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The Elekit TU 8500 Valve Preamp - A Knockout In Value and Sound Quality!


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  • 4 months later...

Anyone have any idea on the output impedence on the elekit 8500? Unable to find anything online. I have had a couple misses with tube pres to match with the Yamaha B2 which has an input of just 25k ohms. thanks!

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6 hours ago, thejt said:

Anyone have any idea on the output impedence on the elekit 8500? Unable to find anything online. I have had a couple misses with tube pres to match with the Yamaha B2 which has an input of just 25k ohms. thanks!

Unfortunately not even the official website has specs for it, even in the Japanese version.

https://www.elekit.co.jp/product/TU-8500

It's a fair bet that an affordable valve preamp will have relatively high output impedance. My guess would be in the 1-2kOhm range.

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On 28/08/2020 at 12:37 AM, thejt said:

Anyone have any idea on the output impedence on the elekit 8500? Unable to find anything online. I have had a couple misses with tube pres to match with the Yamaha B2 which has an input of just 25k ohms. thanks!

I would try contacting this person :

https://tubesoundaudio.com.au/pages/contact-us

 

very nice and knowledge lad.

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  • 5 months later...

Don‘t know who told you the T7 was a low mu version of the U7, but it actually has about 3 x the gain. It is a totally different animal, a lot more like a 5965, and not a direct sub for a U7. Due to this characteristic, T7’s were more often assigned to phono duties while U7’s looked after the line.

 

I saw another review of this pre where a guy subbed in a T7 simply stating it was a lower noise version of a U7. This is utter nonsense. Moreover, it is highly unlikely that this tube’s bias points would have been optimised after simply plugging it in. Output impedance would also have increased (which may or may not be significant). Both these issues lead me to seriously question his credibility as a reviewer. All 12A variants would work in that socket, but.......

.

Personally, i would stick to U7’s from a reputable source. Your Psvane's sound like a really good option.

Hope this helps.

Edited by mach1
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Hi thejt,

I have a very strong suspicion there is a low impedance mosfet follower output stage on the right hand board (the signal would go through just this when gain = zero), otherwise you are looking at an unbuffered 7K anode follower output impedance, which I don’t think is possible (ie it’s a hybrid linestage). This would drive just about any amp with contemptuous ease.

Edited by mach1
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On 19/02/2021 at 11:51 PM, mach1 said:

Hi thejt,

I have a very strong suspicion there is a low impedance mosfet follower output stage on the right hand board (the signal would go through just this when gain = zero), otherwise you are looking at an unbuffered 7K anode follower output impedance, which I don’t think is possible (ie it’s a hybrid linestage). This would drive just about any amp with contemptuous ease.

As far as I'm aware, there is no MOSFET buffering at all, the RH board at the front is all power supply and the phono stage at the rear. I have no problem powering any amp in my stable, loads of output ... but looking over my pics again, I see no FETs anywhere .... unless I am very much mistaken. Main power amp in the system is a modded DIGI 125 amp, with all POOGE-style mods Litz wiring for the PS throughout. Runs beautifully. Great transparency and speed. Alive. I will be sticking with the Psvane 12AU7-T2's when I place the valves,  just so transparent from top to bottom. I may consider a set of matched RCA Black Plates as an option, I hear they are rather good, but have no idea if they have the overall transparency of the Psvanes. 

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  • 1 month later...
On 19/02/2021 at 11:51 PM, mach1 said:

Hi thejt,

I have a very strong suspicion there is a low impedance mosfet follower output stage on the right hand board (the signal would go through just this when gain = zero), otherwise you are looking at an unbuffered 7K anode follower output impedance, which I don’t think is possible (ie it’s a hybrid linestage). This would drive just about any amp with contemptuous ease.

Here is the circuit diagram, the only FET is in the power supply as a ripple filter, no other buffering. This pre-amp still runs as quiet as the day I put it together, the Psvane 12AU7-Ts as well; they've had several years of use now, 2 1/4 yrs in this pre-amp and another 3 or so in my TRI TRV-88SE integrated amp. It hasn't been a constant thrashing, as such, but no doubt a good couple of thousand hours + all up. 

