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Considering the Threshold 400A...

davstev

davstev

Well-Known Member
Hi all,

I am currently running a Kenwood 700M into a pair of Tannoy 12" Golds, which I am happy with. I've encountered a Threshold 400A, a class A amplifier that I am considering, simply because people seem to rave about it.

Somehow, this feels like a big leap to consider. 400A receives huge acclaim for sonics, but, in its own way, so does the 700M. Bigger factor to consider (besides appearance, which the 700M wins hands-down, IMO), is the fact that the Threshold is a 'class A'.

Is this a bigger responsibility? I know they run hotter and consume more power. I have heard strong recommendations that Class A's like the 400A should be powered up 24/7 to minimize stress on the internal components. This sounds totally unrealistic to me, in real-life terms, I won't leave it running all the time. I have little kids, electricity bills to pay.....etc. How much does this matter?

Note: the 400A is selling with the Eichmann eXpress power AC enhancing cable. I am not at all familiar with this.

Any feedback on the pros/cons of a class-A from the standpoint of average use, would be appreciated. Also seeking any experiences with either or both of these amps, especially sonically, in comparison to each other or with the Tannoy 12" Golds.

Thanks in advance.
 
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The 400a should sound a bit better than the 700M (I have both). The 400a is not a pure Class A design, so we are talking maybe 200w at idle, not 400w+. Its biased pretty heavily into Class A for maybe an amps worth depending on how it was biased. The rest is the sliding bias circuit.

These will sound better the longer you leave them on. That would be the only reason I'd think you'd want to leave it on, other than it can do light duty as a space heater in the colder months.

Of note, these are of the age where they will need some work at some point if they haven't already had it. I wouldn't want to go 24/7 without some sort of refresh. With the exception of replacing outputs transistors, these are about as easy to work on as the 700M.
 
Also worth noting, there are several variants of these. The original and the later cascoded version. The cascoded version will say so on the front. At some point between (or maybe when they switched to the Cascode version) they switched from a triple darlington output stage to just a darlington. There are at least 4 driver board variations.
 
FootFungus said:
Also worth noting, there are several variants of these. The original and the later cascoded version. The cascoded version will say so on the front. At some point between (or maybe when they switched to the Cascode version) they switched from a triple darlington output stage to just a darlington. There are at least 4 driver board variations.
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Super great information, thanks FF. It's a Cascoded, says so on the front. I am hearing you say a) it's a marginal improvement soncially over the 700M (presumably especially after recap/all things being equal), and b) you can treat it like a normal amp, not worrying too much on powering on/off issues.

Thanks too for such a quick reply. Just what I was looking for!
 
I haven't heard the 400a cascode in a while, but I have a 4000 cascode I've been working on, and when warmed up, its probably 2 levels/notches above the Kenwood. Definitely not as good looking as the 700m, though, but not much out there is.
 
FootFungus said:
I haven't heard the 400a cascode in a while, but I have a 4000 cascode I've been working on, and when warmed up, its probably 2 levels/notches above the Kenwood. Definitely not as good looking as the 700m, though, but not much out there is.
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So true, the Kenwood is a beauty. Sounds really good too. But one notch, maybe two, sonically. whew, that is a lot. Hard to imagine replacing it with the (rather ugly) 400A, but maybe I can hide the 400A all sounding great, and feature the 700M all looking pretty. Best of both worlds... :rflmao:
 
We all like a killer deal... what would be reasonable to pay for a 400A in good shape, but not recapped, all original?
 
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I think you have to post in a different section for that type of question.

Of note when buying, pay attention to the color of the heatsink anodizing. If they are very pinkish/purple this is an indication that the unit has run hot for extended periods of time. If there is a mismatch between sides, then that's usually an indication one side has a problem (or did at one point).
 
FootFungus said:
I think you have to post in a different section for that type of question.

Of note when buying, pay attention to the color of the heatsink anodizing. If they are very pinkish/purple this is an indication that the unit has run hot for extended periods of time. If there is a mismatch between sides, then that's usually an indication one side has a problem (or did at one point).
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Great advice. Thank you. From memory, after looking at it in detail, the heatsinks were pure black.
 
My experience with the 400A vs Kenwood 700M is that the 700 had a stronger bottom end. Both amps were warm sounding but the 400 was (to me) overly smooth and dry. The 700 was more natural. If you have the 700, then I would spend the money to get it recapped. Echowars is the man to seek out advice on the 700. This is just my opinion based on what my ears told me.
:beerchug:
 
ghamilton said:
My experience with the 400A vs Kenwood 700M is that the 700 had a stronger bottom end. Both amps were warm sounding but the 400 was (to me) overly smooth and dry. The 700 was more natural. If you have the 700, then I would spend the money to get it recapped. Echowars is the man to seek out advice on the 700. This is just my opinion based on what my ears told me.
:beerchug:
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I've recapped the 700M myself, with some considerable help via AK, and Echowars too. I really like the 700M. I can't really find fault with it, but I would love to compare. Perhaps for its good sound and it's aesthetics, I should just settle and be happy, rather than chasing the 400A. But thanks for the input nevertheless, I've heard that the 400A has great top-end sparkle and good range overall, and clarity, but I have not heard anything in particular about it's bottom end. You say too smooth and dry overall...hmmmm.....
 
If your looking to improve your sound I would replace that Thorens with something better. I have a SOTA Sapphire.
 
By vintage solid state standards its probably a very good one. I've never heard one. I've had one sitting waiting for repair for a year, but I'm in no hurry to hear it.

Preamps have come a long way since the 70's. Things started getting really good at the end of the 80's. You are likely going to hear a much bigger sonic gain playing around with preamps.
 
FootFungus said:
By vintage solid state standards its probably a very good one. I've never heard one. I've had one sitting waiting for repair for a year, but I'm in no hurry to hear it.

Preamps have come a long way since the 70's. Things started getting really good at the end of the 80's. You are likely going to hear a much bigger sonic gain playing around with preamps.
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Cool. What are your favourites?
 
Of the ones I've used recently in the price range you mentioned: Adcom GFP-750, Conrad Johnson PF-R (there are some non remote variants, PF I think), Classe CP-50.

There are likely tons of other fine ones to choose from, and that's just solid state. Tubed units are a whole other world unto themselves.
 
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