Quicksilver Audio Headphone Amplifier

This amp has WAY too much gain for Grados. If you want a tube amp for them there are many other low power choices that are great.

 

This is an excellent chart!

The VDC 100, 220 µf caps are the cathode bypass caps for the cathode bias resistor. You wrote you did not know what those caps purpose was. Just letting you know.

The 47 µf 100 VDC cap is for the DC plate feed for the preamp tubes. It comes directly off the choke and connects both plates of pin 1 of both preamp tubes.

Just note that this amp likely does not need the gain out of 12AX7's. Especially from full 2V output DAC's. Can likely more get away with a 12AT7 or even lower. 12AX7's are noisy and lots of distortion. Gain factor is 100. Here the the gain factor list:

• 12AX7= 100
• 5751 = 70
• 12AT7 = 60
• 12AV7 = 45
• 12AU7 = 20

To put it in perspective, here are some other gain factors of other cleaner less distorted tubes that you can use with this amp with an adapter:

• 6N1P/6H1N = 35
• 6N23P = 33
• 6922/E88CC = 33
• 6CG7 = 20
• 6SN7 = 20

Of course a 6CG7 is direct equivalent to a 6SN7. And the 5751 is supposed to be a military equivalent to the 12AX7, but it also has a lower amplification factor. Also ran it with a 12AT7 also did fairly well...much better than 12AX7's.

Trust me...I have this amp now (well..just testing at the moment thanks to @Ksorota), but I just put 6H1N's on and it really changes the character of this amp and really opens it up.

 

I think this amp is perfect for Grados, that's how i use it (RS2e w/G-pads), fed by a DAC that outputs 2.3V and i have the volume pot in the 9-10 o'clock range. I don't think it has too much gain for the Grados, i think it's just right.

 

That is crankin’ loud!

 

Hi my first thread post.

There is some information that needs correction.

A 7189 is a power tube. 7189 is an upgraded EL84/6BQ5 that can take 400 volts on the plate and also has a higher plate dissipation.

The 12AX7 is a superb match for the EL84. They work like a hand and a glove electrically. For lower gain a 6N2P works very well.

The gain of a 12AU7 is about the same as a 6SN7 or 6CG7. From memory I think the 12AU7 mu is about 19.5

 

I feel like this thread needs a gentle bump, so I’ll give a quick update on the tubes I’m currently using in my Quicksilver. I switched from my favorite 1955 Mullard EL84s to a pair of Tungsram welded plates that are also from the 50’s. Both are an excellent pairing with my 1954 long plate Amperex 12AX7s that are basically a permanent roll in the amp at this point. I hope they have many, many years of life left in them.

I think the Tungsrams are a bit more balanced from top to bottom vs the Mullards, which have those amazing mids. In my opinion, the Tungsrams might actually be just as good in the mids while offering a little more bass extension. Both sound great, so I could be perfectly satisfied with either pair.

All my previous experience with the Quicksilver was with ZMF dynamics, but I’ve recently become a planar convert after lucking into a Meze Elite. I can confirm the low output impedance of the Quicksilver plays very nicely with the Elite. The only SS amp I have at present is the Piety, which sounds really good for the cost, but can’t truly match the tube magic of the Quicksilver. I imagine the Caldera will be a good match with the QS as well. I’m the last stop on the Caldera loaner tour, so it will be quite a while until I get a chance to report back on the pairing. Let’s just say I’m really looking forward to comparing the Caldera to my Elite. It’s the only headphone I’m giving any chance to unseat my new favorite. If anyone can do it, @zach915m can!

 

I am a fan of the Tungsrams too.

 

Third vote on Tungsgram EL84’s.

I urge everyone that has this amp to ar least try a good 12AT7 over noisy distorted 12AX7’s. The sound becomes less forward and has much more depth and clarity.

 

What are a few 12AT7s you’d recommend in the Quicksilver? I have focused my tube research solely on 12AX7s and EL84s, so I’m clueless when it comes to anything else.

 

I don't have this amp, but I have a TC-tube amp that does better with 12AT7s than 12AX7s, even though the mfr recommends the latter (12AT7s have less gain, which works out better).

The best I've heard yet are '50s Brimar CV455s.

 

[QUOTEI I urge everyone that has this amp to ar least try a good 12AT7 over noisy distorted 12AX7’s. The sound becomes less forward and has much more depth and clarity.

I agree 12AX7's are not very good tubes. I like to use the Russian 6N2P-EV with a socket adapter instead. I have a couple EL84 speaker amps that have 12AX7 front ends. The 6N2P-EV is much better sounding and has a lower gain more like a 5751.

