passive preamp

[HOEK]

Hello

I wil make a volumepot in my poweramp
Ouputlevel cd-player is 2V at 50K
Impedance poweramp is +/- 40K
What is the most suiteble value for the pot 50 of 100K?




Thanks

 

[dshortt9]

Check the output impedance of your cd palyer again. A 50k Zout sounds too high. Or do they mean thet recommend a 50K load?.

 

[HOEK]

Hello

The loadimpedance must be over the 10K
I guess 50k is the max Outputimpedance off the cd player,
those will than give 2V rms
I wonder what value pot match the poweramp (imp. 40-50K)




regards Hoek

 

[AndrewT]

Hi,
if the source impedance of the CD player is below 1k0, then that fits with the recommendation for a load exceeding 10k.
the power amp will also appreciate a source impedance below 1k0 and even better if below 200r.

A passive pre-amp cannot meet all these conditions.

The best you can hope for is 10k volume pot presenting a 2k5 source to the power amp. This arrangement will desparately need very short cables and even then the filters built into the power amp input will act as variable tone controls as you adjust the volume.

Passives can sound nice but they have their downside.

To answer the power amp source question.
If you wanted to present a 200r impedance to the power amp then you would use a 800r volume pot. That would need a source player that could drive a 600ohm load to 2Vac (3Vpk) from 10r source impedance.

 

[Gordy]

HOEK your CD player output impedance is not 50k. It will be much, much lower than that, typically 50 Ohms to 2k Ohms.

Maybe they recommend a minimum load of 50k? Using a different load will not cause physical damage.

Anyway, between a typical CD player and an amp with a 40k input impedance, the best compromise for a passive volume control would be a 10k potentiometer. As AndrewT said: keep your cables short (...and possibly try and find some with low capacitance).

 

[HOEK]

hello

My source is a sacd-player type scd-555es
ouputlevel 2V rms (at 50Kohm)
Inputimpedance poweramp is 40-50Kohm
Actually it is playing with a log.pot 10K
The sound is very good
lenght signalkable potmeter-input poweramp is circa 60 cm
Is it usefull to put the volumecontrol in the amp?
Will this better the performance?

 

[AndrewT]

Hi,
what filters are built into the power amp input?
What filters are built into the source output?
What is the capacitance (pF/m) of the connecting cable?

Give us the info and we can assess what the 10k pot and long cables are doing to your frequency response.

 

[HOEK]

hello

My amp is a JLH 69 (original)
Capacitance conexioncable and outputfilter in cd-player are
unknown.


regards HOEK

 

[tiefbassuebertr]

