Tube Rolling w/Crack

Dr. Toobz · 749161

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Offline tintin

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Reply #2235 on: November 27, 2020, 04:18:17 PM
I've recently picked up some ECC31 as well as some nice looking 6N7G tubes. I have an ECC31--> ECC32 adapter, and was wondering if this would work for the crack. Would R1 on the speedball board at 470 ohms work for the ECC31, just as it does for the ECC32, or are there other considerations with the single cathode? 



Offline Paul Birkeland

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Reply #2236 on: November 28, 2020, 05:21:52 AM
470 ohms for the R1 on the small board may work for the ECC31.  You'd have to use an EC31->EC32->12AU7 stack of adapters. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline tintin

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Reply #2237 on: November 28, 2020, 01:37:30 PM
470 ohms for the R1 on the small board may work for the ECC31.  You'd have to use an EC31->EC32->12AU7 stack of adapters.

Thanks Paul for the confirmation. I've installed a switch to go between 117, 235 and 470 Ohms and testing it out today. For reference, fresh 12AU7 on 235Ohm reads 65V OA/OB, 6SN7s similar. Very used ECC32 on 470 Ohm tests 90V.

ECC31s on 470Ohm tests 85-93V. 6N7Gs seem to be higher testing at 90-95V. They are all pretty fresh but seem to test a little higher but still barely within the acceptable range. Should be ok for long term use, or should I try up the 470 Ohm resistor value? To me so far, they sound just as good as the ECC32 for a non-silly price.



Offline Paul Birkeland

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Reply #2238 on: November 28, 2020, 03:08:32 PM
Maybe you could nudge the 470 ohm resistor up a bit more to bring the plate voltage down a bit.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Markkr

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Reply #2239 on: November 29, 2020, 03:18:24 PM
I’m absolutely loving this amp.... lets just say I was interested in picking up a couple tubes for them.... Can anyone recommend what to start with? Is there a tube upgrade that is guaranteed to please? (Budget would be less than $200 per amp)



Offline Colonl_Charisma

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Reply #2240 on: November 29, 2020, 08:19:25 PM
For my input tube, I have enjoyed the Mullard CV4003 (~$50 on eBay). For my power tube, I've been really loving the Thomson 6080WA (I bought a matched NOS pair for ~$50 on eBay).

That combo sounds amazing on my Crack (no Speedball upgrade yet).
« Last Edit: November 29, 2020, 08:24:43 PM by Colonl_Charisma »

Ross


Offline Markkr

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Reply #2241 on: November 30, 2020, 10:21:02 AM
For my input tube, I have enjoyed the Mullard CV4003 (~$50 on eBay). For my power tube, I've been really loving the Thomson 6080WA (I bought a matched NOS pair for ~$50 on eBay).

That combo sounds amazing on my Crack (no Speedball upgrade yet).

Thank you. If I understand correctly, the power tube does not make much sonic improvement?



Offline Colonl_Charisma

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Reply #2242 on: November 30, 2020, 11:43:55 AM
You’re welcome. I’m not 100% sure about sonic improvement. I’ll let someone else answer that haha. The other power tubes I have tried are a Russian 6as7g and a GE 6080. I found the Russian tube to have a flat sound, lacking in the low end, and lacking depth. That’s the best way I can describe how it sounded to me. I also didn’t care for the sound of the GE 6080. Both were rolled with the Mullard CV4003.

Ross


Offline cddc

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Reply #2243 on: November 30, 2020, 03:39:16 PM
I’m absolutely loving this amp.... lets just say I was interested in picking up a couple tubes for them.... Can anyone recommend what to start with? Is there a tube upgrade that is guaranteed to please? (Budget would be less than $200 per amp)

If you have a budget of $200, I would recommend you to get a Tung Sol 5998 and a Telefunken/Mullard/Amperex/Mazda 12AU7.

If you are willing to try 6SN7 tubes with adapter, there will be much more choices, it's a deep rabbit hole.



Offline cddc

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Reply #2244 on: November 30, 2020, 03:45:45 PM
Thank you. If I understand correctly, the power tube does not make much sonic improvement?

I don't think so.

My experience is that in Crack the driver tube accounts for 40% and the power tube accounts for 60%.

You need a good power tube to get the most out of Crack. A sucker power tube (like RCA 6AS7G) will doom whatever driver tubes you throw in.

Once you get a good power tube, you can switch different driver tubes for different flavors.



Offline cddc

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Reply #2245 on: November 30, 2020, 03:49:46 PM
Forgot to mention a good starter tube would be the Russian 6H13C (i.e. 6N13S) tube. You can get them around $10 apiece + shipping from Ukraine or Russia.



Offline barbz

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Reply #2246 on: November 30, 2020, 06:55:10 PM
A sucker power tube (like RCA 6AS7G) will doom whatever driver tubes you throw in.

I'm curious to know thoughts on the rca 6as7g and why it's a sucker power tube

Thank you



Offline cddc

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Reply #2247 on: November 30, 2020, 09:24:48 PM
I'm curious to know thoughts on the rca 6as7g and why it's a sucker power tube

Thank you

It has rolled off highs and lows, kinda mid-centric, which is quite typical of the RCA "house-sound". RCA 6SN7 is no different.

When you add RCA 6AS7G or 6SN7 to your Crack, you'll find the overall presentation is veiled, kinda muddy sound that I really dislike.



Offline Doc B.

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Reply #2248 on: December 01, 2020, 08:32:22 AM
Quote
sound that I really dislike

That's the most important part of your post. It's a sound that you dislike. But will someone else dislike it? I will suggest that we all temper our descriptions to include what our own taste might be, as you have done in describing what you are hearing from RCA 6080s or 6SN7s. I don't necessarily disagree with you, particularly about a 6SN7 sounding a little lacking on top. But it's a very linear tube, and it has a great midrange. Some folks absolutely love the sound. After 25 years at this I know for sure that my Crack amp might sound like crap to one person, but not to someone else.

The original idea behind this kit was to offer a cheap way for all of us to roll tubes and form our own opinions. I still think that is the best approach. I'll also suggest that people stop paying stupid money for tubes. I buy tubes on ebay all the time. Not the overpriced ones. IME about half the sellers know jack shit about what they are selling. Caveat emptor. The law of diminishing returns applies heavily. If you see some 6080/6AS7 variant for $400 on ebay, run the other way. It might sound better to you, but it won't sound 26.66 times better than a $15 one. If we all start paying $400 for a 6080 tube pretty soon a Crack kit will be a grand.

Oh yeah, and all of this opinion is useless if you don't say what headphones you are using to form these opinions. Let's be logical here.


Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline cddc

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Reply #2249 on: December 01, 2020, 09:16:11 AM
Hi Doc. B, glad to hear from you.

I agree with you on many levels. While I do hate the sound of RCA 6AS7G and RCA 6SN7, I do find some folks like them, especially those mainly on vocal albums, sometimes Jazz albums. So I stated the reason why I dislike them. I also agree with you on the tube prices. The NOS tube prices were kind of going wild recently. A pair of Tung Sol 6AS7G's were selling for $300+ weeks ago, I was just stunned when seeing the winning bid. People were going crazy, out of rationale, propelled by the tube-mania from head-fi. I got my TS 6AS7G's for $20 a pop just couple of years ago.

BTW, I am using Senn HD800 headphones with my Crack w/ Speedball. :)