Sticking with a 12AT7 or 6N2P/adapter is probably the best advice.

 

Not much love for the 12AX7 it seems. So it’s not only the issue of the higher gain, but you guys feel that 12AT7s and 12AU7s actually sound better? I know my Quicksilver sounds excellent with many of the 12AX7s I’ve tried, so I’d be amazed if things got radically better if I switched to one of these lower gain options being recommended.

As a side note, a few years ago I asked Mike from Quicksilver about using something other than 12AX7s in the amp, and he didn’t recommend it. I never got a real thorough explanation, but he didn’t even want me to use 5751s, which are extremely similar to to 12AX7s though with a lower gain factor. I’ve been hesitant to try anything other than 12AX7s ever since.

Final side note, a bad tube damaged the right channel of my QS when it died, and Mike fixed my amp under warranty at no charge to me. He even paid the return shipping, which I wasn’t expecting. I’m not sure if using tubes other than 12AX7s and EL84s voids the warranty, but I do know you can get this amp sounding extremely good using the two families of tubes Mike intended.

 

If you are satisfied with the 12AX7's don't listen to us. If there is one tube the 12AX7 works well with it is the 6BQ5/ EL84's.

 

I don't think 12AX7s are inherently inferior in any way from 12AT7s. They're just different. The 12AT7s have the situational advantage of never having their prices kited quited as high in the NOS markets as 12AX7s, but that's neither here nor there technically/sonically.

FWIW, the manufacturer of my amp, the Icon Audio HP8, also doesn't recommend any input tubes other than the 12AX7. I ignored that and did better sonically with the lower-gain 12AT7. That's a benefit to me (and not a hardship for the amp) for one external reason that totally matters IMS: I've had gain issues in that system ever since I migrated to NOS DACs that output more voltage than the nominal 2.0 volts standard. My current DAC (which I love the sound of) is the MHDT Labs Orchid NOS w/a tube buffer. Great DAC, but I have serious gain issues throughout the system. To get back to the HP8, I'm already confined to the lower counterclockwise end of the volume pot as is; when I use a 12AT7 instead of a 12AX7, I claw back just a bit of gain.

 

I completely understand wanting more room to work with on your volume pot. I have never had any gain issues in my setup, and channel imbalance has never been a problem at the volume I listen, usually between 8:30 and 9:30 on the pot. I think I’ll stick to 12AX7s in the Quicksilver. Sometimes it’s better to refrain from messing with a good thing.

 

I have a new Liquid Platinum that uses 6922's. Unfortunately, that is the one tube I never used or purchased. I could get some socket adapters which I use for everything and use my vast stock of 12AU7'/5814's. I already have some 2C51/5670 adapters and lots of the 5670 tube. I typically use tube subs and save lots of money doing so. Example 7N7 for 6SN7. But the 7N7 is an exact electrical equivalent of the 6SN7 with a different loctal base. I am not paying more for tubes than the amp.

But the substitute tubes are hard to get in and out of the LP with adapters and like you I don not want to (tear up the tube sockets) mess the amp up. The 6922 ekectrical parameters are off quite a bit from the other suggested tubes too. People report good results but I guess I like the amp so much I do not want to take any chances. Moreover, I am not having any issues with gain that would warrant using a lower gain 12AU7 anyway.

So, I am sticking with 6922's and looking for some of the good Russian 6N23P's or some deals on good NOS 6922 tubes.

 

It really is beyond just volume pot usability. Lower gain and cleaner tubes really do change the characteristic of the sound and takes away the greyness of the 12AX7's. Mike is super picky about his amps, but there is no danger in running lower gain tubes - it only makes it better IMO.

PS - 12AX7 type gain is used in guitar amps to bring them up to level. Once you are already inputting a 2V signal from a DAC, you no longer need that kind of gain. It's only going to add distortion and noise.

And any good NOS 12AU7 would be fine. RCA, Sylvania, TungSol, etc.

 

I think I’ve thrown this out before, but I stopped rolling EL84s after trying Polam and Telam old stock. True timbre, touch, texture, and alive-ness. Guitar players’ raves made me try em’.

 

Thanks for this suggestion. I have not heard of Polam Telam tubes. I guess they are under different labels and often referred to as Polam/Telam. Polish made tubes.

The Tube Store sells them NOS: https://www.thetubestore.com/telam-el84

And I keep telling other people this and they don't believe me, that guitar players usually have good ears for good tone in tubes.

 

Out of stock for quite a while though. I got mine from a seller in Ukraine after reading the review at The Tube Store. Just took a chance and sent my $. Took a couple months to get here, but heck of a deal it turns out.