Passive Preamp Overview

Diy versions
Remote controlled passive preamp - Overview
Diy-Audio-World Onlineshop: Passive Preamp
Passive Pre-amp
Passive preamp grounding questions | Head-Fi.org
IY audio passive preamp
Serra Passive Preamp
https://www.pieroserra.com/serra-passive-preamp/
AUDIOPHONICS Volume Controller / Source Selector
AUDIOPHONICS Volume Controller / Source Selector Alps 5 to 1 Black - Audiophonics
Music First Audio "BABY REFERENCE" / "Classic 2" PRE-AMPLIFIER
Pre Amplifiers
Music First Audio Baby Reference passive preamplifier | Stereophile.com
Khozmo Passive-Preamplifier - Dual Mono Selector
www.khozmo.com - High Quality Passive Preamplifiers
Lab 12 True Passive Attenuator / Input Selector
https://www.audioallianceinc.com/products/lab-12-true-passive-attenuator-input-selector
Malega Audio™ PS1™ and PS2™ Passive Stepped Attenuator
http://malegaaudio.com/product/audiophile-passive-pre-amplifier-ps1-stepped-attenuator/
http://malegaaudio.com/product/audiophile-passive-pre-amplifier-ps2-high-quality-preamp/
TISBURY AUDIO Mini Passive Preamplifier II
http://www.tisburyaudio.co.uk/mini-passive-preamplifier
Marchand Electronics Inc. Model PR141
http://www.marchandelec.com/pr141.html
Hattor Audio - ULTIMATE PASSIVE PREAMPLIFIER
http://www.hattor.com/index2.html#ultimate
icon Audio - Passive and Passive R Pre Amp
http://www.iconaudio.com/main-products/passive-and-passive-r-pre-amp/
goldpoint™ SA4 and SA4M Passive Preamps
http://www.goldpt.com/sa4.html
Tortuga Audio - LDR3.V2 Passive Preamp
https://www.tortugaaudio.com/product/ldr3-v2-passive-preamp/
Rothwell Indus Passive Preamp
http://www.rothwellaudioproducts.co.uk/html/indus_se.html
Luminous Audio Technology Axiom II
http://www.hifizine.com/2012/09/luminous-audio-technology-axiom-ii/
Schiit Audio SYS Passive Preamp
http://www.schiit.com/products/sys
HIFI EXQUIS MeiXing MingDa MC-9 SE Passive preamp
https://hifi-exquis.com/transistor-...mer-balance-preamp-7-times-amplification.html
Hot Audio Solid Maple Audiophile Passive Preamp
https://hotaudio.com/20160824_131105/
Thel Passive Preamp mit Superleitplastikpoti 2CP2500 und Eingangswahl RSL
http://www.thel-audioworld.de/bauteile/regler/passivv.htm

 

[tiefbassuebertr]

check out also this threads:
Input Selector Box (Source Select without stepped Attenuator) post #22
Rotary source selector for audio
Potentiometer/Rotary Switch - parts
Potentiometer Overview - Alps, Penny+Giles, TKD and Vishay and more, what's your fav?

 

[sajti]

I use Khozmo 10k shunt volume controll, in my passive preamplifier. It has nice sound.

Sajti

 

[anatech]

Hi tiefbassuebertr,
Any preference of your own?

Posting all those links doesn't directly help the OP.

-Chris

 

[Cal Weldon]

It's also an 11 year old thread. The OP's last activity here was '09.

 

[anatech]

Excellent point!

-Chris

 

[tiefbassuebertr]

It's also an 11 year old thread. The OP's last activity here was '09.

According the me known rules from diyaudio one should no start a new thread if there are an already exist thread to the same topic. Is this rule currently no longer valid ?

Hi tiefbassuebertr,
Any preference of your own?

Posting all those links doesn't directly help the OP.

-Chris

My own preference are all devices, which are equipped with ELMA 04 or goldpoint rotary switches like
Goldpoint SA4 Level Control / Passive Preamp.
The preamp under
www.khozmo.com - High Quality Passive Preamplifiers
uses for the input selector a cheap and not good quality rotary switch from LORLIN instead an ELMA 04.
I don't understand, why.
But there are also interesting parts - at least from the optical view - e. g. this one:
Passive preamp / Stepped Attenuator w. 46 position control
Maybe other members have heard one of them.

 

[anatech]

Hi tiefbassuebertr,
Lorlin switches are junk! I have had to replace every single one I have built into things - or throw those things out. I never use them these days.

According the me known rules from diyaudio one should no start a new thread if there are an already exist thread to the same topic. Is this rule currently no longer valid ?

No, but ancient threads might be an exception. An old thread will probably be full of broken links. You really are better off beginning fresh instead of reanimating the dead.

-Chris

 

[merlin el mago]

Shallco switches are the best.

 

[anatech]

Hi Merlin,

Shallco switches are the best.

No, they are very good for situations where they shine. A decade resistance box is one where they shine, but other manufacturers also make excellent switches. LORLIN would not be one of them.

-Chris

 

[scottjoplin]

So, let me get this straight, you don't consider Lorlin switches to be very good?

 

[anatech]

Hi Scott,
That's about right. Every single one I have every bought has become noisy to the point where they can't be used. I'll pay the extra for a good switch these days. Even the inexpensive phenolic wafer switches outperform the LORLIN products.

-Chris