SparkoS Labs Gemini Headphone Amp

[jonathan c]

In tubedom, cleanliness is next to ....

 

[plcpitt]

This is the adapter from Garage (made in US). A bit more $$ but looks high quality.View attachment s-l500.webp

 

[jonathan c]

• Excellent, excellent sound from Gemini 'tubed' with Amperex PQ 7308 (a higher 'spec' / tighter tolerance 6922):

 

[tcarlson]

Just received my Sparkos Gemini this week. I've got the bypass to low and the front gain low to get more tube influence. The -15dB jumpers are in, as I'm driving headphones with the combo. I'm still on the stock tube with Amperex Bugle Boy and Ray Select on the way. I'm using my FIIO K9 Pro ESS as the DAC. Sounds great with either the Sennheiser HD660S2 or the Dan Clark Audio E3. Justin Chancelor's bass tones sound more thick and organic than off the THX AAA output.

 

[rlawry]

Just received my Sparkos Gemini this week. I've got the bypass to low and the front gain low to get more tube influence. The -15dB jumpers are in, as I'm driving headphones with the combo. I'm still on the stock tube with Amperex Bugle Boy and Ray Select on the way. I'm using my FIIO K9 Pro ESS as the DAC. Sounds great with either the Sennheiser HD660S2 or the Dan Clark Audio E3. Justin Chancelor's bass tones sound more thick and organic than off the THX AAA output.

You're gonna love it with that Amperex BB tube, especially the spaciousness and detail that it brings. The BB is one of the best tubes ever made.

 

[tcarlson]

Just received my Sparkos Gemini this week. I've got the bypass to low and the front gain low to get more tube influence. The -15dB jumpers are in, as I'm driving headphones with the combo. I'm still on the stock tube with Amperex Bugle Boy and Ray Select on the way. I'm using my FIIO K9 Pro ESS as the DAC. Sounds great with either the Sennheiser HD660S2 or the Dan Clark Audio E3. Justin Chancelor's bass tones sound more thick and organic than off the THX AAA output.

 

[plcpitt]

6DJ8 Bugle Boy vs GE 5670 w/ Garage1217 adapter. Great build quality of adapter! 5670 GE JAN tube on low gain lacks dynamics. On high gain (less tube) it starts to sound closer to the Bugle Boy on low gain k( more tube) but the BB is smoother and fuller sound. Bugle boy on high low gain ( more tube) is my preference. But adapter is a great way to try other tubes. A 7308 Amperex is on order. Looking forward to the BB vs the 7308 PQ.
NOTE: Corrected review 3/17/25. Thanks rlawry.

 

[rlawry]

I wanted to cite the Gemini users' manual as it lists 2 ways to change what portion of the overall sound is influenced by the tube as opposed to the solid-state output stage. The sound can be changed through these two settings as well as the type and brand of tube.

First, the user can change the amount of bias current applied to the tube by changing the appropriate jumper inside the unit. Setting the bias to low bias makes the Gemini use more of the tube so its sound will use more of the characteristic sound of the tube. Setting the bias to high will use the tube less and result in more solid-state sound.

Second, the user can change the gain button on the front panel. If the button is pushed in (set for low gain), the Gemini will use the tube more which will result in more tube sound. If the button is pushed out the gain will be high and the tube will be used less, resulting in more solid-state sound.

I found that in most cases with my headphones and on most recordings I preferred the low bias and low gain settings so that the sound was more influenced by the tube, regardless of the tube type/brand used in the unit. There were some recordings, like Thin Lizzy's Renegade for instance, where I liked the greater bass impact of solid-state. As usual, it will be instructive to listen to all of the modes and draw your own conclusions.

 

[plcpitt]

I wanted to cite the Gemini users' manual as it lists 2 ways to change what portion of the overall sound is influenced by the tube as opposed to the solid-state output stage. The sound can be changed through these two settings as well as the type and brand of tube.

