Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Smash => Topic started by: Doc B. on April 18, 2014, 10:43:18 AM
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We have had many requests for a replacement for the much loved, now retired Foreplay preamp. While we feel that we have learned enough over the years that even our $99 Quickie battery powered DHT preamp design sounds a little better than everyone’s old favorite Foreplay, we understand what people are asking for. And so we have created a new AC powered preamp that fits very nicely between the budget minded Quickie and our top line BeePre 300B preamp.
Smash is a directly heated triode design like our other preamps and it incorporates many features found on the BeePre –
• Three pairs of inputs
• Two pairs of outputs
• Separate volume and balance controls
• Shunt regulation of the high voltage supply
• Regulated filaments
The Smash uses directly heated 4P1L tubes wired for triode operation as voltage amplifiers. Cathode bias is achieved by our tried and true HLMP6000 LED method. Shunt regulation of the solid state high voltage supply (using ultrafast recovery rectifiers) is via a 0D3 gas regulator and filament supply regulation is via an L200C regulator. The audio circuit is completed with the simple addition of high quality plate resistors and output capacitors.
Three pairs of inputs allow for multiple sources and two pairs of outputs allow for the connection of two amps per channel for multi-amping speakers, or a single power amp for speakers and a separate subwoofer amp or dedicated headphone amp. RCA jacks are gold plated.
We have had many requests over the years to incorporate a balance control into our preamps. We introduced a balance control in the BeePre 300B preamp and we have carried that implementation over in this preamp.
The chassis arrangement is similar to our other kits. We provide the usual high quality level of American made transformers, an American manufactured 10†x 10†chassis panel with our cool new random brushed artisanal finish and lovely Pacific Northwest milled alder wood base that glues together easily and looks great with a wide range of builder-applied finishes. Sockets are ceramic.
Specifications:
Gain @1kHz: 10dB
Maximum output: 7Vrms
S/N: -88dB @4V rms output
Channel Separation: 120dB @500Hz
Input impedance: 56Kohms with volume and balance controls centered
Output impedance: 1.6 Kohms
So how does it sound? Just as its price indicates the sonic character of the Smash falls between the Quickie and the BeePre in terms of resolution. It has the same “DHTness†- that sense of delicacy and realism - as our other two preamps. It will make a great match to the Reduction phono preamp, will work nicely with Paramounts and, yes, we have plans for the introduction of a new power amp to fit this middle price range in the near future.
Why Smash? One day Grammy winning mastering engineer Paul Stubblebine came to Bottleheadquarters for some listening, and he asked to hear the new preamp prototype. Josh brought the preamp up from the lab and on the way to the listening room it slipped out of his hands and Smash! It looked pretty sad with a big bend in the chassis but it fired right up and sounded great.
The regular price for this kit will be $399. As an introductory offer we are pricing the first 20 Smash kits at $349. We have yet to write the manual and get all the parts in stock, so it will be an estimated six weeks before we deliver the first kits.
http://bottlehead.com/smash-dht-preamplifier-kit-specs/ (http://bottlehead.com/smash-dht-preamplifier-kit-specs/)
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Amazing. Congrats on the new oroduct!
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Very nice kit, and an interesting sounding circuit too. Are those regulators the funky purple variety?
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Interesting can we see a under the hood shot?
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Yes, it uses a 0D3 gaseous regulator like we supplied in the Foreplay III, with the characteristic pink/purple glow.
We will have a shot of the underside when we complete the production prototype. The functional prototype in the photo looks slightly different than the production version on the underside.
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Nice ! Time to sell the preamp the Quickie has been beating up on, and get one of these ordered.
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Does this design use AC or DC heaters? -Thx.
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I really like the ventilation slots around the tube sockets. Nice touch.
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Does this design use AC or DC heaters? -Thx.
DC.
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How microphonic is the prototype? vs BeePre? vs Quickie?
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It's actually right in the middle between the Quickie and the BeePre. The locking socket really grips onto the tube, so the approach to minimizing microphonics with this preamp will be more along the lines of lowering the resonance of the entire preamp as a whole.
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Sounds logic. Thanks.
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The layout looks similar, but is the Bee Quiet attenuator compatible with the Smash preamp?
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The layout looks similar, but is the Bee Quiet attenuator compatible with the Smash preamp?
Yes indeed!
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Nice. Looks like some very nice specs and design elements for $400 -- but that's what we'vee come to expect from BH.
Wish I could justify getting onee, but not at least until the backlog is taken care of.