 I may consider upgrading a few parts yet, possibly the power supply caps for Nichicon KG Gold Tune versions, or similar (they have been stunning in my restored 1977 Perreaux SP100 pre-amp, dropping the noise floor to so low it's not worth even listening for it at full volume and allowing for a new level of bass depth and impact, as well as a more 3D sound stage and dimensional vocals with a new silence around them).

In the Elekit TU8500, I have Mundorf polypropylene caps in the Line stage and  good quality polyester caps from from output of the phono stage, so I may move the line stage caps to the phono output and replace them with higher level Mundorfs. Just a thought at this stage. As a pre-amp to the hotrodded Silicon Chip headphone amp - with other mods in-between - the results are superb with the venerable Sennheiser HD540 Reference 600 ohm headphones, which have their own upgrades in Mogami cable and pleather pads. 

P4256735.JPG

Edited by Lightstream
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  • 3 months later...

PSA: 

 

I emailed Elekit directly to inquire about the output impedance of the Elekit TU-8500 and this was the response from EK Japan Co LTD: 

 

Regarding your question, the output impedance of TU-8500 is approximately 200ohm when with 12AU7.

 

It can slot right in to any chain with ease. 

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  • 3 weeks later...
  • 4 weeks later...


23 hours ago, PauliD said:

if anyone needs a refresher on what the stock kit looks like.

My dad put it together for me. This thread has me thinking now 😂

 

IMG_1197.thumb.JPG.802924a70f958bca846d99c96654b800.JPG

Wow! Shows what a stretch it was to get the Z-caps in there!

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  • 2 weeks later...

I replaced the original 0.47uF caps for Z-Caps this morning, pics later when I get home from work.

It is a bit of a squeeze.

 

Edit:  Just took a couple of cheeky pics with my phone.

303993430_TU8500caps1.thumb.JPG.ca62ab88a6d0878ed082fa9469049033.JPG

 

1361695906_TU8500caps2.thumb.JPG.00db4b3b0b9a37797ce01a2784464936.JPG

Edited by Batty
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2 hours ago, Batty said:

I replaced the original 0.47uF caps for Z-Caps this morning, pics later when I get home from work.

It is a bit of a squeeze.

 

Edit:  Just took a couple of cheeky pics with my phone.

303993430_TU8500caps1.thumb.JPG.ca62ab88a6d0878ed082fa9469049033.JPG

 

1361695906_TU8500caps2.thumb.JPG.00db4b3b0b9a37797ce01a2784464936.JPG

Great!! Looks good, now, if you have not done it yet, please change the plastic sleeves which hold the pots' shafts and replace it with rubber grommets from jaycar. Then, grease it, much, much better feel when turning volume knob and selector, feels more "pro".. easy and very cheap upgrade.👍👍

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4 minutes ago, Claudiones De Bologna said:

Great!! Looks good, now, if you have not done it yet, please change the plastic sleeves which hold the pots' shafts and replace it with rubber grommets from jaycar. Then, grease it, much, much better feel when turning volume knob and selector, feels more "pro".. easy and very cheap upgrade.👍👍

Done that too. Thinking of a pair of Burson V5i op amps for the phono stage as I have them lying around somewhere.

 

Fitted JJ valves too.

Edited by Batty
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8 minutes ago, Batty said:

Done that too. Thinking of a pair of Burson V5i op amps for the phono stage as I have them lying around somewhere.

 

Fitted JJ valves too.

I have heard they work well with muse 01 op amp.. not sure though and they are quite costly. Let me know what you think of the Burson.. believe it or not, I have not used the phono section yet..😂😂

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1 hour ago, Claudiones De Bologna said:

I have heard they work well with muse 01 op amp.. not sure though and they are quite costly. Let me know what you think of the Burson.. believe it or not, I have not used the phono section yet..😂😂

Me neither, I have a DIY Akitika MM and a Vincent Pho-8.

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The Akitika is good, actually very good and if you use DIL sockets you can swap the ICs. :) I actually sold my MF X-LPS v3 once this had run in and I put some better chips in.

Vincent is awesome too. Hard to chose between them.

 

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