surprising comparison of tube preamps
Hi and thanks for your help. I have been using an ARC LS25 II preamp going into a Mcintosh Mc462 amp. One source is a turntable going into a Parasound JC3+ phono pre. When the ARC broke, I tried a Bottlehead Crack headphone amp as a preamp. I was very surprised to see how beautifully this worked. Really rich sound. Maybe it was less accurate (could not do a direct comparison with the LS25), but it was certainly great to listen to, for my taste. I looked into this some and wondered if the lush sound came from the fact that the Bottlehead was using a simple SET OTL circuit, compared to the hybrid circuit in the LS 25. Still you would think that the ARC unit, costing so much more, would sound better. I am wondering if people have an explanation for this but, more importantly, have been looking into getting a very simple tube pre to use for the phono part of the system. Mapletree audio sells a simple preamp that I believe is a SET OTL (are all preamps OTL?). Al Freundorfer, the designer and owner, kindly agreed to make me a modified version to test. Some circuits, including a buffer he sells, have the ability to adjust the 'warmth' and extent of tube sound - he would build this into his amp for me (it is available on some of his other products). Is this a good idea? Could I reproduce the effect I heard with the Bottlehead? Not sure how those 'warmth adjusters' work. Thanks a lot for your help.
This is exactly the question I've been researching. I put a $400 Schiit Valhalla 2 tube headphone amp in place of my SS preamp. It sounded good from the start but really opened up when I configured it differently. I run the Valhalla with no attenuation, bought a Schiit Kara, and use it in passive mode as a volume control. Now I'm looking at upgrading that config with an LTA Velo headphone amp/preamp. I'm also looking at some others. But I agree that the simplicity of the design is key. |
@akgwhiz To the first, perhaps; integrated amps do have the advantage that a passive volume control will work fine in them and there's no interconnect issue between the preamp and power amp sections. But often separates are built to a greater scale with less internal compromises. To your second question, they don't need to be balanced but it helps, since the power supply is often the key compromise in an integrated amp. Balanced circuits impose less noise on their power supplies. |
I followed up the idea in this thread - what happens when a good headphone amp is used as preamp in a speaker system. I have actually not tried this before in my main system. Or not since way back. So I brought Audiotailor Jade OTL down to the main listening room, disconnected the preamp, and connected Jade instead. The result was quite good, but not on the level of my (much more costly) preamp (Einstein The tube mk2). It would have been a sensation if it sounded better. So my experience is that inserting a good tube preamp into the amplification chain depends on the quality of the rest of the gain stages in the chain. For example, the Jade easily beats small s-state amps in active speakers, from my testing so far (low to mid price). But if the other gain stages are in fact of comparable or higher quality than the Jade, the effect can be zero, or reversed. |
Note that, in my other systems, testing with the OTL headphone amp as part of the sound chain, the chain has been like this: Source (DAC) - > Jade - > preamp -> amp. In my main system, however, I had to connect this way; Source (phono riaa + preamp) - > Jade - > amp. I was not able to insert Jade as the first gain stage. Something is wrong when it is connected as the last gain stage. I tap on a tube in Jade and hear scratching noise in the speakers. So the sound impression, described above, may be misleading. Maybe this isn't a fair playground for Jade. Connecting a headphone amp as the last gain stage, with output to the amps, is not the right way. Even if it works fine as the first gain stage. |
