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November 30, 2020, 01:21:14 PM

Author Topic: basic question about Smash suitability for non-bottlehead products  (Read 1411 times)

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Offline tfrei

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My assumption is that a good pre-amp is a good pre-amp and can be used for good effect on any of the bottlehead amplifiers and any amplifier from other manufacturers that could benefit from having a good pre-amp.

I realize that the number of variables make it difficult to generalize, but is my assumption valid in general?

Offline corndog71

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Re: basic question about Smash suitability for non-bottlehead products
« Reply #1 on: February 29, 2016, 06:08:29 AM »
I've been using Bottlehead preamps with lots of other amps for years.

The world was made for those not cursed with self-awareness.

Rob

Offline Doc B.

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Re: basic question about Smash suitability for non-bottlehead products
« Reply #2 on: February 29, 2016, 07:00:31 AM »
Yup, your assumption is certainly valid in general. The Smash has a little bit higher output impedance (1.6K ohms) than the old Foreplay(1K) or the BeePre (500ohms single ended), so the one situation where you need to be careful is if the amp you want to run has a very low input impedance. This in not usually a problem with tube amps which tend to have a very high input impedance or with most solid state amps, but it might be a consideration with gainclone or Nelson Pass types designs which sometimes have a quite low input impedance. If the amp's input impedance is above 15K ohms you should be fine, and you might even be able to get away with a bit lower (say 10K) without noticing any negative effects like soft bass or HF rolloff.

The other consideration is amp sensitivity. A very sensitive amp might tend to emphasize any of the naturally occurring microphony inherent in these amazingly natural sounding directly heated type tubes. That's a design trade off that we find acceptable for all three of our current preamp kits and luckily it's not really a deal breaker. The simple and quite effective solution is to put an inline attenuator between the output of the preamp and the input of the amp, thus lowering any noise that is upstream of the sensitive amp.

I will add that I find the Smashup active load upgrade a particularly worthwhile improvement to the sonics of this kit. Gives it some additional headroom that is nice if the amp is not super sensitive.
Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.

Offline tfrei

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Re: basic question about Smash suitability for non-bottlehead products
« Reply #3 on: February 29, 2016, 08:11:22 AM »
Thanks for both replies.  Explanations were very helpful.


Offline tfrei

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Re: basic question about Smash suitability for non-bottlehead products
« Reply #4 on: February 29, 2016, 09:35:33 AM »
Also, I know about microphony a little with my experience with the Quickie pre-amp.  Your comment also reminded me of something I always wonder about: is the default (basic) starting point for a pre-amp/amplifier combo to have a high setting for the amplifier (assuming it has a volume knob) and adjust the volume with the pre-amp? Or are there possible advantages to finding settings in the middle, i.e., medium setting for the amp; and adjust the volume with the pre-amp from there?

In other words, is there a default system in the design of the circuit, or is it whatever sounds best to you?


Offline Doc B.

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Re: basic question about Smash suitability for non-bottlehead products
« Reply #5 on: February 29, 2016, 09:45:34 AM »
Definitely whatever sounds best to you is the proper setting. Some people get hung up on one thing, for example "the pot has the least influence on the sonics when it is turned up all the way." But the actual situation might be that the amp is very sensitive as mentioned before and things could sound better with the amp level turned down, or that the tonal balance is more pleasing to your ear the amp is turned up and the preamp is turned down, or some other thing in between. It's best to play with it a bit to find the best setting for the particular combination of gear that you are using.
Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.

Offline Paul Birkeland

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Re: basic question about Smash suitability for non-bottlehead products
« Reply #6 on: March 10, 2016, 06:25:17 AM »
I would echo what Doc B. said about system sensitivity.  If you have Klipschorns and 1000 watt McIntosh amplifiers, you are not likely to be happy with our preamplifiers (or many others for that matter).  If you took that same amplifier and paired it with a pair of Magnepans, you would likely be incredibly happy. 

-PB
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man