Selectable gain on pre-amp

KSondergard · « **on:** 22 Sep 2003, 09:05 am »

Hi

I've just finished building my NLE11/19 pre-amp.

NLE 11 = attenuator
NLE 19 = line buffer, 2 channel.

The NLE 19 has selectable gain 0, 6 or 12dB. Which setting would you recommend for the AKSA 55 ?

Regards, Kent

AKSA · « **Reply #1 on:** 22 Sep 2003, 09:31 am »

Hi Kent,

The AKSAs both have gains of 31.6dB. Given the output from modern digital sources, and even RIAA preamps, I'd suggest the 0dB setting.

Cheers,

Hugh

Malcolm Fear · « **Reply #2 on:** 22 Sep 2003, 11:47 am »

I think the NLE gear is in fact DACT gear.
Keep the stepped attenuator. Set it up as a shunt, using a Riken Ohm resistor.
Use this as a passive pre amp.
Throw the NLE 19 away, or the AKSA 55.
I have a NLE 19 (DACT line stage). It is very hi-fi. It pulls the music apart. It is dynamic and detailed, but not musical. If you use it at 0 db gain, watch out for oscillation This line stage spoils all the good things that an AKSA 55 does.
Use the attenuator as a passive until you can afford a GK-1.

Anyone in Australia want to buy a cheap DACT linestage?

See
http://http://www.audio-link.dk/NLE.htm
and compare to
http://www.dact.com

Jens · « **Reply #3 on:** 22 Sep 2003, 12:49 pm »

Quote from: Malcolm Fear

I think the NLE gear is in fact DACT gear.
Keep the stepped attenuator. Set it up as a shunt, using a Riken Ohm resistor.
Use this as a passive pre amp.
Throw the NLE 19 away, or the AKSA 55.
I have a NLE 19 (DACT line stage). It is very hi-fi. It pulls the music apart. It is dynamic and detailed, but not musical. If you use it at 0 db gain, watch out for oscillation This line stage spoils all the good things that an AKSA 55 does.
Use the attenuator as a passive until you can afford a GK-1.

Anyone ...

Hi Mal,

You are correct, the NLE is the same as the DACT.

I happen to know the guy who makes them (very nice guy). The explanation is that the NLE name is used for marketing in Scandinavia, which he does himself. The DACT name is used for marketing in the rest of the world, which has been commissioned to an outside company.

Kent,

Nice to hear that you finally got this far. Malcolm does have a point with the sound of the NLE 19, which is a bit clinical. I don't remember it as being as bad as he describes it, but then it is a long time ago I heard it - and not in my own system. You could try Malcolm's solution for the attenuator and see what you like best.

By the way, I have made various improvements to my system since you were here last - do come by, if you can find the time.

Cheers,

KSondergard · « **Reply #4 on:** 22 Sep 2003, 01:26 pm »

hmmmm

If I remember correctly, I saw an article/test regarding the eAR amplifier from Acoustic Reality, where the author stated that Acoustic Reality uses the NLE11/19 configuration for their pre-amp eAR Pre Two. I don’t know if it’s true, but if it is then they must have altered the NLE19, because both the author and many other people speaks highly of this pre-amp, and now you tell me that it’s not that good????

Now I'm confused

Well, since I have built the pre-amp with the NLE19, I’ll test this first and then later I’ll test Malcolm Fear’s suggestion

BUT!!! Before all that, I need to find the time for building my AKSA55, and this also demands for me to order one from Hugh first… Well is starting to get cold I Denmark, so I do need some indoor activities

Thanks for your response

Jens: I have tried to find the cable you asked for, but unfortunately I have not been able to do so.
Regarding your improvements to your system, pleas tell more!!!!

Regards, Kent

SamL · « **Reply #5 on:** 22 Sep 2003, 10:58 pm »

Quote from: Malcolm Fear

Keep the stepped attenuator. Set it up as a shunt, using a Riken Ohm resistor.
Use this as a passive pre amp.

Hi Malcolm,

I've got DACT as passive preamp but not sure how you switch it to stepped. Did you actually desolder all the tiny resistor on DACT and replace them with the Riken Ohm? That's not much room for soldering.

Sam

JohnR · « **Reply #6 on:** 22 Sep 2003, 11:22 pm »

No, just disconnect the "input" wire, solder it to the shunt resistor, and solder the other end of the shunt resistor to the wiper.