-- Jim
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Wish I could justify getting onee, but not at least until the backlog is taken care of.
Yeah, you sure have a lot of projects going!
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Paul,
How complicated is the build? Again, the quickie being one and the BP 10 I would assume a five.
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PB,
Yes, but now I have a lot more energy and overall better health plus a nice electronics work area and a decent wood shop, so other than idintifying terminals and dealing with circuit boards, no real roadblocks. Oh, and with the analysis paralysis out of the way and a real plan in hand, the work feels fun and nicely mapped out for me.
-- Jim
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Crackphones and Smash in a couple of months. It doesn't sound like anybody at BH headquarters is coasting.
I want 'em both!
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Doc,
Can you give us some hints of what this new (middle price range) power amp will be?
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It will be EL84 based, about 4.5 watts per channel. As usual we are doing things a little differently than others. I will give some more info once we are a little farther along with the project.
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I thought I'd also mention another feature in this thread that didn't make it into the announcement.
With the particular regulator that we are using, I am able to limit the maximum available current that the regulator will output. For a directly heated tube, the filaments draw considerable more current when cold than when warmed up. This puts a reasonable amount of stress on the filaments, so by limiting the current draw at start up, we can extend tube life a bit.
It is worth mentioning that this is a phenomenon that tube manufacturers are aware of and design for, so it is not mandatory and we do not plan to retrofit it into other kits.
-PB
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I hope I didn't miss something in reading about this, but the specs say one of the outputs can be used for a dedicated headphone amp. Does this mean one of the outputs can be wired as a fixed volume line out? Will there be instructions to do this?
Thanks!
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You could wire a Tape Out to one of the outputs for this purpose, but I would instead recommend using the Smash as a buffer to drive your headphone amp instead.
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It will be EL84 based, about 4.5 watts per channel. As usual we are doing things a little differently than others. I will give some more info once we are a little farther along with the project.
Doc, am I assuming correrctly that the price range of the new amp will be below the Stereomour?
I cannot quite swing the $$ for Paramounts but I was toying of building Stereomour poweramp - sans selector, volume etc to run off my foreplay III (and soon my Smash).
How will the new amp compare with the stereomour? When I read "EL84", which is a nice sounding pentode for sure, I'm thinking it's not going to be able to compte with a 2A3 stereomour no?
Thanks
Cleet.
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Yes, the EL 84 amp is intended to cost less than the Stereomour and give the same or a little more power. We are still working up the design at this point and thus it's premature to make some definitive statement about how it sounds.
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Out of curiosity, does rolling the center VR tube do much in terms of affecting the sound?
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Rolling the bypass cap on it probably has more impact.
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Rolling the bypass cap on it probably has more impact.
Are you talking about the .1 uf 400V film capacitor? I was wondering about that.
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If Smash follows the FP III regulator circuit a USSR Military surplus 0.1uF@600V bypass will sound better there.
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I've been reading about Russian capacitors for awhile now. Would a .1 uf 600 volt FT-3 teflon capacitor be a good choice?
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Yes, that is just the thing.
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Thanks for tip. However, I think I'll wait for the C4S upgrade to come out before I make any changes.
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Gosh darn, What an awesome idea! This DHT thing seems to be catchin on. :)
Is an all DHT amp in the works?
Just thinkin.......
Such awesome stuff gettin created here. Wish I had more time to play.
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Yo Bob! How are you? We are fooling with a lot of different things these days. Actually our most recent release is an all indirectly heated pentode SE amp design:
http://bottlehead.com/smf/index.php?topic=6741.msg65638#msg65638 (http://bottlehead.com/smf/index.php?topic=6741.msg65638#msg65638)
But that's not to say we don't have more DHT ideas to play with. And DACs. And speakers. And all sorts of other stuff.
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Hey Dan. Been busy with crazy things. Wow , I love the el84. If I were to pick a favorite pentode that is IT!
I wonder how it drives Fostex T50RP's? Stopped listening for a while when I was soo busy and fired everything back up. Man looking back life is a void without beautiful music!!
Photography is geat but 2 weeks of February in Iceland chasing auroras will kick your butt. Love all the new stuff.
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But that's not to say we don't have more DHT ideas to play with. And DACs. And speakers. And all sorts of other stuff.
How about something DHT to compete with Wavelength's USB Dacs?
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That would mean tacking a DHT output stage onto a SS DAC circuit. We did a lot of experimenting with tube DACs and found a solution that we feel sounds better. You can always add one of our DHT preamps after it and have a DAC with a DHT output.