[karangovil]

A two stage single ended tube amp is really an integrated amplifier; it has a preamp stage and a power amp stage in one box. Usually the pre-outs are taken at the output of the preamp stage so it can drive a different power amplifier stage.

I think this explains why Donald doesn't want to do preamp outs on his amps. Thanks for the explanation!

 

[L0rdGwyn]

Thanks for a good explanation. I always thought headphone amps preamp section were mostly very basic and not a lot going on outside of a volume pot. I’ve talked to a few builders that say they try to make the circuit as simple as possible. I always thought most pre outs on a headphone amp was meant for convenience more or less.

You can do a passive preamp by running the outputs out of the volume pot, but if you want any gain, then it has to come from the preamp stage. The topology of some headphone amps is very similar to that of a preamp, so the outputs might be taken from the same output as the headphone (after the power stage). A good example of that would be a cathode follower OTL. Many times a preamplifier will consist of a voltage gain stage followed by an output buffer, which is exactly the same topology as a cathode follower OTL, only difference is a headphone OTL usually needs a heftier buffer than a preamp since headphones require a lower output impedance, but that doesn't make it function any less well as a preamp. So in that case, outputs might be taken after the cathode follower. But in a conventional SET design, usually it is after the preamp stage, you don't need a SET power stage to drive another power amplifier. For preamp / power amp matching, the typical rule of thumb is you want the ratio of the output impedance of your preamp to the input impedance of your power amp to be 1:10 minimum. This applies for source components as well (DACs, phono stages, etc.) going into preamps.

 

[Dawgfish]

Beautiful blue color on that nautilus and ofc the ZMFs are stunning.
Have you tried KT88s? I tried a pair of tung sol NOS 6550s but I found that although it really amped up the bass, I lost some of the mid emphasis that the zmf atriums have, especially with a pair of 5AR4s (NOS mullards black base). Pairing 5U4G was better imo with the 6550s. This could also all change depending on which 9 pin tube you're using.
The 12AU7 discussion has me wondering about those. I have a RCA 7025a in the slot.

You might want to try the vintage GE 6550s. They have more forward mids compared to the Tung Sol. They also have incredible bass, slightly relaxed highs, and great staging and imaging. I prefer them to the Tung Sol in many amps.

 

[RonPlata]

Pendant owners, what are some nice upgrade tubes I can buy? Under $200 would be good.

 

[Thaddy]

Currently using the WA22 and GSX-Mk2 with my Koa VC's and Cocobolo Atrium's. I much prefer the WA22 with both headphones, it adds just a bit of heft that I don't get with the GSX-Mk2. However, it's hard to not appreciate the dead silent background of the GSX-Mk2. I use that with the VC's when listening at low volumes.

I plan on adding the Caldera's when they become available and also have a custom SET Odyssey from UltraSonic Studio being built later this year. Tung-Sol 6550's, GEC KT66's, and Mullard xf2 EL34's are already waiting for that amp to arrive

 

[Dawgfish]

Currently using the WA22 and GSX-Mk2 with my Koa VC's and Cocobolo Atrium's. I much prefer the WA22 with both headphones, it adds just a bit of heft that I don't get with the GSX-Mk2. However, it's hard to not appreciate the dead silent background of the GSX-Mk2. I use that with the VC's when listening at low volumes.

I plan on adding the Caldera's when they become available and also have a custom SET Odyssey from UltraSonic Studio being built later this year. Tung-Sol 6550's, GEC KT66's, and Mullard xf2 EL34's are already waiting for that amp to arrive

Congrats! You've got some really nice tubes in hand when the Studio arrives. Nice current setup also!

Where did you get the headphone stand (the phrenology one)? I really like that!

 

[Thaddy]

Congrats! You've got some really nice tubes in hand when the Studio arrives. Nice current set up also!

I got some great direction and suggestions from @UntilThen and fortunately my tube supplier had some premium tubes in stock. I also have some RFT EL34's and La Radiotechnique EL39's. The Odyssey takes a 5U4 rectifier and 6SN7/6SL7 preamps tubes, of which I have TONS from years of owning the WA22.

After many many years of being in this hobby and having the opportunity to hear a lot of different headphones, I've come to the conclusion that the ZMF house sound + tubes is exactly what I prefer.

 

[Mau10]

Pendant owners, what are some nice upgrade tubes I can buy? Under $200 would be good.

It has been discussed in the pendant thread, asking exactly for the same budget.

https://www.head-fi.org/threads/zmf...-and-general-discussions.939249/post-17068883

If you are looking for different "budget friendly" input tube options for the pendant:

https://www.head-fi.org/threads/zmf...-and-general-discussions.939249/post-17081319

cheers!

