Looking for feedback on Bottlehead amps

[agweeks]

I just finished law school and finally have the time necessary to build a tube amp—a desire I have had for almost 3 years now. I am tempted to purchase Foreplay III by Bottlehead but am unfamiliar with the DIY community and worry about the fact I haven’t heard the amp and am unable to find any reviews of the bottlehead amps.

I was hoping that someone on the forum either owns or has had a chance to audition the amp would be willing and able to give me some substantive feedback.
Thanks,
Adam

 

[Eli Duttman]

Adam,

The Foreplay 3 is a nice enough preamp. What you get is source selection, volume control, and some (perhaps too much) gain. You still need power amplification. The Bottlehead SEX will work using a CDP and speakers, BUT those speakers have to be very efficient.

You really have to think of the amp and speakers as an organic whole. Have you given thought to the sort of speakers you intend to use?

 

[agweeks]

I have a pair of klipsch SB2 speakers. The plan was to get a pair of the bottlehead monoblocks-but as I am new to all of this and unableto hear any of these amps, all of this is up in the air. As of now, my system cosists of a JVC amp, the klpsch spaekers and my samsung dvd player for cd's and an old Technics turntable.

Thanks for the response.

 

[agweeks]

Thanks Eli,

I have a pair of Klipsch SB2's with an efficiency rating of around 92--I think. These are the speakers I plan to use.

I am currently using a JVC integrated amp that was given to me by a friend. I am so very disappointed with my setup right now; it is driving me crazy. The sound stage is undefined and very flat. I'm chomping at the bit to improve my system but want to get it right and want to have a hand in doing it myself. For these reasons, I want to first learn about DIY amps and speakers and map out a roadmap.

Right now I'm studying for the bar exam (which will take place tue, wed, and thur of next week). After I am done with that, I plan to turn my laser focus on learning about amps and tubes, and speakers and such.

As of right now, in terms of components, all I really have are the Klipsch speakers, an old technics turntable, a samsung dvd player, and an iPod--yes folks, its true, I listen to music on an iPod. The attraction of having all that music right there at my fingertips is just to irresistible.

Is it possible to run a preamp into an amp like the JVC that I have?

Thanks for the response; I appreciate it.

AGW

 

[dsavitsk]

Right now I'm studying for the bar exam (which will take place tue, wed, and thur of next week).

When I was 4 days from the bar, the last thing I was thinking about was flat soundstage.

Is it possible to run a preamp into an amp like the JVC that I have?

Yes, but it isn't going to do you much good. Chaining a decent preamp before the bad one is not going to improve anything.

If you are interested in a DIY solution, my advice would be to build a quick Gainclone power amp, then a tube preamp. The Bottlehead is fine, if a little heavy on gain. There are better designs floating around here, most of which will be cheaper though they will require more thought on your part. I'd search for the 12B4 preamp threads. Tube power amps generally require more care and more work, and are probably best not rushed into.

Good luck on the bar. I rather enjoyed it myself.

 

[zobsky]

92dB efficient multi-way speaker is MARGINALLY sufficient for a 3.5w 2A3 amplifier. Okay for normal level listening, but maybe not as dynamic as needed. Keep in mind that the crossover will rob some power.

I went through a similar exercise a couple of weeks ago listening to a 1.5W SET on various speakers . Only the mid-high efficiency single drivers speaker (fostex 166E) or the high efficiency multi-way (15" co-ax) were worth listening to long term.

I haven't heard BottleHead 2A3 with mid-efficiency speakers, but they aren't too bad with higher efficiency speakers.

If I were you:
1. consider higher efficiency (and larger speakers) and build your 2A3 amplifier
OR
2. Look for a higher power amplifier (maybe 300B, EL34, 6L6 ....). Something about 10 W should work for "normal" sized speakers . Might be worth looking into tubelab products .

(2) might be the more sensible alternative for now unless you are willing to get into speaker building, in which case (1) would be superior.

Pick your poison

 

[Eli Duttman]

As of now, my system cosists of a JVC amp, the klpsch spaekers and my samsung dvd player for cd's and an old Technics turntable.

Adam,

By some miracle, does the JVC amp have a preamp-out/amp-in feature? Should that be the case, implementing a better sounding system, in stages, becomes easier.

In order to use the TT, a phono preamp is necessary. I assume that the JVC integrated has a phono section. Even if the JVC unit lacks the preamp-out/amp-in feature, you can still use its phono section and source selection capabilities. Whatever source, including phono, you select appears at the recording O/Ps of the tape monitor loop. So, that's where you take the signal from, to drive the tubed stuff you will build.

