[larcenasb]

Anyone here have experience rolling different bypass caps for the Crack's last power supply cap? With this extra time at home, I spent hours switching out and listening with the two bypass caps I have: Jantzen Superior Z-cap 0.68uF 800V & Audyn Tri-Reference 0.68uF 600V ($15 & $25, respectively...neither grossly expensive).

This obviously isn't ideal because it's not a blind test, and there's a good chunk of time between listening with each bypass cap. Also, I am a highly skeptical person and am constantly questioning things to make sure I'm not fooling myself. Yet, every time I switch to the Audyn Tri-Reference, I am confident there is a noticeable tone and quality shift for the better. Specifically, the Audyn allows for a larger and deeper soundscape, precise placement of instruments within that soundscape, and a delicately handled treble with no loss of tantalizing bite. So, I soak in the sonic pleasure...then my skepticism cuts in again. I proceed to unplug everything, take my amp downstairs to the garage, and switch the cap back to the Jantzen again. And again, the sound is comparatively closed in, the distinct placement of instruments not so apparent, and treble a bit screechy...or so I think.

At this point, I feel like I'm going nuts... On one hand, I feel nourished and enthralled by my music in a substantial way with the Audyn, but, on the other hand, I know that there's nothing easier than fooling oneself. Another reason to think it's placebo is that I adore the marketing of the Audyn caps. Audyn's description of their True Copper Cap on Hificollective's website states that there is "no contamination by strange mixture of various metals and fairy like oils (LOL)," and the Tri-Reference is very similar with its copper-foil construction. Conveniently, the Jantzen is "made from polypropylene film metalized with aluminum and zinc particles (from partsconnexion)," i.e. a stange mixture of various metals haha. So those descriptions could be swaying my thoughts. But, Jantzen does go so far as to describe what their cap's sound is like, saying it has "good detailing and soundstaging with natural tone reproduction," but that's what I hear with the Audyn, not the Jantzen. But that is likely my bias towards Audyn, and trusting their marketing more to begin with. Buttttt maybe marketing and truth are not always mutually exclusive! AHHHHHHHHHHfjodyasknfd456%$^#5njkfbnas###!!

If anyone has done similar tests or has other opinions, I'd love to read about them as I gather more info about this mystique of judging musical reproduction.

(For reference, my Bottlehead Crack specs can be found on my profile page: About > Audio-Related Tweaks.)

I hope all of you and your loved ones are staying safe and doing okay amid our physical social distancing. Cheers

 

[Tom-s]

Anyone here have experience rolling different bypass caps for the Crack's last power supply cap?

IMHO, while the gains may vary. Rolling a bypass fancy type cap just for the sake of experimentation, to experience how the PS influences the sound, is a good thing to try.
Especially with cheap / Russian caps, go ahead.

At this point, I feel like I'm going nuts...

To be honest, i feel you're not the only one here . But in a good way.

It's the good kind off Crack to escape this weird reality for a while. Last weekend I had a perfect high made possible by the great adapter dealer @Deyan .

 

[larcenasb]

It's the good kind off Crack to escape this weird reality for a while. Last weekend I had a perfect high made possible by the great adapter dealer @Deyan .

Thanks for the reply! And whoa! Please tell us what tubes and adapters those are! And how would you compare the sound to a 6AS7G+6SN7GT combo!? Thanks!

 

[Tom-s]

The following should be read with this in mind. I have enough tubes to not have a single clue anymore on how every single one sounds.

The driver tubes are Sylvania 76's, that's some sort of grand father version of the 12AU7 and 6SN7/7N7 that became 6J5 and went into a single envelope ->> 6SN7 was born.
In general these have a big band, cathedral kind of sound to them. It's like a S3X, you are placed somewhat further away from the podium in a bigger hall. This makes them sound very very good, similar to when you are used to 6J5's, that also have this kind of effect on presentation. I don't roll 6SN7's that often, so don't know exactly how they compare. The National Union, Sylvania and RCA's 76's i own all have a different flavor but share the "big band" sound that makes you want to turn up the volume. Before i was using an adapter tower, this @Deyan adapter looks better imo.

The output tubes are some variation on the A2293's (see previous pages), another "half 6080" type of tube, Russian 6C19P, there's actually a few OTL tube amps based on these. It's technically not much better than 6080 on datasheet. And I couldn't find many comparisons with these, luckily Deyan was kind enough to build me an adapter for this purpose.
In general i feel this tube does sound very good. It's not the best on every level, but very very capable overall. But i've started to notice these need time to warm up, like a Bendix 6080 that sounds better after 30 mins or so. I'll do a, single triode per envelope that fits half a 6080, comparison one day.

 

[bagwell359]

Got a kit, have stared at it for two weeks while I read up on all the design concepts, suggested mods, tossed in my own experience building kits through the years.

I decided to build it in versions:

1. stock - but go with different attenuator, and locking headphone jack
2. add speedball
3. add caps & other mods

so I'm using insulated clips to I don't have to solder and re-solder over and over. When I'm done I'll hard solder it.

Also, I dislike the way the amp looks with the RCA's and power cord sticking up like rooster feathers. So they are going in from the side, and I'm hard wiring the RCA's, using a well insulated cable (3-5') (using cable ties as strain relief for both). I'm bypassing the input plug and on/off as well. Don't worry, I'll pretest the "right way" and "my way" to be sure I haven't done something idiotic.

