Tannoy Westminster amp matching question.

Wow, this thread has taken on a life of its own. Excellent !! I thought I'd drop in to give a quick update on where I am with the power amplifier experiments with WMSE.

1. So I bought the Sophia 300b monos and a new set of tubes ( psvane 6sn7 / Sophia royal princess 300b / RCA 5u4g rectifiers ) all together not cheap. In my system I found this match a little underpowered in the bass. there is plenty of it but its not as controlled or defined as I was hoping. That's not to say that some things don't sound fantastic with them. But its not a combination that I enjoy listening to complex, rhythmic, dynamic music on. having said that solo guitar etc sounds fabulous. I'm keeping these amps they do some things very well. But I need more control so ..

2. I took a risk and bought some (not so cheap)Chinese 845 monoblocs. I was very impressed with the PSvane tubes I'd bought and so I bought a pair of Psvane 845T ref Mono blocs. 2x Two 845's in parallel driven by a 300b and 6sn7 . they are fabulous looking things and they certainly give me more control and better imaging however they are very difficult to match a pre-amp with. The power amps present a 600ohm input load( ridiculously low) to the preamp. My first attempt was with a SS plinius pre-amp I had on hand. This was a fiasco and rendered me an ear bleeding top end and and next to no bass. At this point I am almost crying into my empty bank account. However I have just swapped in my schitt Lyr headphone amp with a set of pre outs on it. This is superior by far. Now I have bass ( thank the hifi gods )- Its still not the most tuneful but at least I know the power amps respond to different pre-amps and can do bass.

I'm interested in trying to get the best out of these amps ( not least because my wife will get the disembowelling cutlass' out if I have to buy more power amps ). I have a friend who has a Cat ultimate mk2 and a Einstein the tube pre-amps and I hope to try these over the next couple of weeks.

In the meanwhile I throw myself open to suggestions as to pre-amps that are good at driving difficult loads. Namely 600ohms. I don't know why they would design a power amp like this. Maybe its because they want to sell their pre-amp that is designed to match. I'd be happy to do that but I don't want to go throwing good money after bad if its not going to improve things.(If you know what I mean).

I'd also like to hear experiences in pre-amp / power amp miss-matches. Has anyone else come across a bassless performance as I describe above and solved it with a preamp switch out. Or should I consign the Chinese power amps to the great transformer graveyard in the sky ??

Yours hopingly,
Myron.

Driving a 600 ohm load is an unusual task for most home audio preamps. We make the only tube preamps that can do it. There are a few solid state units too, but as you found out just because its a transistor unit does not mean it can drive this kind of load.

I think its important for a preamp to be able to drive such a load, but practically speaking it would be a lot easier for you if the amp was modified to have a more traditional input impedance. The way it is set up right now it kind of sounds like there is an expectation that it will be used with professional broadcast/recording studio gear. There is no reason why an amp like this can't have a 100K input impedance, which would increase your options quite a lot.

Wow, 600 ohms input -- what were they thinking?? Sometimes it's hard to tell whether such a wacky spec is real, or a result of "lost in translation". Based on your experiences, sounds like this one is real.

Preamps that will handle 600 ohms are very rare. I have no experience with Atmasphere's products, but from all indications I've seen, they'd be an excellent choice. Another route (as you learned with your Lyr) is to look for headphone amps with preamp functionality. I'd look for something tubed that doesn't use electrolytic output caps -- which are the typical way that cheap tube headphone amps handle the low impedance loads. I used to have original Eddie Current Zana Deux; it served very nicely as a preamp and had an output impedance of only 16 ohms (no remote, though).

To be honest though, it doesn't make much sense to go down a route you wouldn't otherwise, just for amps that are WAY off the beaten path. The Atmasphere may be a good option because it'll serve as a top flight preamp whether you stick with these amps or not.

Thanks for your ideas gents.

Ralph, financially I like the sound of modifying the input to present a different impedence. Is this a "difficult" thing to achieve ?? I know that's a nasty question given the lack of info.

Would both the mp1 and the mp3 drive this load well ??

I do know a very experienced, local tube guy who repairs/designs amps for the domestic and professional music industry here in NZ. Perhaps I'll get them over on his bench and he can have a look see.

I didn't consider modifying the input as I expected that there was a good reason for 600ohm implementation. Its good news that you think this can be done.

I certainly didn't expect it to have this much impact. I never considered input and output impedance previously. Its opened a whole new area for me :-).

I'm very grateful for your help, as always.