 

[Dawgfish]

I got some great direction and suggestions from @UntilThen and fortunately my tube supplier had some premium tubes in stock. I also have some RFT EL34's and La Radiotechnique EL39's. The Odyssey takes a 5U4 rectifier and 6SN7/6SL7 preamps tubes, of which I have TONS from years of owning the WA22.

After many many years of being in this hobby and having the opportunity to hear a lot of different headphones, I've come to the conclusion that the ZMF house sound + tubes is exactly what I prefer.

I've come to the same conclusion regarding ZMFs and tubes. I'm getting ready to sell off a lot of my non ZMFs as I just don't listen to them anymore.

I've accumulated a lot of EL34 and KT88s (and variants) over the years for tube speaker amps so I have a pretty good stash of these including the ones you mentioned in post 305. Fortunately I purchased most of these 12-15 years ago when the prices were much lower. I don't know if I could afford the prices some of these tubes are going for now. I finally have a tube headphone amplifier on the way (Ampsandsound Mogwai) that can run EL34s, 6L6s, KT88s, etc to take advantage of my vintage power tube stash. I'm really looking forward to hearing it!

Congrats again on your new amp and please let us know your impressions when you've had a chance to listen.

 

[RonPlata]

It has been discussed in the pendant thread, asking exactly for the same budget.

https://www.head-fi.org/threads/zmf...-and-general-discussions.939249/post-17068883

If you are looking for different "budget friendly" input tube options for the pendant:

https://www.head-fi.org/threads/zmf...-and-general-discussions.939249/post-17081319

cheers!

thanks

 

[Pharmaboy]

Thanks! I’m not sure but I think sapale. I bought it at a craft fair about 10 years ago so it’s been a while.



I’m a total sucker for nice looking wood. Last year I remodeled a bathroom and went wood counter for the sink (Alaskan Birch)

Love both pieces. Birch doesn't get enough credit for looks.

The table has some truly subtle design elements: the asymmetry for one; for another, the way those sapele inlay lines thin out as they get farther from the center/thickest line. That plus the beautiful quilting gives the piece inner life.

 

[UntilThen]

I got some great direction and suggestions from @UntilThen and fortunately my tube supplier had some premium tubes in stock. I also have some RFT EL34's and La Radiotechnique EL39's. The Odyssey takes a 5U4 rectifier and 6SN7/6SL7 preamps tubes, of which I have TONS from years of owning the WA22.

After many many years of being in this hobby and having the opportunity to hear a lot of different headphones, I've come to the conclusion that the ZMF house sound + tubes is exactly what I prefer.

Hello Thaddy, nice to see you again. Yours will be the 3rd Odyssey in this world. Actually the 4th because the 3rd currently being built now is a Odyssey Push Pull which has manual adjusting bias and inifinite adjustments with the ability to use 6.3 or 12.6v drivers. It will even accept Russian GU50 power tubes.

Your black Odyssey will look stunning but it's the sound. Tomas, the Swedish amp builder like all humble talents refuse to commend on the sound of his amps. All I can say is that it's guaranteed to impress.

 

[UntilThen]

I've accumulated a lot of EL34 and KT88s (and variants) over the years for tube speaker amps so I have a pretty good stash of these including the ones you mentioned in post 305. Fortunately I purchased most of these 12-15 years ago when the prices were much lower. I don't know if I could afford the prices some of these tubes are going for now.

Those who have a stash of these NOS tubes are in a very good place now. How fortunate of you. I have to spend quite a bit for my glass eggs.

 

[Dawgfish]

Those who have a stash of these NOS tubes are in a very good place now. How fortunate of you. I have to spend quite a bit for my glass eggs.

Thanks! I'm certainly glad I bought all of those back then. The prices for NOS tubes is getting ridiculous but that's the price we pay for tube goodness.

 

[gonintendo]

On my nautilus I had tried

RCA 5u4g NOS
RCA 7052 (quiet 12ax7 variant)
Tung sol 6550 NOS

So similar to yours but I didn’t like it. What I settled on and really enjoy was swapping out the 5u4g for nos mullard 5ar4 and the bigger difference was swapping the 6550s for kr audio kt88 new production.

Kron audio was started but a Czech guy obsessed with tubes and it shows. He’s deceased and now run by his wife.

The first setup was a little closed off and the beautiful mids on the atrium is recessed.

Second setup you get a fuller sound with the mids sparkling. Plus 5u4g is directly heated so it’s powered up right away and slams the other tubes with current before they’re ready… heard it shortens the life as it strips the cathode. The kt88s are my gems so I’d rather use the 5ar4 anyway

The KR KT88s are on order so looking forward to trying those out. I did grab a cheap 5ar4 to try out with my JJ KT88s and I did find that that tightened up the sound nicely and that’s now my preferred pairing for the atrium