Where a preamp-out/amp-in feature helps is that the SS line level circuitry can be completely taken out of the signal path. "Dummy" loads are placed in the preamp-out jacks and the amp-in jacks are driven by tubed line level circuitry.

OTOH, should the JVC integrated lack the ability to separate the line and power sections, you will not be able to make use of anything SS, except the phono section.

The rest of the "crew" here and I need to know exactly what is available to work with, in order to make good recommendations. The fact that 15 HONEST WPC should be enough to drive your Klipsch speakers definitely works to your advantage.

 

[agweeks]

Hello All. Just came up from taking a long practice exam. Thank you for your responses. They're much appreciated.

In response to Eli's inquiry regarding a pre-amp in or out, I can't find that the JVC has such a feature. It has the normal integrated amp inputs, including: cd, video, tape in and out, phono, VCR, TV. It has a sub out i noticed; but no preamp input output is to be found.

I'm not adverse to scraping the whole amp. I've been investigating zobsky's suggestions and found the TubelabSE to be attractive. It looks as though for a portion of the price of a bottlehead, I can get 15 watts per channel.

I'm a bit unclear on this point: does the type of tube used in the amp adjust the output level to the speakers? I've seen this referred to as tube rolling. I'm imagining a tube cellar next to my wine cellar and me emerging from both with "bottles" in both hands saying "honey" tonight we having an '04 Napa Cab and a NOS RCA.

Are there other folks out there that make and sell pc boards like tubelab? I'm getting the sense that the only real assets I have are my Technics turntable and my speakers. I, therefore, need to examine my options for a pre-amp and an amp in relation to my Klipsch's.

(I'm guessing this will be a life-long passion for tinkering so your suggestion Zobsky that I take up speaker building will come later I'm sure.)

Again, thanks everyone for the input. It's much appreciated.

AGW

 

[boywonder]

AGW:

Tube rolling simply refers to swapping out different brands of tubes (NOS tubes (old Mullards, RCA's etc or new Russian, Chinese, etc) to tweak the sound to ones liking. Depending on the amp, the differences are sometimes subtle, sometimes not. Things like high freq extension, soundstage, lush creamy midrange, etc are some of the parameters that you can experiment with.

FWIW, I am also a tube newbie and I'm just finishing my first tube amp build (Gingertube's "baby huey" EL84 12W PP found on this forum) and the amp has exceeded my expectations and changed my opinion on how much power you really need. It has also been an extremely satisfying experience.

You may want to summarize your electronics experience for the folks here, that will help determine where you should jump in as far as kits go, etc. Do you know which end of a soldering iron to hold on to? Multimeter experience?

You can always build an integrated amp kit (has a vol control and possibly a source selector) and later modify it (remove the controls for a pure power amp) when you've built a dedicated preamp, or if you build an integrated with just a vol control you can use Eli's "tape out" suggestion above. That will use your JVC amp as simply a source selector.

Also keep in mind that kits (or scratch built amps) can use printed circuit boards or "point-to-point" wiring which uses no PCBs, just wires sockets and terminal strips. I'm not sure that either style is much easier or harder than the other, just different.

 

[agweeks]

You may want to summarize your electronics experience for the folks here, that will help determine where you should jump in as far as kits go, etc.

To summarize my electronics bona fides, I do know which is the business-end of a soldering iron and I can read a multi-meter. That being said, this experience was earned years ago while in college. In order to put myself through school, I worked as an electrician's apprentice and then installed phone switches for a year after graduation. So I have a basic understanding of electronics and a GREAT respect for safety.

I would feel comfortable constructing either a circuit board kit or a point-to-point kit but less comfortable sourcing and constructing an amp from a schematic alone.

It also occurs to me that it may be helpful to summarize my listening habits and music tastes. I live in a loft apartment--it's actually a renovated nineteenth century elementary school classroom. The ceiling is about eighteen (18) feet tall. I'm sure that my speakers are not adequate for the room but it is an apartment and I do have concerns about offending my downstairs neighbor. The Klipsch's I run are on stands. The lack of bass in them kind of works to my advantage in that regard.

The listening area is only a portion of the apartment. The seating is about fifteen (15) feet from the speakers. The speakers are about a foot from a wall.

For the most part, I listen to alternative rock music (lots of guitar). I love Tom Waits, Guided by Voices, Spoon. I also listen to artists such as Randy Newman (lots of piano), Nina Simone (intimate female vocals), and Miles Davis (Jazz Jazz Jazz).

