Tube amp questions

So in the past few weeks i researched about a good OTL tube amp to match my 660s since i always heard Sennheisers sound very good on OTL amps.

My setup would be Foobar2000–>USB in XD-05–>3.5 out to rca into tube amp

i have 2 main questions:

  1. i mainly listen to metal, rock and some opera/classical, will a tube amp be worth for those genres?
  2. how will a tube amp change the sound? This is my main concern. I have fear that the more relaxed/less detailed approach of a tube amp won’t please me.
    So, how will the detail get affected? will i lose a significant amount of it? how will the bass/mids/treble response change?
    Also, how will changing the stock tubes to better ones (without spending a lot) improve the sound?

I know that it is difficoult to say how exactly a sound will change, especially when i’m considering a tube amp wich i don’t think anyone on here has heard of ( it will be either a TPAudio CF-4T-OTL (240 euros) or a CF-OTL 6080 (370 euors), those are well regared in Italy).
I would like at least to know what i’m getting into and if my purchase will make sense or not.

I’ll list the specs of the two amps if it can help:
Ideal for headphones between 30 and 600 ohms
0.7 watts output
It uses 2 EC86 and 2 ECC88

CF-OTL 6080:
Ideal for headphones between 30 and 600 ohms
1.8 watts output
It uses 2 EC86 and 2 6AS7-6080

I’m not familiar with either model, but the build looks very nice for the price. It’s tricky to know how they will change the sound, especially when a change of tubes can make a huge difference. But that’s part of the fun if you enjoy it. If you really like the 660s off of a tube, I would suggest looking for a good price on a used HD600. They are a completely different headphone off of a tube


IMO, the tube sound is better on almost everything. My listening tastes are similar to what you describe; mostly just about every subgenre of rock and metal but sprinkle in some classical, EDM and even some hip-hop here and there.

The sound changes in ways I didn’t expect. The warmth does increase on tubes. I originally was worried about tubes because my ears are mid-sensitive and many products that had been described to me as “warm” sounded shouty or honky. Tubes actually smooth out the mids a bit and make them sound more natural to my ear. Overall tubes do sound smoother, but I don’t think I agree with those who say that translates to less detail. When listening really intently most of the details are still there on tubes, they’re just not as - for lack of better term - “finely pointed” as they can be on solid state. As in the details are all present, they’re just not as in-your-face as solid state can be.

Your Senn’s will also likely experience some frequency extension in both directions on a tube. My 6XX certainly do.

The biggest advantage I hear with tubes though is the “holographic” spatial presentation. The soundfield sounds more cohesive and full to my ears.

For context my tube experience includes a Loxjie P20, a cheap Chinese tube buffer with tone controls, and a Darkvoice for the last 10 days. On all three of those units I found tube rolling to higher quality tubes made noticeable, but not huge, improvements to the sound. The stock tubes on all that Chinese gear distorted the sound a bit too much and did sacrifice detail more than I wanted. However, still relatively inexpensive tube upgrades brought back a lot of the subtle details and also improved the spatial presentation.


It is really hard to give advice about an amp that I haven’t heard.
I have I owned a Loxjie P20, Schiit Vali 2 and an XDuoo TA-20. None did anything for me, but they were all hybrid.

My 'phones are pretty much all very efficient so I didn’t see any use in an OTL amp. I recently bought a low impedance amp and it is AMAZING! It transforms the HD600’s and the HD58X’s light up nicely.

It does not however like the Focals and is indifferent to the Fostex’s.

Every amp is different though. If you provide all the specs and tubes maybe someone here can give you better advice.


As of right now i am interested in just the amp. If i’ll decide to buy it, i’ll defenitely get a used 600 in the future just to try it.

Thanks for the help, what you are describing seems to be what i am looking for.

This would be very interesting to hear.

Yeah i read that the cheper model (CF-4T-OTL) had some grain to it, where a tube swap would very much improve it making less grainy, but this was from a thread from 2012.
From what i know the quality of the amps has been improving over the years, so i hope i will not find this grain.

You are right, i’ll list the specs of the two amps.