Alright everyone, I have the next big modification to my franken-crack ready. Meet the tube-rectified bottlehead crack! I completely re-implemented the power supply with an oversized power transformer capable of supporting a tube rectifier. The high-voltage winding is maida-regulated for a consistent, stable, low-ripple B+ voltage no matter what rectifier is plugged in. Any 5V rectifier is supported. I've tried 5U4G, 5U4GB, 5AR4, and 596 rectifiers with great success.
One neat thing here is that if I wanted to go back to SS rectification, I can! I have a SS plug-in rectifier that fits in the octal socket. This was tons of fun, and I learned a lot about power supply design in the process!
Under the hood you can see the maida regulator for the HV winding, as well as the massive heatsink attached to it. I managed to fit this while keeping all the previous upgrades in place, including the onboard DAC.
I also replaced the input wiring with shielded cable, as there were now AC lines closer to the input wiring. With the shielded wire in place, the amp is completely silent with no hum whatsoever from the new PT. It's silent using both the RCA inputs as well as using the onboard DAC.
Overall I am very pleased with how this turned out. The differences in sound are noticeable, and my BHC has never sounded this good! Aesthetically, it came out better than I expected too. I managed to fit the new transformer in such a way that it covered the massive hole in the top plate from the original transformer.
The regulated PSU definitely made the biggest change out of all the upgrades (aside from the speedball). Early impressions are that the sound is just flat-out cleaner and more resolving, and the bass is more defined and punchier.
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Thanks! I like having ultimate flexibility of either tube or SS rectification.
The impedance of the Rad0 is only 29 ohms, so this amp is a bad pairing. This amp is more suited for high impedance headphones like Sennheiser and ZMF (200-300 ohm or above headphones).
I bought this amp — using w/ ZMF Auteur & Atrium, as well as 6XX. Definitely good synergy w/ ZMF — haven’t tried 6XX yet as I just picked the amp up yesterday.
Funny part is how I fell into this amp — was hoping to do a try-out and someone posted a link to the listing — didn’t realize the seller was (relatively) local until we chatted.
So now I need power tube recommendations (already have lots of input tube choices) to synergize best w/ my ZMFs. My initial read suggests that Tung Sol 5998s are the ‘cream of the crop’. Concur/disagree? Any other recs — I’m looking for ‘max disciplined tubiness’ if that makes sense.
And I wouldn’t mind spending less than the ~$250 a TS 5998 will end up costing.
I bought this amp — using w/ ZMF Auteur & Atrium, as well as 6XX. Definitely good synergy w/ ZMF — haven’t tried 6XX yet as I just picked the amp up yesterday.
Funny part is how I fell into this amp — was hoping to do a try-out and someone posted a link to the listing — didn’t realize the seller was (relatively) local until we chatted.
So now I need power tube recommendations (already have lots of input tube choices) to synergize best w/ my ZMFs. My initial read suggests that Tung Sol 5998s are the ‘cream of the crop’. Concur/disagree? Any other recs — I’m looking for ‘max disciplined tubiness’ if that makes sense.
And I wouldn’t mind spending less than the ~$250 a TS 5998 will end up costing.
A personal favorite of mine is the Chatham 6AS7G. That tube basically never left my BHC. They are less pricey than the 5998s, but still up there. Unlike the 5998s though... the Chatham 6AS7G can be periodically found for much cheaper. I got all of mine for $25-$30 per tube just by being a little patient and waiting for the right deal to pop up.
I bought this amp — using w/ ZMF Auteur & Atrium, as well as 6XX. Definitely good synergy w/ ZMF — haven’t tried 6XX yet as I just picked the amp up yesterday.
Funny part is how I fell into this amp — was hoping to do a try-out and someone posted a link to the listing — didn’t realize the seller was (relatively) local until we chatted.
So now I need power tube recommendations (already have lots of input tube choices) to synergize best w/ my ZMFs. My initial read suggests that Tung Sol 5998s are the ‘cream of the crop’. Concur/disagree? Any other recs — I’m looking for ‘max disciplined tubiness’ if that makes sense.
And I wouldn’t mind spending less than the ~$250 a TS 5998 will end up costing.
The TS5998 is a good one though I wouldn't necessarily describe it as lush and tubey. It's actually quite extended in the highs. It is a great power tube however. What really impresses me the most about it is the size of the soundstage and holographic nature of it. If you are patient you can find one below $250. I think I paid $150 for mine and it measured NOS.
