[Tom-s]

Another day, another tube to try in Crack. Today from the type 37 collection. This is an 1931 (december) pair Sylvania 37 that I picked up recently. I've always wanted to try an old mesh plate tube in Crack. But since it's for 6.3V indirectly heated only, the options are very very limited. There are these old globe's, that are very rare and have a huge potential to hummmmm.
And that last part, is just what they do (continues loud hummmmm). They are not microphonic, they just hum away. This may indicate a grounding issue i've never noticed with any other tube of be due to the fact that the amp is AC heated. This is most likely as the hum does not change with volume and these were designed in a mostly DC era, to be used in cars using 6V heater from the car battery. Unfortunately, the hum makes them unsuitable for my Crack.
Sound: With the volume up (because of the low volume hum), there's beautifully clear dynamic music. Tight bass with good authority, very precise defined high's, good soundstage, nice natural tonality overall. It's very unfortunate that no modern manufacturer is making a mesh plate indirectly heated driver tube (without hum issues).

For now, i'll investigate the hum further, to hopefully be able to use these in the future. A DC heated driver socket (another Crack) is sort of a last resort.

 

[GreenNeedle]

3) Yeah, as I mentioned earlier, I've been listening with a Bottlehead Crack since 2010 and am supremely happy with my setup. Plus, you also have K240 Sextetts that I imagine you enjoy...well, the combo of Sextett+Crack is again my favorite I've encountered so far. When I "upgraded" to the Beyer DT 1990, I still preferred the Sextett...the Beyer sounded harsh and the mids were nowhere near as present or lifelike, they were scooped out unforgivably (after hearing the Sextett, many owners often won't compromise on mids). As for the resale value, stock Cracks tend to sell for around $600 on eBay. I was pm'd here on head-fi by someone offering $1000 for my build! That made me really proud. My advice to you is to really take your time with the build--when people see the guts of the amp, it should inspire confidence and, hopefully, awe.

A DAC with analog inputs isn't common. You can do research here to try and find some models, but I've only seen in it very expensive receiver-sized type DACs which prioritize features/options. Emotiva had one but it was still around $350. I think the best way to test your Denon CD player's DAC would be to simply connect it to your amp directly via RCAs (Denon -> RCAs -> Bottlehead Crack), listen to music critically; then add your new DAC to the chain (Denon -> optical cable -> DAC -> RCAs -> Bottlehead Crack), listen to the same music critically. Then go back and forth comparing. And yes, if you did get a DAC that has analog inputs, the Denon's signal would bypass the new DAC circuit (since there is no digital signal for it to convert), and it would just be sent out analog the same as how it entered...unless it's some strange model that I'm not aware of.

4) The Topping seems like a smart buy. It's all-metal with sturdy toggle switches and has fantastic reviews.

5) I'm not sure I understand what you mean when you said "replacing the big tube with another small tube." What I meant was the opposite. The stock driver/input tube is a small tube (12AU7) and some listeners opt to buy a 6SN7-to-12AU7 (6.3V) adapter to use the bigger (6SN7) tube. In general, a 6SN7 will make the presentation sound bigger, bass will reach deeper, voices will have more body, and there will be an overall sense of lushness to the sound. Lots of people though, including Doc of Bottlehead, prefer a good NOS 12AU7 (Mullard, Telefunken, Brimar, Amperex, et al.). So, it's all just options as you search for the presentation you like. Supposedly, many audio engineers in the 50s were upset about the advent of the 12AU7, saying it was clearly inferior to the octal predecessor, but was cheaper to make. To really simplify, some say the 12AU7 has a cleaner more solid-state like sound in general, and the 6SN7 has more character and bloom giving it the quintessential tube sound. It's nice the Crack allows for sooo many options to finetune your sound.

And yeah, same here, my setup is the culmination of a lot of research and small, informed steps. I like finding great values most of all and being happy with what I do have, as the quote in my sig alludes to.

6) Well, I think the Bottlehead Crack and AKG K240 Sextetts will likely offer you plenty of satisfaction for a long, long time. Lol, it's nice that I have those two pieces as part of my main setup, so it should inspire a bit of confidence in you that it's worth it.

7) Yeah, have fun with the build! But if I may elaborate on what I meant about really taking your time with the build... I don't know how much soldering experience you have, but I'll say just in case: Try to make the wiring decent at the very least, without overlong wires or messy routing (that will really help with resale value). And remember to make a good mechanical connection before soldering. I've seen so many builds where people put solder on a wire lead, heat up the joint, then move the wire to the joint... It's best to not rely on the solder to make the connection, it should just be bolstering an already-made connection. I like to make a nice curved hook with the wire lead, secure it on the intended joint and either use helping hands to hold the other end of the wire to pull it taut, or even use pliers to pinch the hook and make it tightly fit around the wire/socket tab...then solder. The solder shouldn't be a bridge, it should be a straitjacket. Hope this helps! Take care!

