Audio Horizons TP 2.0 Preamplifier

Folks, I just purchased a AH 2.1nbr preamp and have a few questions about it...

It has basic EH tubes in it, and I would like to upgrade those to a better quality tube. Any recommendations for a first roll? I'd prefer to no be purchasing $200/tube valves for this. Maybe some mullards? Actually, this thread is so large that I know that there has been some discussion about what the various tubes impart to the sound; I'm wondering if there is a good summary somewhwere.

I think someone long the way may have made a mod or two... the fuse housing to the right of the IEC outlet is not hooked up. I'd prefer to have some protection for the preamp to keep it from burning up if there is a problem. There is a fuse on the board nearest to the IES socket, but I am speculating that it is a secondary fuse. Can someone provide me with a photo or two showing how the input power fuse is supposed to be hooked up? I'll get it wired up from there.

The main ON/OFF switch on the preamp was damaged in shipping, and I need to replace it. Joseph says it'll be $25, but he is out of the country for the next month. Does anyone know exactly what the switch part number (manufacturer, etc.) is? If it's nothing special, I'll find it from another supplier and wire that up as well. Id rather not wait for Joseph to return, although I am able to get the switch to work (for now, not sure for how long, though).

Lastly, there is a bit more hiss with the preamp in the system than I had expected based on comments I have seen, so I'm wondering if this is somewhat dependant on the tubes? I don't believe the hiss is volume dependant, but it does change as the preamp goes through it's warmup. It's currently hooked up via RCA, but I'll eventually get a balanced-capable amp, which hopefully will reduce this effect if nothing else will.

Thanks,

---Michael

hmmm...

I am having problems with the left channel popping and increased hiss on that side. I think there is a problem with this preamp. I reversed the tubes to see if it was them, and the problem stayed on the left, so I suspect there is a problem in the preamp somewhere...

This explains the higher hiss than I was expecting I think. It's really unfortunate because it sounds great when it's working fine, but I think this one has problems somewhere...

I'll talk to the seller and see what my options are.

---Michael

A few years ago, I posted about problems with the used 2.1 I purchased... Then, I ended up moving across the country, and dropped off the Gon for a while.

Anyway, I did get some relief from the seller, so that was fine. I haven't fixed it yet, but I did trace the problem to a poor solder point on one of the caps. I turned it on with the lid off, and tapped the components one by one with a chopstick until I found the one that does it.

Anyway, I happen to have moved to Sacramento, so I'm going to have Joseph repair it and maybe upgrade it to a current model.

Lastly, I've been running a quad of Siemens ECC88 tubes, and thought I would upgrade these a bit. Does it make sense to quad match a set in there, and can anyone tell me what the sonic characteristic of of the two positions on each side?

If I splurge on some high wire tubes, what positions should they go in?

I can actually do a little testing, as I have a few pairs of amperex tubes, a quad of EH's, but I want to have an idea what I'm doing before I go there.

Does one position affect imaging more than the other, does one affect noise levels more than the other, etc?

Blending a pair of Mullards and Tele's, do I get great imaging with a great midrange?

Any thoughts on this would be appreciated.

---Michael

Reading through (very long!) thread, I see that positions 1 and 3 are the most important... I'll put some good glass in there.

I guess I'll roll things around to see what the impact is on the sound otherwise, since this thread is mostly dead.

---Michael