Optimizing set-up with a near maxed TU8600

Wansmith

Member
2017-02-01 4:38 am
Hi there

I have recently acquired some Elrog 300b's for my TU8600, meaning that my TU8600 is near maxed out, with WBT silver solder, lundhal transformers, alps R27 pot, takman resistors and mundorf caps.

My current setup is DAC + Turntable -> TU8500 -> TU8600. I use the TU8500 to switch between DAC and Turntable.

My TU8500 has a few capacitor upgrades but otherwise it is close to stock, and I used regular solder to build it.

My issue is that I feel the TU8500 is the weakest link and limiting the sound quality that I could be getting from my DAC compared with if the DAC was directly connected to the TU8600. Also the Alps R27 seems to be a weak link in the TU8600. I am happy to keep using the TU8500 as the phono pre for my Turntable.

I have mapped out the below as my options.

Option 1: "Plug and Unplug" solution
Have my DAC directly connected to the TU8600. When I want to listen to my Turntable, then unplug the DAC from the TU8600 and plug in the output of my TU8500. Advantages: Direct connection with DAC. Disadvantage: very annoying to plug and unplug RCA into the TU8600.

Option 2: Luxman as-4iii selector switch + TKD volume upgrade
DAC -> Luxman; TT ->TU8500 -> Luxman; Luxman -> TU8600
Advantages: allows direct connection of DAC, reviews suggest the Luxman is practically transparent. Disadvantages: None?

Option 3: Stereocoffee LDR passive preamp + keep TU8600 alps volume pot at max position
Advantages: passive preamp meant to be transparent. Higher quality volume controller compared with what can be achieved with TU8600. Alps volume pot at max position as I understand that this is the position that the volume pot is least likely to negatively impact sound quality.
The LDR Kit Details & ORDERING | ldrpreamp

Option 4: modify PCB & chassis and add a second input to TU8600 + TDK upgrade
This would be great, but I am not confident to modify the PCB or case (and I am reluctant to do so), and also the input switch will be at the rear of the TU8600 which will be hard to access for me.

I can rule out Option 1 because of inconvenience. Option 4 I will probably also rule out unless someone tells me this modification is easy to do.

I am not sure whether to go Option 2 or 3 (they are both similar price) and would like any suggestions or guidance from you wise folk on this forum.

Many thanks!
 
Wansmith, I have similar issues so I'm particularly interested in your post.

Ideally, I would like the Elekit to have the following features OR at least upgrade-ability:

-multiple RCA single ended inputs (at least 2--one for digital and one for analog sources)
-ability to bypass the volume attenuator and run the amp as strictly an amplifier
-enough room in the chassis to add a remote volume motor
 
My issue is that I feel the TU8500 is the weakest link and limiting the sound quality that I could be getting from my DAC compared with if the DAC was directly connected to the TU8600.

I assume you made a double-blind A/B comparison listening with the volume levels within 0.1 dB that led to this conclusion.. :)

Note that the TU-8500 inverts the signal polarity, which can also lead to audible differences.

Also the Alps R27 seems to be a weak link in the TU8600. I am happy to keep using the TU8500 as the phono pre for my Turntable.

It is most likely less a weak link than the opamps in the TU8500 phono section.

Option 2: Luxman as-4iii selector switch + TKD volume upgrade
DAC -> Luxman; TT ->TU8500 -> Luxman; Luxman -> TU8600
Advantages: allows direct connection of DAC, reviews suggest the Luxman is practically transparent. Disadvantages: None?

From my experience the TKD pot is not an upgrade to the RK27 at all.

Option 3: Stereocoffee LDR passive preamp + keep TU8600 alps volume pot at max position
Advantages: passive preamp meant to be transparent. Higher quality volume controller compared with what can be achieved with TU8600.

From looking at the marketing brochure of this passive preamp, I would not buy it. Eliminating mechanical connections is a good idea but not when you potentially introduce noise and linearity issues at the same time.

I vaguely recall a few companies selling amps with this type of volume control a few decades ago, but the idea was dropped for reason.

Alps volume pot at max position as I understand that this is the position that the volume pot is least likely to negatively impact sound quality.

If the Alps is your major concern, why don't you bypass it with two resistor pins on the PCB side?
 
@Paczeltf, Thank you for chiming in. Can you help explain what type of resistor pins I would need? I'm not sure what values I should use. I would be happy to remove the pot and put resistors in, using the 8600 as a power amp only. That would give me the ability to use a great preamp with a remote as well.
 
Can you help explain what type of resistor pins I would need? I'm not sure what values I should use. I would be happy to remove the pot and put resistors in

Sorry, I may have not been clear. While building the amp, you will have loads of resistor pins chopped off, you can bend any to create a shortcut.

It is even better to remove or disconnect the potmeter and replace it with a pair of resistors between 3.3k - 4.7k as to some extent, the pot works as a grid stopper and reduces RF interference at lower volumes.
 

gavinb

Member
2009-05-16 9:10 pm
I am not a fan on the Alps RK pots and have replaced the Alps pot with a ELMA 49 position stepped attenuator in the TU-8340VK.

Space was very tight. Approximately 36 x 36mm / (Length 42mm)

https://hfc-fs.s3-eu-west-1.amazonaws.com/s3fs-public/elma-a47-series-smd-datasheet_1.pdf

elma-a47-stereo-smd-series-stepped-350.jpg


Elma A47 Series SMD stepped attenuator - STEREO version | Hifi Collective

What about a PGA2310 with rorary Encoder? Not sure if this board will fit?

volume-control-module-pga2310-with-rotary-encoder.jpg


Volume control module PGA2310 with Rotary Encoder - Audiophonics
 

Alan de

Member
2019-11-01 3:58 pm
Just found this thread and am very interested. I also run a TU-8600 and am delighted with it.

I do use 2 sources, dac and phono-pre. My solution has been to use a simple AB switch. The one I am using is the "Rek-O-Kut Low Noise Stereo Phono/Aux Switch". In several months of use, I don't hear any audio degradation.

Is there a good reason for me to be looking at using a pre-amp, either passive or powered?

Thanks, I welcome your responses.
 

Wansmith

Member
2017-02-01 4:38 am
There are two options for the switchgirl:

S506v (voltage-mode): Inputs: 3 x Line
S506i (current-mode): Inputs: 1 x Line for voltage mode, 2 x Line for current-mode

Can you please explain what the difference between these two options is? I've been researching but can't quite understand it in the context of a switch.

The website suggests that current-mode is superior. Is that compatible with all input sources? Why then would they make a voltage-mode?

Many thanks