reply to 3: The Sextetts were a suggestion out of the blue from Monsterzero. Never heard of them before. I managed to get an LP and like it a lot. Reading on I bought an MP but preferred the LP. A year or so on with new genuine AKG pads and I'm not so sure anymore. The MP is sounding really nice. I also bought the Senn 580s from reading on here and they are now complete with genuine new pads, 650 cable and 600 grilles. They sound amazing too. To be honest I tend to prefer the 580s to the Sextetts for most music however they can't compete on some music. It's always the Sextetts for ACDC - Back in black. No competition there. The Sextetts sound perfect for music that is closer to a "live" recording. The BH Crack just seems from the reviews an amp which will be perfect for both the Sextett and HD580. I wouldn't have any of these were it not for this forum so a collective thank you to all.

reply to 5: My bad. I was assuming 6 = small and 12 = big. lol. I get you here. Will have to see where we go over time on this. I can;t afford to buy a selection of tubes trying out things but over time, a tube here and there. They hold their value I suppose even at the lower end.

reply to 7: I'm no electrician nor have much knowledge of electronics but I do have internet access which is great for learning and being able to try things yourself that in my/our younger days would have needed a lot of reading books or taking courses to achieve. I can solder though. Research and trying led me to building this luminaire in 2012. This was actually an aesthetically improved version. I had made 2 more before this in boxes but I am a very vain person and aesthetics are key (Bottlehead crack looking great is important as how it sounds. I have also replaced lamps in several old stereo receivers as well as replacing headphone jacks etc, so I do have a fair amount of practice with soldering. This is why the bottlehead crack appeals to me because (if all the reviews and write ups are true) it doesn't really need knowledge of electronics. Simply an ability to solder and follow instructions is the selling point in my eyes. The below is very simple; 2 Led drivers. 1 driving 2 outer rows (12 x 3W LEDs.) 1 driving the centre row (6 x 3W LEDs.) Using stars so easy to solder them. Wires hidden under the heatsinks so you can only see them from below. I did this from using other people's knowledge and adapting what can be done to what I wanted to do. Someone with electronics knowledge would have been able to do it much better. I did it by using 2 plugs. I'm very much a "can do" type of person. I like to see if I can do it before I say I can't :



To be quite honest here, for all my tall of frugalness I do have thoughts in my mind to have a go at a S.E.X. for my speaker setup if this goes well. I am quite lucky in that I don't have any credit, and a few months "cover money" in the bank.

I would still use the Trio receiver, just to connect everything up and then use the "tape rec" as a line out to the S.E.X. The Trio looks beautiful lit up and I have invested time and money refinishing / veneering that. lol.

That is some way off though. Let's see how the crack goes first. Many thanks for your help though. I'll order the crack+speedball tonight. IT was Lugnegaard's finish that really appealed to me. Dark outer, polished plate, rounded edges. Not decided whether I will try and veneer it or just dye the existing wood yet. I have time to think on that. Veneering is hard on rounded edges.

 

[GreenNeedle]

Sorry another question for anyone who knows the answer. I have tried searching the internet but it seems there used to be a 240V version of this kit that people in Europe and UK ordered.

There is just one Crack kit on the site that I can see. Is there some clever wiring that allows it to be used at 240V in the UK? or is the kit they sell at the moment only to be used on US 120V wall outlets? Like those SS amps that have a switch on the back that you slide as applicable to your wall outlet supply?

 

[Tom-s]

There is just one Crack kit on the site that I can see. Is there some clever wiring that allows it to be used at 240V in the UK?

Yes. It comes with a universal powersupply that can be wired for both 120 and 240v.

 

[GreenNeedle]

Yes. It comes with a universal powersupply that can be wired for both 120 and 240v.

Thank you, ordering the Crack now.

Oh and after researching the S.E.X. that is a no goer. My speakers are 88db.

 

[PsilocybinCube]

Need some help with a noise coming from the Crack w/Speedball. I bought one second-hand a few weeks ago and can't get a faint sound (only playing on the right channel) to go away. It sounds like a lightbulb warming and then maintaining the 'warming' sound throughout the time it is on. I think it's the power tube...currently RCA 6AS7G in that slot.

I've tried a few different things:

Swapped 12AU7 tubes (no change)
Tried different power cords (no change)
Purchased a power conditioner (very, very slight improvement)
Swapped RCA cables (no change)
Moved closer or further from other devices (no change)

I don't think it's interference. I do think it's the power tube...but I'm wondering if anyone can think of other things to try. I have zero DIY experience with amps, but I'm fairly handy and want to learn. I just don't even have any clue where to start when I look at the underside of the board and all the connections.

The amp also has Mudorf caps and ALPS potentionmeter. I don't even know what that means...so I'd love to learn.

Other than the slight hum - which fades into the background when listening to music at reasonable levels - the Crack sounds great.

