only replace one component at a time and enjoy the music along the way.
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Very nice manual. Thanks
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Credit to Josh and PB for the manual. They've been doing them for many years now and have it down to a science.
A little update on getting the first kits out -
I've been getting parts bags kitted as the last few small parts come in. The holidays always throw a wrench in the works regarding shipments from our vendors, and so we have a couple of things left to show up before we can finish the packing process. Chokes and output transformers should be coming soon and some of that $$$$$$ Teflon wire seems to be temporarily lost in the shipping void. Those things will all hopefully arrive over the next week and we will be boxing things up.
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Has there been any discussion about a future 2A3 based preamp to match the MonAmour or would you just stick with the BeePre?
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I'm using the BeePre with the MonAmours and it is a very good pairing.
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Has there been any discussion about a future 2A3 based preamp to match the MonAmour or would you just stick with the BeePre?
You can also plug 6A3s into a BeePre or 6B4Gs with an adapter.
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We shipped the first half of the MonAmour orders in our queue this afternoon. We're just awaiting some resistors that should be here early next week to finish packing the second half of the orders.
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Hi Doc/Paul,
I received the notification of the shipment. Very excited
Has the manual ready? Can I download it?
Thanks
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The manual was released a week or so ago. At that time I emailed all purchasers of the kit directly with instructions on how to download. I just resent the email to the only person who has not downloaded the manual now.
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Hi Joshua
I have not receive any email instruction on how to download the manual.
But I did receive invoice (no 16863) and tracking notification
Could you please check?
Thanks
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From posting your invoice number I can tell that I have correctly identified you. I sent both the email a week ago and the one from this morning to the hotmail address that you provided with that order. Since you received the tracking and order confirmations, that means that the address is correct, so perhaps my messages were caught by your spam filter?
I have now resent the message through the shopping cart system. Hopefully that will go through.
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Got it now.
Thank you very much Josh
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Hi Josh/Paul,
I've been studying the manual as build preparation and try to understand the steps/circuits.
I just have one thing that I don't understand : on page 62, one of the step is to connect red wire from A6 to Kreg on A side of circuit board. Isn't the A6 the anode of the tubes that should be connected to OB instead? I think Kreg should be connected to Cathode A8?
Thanks
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You are correct, we will get that revised. Thankfully the photo shows the correct procedure and there's no wire poking up from A6 at that juncture.
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Hi,
MonAmour build finished!
I decided not to use the power trans cover and showing painted transformer bell instead.
There is some faint hiss that I can hear 2 meter away from the speaker. I suspect its due to TL431 in the cathode. The Stereomour also has the same hiss until I change to simple cathode resistor. Note that my tweeter is very sensitive (Fostex T90A, 106dB/W/m). There is no hiss if I connect the amp to Harbeth P3ES (LS3/5 variant)
The sound : its very clean sounding. Treble is very nice and extended.
Using Sovtek, I thought the mid is slightly harsh at the beginning (relatively, compare to Paramount, not harsh at all in the absolute term). After some break in and switching to JJ 2A3-40 it smooth out and very clean sounding. I think its less forward compare to Stereomour 45.
I can't comment on bass since my speakers have active bass from 200Hz down.
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Excellent work! If you want to change to resistor bias at the input, a 930 ohm resistor should set you up nicely. The gain will drop a little in the process, but with tweeters that sensitive, that certainly shouldn't be an issue!
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Amp Envy!
Triode, I like your idea of leaving the cover off. I initially liked the cover, thinking it gave the amps a more "finished" quality. Yours has the classic BH look. Good work.
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Need some help please. When I went to complete the bias checks, both amps showed low on the meters with the toggle switch in both positions. Are these readings within acceptable tolerance or do I need to go back and check on some things?
Not sure if it makes any difference but the voltage readings during my power checks were all at the high end of the allowable tolerances.
Thanks
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Thanks Paul, Karl.
Paul, if I want to change to 930ohm resistor, should I leave the 5k and 10k trimpot in parallel (giving resistance from cathode to ground around 785-875 ohm range) or just took the whole thing out and replace by 930ohm? Maybe also put capacitor in parallel?
Completely different subject (just a thought): How to convert to 45 output tube? I would imagine we need to change the 130ohm HT dropping resistors (to 560ohm?), add filament dropping resistor (by 0.47ohm?) and change the 270ohm cathode resistor (to 750ohm?)
