passive preamp

scottjoplin · 2018-02-16 11:45 pm

I know they're nothing special, but I've always thought they were good value and they do have silver plated contacts

anatech · 2018-02-16 11:46 pm

Hi Scott,
Don't feel bad, I thought the same thing. Then, they began to fail.

-Chris

scottjoplin · 2018-02-16 11:49 pm

Well, thanks for sharing your experience, I'll get over it

simon7000 · 2018-02-17 2:53 am

I have had Lorlin rotary switches in use for over twenty years. Only failed when there was mechanical damage. They are used to switch 70 volt loudspeaker lines. The silver plating is very thin and I suspect the internal lubrication is not up to the job for low level signals.

anatech · 2018-02-17 2:58 am

Hi Ed,
That is probably true. I've had them in use for signals, relay switching, speaker switching. The relay coils had diodes across them. In my experience, they are basically unhappy doing anything I've tried with them. I did like that you could select the number of positions yourself. Fantastic idea. Too bad the switches just don't stand up.

One thing about my use that might differ from yours is that they are used quite often. What I really did not like about them is the mushy detent as you change positions.

-Chris

tiefbassuebertr · 2018-02-21 12:49 am

anatech · 2018-02-21 3:03 am

Hi tiefbassuebertr,
Why do you just post links? I don't understand your motivation for the time it takes.

-Chris

tiefbassuebertr · 2018-02-21 9:28 am

anatech said:
Hi tiefbassuebertr,
Why do you just post links? I don't understand your motivation for the time it takes.

-Chris

Many integrated amplifier devices are basically completely worthless, because of the high repair efforts/costs at all switches in it's preamp sections (by rc controlled devices also the troubleshooting in MCU/st-by sections) - go to
REPAIR BLOG - Amplifier Repair Services
Alps Rotary Switch Dropout Issues for Input Select (e.g. Onkyo, Yamaha, Creek)
for any few examples.
But one possibility always remains: bypassing the source selection without or with the volume control/attenuator potentiometer (sometimes disconnecting the MCU unit in case of remote controlled versions).
Both are then replaced by external components - either by only an input selector box, go to post #22 under
Rotary source selector for audio
or by a passive preamplifier.
A great improvement in sound was always noticeable to the users after realization of this thing.

Without such an overview, a choice is difficult and one tends then rather to replace the entire amp device with a new one, although the remaining parts of the old amplifier like power supply/power stage and sometimes the volume control are still flawless.
That's the main motivation for creating this line up.

BTW - various links are death after a short time. This is basically a disadvantage. But then you can check the links nevertheless in most cases by this portal:
Wayback Machine
my own website don't exist since any years - but you can check it while it's whole lifetime:
Wayback Machine
even useful for still exist websites for checking old models and their manuals of audio components - e. g.
Wayback Machine

anatech · 2018-02-21 4:52 pm

Yes, but most people won't check more than two or three links at the most. When you post a huge list of links, much of your time is wasted.

Just saying.

-Chris

tiefbassuebertr · 2021-03-15 10:46 am

to get a whole line up with as many existing models as possible the listings sometimes get longer although it is actually a hard-to-find kind of device.
In this respect it is not a waste of time.
If it had been an attempt to put all usual preamplifiers together in an overview,
it would indeed be a waste of time.

Now an other question:
I am looking for commercial available preamplifiers with only one stage as a clean current stage (unity gain) like a source-follower, emitter follower or in case of used tube cathode follower.
Such preamps I don't find.
Who can post some examples ?

P.S.: in post #1 under
Delivery Source wanted for this Cinch female Connectors in special Outline
you will find a diy version of such a preamp. The used circuit is based on Andrea Ciuffoli's power follower but with an IRF510 and only 9VDC supply voltage and therefore high idle current of 1A/channel - go to
the Power Folllower
This preamp bown away all top class commercial line preamps I know like e.g. Krell KBL, Pass Aleph P and Threshold FET series.