I'm coming from a DX7Pro, so this change to SE and tubes is definitely a big change.

 

[Wes S]

Need some help with a noise coming from the Crack w/Speedball. I bought one second-hand a few weeks ago and can't get a faint sound (only playing on the right channel) to go away. It sounds like a lightbulb warming and then maintaining the 'warming' sound throughout the time it is on. I think it's the power tube...currently RCA 6AS7G in that slot.

I've tried a few different things:

Swapped 12AU7 tubes (no change)
Tried different power cords (no change)
Purchased a power conditioner (very, very slight improvement)
Swapped RCA cables (no change)
Moved closer or further from other devices (no change)

I don't think it's interference. I do think it's the power tube...but I'm wondering if anyone can think of other things to try. I have zero DIY experience with amps, but I'm fairly handy and want to learn. I just don't even have any clue where to start when I look at the underside of the board and all the connections.

The amp also has Mudorf caps and ALPS potentionmeter. I don't even know what that means...so I'd love to learn.

Other than the slight hum - which fades into the background when listening to music at reasonable levels - the Crack sounds great.

I'm coming from a DX7Pro, so this change to SE and tubes is definitely a big change.

I would try a different power tube, and this would be the first thing I would try. I have had some noise before, and it has always been the power tube or driver tube. A tube swap with a better tube has always done the trick.

 

[larcenasb]

I would try a different power tube, and this would be the first thing I would try. I have had some noise before, and it has always been the power tube or driver tube. A tube swap with a better tube has always done the trick.

Same here. I've had a few noisy 6AS7G tubes... but they are pretty cheap and I love their sound over the 6080, so a few bad eggs in the basket are more than tolerable for me.

 

[PsilocybinCube]

As a new person to tubes, I'm a little lost on where to order them. I bought some of the Soviet Winged 'C' tubes...but then realized they probably won't come forever because they are being shipped by Putin's personal assistant direct from the Kremlin.

For purposes of an inexpensive tube (mostly to narrow down if the power tube is indeed the issue), what would you recommend buying that could get to me quick? (I'm in US, btw)

 

[DenverW]

A rca 6as7g is cheap and plentiful. A tung sol 6080 or 6as7g....I can’t remember which tube I sent to you with the crack.

 

[PsilocybinCube]

It's the RCA 6as7g which it seems a lot of people say have some microphonics (I think that's the term) that cause some noise.

 

[GreenNeedle]

Hello, me again. I'm considering making my own base rather than trying to veneer rounded edges. Can anyone give me the thickness of the wood? I see the chassis plate is 10" x 6" and the planks about 3.5" high, so what I am after is the actual thickness of the wood for the base below the rebate/rabbit.

I know I said dark but I am going to use Santos Rosewood to match what I did with veneer on my Trio turntable and Stereo Receiver:

 

[PsilocybinCube]

It's the RCA 6as7g which it seems a lot of people say have some microphonics (I think that's the term) that cause some noise.

I swapped out the power tube and troubleshooted other buzzing (all electronic interference from devices, mostly a printer) and now it is dead silent and sounds great!

Computer interference was a bit of a pain and is still occurring to a degree, mostly when running very intensive programs. Moving the amp and DAC away from the my PC ameliorated that issue, but it's hurt the feng shui of my desk!

Looking forward to continuing to use the amp. I swapped the power tube for a super cheap SINO tube from Tube Depot. I have the Soviet Winged C tubes on order and look forward to trying them once they come in. At some point, I'll have to give some different 12au7 tubes a try, too.

 

[Wes S]

Hey fellow Crack fans! For the past year, I have been in a pretty intense love affair with the 12AU7, and having a blast. However, as the tube rolling addiction goes, I decided to see if the grass was greener on the other side, and got some adapters to roll some of my top tier 6SN7's. Well it turns out, this time it actually was greener on the other side. This is my current tube roll and one I will not be changing any time soon. The Tung Sol 6SN7GT VT231 BGRP, is the real deal. Everything about this tube is perfect, when paired with a Bendix 6080WB, my Atticus and Gumby. The detail, depth, impact, and realism are all the best I have heard from my BHC. The 6SN7 is a killer tube and worth giving a try, no doubt.

 

[PsilocybinCube]

Hey fellow Crack fans! For the past year, I have been in a pretty intense love affair with the 12AU7, and having a blast. However, as the tube rolling addiction goes, I decided to see if the grass was greener on the other side, and got some adapters to roll some of my top tier 6SN7's. Well it turns out, this time it actually was greener on the other side. This is my current tube roll and one I will not be changing any time soon. The Tung Sol 6SN7GT VT231 BGRP, is the real deal. Everything about this tube is perfect, when paired with a Bendix 6080WB, my Atticus and Gumby. The detail, depth, impact, and realism are all the best I have heard from my BHC. The 6SN7 is a killer tube and worth giving a try, no doubt.

Which adapter do you recommend? I've been considering this myself.