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Your journey with lower-watt tube amps -- Can a kit be good enough?

Looking for stories about your low-watt amp journeys.

Here's the situation: I have new speakers, 97 db. Trying them with lower watt tube amps (45/211, 300b, etc) seems generally wise. I am attempting to borrow some from audiophiles in the area. 

The horizon beyond trying these things involves actually buying some. I'm looking at a budget limit of about $5k.

Curious as to folks' experience with lower-watt amp kits vs. those of good makers (e.g. Dennis Had, etc.).

If you have any thoughts about the following, I'd be interested:

Did you start out with a kit and then get dissatisfied? Why?

Did you compare kits vs. pre-made and find big differences?

Did you find you could get the equivalent level of quality in a kit for much less than the same pre-made version? How about kit vs. used?

Also: did you find there was a difference between "point to point wiring" vs. "PCB" in these various permutations?

I realize that there are good kits and bad ones, good pre-made amps and bad ones. I'm hoping you'll be comparing units which seem at comparable levels of quality and price-points.

Thanks.

hilde45
atmasphere's avatar
atmasphere
12,180 posts
 

@rankaudio The problem with using a solid state rectifier in the ST70 is the plate Voltage tends to run a bit on the high side. If the filter caps and operating points of the power tubes are not addressed on this account, it could lead to trouble. 

Dyanco really needed to use dual 5AR4s in the ST70; as a result the 5AR4 is the most likely tube to die in the amp. It is possible to run dual rectifiers in it but you need a different power transformer (which is available from Triode Electronics in Chicago) and someone willing to do the surgery. Of course if a different power transformer were to be used it should also be possible to have one that puts out the right Voltage for use with a solid state rectifier...

rankaudio
180 posts
 

What are your thoughts on reducing the bias a bit on the voltage?

hilde45's avatar
hilde45 OP
5,453 posts
 

Brief update on my ST-35 -- my tech and I will be adding a switch so it can run in triode mode. If anyone has done this and has advice, we'd be happy to hear it.

atmasphere's avatar
atmasphere
12,180 posts
 

What are your thoughts on reducing the bias a bit on the voltage?

@rankaudio The power tubes can handle it well enough. But that will affect the distortion signature of the amp but by how much is hard to say.

my tech and I will be adding a switch so it can run in triode mode.

@hilde45 Doing so will change the feedback since the loop gain of the amp will be reduced. You may actually wind up with higher distortion; partially because the EL84 is normally an easy tube to drive; as a triode it will be harder so the driver circuit is likely to make more distortion of its own on this account.

The ST35 employs ultra-linear operation in its output transformers, which allows the power tubes to have linearity approaching that of triodes (and in some cases, having exactly the linearity of triodes). So my thoughts are this will be detrimental. 

If you really want to find out what the EL84s and the Dynaco transformers can do I recommend getting a different chassis like this one and building up a different circuit on that. If I were to do something like that I'd arrange a 12AT7 as a differential amplifier to drive the power tubes instead, with possibly a constant current source for the power tubes as well as one for the input tube. 

 

hilde45's avatar
hilde45 OP
5,453 posts
 

@atmasphere I'll convey that to Mike and see what he says. Thank you.

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