First, the user can change the amount of bias current applied to the tube by changing the appropriate jumper inside the unit. Setting the bias to low bias makes the Gemini use more of the tube so its sound will use more of the characteristic sound of the tube. Setting the bias to high will use the tube less and result in more solid-state sound.

Second, the user can change the gain button on the front panel. If the button is pushed in (set for low gain), the Gemini will use the tube more which will result in more tube sound. If the button is pushed out the gain will be high and the tube will be used less, resulting in more solid-state sound.

I found that in most cases with my headphones and on most recordings I preferred the low bias and low gain settings so that the sound was more influenced by the tube, regardless of the tube type/brand used in the unit. There were some recordings, like Thin Lizzy's Renegade for instance, where I liked the greater bass impact of solid-state. As usual, it will be instructive to listen to all of the modes and draw your own conclusions.

Thanks for posting. I need to organize my thoughts better before sharing. The Bugle Boy on low gain was my preferred setup. The 5670 on low gain was not as dynamic. A follow-up listening session will be done tomorrow. I am only changing the gain for now but will try the bias soon.

 

[jonathan c]

I wanted to cite the Gemini users' manual as it lists 2 ways to change what portion of the overall sound is influenced by the tube as opposed to the solid-state output stage. The sound can be changed through these two settings as well as the type and brand of tube.

First, the user can change the amount of bias current applied to the tube by changing the appropriate jumper inside the unit. Setting the bias to low bias makes the Gemini use more of the tube so its sound will use more of the characteristic sound of the tube. Setting the bias to high will use the tube less and result in more solid-state sound.

Second, the user can change the gain button on the front panel. If the button is pushed in (set for low gain), the Gemini will use the tube more which will result in more tube sound. If the button is pushed out the gain will be high and the tube will be used less, resulting in more solid-state sound.

I found that in most cases with my headphones and on most recordings I preferred the low bias and low gain settings so that the sound was more influenced by the tube, regardless of the tube type/brand used in the unit. There were some recordings, like Thin Lizzy's Renegade for instance, where I liked the greater bass impact of solid-state. As usual, it will be instructive to listen to all of the modes and draw your own conclusions.

I also found that for some efficient headphones (e.g. some Grados), regardless of Jumpers #1 and #2 settings, the front gain button had to be "in" -- to get any useful volume knob rotation .

 

[tcarlson]

Received a 5670 to 6922 adapter and GE JAN5670W (5/1985) from Tube Depot yesterday. A different flavor from the Amperex Bugle Boy (Arizona Tube Supply) and stock Electro-Harmonix 6922EH from Russia (9/22). Still running low bias jumper and low gain on the front. Sounds very clean and has nice harmonics.

 

[plcpitt]

What headphones are you using? It is nice to have an adapter to try the 5670 tube variants with the Gemini.

 

[fortunate son]

+1 for the NOS Telefunken 801S.

Update: I had forgotten that I had a rare Brimar 1950s Yellow Tag 12AT7 tube. It is now in use and has added a delightful ever so slightly creamy texture to classical music playback which I enjoy very much.
------------------------
The tube is so old and it didn't last very long before it went kaput. It sounded great while it lasted. Such is life.

 

[tcarlson]

What headphones are you using? It is nice to have an adapter to try the 5670 tube variants with the Gemini.

Dan Clark Audio E3 and Sennheiser HD660S2.

 

[DangerToast]

Absolutely loving my Gemini. My only complaint (a minor gripe, really), is that I can't see the tube glowing when the cover is on, LOL. I thought about trying to 3D print a translucent cover. I'm wondering if A) anyone is aware of people selling aftermarket translucent covers for the Gemini and B) if anyone has the STL files for the cover.

Also, popped the Amperex bugle boy in and I'm absolutely loving the sound. In my case, I would say it's similar to the sound from the included Electroharmonix tube, but just a step above in clarity, definition, stage, and possibly bass response.