Other power tubes I really enjoy with the BHC are the Chatham 6AS7, Wing C 6H5C, Tung Sol 6AS7, and RCA Black Plate 6AS7. The Chatham and Tung Sol 6AS7s (early production were two different tubes until Tung Sol bought Chatham and produced tubes for both labels later on) can be pricey though not as bad as the 5998s (typically around $100-150 per tube).
The Wing C 6H5C and RCA Black Plate 6AS7 are the best bang for the buck IMHO. You can find the 6H5C from AliExpress: https://www.aliexpress.com/item/32809963593.html
I purchased mine from them and its an excellent tube though its took about a month to receive it. It has great tonality though its not quite a holographic as some of the others.
To me its hard to go wrong with a RCA Black Plate 6AS7. Its a great sounding tube and can be regularly bought for around $50-60 apiece. Imho anyone with an amp using 6080/6AS7/5998 type power tubes should have a few of these since they offer great sound and don't break the bank.
A personal favorite of mine is the Chatham 6AS7G. That tube basically never left my BHC. They are less pricey than the 5998s, but still up there. Unlike the 5998s though... the Chatham 6AS7G can be periodically found for much cheaper. I got all of mine for $25-$30 per tube just by being a little patient and waiting for the right deal to pop up.
I bought this amp — using w/ ZMF Auteur & Atrium, as well as 6XX. Definitely good synergy w/ ZMF — haven’t tried 6XX yet as I just picked the amp up yesterday.
Funny part is how I fell into this amp — was hoping to do a try-out and someone posted a link to the listing — didn’t realize the seller was (relatively) local until we chatted.
So now I need power tube recommendations (already have lots of input tube choices) to synergize best w/ my ZMFs. My initial read suggests that Tung Sol 5998s are the ‘cream of the crop’. Concur/disagree? Any other recs — I’m looking for ‘max disciplined tubiness’ if that makes sense.
And I wouldn’t mind spending less than the ~$250 a TS 5998 will end up costing.
Tung Sol or Cetron 7236 is another power tube to try. Not quite as sought after as the 5998 but I would say they deliver on the discipline criteria you asked for. Cream of the crop would be GEC 6as7g/a1834, Bendix 6080wb and Tung Sol/Chatham 5998 but they are priced accordingly. If you look up the Bottlehead Crack tube rolling thread there are some posts that rank the power tubes.
Another alternative to the 5998 that’s often mentioned is the Tung Sol (and later Cetron) 7236. Similar in sound if a little more solid state sounding. Can be found quite a bit more widely and cheaply. But count me as someone who would take the Chatham/TS 6as7g and the Russians before the 5998.
Another for “max discipline tubiness” is a GEC (NOT GE) 6080. Langrex had a bunch, hope they still do. That’s probably the perfect description for that tube. Pricey but still less than 5998 prices.
I bought this amp — using w/ ZMF Auteur & Atrium, as well as 6XX. Definitely good synergy w/ ZMF — haven’t tried 6XX yet as I just picked the amp up yesterday.
Tung Sol or Cetron 7236 is another power tube to try. Not quite as sought after as the 5998 but I would say they deliver on the discipline criteria you asked for. Cream of the crop would be GEC 6as7g/a1834, Bendix 6080wb and Tung Sol/Chatham 5998 but they are priced accordingly. If you look up the Bottlehead Crack tube rolling thread there are some posts that rank the power tubes.
A personal favorite of mine is the Chatham 6AS7G. That tube basically never left my BHC. They are less pricey than the 5998s, but still up there. Unlike the 5998s though... the Chatham 6AS7G can be periodically found for much cheaper. I got all of mine for $25-$30 per tube just by being a little patient and waiting for the right deal to pop up.
I'm running the RCA 6AS7 black plate / 12AU7 clear top combo and I have to agree, it's tremendous. The tubes the Crack ships with are fine, but yeah, these are a huge upgrade. I got a strong matched pair of each for $80 total, so I'm set for life. You can probably get one of each for under $50 total easy. Huge value.
I'm running the RCA 6AS7 black plate / 12AU7 clear top combo and I have to agree, it's tremendous. The tubes the Crack ships with are fine, but yeah, these are a huge upgrade. I got a strong matched pair of each for $80 total, so I'm set for life. You can probably get one of each for under $50 total easy. Huge value.
Agreed! I think it may be the best value combination for the BHC or at least right up there. I honestly think I paid around $50 for both combined. Like you said huge value!
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