It is important to be able to attenuate the volume and select the source. But I embrace the home-brew aesthetic and approach to these amps. The musical listening experience is what is most important to me. I want to feel as though the performers are in the room with me--but hey, who doesn't right?

I need a system that will appease me immediately. I will eventually replace each component over time. For now, however, I want to spend $500 and pull myself out of this black hole I currently find myself in. To that end, any suggestions on amp kits (be they point to point of CB based) that are out there are great. That is what I really need.

Thanks again for all of everyone's kind consideration, I look forward to reading your responses.

AGW

 

[Eli Duttman]

It also occurs to me that it may be helpful to summarize my listening habits and music tastes. I live in a loft apartment--it's actually a renovated nineteenth century elementary school classroom. The ceiling is about eighteen (18) feet tall. I'm sure that my speakers are not adequate for the room but it is an apartment and I do have concerns about offending my downstairs neighbor. The Klipsch's I run are on stands. The lack of bass in them kind of works to my advantage in that regard.

Adam,

That info. is very important. Comparatively speaking, your listening space is a cavern. Paul Joppa's 102 dB. rule does not apply to your situation. You need 30+ WPC in combination with the Klipsch speakers. SE amps at that level of power O/P are HIDEOUSLY expensive. Go push/pull.

It is definitely excellent that you have experience with electronics and that you understand the importance of safety, when working with electricity. Don't worry about sourcing parts for a project built from a schematic. The guys here will get you "connected" to sources for parts.

I suggest you build an "integrated" stereoblock using Mullard style topology. I recommend a 12AT7, 2X ECC99s, and 4X EL34s, as the tube complement.

Believe it or not, your "local" WalMart is a source for a chassis. Buy a large, deep, plain Aluminum, baking pan. If being "purty" matters, you'll get finishing tips galore, from the DIY "crew".

 

[Burnedfingers]

I've never been afraid of having too much gain. That is why there is a volume control that can be adjusted up or down. The preamp from Doc will work fine however I personally believe an Aikido would be much better. If your worried about your ability to put one together rest assured there are people here only to happy to be able to give you instructions.

The amplifier should be able to provide for your modest needs and for this I would suggest a Dynaco Stereo 70 or something along this line. The reason is it will provide a lot of bang for the buck. You will be able to enjoy it and then promptly send it down the road at a hefty profit.

 

[rhing]

Try the Bottlehead Forum

Have you tried the Bottlehead forum at http://www.audioasylum.com/forums/bottlehead/bbs.html? If you are serious about Bottlehead gear, most of the Bottlehead users are accommodating if you post for a listening session at their home around your area.

I can appreciate everyone's input on this thread in terms of alternatves to Bottlehead amps. You might also consider some of the diyTube push-pull amp kits for power amps (http://www.diytube.com/phpBB2/index.php). These kits are largely based on Dynaco amplifier designs. The diyTube kits are basically boards that you need to populate. Most of their instruction manuals include Bill of Materials (BOMs) for guidance on purchasing components including transformers, coupling caps, resistors, etc.

For a preamp, I would consider John Broskie's Aikido linestage amp kits (http://glass-ware.stores.yahoo.net/index.html). You'll have to add your own power supply and power transformer. The Aikido kits are flexible enough for you to configure it to your needs. The nice thing about the PCB-only kits is that you can get creative on enclosures and still have the relative simplicity of working with a PCB to keep things organized. For a complete kit, the Transcendent Sound Grounded Grid is a nice linestage to consider.

 

[Eli Duttman]

Guys,

Adam's budget is $500. Unless considerable care is exercised, the magnetics alone will consume the available cash.

The $62.27 Edcor CXPP60-8-4.2K seems quite suitable as the O/P trafo.



AnTek is a source for affordable toroidal power trafos. The $50.00 AnTek model AN-4T360 will provide for all needs, except the C- bias supply. The $10.00 model AN-0124 takes care of that need.

I envisage the 2X rectifier windings of the AN-4T360 being connected in parallel and SS bridge rectification being employed. 600 PIV diodes will be quite safe in this regime. Snubbed General Semi PN junction parts go on the ground side and Cree SiC Schottky parts go on the B+ side. IIRC, Jim McShane carries the rectifying diodes, along with all the tubes needed.

A CLC filter using a 4.7 μF. 'lytic in the 1st position keeps the power trafo cool, reduces "hash", and holds the B+ rail voltage down a bit. a Hammond 193M would be the choke.

As the B+ rail voltage will still come in on the high side for an EL34 amp, let's turn a liability into an asset by employing combination bias. A shared RC bias network under each pair of EL34s "eats" the extra B+ Volts and allows the use of a single bias trim pot. in each channel.