Malcolm Fear · « **Reply #7 on:** 23 Sep 2003, 12:43 am »

Hi Sam
A shunt mode attenuator, has the signal going through a resistor (say 27K, and you may as well get the best, hence the Riken Ohm). The DACT is used to shunt the signal to earth. John R did this with his DACT. It sounded a lot better than my memory of my DACT set up as per normal.
I have since made the change to my GK-1 (using a DACT).
You don't touch the resistors that are in the DACT.
The following site has an awful lot on attenuators, including how to wire a shunt attenuator.

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

SamL · « **Reply #8 on:** 23 Sep 2003, 04:00 am »

Hi John & Malcolm,

Is this what you all refering to?
http://www.goldpt.com/schm_shunt.html

Well, my DACT is a 10K volume control. By using the 27K that Malcolm mention, does it mean that it is now a 37K volume control and more compatible with TLP & GK1?

Thanks,
Sam

AKSA · « **Reply #9 on:** 23 Sep 2003, 04:32 am »

Sam,

The higher the shunt resistor used, then the less the signal strength to the tube, in fact the relationship is Rv/(Rv + Rs). Thus signal loss from input to output with 27K shunt and 10K DACT is 10/37, which is 27%, or -11.4dB. A lot. If you reduce the shunt resistor to maybe 10K, then signal loss is 0.5, or 50%, or -6dB, a lot less.

This would be my choice, in fact.

Cheers,

Hugh

Malcolm Fear · « **Reply #10 on:** 23 Sep 2003, 05:28 am »

Hi Sam
Yes, that is the site.
I have a GK-1, AKSA 55, 93db efficient speakers and a smallish room. I use a 39K shunt resistor. I took the GK-1 to a friends with 86 db efficient speakers. He would be better suited with a 10K to 20K resistor.
My DACT stepped attenuator is also 10K

SamL · « **Reply #11 on:** 23 Sep 2003, 07:25 am »

Quote from: Malcolm Fear

Hi Sam
Yes, that is the site.
I have a GK-1, AKSA 55, 93db efficient speakers and a smallish room. I use a 39K shunt resistor. I took the GK-1 to a friends with 86 db efficient speakers. He would be better suited with a 10K to 20K resistor.
My DACT stepped attenuator is also 10K

Thanks for the info. My current DIY speaker is 87db. I am hoping to build something around 90 - 92db but that will be after my long list of "toy" that I wanted to buy & build.

Will pick up a few more Riken Ohm resistors when I visit M'sia in 5 weeks.

Cheers,
Sam

SamL · « **Reply #12 on:** 29 Apr 2004, 10:05 pm »

Quote from: Malcolm Fear

Hi Sam
A shunt mode attenuator, has the signal going through a resistor (say 27K, and you may as well get the best, hence the Riken Ohm). The DACT is used to shunt the signal to earth. John R did this with his DACT. It sounded a lot better than my memory of my DACT set up as per normal.
I have since made the change to my GK-1 (using a DACT).
You don't touch the resistors that are in the DACT.
The following site has an awful lot on attenuators, including how to wire a shunt attenuator.

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

Sorry to bring this post back to life. While answer another post I found another piece of info that you all may be able to help.

The shunt mode on goldpoint is using a shunt resistor between the input connector and output connector.
http://www.goldpt.com/schm_shunt.html
I found an artical over ESP site and it recommend to connect the shunt resistor between the output and gnd.
http://sound.westhost.com/project01.htm
Refer to Pt1.

Which method is better?
Sam

CButterworth · « **Reply #13 on:** 29 Apr 2004, 11:12 pm »

Sam,

Although I am not using a DACT, I did do a couple of listening tests with my DIY passive. I wired the 50K Alps pot inline between signal IN and OUT (how a pot should 'normally' be wired). Things sounded pretty good until I rewired according to Malcolm's instructions. Basically, the idea is similar to that the the Goldpoint shunts:

Signal IN OUT is direct, except for a 30 - 50K resistor (I use Vishay Dale). This causes attenuation which can be calculated. From the ourput of the resistor, I wire the pot between SIGNAL and GROUND. It is wired backwards.

I sent an diagram to your private email.

Let me know how it sounds as I got much better sound quality when the pot was effectively removed from the direct signal path.

In fact, I made a small circuit with gold sockets that will allow me to change the value of the shunt resistor.

Regards,
Charlie[/img]

Larry · « **Reply #14 on:** 1 May 2004, 12:11 am »

Quote from: Malcolm Fear

Keep the stepped attenuator. Set it up as a shunt, using a Riken Ohm resistor.

This is a way to make a fake shunt attenuator, which is a better wiring scheme than a series attenuator most people believe, but not as good as an anthentic attenuator. To have an authentic shunt attenuator, you have to get a shunt selector to start with. You can not have an anthentic shunt attenuator by tweaking a series attenuator.