Hitmanray,
That what the meter shown in mine too. I think its OK. When I measure the voltage and resistance an do the calculation, its actually biased on 53mA and 64mA. It,s just the meter not really accurate. You can adjust the meter a bit by turning the screwdriver slot in the bottom of the meter
Thanks
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Awesome, thanks Triode.
I figured it would be OK, but so far everything has been right on the money in line with the awesome instructions and I figured there would be a tolerance stated if allowable.
Will keep pressing on unless one of the gurus jumps in and tells me otherwise.
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There is a bit of tolerance on the meter and what actual current will show, that's not super surprising.
When you change to the 930 ohm resistor, the shield pin on the 5670 goes to the same grounding point as the signal ground to the chassis, so I wouldn't be too bothered if you just put the 930 ohm resistor between the shield pin and the driver cathode pin. You can leave all the components on the PC board related to biasing up the driver cathode and just disconnect the wire between the PC board and driver cathode.
Very technically, running the cathode bias resistor between the shield and cathode is "wrong", but in this instance the signal levels are large.
To convert to a #45 tube, you need to drop the B+ a lot (as you've observed), the 0.1 ohm filament dropping resistor needs to be increased since the #45 doesn't draw as much filament current as the 2A3, and lastly you'd adjust the cathode bias resistor. The 3K output iron can work with a #45, but it will require a little bit of a different operating point compared to what's in the Stereomour. I would want to run the #45 at the maximum allowable current, but a cursory glance at the datasheets isn't exactly informative as to what that is. Maybe 250V PK at 40mA would be a place to start (or buying the SEX iron ugprade and using the 4K transformer out of there instead of the 3K transformer in the MonAmour).
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Thanks Paul.
I'll stick with 2A3 for now
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WOW!!!!
Tonight I finished up the amps and just got through about an hour of low volume listening (because everyone else in the house is in bed already). I am already totally blown away by the improvement in my system. I am upgrading from a pair of Amp Camp Amp Class A solid state mono blocks that were very enjoyable build projects, and until about an hour ago, I thought sounded great. The step up in performance, even with "fresh out of the box" MonAmour amps with zero hours on them is frankly amazing. I can't really put my finger on anything specifically yet but they just do more of everything and better. The system is very musical and I found myself skipping through various favorite tracks and just grinning like a fool when I hear tracks I've heard countless times before but they are just better than I've ever heard.
Will get some more time on the amps and provide some more detailed feedback, but so far I am beyond impressed by what you guys have designed in this kit.
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Thank you!
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I finished my MonAmour amps on Tuesday and now have 12 to 15 hours of listening to them. I am upgrading from a pair of 18 year old Paramours with Sovtek 2A3 tubes driven by the BeePree. The biggest difference is how much quieter the new amps are compared to the Paramours. I use Voxativ full range drivers that are 100 db/w efficient and I don't detect a noise floor unless I put my ear to the speaker. Wow! The extra power and clarity are immediately noticeable, even on the lower voltage setting. Everything is bigger, faster, cleaner and extremely engaging. I was correct in figuring the Paramours were the weak link in the system. The MonAmours are a noticeable and significant upgrade. An absolute bargain in the world of vacuum tube audio. Highly recommended.
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Thank you so much! The period between shipping the first batch of a new kit and the completion of those kits and receipt of feedback is always kind of a nail-biter. I appreciate the positive reports!
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Since I'm stuck "working" from home for at least a few weeks and may be looking for something to do if this drags out, I'm curious if anyone can compare their new MonAmours to a Kaiju. I haven't heard 2A3s before and am curious how these might compare. I currently have a BeePre/Kaiju setup with Zu Soul Supremes.
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The sensitivity of the Soul Supremes certainly invites trying the MonAmours. I've been listening to MonAmours in my system pretty much since a couple weeks after we moved into the new space. My sense is that the similarities are greater than the differences. That said I think the MonAmours win out in the things that a little more open top end benefit from, like resolution and hall ambiance. The Kaijus win out in punch and rich lower midrange. I'm happy with either. Too bad the Soul Supremes can't be biamped. My next step is Kaijus on the Jager woofers and MonAmours on the tweeters - best of both worlds.