jameson_bh
New Member
Hey there, Jameson from Bottlehead here. I'll copy and paste a comment Paul Birkeland made on Facebook in reply to a similar question that was asked:
Bottlehead releases an 805A monoblock amp kit
- Thread starter BmWr75
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jameson_bh
New Member
Correct, that's a photo of the Crackatwoa. I arranged everything, photographed it, and used it in one of our articles about what comes in a kit.
Well, there you go! Very clever.
jameson_bh
New Member
I did also want to show what a kit could look like with some customizations. This is my personal set (please ignore the messy basement background; we just moved and are still settling in). I had some walnut bases made, and I painted the chassis plate a gunmetal grey and all the other topside components a matte black. We also offer some lit meters.
These kits are really ripe for customization, and we tend to focus on how they sound instead of offering a lot of aesthetic options. That keeps our inventory more sane and our costs lower, which keeps the prices in check as well.
A couple notes on pricing while we’re at it. Our margins on these are similar to what our margins are on other products. There are three beefy chokes and transformers we have made bespoke for us, the top chassis plates’ thickness had to be increased to support the weight, and we include all the tubes you need. None of these components are cheap (well, two of the three tubes per monoblock are sub $10), and you have double the bill of materials because there are two of everything per kit.
I also acknowledge and am frustrated by the badge not being included in other kits (although we did price them into the Paradyne). We offer those to our customers at our cost, and we have not yet found a more cost effective way to produce those at a level of quality we expect. We investigated tossing those in as a freebie for all kits, but those costs exceeded what we could absorb.
In any case, we’re feeling very pleased with how the launch has gone. As new owners and new entrants into the audiophile game, we’re learning as we go and are grateful for everybody’s feedback and patience. We’re also thrilled with the partnership we have with the Pauls and happy to say that we have a wealth of knowledge from Dan and Eileen that we can draw on.
These kits are really ripe for customization, and we tend to focus on how they sound instead of offering a lot of aesthetic options. That keeps our inventory more sane and our costs lower, which keeps the prices in check as well.
A couple notes on pricing while we’re at it. Our margins on these are similar to what our margins are on other products. There are three beefy chokes and transformers we have made bespoke for us, the top chassis plates’ thickness had to be increased to support the weight, and we include all the tubes you need. None of these components are cheap (well, two of the three tubes per monoblock are sub $10), and you have double the bill of materials because there are two of everything per kit.
I also acknowledge and am frustrated by the badge not being included in other kits (although we did price them into the Paradyne). We offer those to our customers at our cost, and we have not yet found a more cost effective way to produce those at a level of quality we expect. We investigated tossing those in as a freebie for all kits, but those costs exceeded what we could absorb.
In any case, we’re feeling very pleased with how the launch has gone. As new owners and new entrants into the audiophile game, we’re learning as we go and are grateful for everybody’s feedback and patience. We’re also thrilled with the partnership we have with the Pauls and happy to say that we have a wealth of knowledge from Dan and Eileen that we can draw on.
jameson_bh
New Member
double post, sorry
FreaK
is his own damn self
This might be weird timing in this thread, but, can anyone, maybe one of the Pauls, explain exactly what “parafeed” is?
I feel like every couple years I dip my head inside of amplifier design and discover I never even really knew what I thought I knew before.
5k sounds too much for me right now, but it sounds pretty good for 35w set. Are there listening reports yet?
I feel like every couple years I dip my head inside of amplifier design and discover I never even really knew what I thought I knew before.
5k sounds too much for me right now, but it sounds pretty good for 35w set. Are there listening reports yet?
A simple internet search can provide the information you seek.
Here is an example of a parallel feed SE amp that I built a couple of years ago from a schematic by Paul B and some advice since his original design was series feed. Notice that the output tube has a choke for a plate load to provide the DC feed to the tube. The output transformer is capacitor coupled to the plate to prevent DC current. This allows the output transformer to be made without a gap in the lamination stack. This isn't anything new as it is discussed in some of the old text books from the 1930's. The RDH4, Radiotron Designer's Handbook V4 and which you can download, discusses this on pages 519 and 645.
FreaK
is his own damn self
I asked, in THIS thread because it’s very relevant to Bottlehead’s offerings, and specifically this very one and there’s no explanation on Bottlehead’s site. Which is quite something as they are also one of the only companies I’ve ever heard of to offer this topology commercially and declare it openly.
albusark
Dynaco Fan
Have you considered selling amps with a metal chrome plated chassis? I'm not a fan personally of the old furniture look
You got the response you did because there is nothing unique about the way Bottlehead uses parafeed, which is one of the basic configurations of output transformer connection, along with series-feed and push pull. So general information about parafeed will be as useful as anything specific to Bottlehead. But basically it adds a coupling cap and removes DC in the OPT primary.
One potential problem with that approach is that the blocking choke and output transformer primary are effectively in parallel to signal ground. The transformer may or may not have sufficient inductance under those conditions for the amplifier to produce low bass. Also, core flux increases significantly when the signal frequency moves into the first octave. It's the same effect as DC. Whether the transformer can produce acceptable performance will depend on many factors. Unlike a dedicated SE transformer that carries manufacturer's specifications, the end result can't be known until it's tested in this mode.
Jack
Jack
Paul Joppa
New Member
I don't have my notes handy, but IIRC the plate choke and output transformer were designed to operate down to 30Hz at 35 watts, using a relatively conservative 13,500 Gauss peak with M6 laminations. In an earlier post (#13) the measured performance confirms the design.
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Just to be clear, my earlier comments regarding flux and parallel inductors weren't aimed at your product. I was referring to the post by @nerdorama about the possibility of repurposing a push-pull transformer for parafeed. Are any companies still producing parallel feed transformers as an OTS product? Or was Magnequest the last one?
Jack
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