I'm putting a pair of 270 ohm chokes on top over the RCA and power in holes. If there is notable hum in that position I'll try others or metal sheets to block them from the PS. It seems that there could be some hum due to the wiring, so twisting, re-routing, insulation, and magnets may be employed.

Finding any of best power tubes very tough to aquire. The input tube is easier. I'd say tubes are 3x more expensive then around Y2K when I had the last of my tube stuff. Haven't bought anything yet.

Will buy speedball and Cree Shottky's & board this week. Have a pair of 1.0 uf Clarity Caps from another project I didn't use - so they will be my first bypass attempt. I like the Obliggatto 100uf, esp with the Supreme oil bypass. The 2 220's for the PS might not get updated (but will get bypassed) but the 3rd one is. There is a Mundorf Mlytic meant to be mounted on a board that looks good for that (not film).

I'm changing resistors in the signal path to Mills, and that pair of 5 watt coffins is gone, and I'll mount a spherical heat sink on the Mills. Probably heat sink the Cree Schottky as well. Actually only the single 1 watt to dissipate voltage is likely to be the only one in the kit I use in the long run. I want a dead on match for the headphone and vol pot. Haven;t tested the kit resistors yet, but doubt they are that tight.

 

[Bullpride]

The ZMF Aeolus, without a doubt. I own the BHC Speedball, HD650, and Aeolus. I can honestly say, that the Aeolus improves on every aspect of the HD 650 while maintaining a similar sound with the BHC, and it is a match made in heaven.

I have a BHC Speedball on the way (ordered this morning). I also have the Atticus, which is what started me down the tube route. Are you running the stock tubes with your BHC? If not, where should I start with the best pairing for The ZMF cans?

I am also already working on an upgrade from the crack, but its at least a few months away. I am hoping the crack shipping soonish so I have some time with it.

 

[Wes S]

I have a BHC Speedball on the way (ordered this morning). I also have the Atticus, which is what started me down the tube route. Are you running the stock tubes with your BHC? If not, where should I start with the best pairing for The ZMF cans?

I am also already working on an upgrade from the crack, but its at least a few months away. I am hoping the crack shipping soonish so I have some time with it.

Nice! The BHC sounds amazing with my Aeolus and I can only imagine the Atticus would sound great too. I am currently running some of the best NOS tubes ever made, and could not be happier. My current tube combo is, the Bendix 6080WB Graphite Slotted Plate for power tube, and the Valvo ECC82 Long Plate Foil D Getter from Hamburg Germany 63' as the driver tube. These tubes are expensive, but can't be beat in my setup, with my heaphones and taste. I would look for any Bendix 6080WB Graphite plates for power tube, and my other 2 favorite driver tubes are the 7316 Long Plate Foil D Getter, and Sylvania 5814a Triple Mica Square Getter with Grey Plates.

Happy tube hunting!

 

[m17xr2b]

I'm thinking this is the last upgrade to my Crack, a dual PSU setup, a shared CLC then a split LC.

In addition, SIC input bias and gyrator for the input. Now the amp has matured into a different beast and while I'm having even more upgrade ideas this has to be the end.

I did run for a while clarity cap TCs for the PSU, uber sound but impractical and now part of a different amp.

 

[Toad_of_Toad_Hall]

.

 

[Bullpride]

New build totally devoid of electrolytics.

Is that a custom base? Taller than the stock? Any suggestions for building one myself? I have one on its way, and want to build a taller base with African Padauk to match my Headphones. I can PM you if you prefer.

 

[JamieMcC]

New build totally devoid of electrolytics.

Nice work you must have had a blast building it.

 

[Toad_of_Toad_Hall]

.

 

[Toad_of_Toad_Hall]

.

 

[Tom-s]

When paying tax makes beautiful.

Below is an example from the Fivre factory in Milan, Italy (a company that produce US tubes in Europe under RCA license).
It's a pair of type 76 tubes, used as drivers in Crack (with an @Deyan adapter). *Click on image for full size.
The stickers are from the ministry of finance, they were proof tax was paid on the tube (tax was based in weight and type of tube if i'm correct).
I was very lucky to find these. I found the first tube long ago in Belgium (grabbed it untested, based on looks), just recently I found another in the Netherlands (and both are NOS). The search was diffucult as the top mica support construction is rare. Other Fivre 76's were found with normal RCA type top mica construction, but I couldn't find another reference of this construction type anywhere on the internet. And as fate would have it, both came with the exact same tax sticker on them dating 9.9.42 (and matching code above it).
It may have to do with the fact that the Italians didn't get along with the rest of the world those years, that these look different. The construction may have changed due to lack of supplies from the RCA company USA (or other war-time related shortages). I've only seen 6C5's from that era with the same construction top "springs?" https://www.ebay.com/itm/254507568343 .

The sound is typical 76. These are detailed, with a sort of "bigband" enveloping type of sound to them. The bass is less pronounced compared to other tube types, still they sound full, very enjoyable. These mate well with Bendix 6080's or Tung Sol 5998's, or as seen in pictures with GEC A2293's. Are they much different from other RCAs type build 76's, no not really. Do not pay crazy money for this kind of tubes (above hyperlink). A 20$ RCA pair 76's sounds close to the same to me.

 

[D P C]

Been looking at these myself just lately and thinking is a kit for me or just buy one done? Thats the question