stepped attenuators

Hi Everyone.

Well, I finally got my system working 100% well, with no hum (at frigging last!!).

So.........!

Thought this would be a good time to start messing with it again!:JOEL:

From here on in, no more box swapping, Im satisfied they are of reasonable quality now, its DIY upgrading the bits Ive already got.

First up for the chop will probably be the volume control on the pre.

Here is a picture/description of it...

http://www.vintagehi-fi.co.uk/l1.html

From the picture you can see that the volume control (on the left) has a white ribbon attached to it. I was thinking along the lines of a stepped attenuator.

Anybody know if this is a suitable DIY job, or better left to proffesionals?

NB, its a nice little pre - but anyone think this is a LITTLE OTT?


Audio Innovations L1
For Sale at $2500, 95% new. With original box. Unmodified. With 1 Telefunken ECC82 (12AU7, with diamond mark at the bottom. One of the best tube Pre-Amp under $5000. Interest parties please email to me for purchase arrangement.


NB I know this should be in DIY, but.. well, its here instead! hehehe

Chris

 

If your building the attenuator from scratch contact me as I have about half a million holcos of various values sat in the loft.

 

YIKES!

god no, pete - I cant build one.

I meant more is it a home dodgy bodge DIY do-able job to buy a tepped attenuator and stuff it in myself? 0r is that actually a pretty hard DIY job?

Chris

 

Found a great site..

http://www.goldpt.com/

 

Its not hard, once you have decided which route/design to go for. Is sourcing decent switches at modest price that's the real problem.

Constructionally if you can solder its justs tagging resistors to switch connections.

What was the fault on the TT ?

 

World Audio Design PAS-II Kit

PAS II A hi-end stand alone passive pre-amplifier, featuring an audio grade 23 stepped attenuator, gold plated insulated phonos, selector switch, tape/source switch, with 5/6 line level inputs fully switchable at the front. High quality interconnect wiring throughout a beautiful piece of kit.

Or 23 Stepped Attenuator

 

if anyone knoiws of a cheap source of 24(minimum) way 4 pole switches, id be a happy hippy,cheapest so far has been £60
chris are you intending to build pre or just upgrade your exesting?

 

Hi Andy - thanks for the heads up - Ive tried the WAD passive pre in my system (I live down the road from WAD) and not too keen.. but thats because I prefer an active pre-amp to a passive in my sytem (so far).

Hippy- just upgrading the one Ive got.. Ive called an end to the box swapping for now. The volume control looked like a sensible place to start..

clickety click!

Chris

NB Pete - I sorted the hum by not attaching the TT earth to anything, and using a shielded cable on the conrad johnson. I get zero hum now. yipeee!

 

Ah i see,make sure any new bits will physically fit before spending out the cash

youve cure the turntable hum then,what was the problem? or did you just run over it with the minidigger

 

Well done, I bet it sounds the biz now.

Have you just though of swaping the vol. pot for a different type ? I've had very nice results using a Bournes Conductive plastic pot on an old NAD 3020, thats just a straight swap.

If I went stepped I look to the shunt type, it uses twice the number of resisters but always keeps the impedance constant, regardless of switch position.

 

Hi Chris,


It should be worth changing the pot. I think the pot in the Audio Innovations would be a open frame type. Changing to a better noble or Alps would improve. A Panasonic pot would be better still be these are not cheap.

One stepped attenuator worth looking at is the DACT pot. This is very good. You get them from here. These cost over £100 but you can get them cheaper from overseas sources.

This pot should give you an improvement. You could go for a fancier stepped attenuator but the cost would go up. I would look at other areas first. ( The power supply would be the first to look at.)

In the right system passives can be great. Having little in the signal path & no power supply noise, you can get great detail, resolution & transparency. the downside is that they have no drive capabilities so they rely on the source drive, the electrical properties of the cables & the various input & output impedances.

I think your power amp may not have a sensitive input & may have a lowish impedances. I don't know what the specs are for your amp. Passives like high sensitivities & high impedances on power amps.

As for which type is the best, some people go for the ladder type which has two resistors in the circuit at any one time. This is the type that will have a constant input impedance.

The shunt type will have a varying input impedance but would have again only two resistors in the circuit at any one time. The number of resistors are reduced with this type.

How good these get depend on the resistors used, the switches used & how well it's put together.


SCIDB

 

I meant to say the ladder type was best, but my brain got away from me.....

have you seen this site

http://www.goldpt.com/how.html

 

Hi Pete!

yup .. seen that site... in fact I posted a link to it a few days ago (above).

Border Patrol do audio innovations upgrades, so I'll probably either get them to do it long term, or just buy parts from them.

Seems the safest way to get it right.

Chris