My earlier suggestion that a 12AT7 section be used as the voltage amplifier was anything but accidental. The 'T7 sounds TERRIFIC in PP amps and its low Miller capacitance allows the use of 510 KOhm grid leak resistors, without incident. That in turn allows 50 KOhm volume controls to be cap. coupled to the 'T7 sections. A 12 nF. coupling cap. puts the 3 dB. down point at 26 Hz., which should be FINE. Remember, Adam's Klipsch speakers don't go there. Does anybody know where a good deal can be had on 12 nF. PIO capacitors? Obviously, 15 nF. parts would work too.

 

[audiowize]

There are lots of kits out there that are done on boards, seem cheap, and become very tempting. What you have to remember is that there is a lot more to doing this than just mounting the parts. The Bottlehead kit will teach you a little about general grounding and layout, and because you are not reliant on board traces, you will make all the connections yourself. There is also an upgrade path, and a few curious projects where people have put alternate double triodes/directlt heated single triodes in place of the 12AU7's.

As for the Klipsch speakers, a 300B might keep you happy, but I wouldn't bet on 2A3's. I think you could do some investigation over on their forum about using type 50's in the Paramour with the upgraded iron to possibly get some more power. If you keep your eyes open on your local Craig's List, you will likely be able to find a pair of 95+db Klipsch speakers cheaply. I found some 102db efficient Klipsch CF-4's for $500, and they have been quite nice for me.
-Paul

 

[w5jag]

I would look hard at Tubelab's Simple SE as a first project.

It sounds excellent, is easily driven by the line output of a CD / DVD player, can meet your power requirements, can be inexpensive or expensive as you wish, is well documented, and a lot of people on here run them.

Can't help you with the Arkansas Bar, it's been a couple of decades since I took it, but you should do fine. I thought the multistate was the hardest part.

I'm in Fort Smith, btw.

Win W5JAG

 

[Jim McShane]

I think Eli's got the best idea. Remember, $500.00 budgets and 30 watt SE amps don't go together well.

The topology Eli mentioned is going to make a very nice sounding amp with enough power to take care of his large room, and work within the budget too.

The lowest bass may be somewhat lacking, but that's probably the optimum tradeoff in this set of circumstances.

 

[GordonW]

Are we worried about the output transformers saturating on low bass? Otherwise, I would, from experience, probably be inclined to hedge the f3 point a bit lower... I hesitate to spec anything above 20 Hz, for a rolloff point. Probably something like a 22nf (.022uf) coupling cap... for an f3 of around 16 Hz, or so... that would still do a good job of not passing "turntable rumble" or other LF hash/trash... but would not EXACERBATE the rolloff of the speakers (remember, rolloffs are CUMULATIVE... you add the rolloff of an amp to the rolloff of the speaker, and you FURTHER lean out the bass, along with exacerbating the group delay below 40 Hz).

I agree with the idea of limiting the amount of LF current through the OT's... but IMHO, it needs to be a little less "intrusive" into the audible range...

Just speaking as a speaker designer, as well as a tube amp tweaker...

BTW: I'm also a big 12AT7 fan... in fact, one of the next amps I'm planning to build is a clone of an early Stu Hegeman design... the HK A250 amp section. 12AT7 in a neat positive-feedback (to the phase splitter) configuration. I've got the same design amp (the Award A300) using a 12AX7, a 12AU7 and 6V6 output tubes... the amps I'm planning on will be monoblocks, with a 12AT7 and PP 6L6 outputs, for about 25w/ch. I'm thinking the amp with the 12AT7 may actually have more "magic" than even the one with the 12AX7 and 12AU7...

Regards,
Gordon.

 

[agweeks]

Thanks everyone for the input and ideas. I'll be finished with the bar exam at 11 a.m. tomorrow. Until then, don't take my lack of participation as a lack of interest. I look forward to reading all of your posts and exploring the ideas and putting together my project.

Thanks again,

AGW

 

[Eli Duttman]

Are we worried about the output transformers saturating on low bass?

Gordon, I always worry about core saturation in circuits that employ loop NFB around the O/P trafo. My level of concern is increased, when the O/P "iron" is not "top notch". By all accounts, Edcor O/P trafos are an excellent value, but I prefer to avoid an attempt at squeezing blood from a stone.

510 KOhms combines with 18 nF. to "corner" at 17.3 Hz. I don't think we should press our luck any further.

Can any member suggest a source for low WVDC 18 nF. PIO capacitors?