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September 27, 2021, 07:04:36 AM

Author Topic: Low impedance headphones (25 Ohm)  (Read 268 times)

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Offline ipetruk

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Low impedance headphones (25 Ohm)
« on: September 14, 2021, 12:25:50 AM »
Hi, I have already built Crack+Speedball and it is my faviourite amp of all, no contest! Thank you very much for your products.

One of the side effect of this is that I unfortunately cannot use some of my nice headphones. For example Klipsch HP-3 25 Ohm, 98 dB sensitivity. I was thinking of getting another amp and I am considering S.E.X. or Mainline. What are the lowest impedance headphones those could drive?

In the documentation to Mainline it is more clear - minimum is 32 Ohm. Would 25 be an issue? What problem can I expect? Is it no tubiness or is it unpleasant distortion? With S.E.X. it is less clear. The product page does not seem to indicate minimal headphone impedance, but some articles on the internet say it can be wired to drive headphones as low as 16 ohm. Is that true? If yes, is it a standard wiring explained in a manual or is it a more complex mod?

To be honest I have an itch to try Mainline as your flagship amp over S.E.X. Most of my headphones are beyond 300 Ohms, also I will soon by Verite Closed. Price for either amp is fine with me. Tubes for both amps are not a deciding factor, afaik people generally do not roll tubes on either.

But I'd like to have an option to run my 25 Ohm Klipsch. Do you think it will be much worse with Mainline over S.E.X?
« Last Edit: September 14, 2021, 12:53:51 AM by ipetruk »
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Offline Doc B.

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Re: Low impedance headphones (25 Ohm)
« Reply #1 on: September 14, 2021, 03:33:10 AM »
I think either amp would work well, and I think that it really boils down to a matter of which sound you prefer more than any potential issue from the tiny impedance mismatch (25 vs 32) with Mainline. The Mainline is a bit more refined, has better resolution and a more neutral character. The S.E.X. amp will be more robust and romantic sounding with a bit more technicolor presentation and weight, i.e. a little more tubey.
Dan "Doc B." Schmalle
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Bottlehead Corp.

Offline ipetruk

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Re: Low impedance headphones (25 Ohm)
« Reply #2 on: September 14, 2021, 04:05:12 AM »
Than you, very interesting response.

Meanwhile I was reading these reviews:

http://passionforsound.lachlanfennen.com/bottlehead-s-e-x-diy-amplifier/

http://passionforsound.lachlanfennen.com/bottlehead-mainline-diy-amplifier/

Especially the section on bass, the reviewer says that Mainline bass is deeper and bettern controlled and on S.E.X. S.E.X. is described as rather cold. This seems the opposite to the experience you are desribing.

In general while I enjoy resolution, "robust and romantic" as you say sounds amazing. And this is what I really enjoy in my Crack+SB. I would like to avoid getting a solid state sounding amp.

What do you think balanced connection contributes in Mainline, given S.E.X. still seems to deliver much more power? Is this about better separation or right+left channels, or?
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Offline Doc B.

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Re: Low impedance headphones (25 Ohm)
« Reply #3 on: September 14, 2021, 05:01:12 AM »
The answers are actually contained in your questions ;^)

Yes the Mainline goes a little deeper in the bass with a little more control. That is a characteristic that one might call "solid state sounding". For me balanced connections to speakers and headphones contribute to that deeper more controlled bass.

I disagree with the notion that the S.E.X. amp sounds cold. I respect Lachlan's opinions, and I know from them that he hears differently than I do. Bear in mind also that amps sound very different with different headphones. You have to try these things yourself. There is no life to be lived depending on the opinions of others.
Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.

Offline ipetruk

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Re: Low impedance headphones (25 Ohm)
« Reply #4 on: September 14, 2021, 05:06:31 AM »
I do think I will go with S.E.X. I enjoy tubiness (within reason) over solid state, accurate presentation. The thing is - I am pretty happy with bass and the rest of what Crack+SB provides, so my expectation is that S.E.X+upgrade can only deliver more better quality. Also Lachlan confirms this too, S.E.X. with C4S does more than enough.

I am interested in the speakers aspect of S.E.X., even though my current speakers are insensitive as it gets (KEF Q550). But who know what I get next.

Thank you very much.
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Offline ipetruk

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Re: Low impedance headphones (25 Ohm)
« Reply #5 on: September 15, 2021, 03:01:21 AM »
A few reviews say that along progression of Crack -> S.E.X. -> Mainline, the latter becomes again slightly similar to Crack in sound signature. I am not sure what do they mean. And they describe S.E.X. as lean and cold, which is again different from Doc's comment in this thread.

I am fairly confused
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Offline Paul Birkeland

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Re: Low impedance headphones (25 Ohm)
« Reply #6 on: September 15, 2021, 04:13:17 AM »
I would not describe the SEX as clean and cold vs. the Mainline either.
Paul "PB" Birkeland

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Offline Chris H

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Re: Low impedance headphones (25 Ohm)
« Reply #7 on: September 15, 2021, 12:27:24 PM »
Sorry to chime in - I read those reviews before I bought the SEX (after already having the Crack+SB).
As noted, different people hear or perceive things differently so I found the reviews particularly helpful as they provided a comparative.
I couldn't, however, find any mention of the SEX being cold, rather I thought he said "cooler but not cold" when comparing to the Crack.
I too would never, ever describe the SEX as cold.
The analogy used as Crack being front row seat and SEX 10th row was a good one for me and this may be what contributes to a description of coolness by some but I am not sure this is the same thing.
In my opinion, it gives the SEX a sense of greater seperation and amazing depth as the review noted, but definitely not cold.
It's similar with "tubiness" which some may associate with being warmer or less detailed.
A tube amp that is detailed and neutral is often described as sounding less tubey, almost solid state (I'm still never clear whether this is intended as criticism or compliment but it must depend on taste).
For me, tubiness is neither the level of detail or warmth, but the liquid smooth delivery which both the Crack and the SEX have in abundance.

In terms of speakers for the SEX, I use mine with headphones and nearfield speakers in a desktop setup (83db sensitivity) and it is currently my most used amp.
I have tried it through my 90db Spendor D7s in my main sytem and was shocked at the volume achievable.  It does depends on the size of the room and usual listening volume though.
As for sound, the Spendors can sound lean or even harsh depending on partnering equipment but with vinyl into Eros into SEX, Wow! Nothing lean or cold about the SEX.

Offline ipetruk

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Re: Low impedance headphones (25 Ohm)
« Reply #8 on: September 16, 2021, 11:29:50 PM »
Thank you very much everyone.

After reading even more reviews I've ordered a Mainline.

Another Bottlehead journey on the way!
Roon -> Raspberry 4 -> Khadas Tone in Bottlehead Crack+Speedball -> detachable cable modded DT880

Offline Paul Birkeland

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Re: Low impedance headphones (25 Ohm)
« Reply #9 on: September 17, 2021, 04:12:41 AM »
Awesome!  The Mainline is a rewarding build.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man