The AKSA ' 'TLP' - a great solution to a digital issue! :-))

[andyr]

The 'TLP' is a tube buffer which Hugh produced before he developed his GK-1 preamp ... which then led on to the GK-2, which I have. So it's a product from long ago ... which languished, after the GK-1 came out.

Now, I have just dipped my toe into the digital waters ... replacing the 3-way analogue active XOs I've been using with my Maggies for 15 years with a miniDSP unit (10x10Hd). I did this because I added a pair of subs to my Maggies, so:
1. I needed a 4-way XO, and
2. I needed to use DSP to delay my Maggies, to line up with the subs which are about 1.3m further away from my ears.

As a result, I have just bought 2x TLP kits!

Now, my system currently is: sources --> GK-2 --> miniDSP --> power amps.

The beauty of the GK-2 is that it has 2 outputs:
1. the ss (sub) output. (This bypasses the unity-gain tube output stage of the GK-1/GK-2.)
2. the tube output.

If you are running active speakers, it is a well-known fact that you should feed your woofers from the 'sub out' and your tweeters (& mids) from the 'tube out'. The reason is:
* ss out gives better definition of the leading edge of bass transients (than the tube does), and
* tube output gives a more entrancing delivery of mids & HFs than the sub out does.

So currently:
* my sub out feeds subs + bass panels, and
* my tube out feeds mid panels + ribbons.

This is fine ... but as the next component in the signal chain is my miniDSP unit, it is possible I don't hear the full beauty of the 'tube out' coming from the speakers that I did when I had analogue active XOs?

So I am going to re-arrange my component chain and remove the GK-2. This is not a simple exercise as I need to have:
* source selection, and
* volume control.

My component chain now becomes:
* phono stage ---> ADC
* 4x digital sources (phono ADC / CDP / DAB+ tuner / Foxtel box) to digital source selector (Audio Authority 1177A-1)
* output from 1177A-1 ---> miniDSP (digital input)
* 8x RCA outputs from the miniDSP 10x10HD ---> an 8-channel volume control (DIY "Relaixed", out of Holland)
* 8-channel output from the Relaixed volume control --->
-- 4 channels of TLP, for mids & ribbons ---> power amps
-- 4 channels direct, for subs & bass panels ---> power amps.

So, this way, I should really be able to hear the 'tubeyness' of the TLP, as it is directly feeding the mid & ribbon power amps ... in contrast to my current situation where, really, I am "listening to the sound of" the miniDSP output DACs (which cannot be very good, given the price of the miniDSP!).

I will report back when it's all come together!

Andy

[Fitero]

I am curious to learn your impressions.

[andyr]

Originally Posted by Fitero

I am curious to learn your impressions.

Sorry, Fitero ... "listening impressions" won't happen for about 6 months!

Andy

[andyr]

No listening impressions, yet, but the 2 TLPs are built and tested with sig-gen and CRO ... they are working to spec.

I will add a pic, later.

Andy

[andyr]

Pic is here ... the space in the middle is for my 2 RelaiXed PCBs - which give me an 8-channel, digitally-controlled analogue volume control.

These 4 channels are for mids & ribbons - they are fed by one of the Relaixed boards. Subs & bass panels are fed directly from the other 4-channel Relaixed board.

Andy

[AKSA]

Hi Andy,

I can see the custom EI transformers set up for the two TLP - four channel - preamps, what are the toroids being used for? Smallish, too, maybe 25VA?

Hugh

[andyr]

Originally Posted by AKSA

Hi Andy,

I can see the custom EI transformers set up for the two TLP - four channel - preamps, what are the toroids being used for? Smallish, too, maybe 25VA?

Hugh

Hi Hugh,

Each powers 1 RelaiXed 4-channel volume control board. Yes, I think they are 30VA.

There is a 3rd small toroid mounted on the case side - this powers the digital control circuit.

Andy

[andyr]

Originally Posted by Fitero

I am curious to learn your impressions.

Well, it's taken 14 months - not 6! - but I finally listened to the new setup, yesterday!

First impressions are:

* it sounds great!
* but I can hear some hash on the mids & ribbons - not hearable at the listening position but certainly noticable when your ear is right at the driver. I was afraid this might happen so I think I know how to solve this problem. (Put an earthed shield over the 6v & 15v feeds from the power transformers that run close to the I/O wiring, on the other side of the steel divider between transformers and signal boards).

Monday is the "real test" - when my panel of 'golden ears' (including Hugh) comes round for a listen.

Pics attached.

Andy

[meanman1964]

Which tubes are you using ?

[andyr]

Originally Posted by meanman1964

Which tubes are you using ?

They are the standard ones which Hugh supplies. And because of the way I've had to configure the system, in the short term, I can't take the lid off, to investigate.

Do you have any recommendations?

Andy