Bigun · 2021-03-23 2:21 am

this thread is in a strange spacetime continuum

artmic · 2021-11-16 5:35 pm

Well, I find it very useful.

Thinking about change in my system, found this list of vendors and didn't
have to use Uncle Google

Cheers!

tiefbassuebertr · 2022-05-16 8:44 pm

anatech said:
Yes, but most people won't check more than two or three links at the most. When you post a huge list of links, much of your time is wasted.

Just saying.

-Chris

In real live this is correct in most cases for most guys - but OTOH - to find out both best buy economic and the top quality units an extensive overview is essential which is nearly completely (in German we say "market overview").

Who now the type of used rotary switch in this at first glance interesting units from Aikido OTTO (Musik-Mate):

1) Input selector for phono-MM with low capacitance rotary switch:
https://www.ebay.de/itm/29497119391...0221&toolid=10044&customid=349308261204965492
2) passive preamp:
https://www.ebay.de/itm/294680167822?hash=item449c4e858e:g:N7cAAOSwBRdgOPW3

Best thanks for an advice.

anatech · 2022-05-17 2:27 am

Hmm, low capacitance doesn't matter below a certain point for one. Especially if you're switching current.

Look at it from an electronics circuit perspective, figure out what is really important for the situation. Grabbing for "the best" of whatever doesn't make sense and may not be the best for your application.

tiefbassuebertr · 2023-01-07 12:20 pm

check out concerning the choice of right resistance for passive pre-amplifiers this thread:
https://www.diyaudio.com/community/...meter-as-a-passive-preamplifier.219342/page-8

anatech · 2023-01-07 4:28 pm

You can't ignore the circuit impedance, and loading on what you are driving it with.

"Passive" control of volume level can be problematic, period. You can reduce s/n doing things that way (shocker eh?) and increase distortion of the source. It is an expedient and it functions, so it can get the job done, but not well. Keep in mind you are driving a shielded cable and also an input circuit that typically has RF filter capacitors in it. You need to drive that with a lower impedance.

How do you do that? With an active circuit. A competently designed circuit will have lower noise than a high impedance cable.

A switch and pot does not constitute a "preamp" people. Let's get the terminology right for starters. A switch and pot constitutes an input selector ... and a pot. It is not a preamp by any description, and will never present a low output impedance which is used to reject interference from outside signals. By the way, cable shielding is not perfect, it only attenuates interference and part of that equation is the output impedance of the signal source.

-Chris

rongon · 2023-01-07 5:01 pm

Then there's this...
intact audio - Autoformer Volume Control FAQ

anatech · 2023-01-07 6:55 pm

They are correct, but it greatly depends on the quality of the autoformer - which is in fact a transformer. Transformers are typically limited in frequency range and phase response (the weak link in transformer coupled amplifiers).
Thankfully the audio passband is normally pretty good. This depends entirely on the quality of the magnetics and winding. Therefore you can not generalize that these are a better way to go than a passive control - but a good one probably is.

A clean audio output stage is still your best bet ...

rongon · 2023-01-08 5:14 pm

The whole idea of the intact audio AVC is that the quality of the core and winding is second to none.
They are expensive when compared to a potentiometer, of course. But people are mentioning 'high-end' stepped resistive attenuators like Goldpoint, and they're fairly expensive too.

Goldpoint's 24-step stereo attenuator is $168 ($123 for blank switch/pcb combo, you buy the resistors). https://www.goldpt.com/prices.html
intact audio's least expensive pre-wired stereo attenuator module is $400/pair - https://intactaudio.com/module.html

anatech · 2023-01-08 5:20 pm

That's true in concept only. It remains to be seen that the construction and materials / design is the best. Meanwhile the cost of a very good pot and excellent active circuit is lower.

Hmmm, you tell me. The active circuit has huge advantages as well.

passive preamp

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