Domesticating & Documenting the Little Bear

the thin end of the wedge
ROY_H
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Re: Domesticating & Documenting the Little Bear

Post by ROY_H » 02 Sep 2019 09:18

Hope they make sense. wasn't sure how to add captions (adding pics took me some time :? )

If you're handy with a soldering iron it was pretty straightforward as the board is well proportioned unlike some SSD boards.

T68
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Re: Domesticating & Documenting the Little Bear

Post by T68 » 02 Sep 2019 10:43

Well, a I feel pretty confident with the iron but will probably practice on some other projects before I take a shot on the bear.
Like it really a lot in its stock setup. So no hurry. But of course interested in getting it's full potential.

Glenn Gavryluk
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Re: Domesticating & Documenting the Little Bear

Post by Glenn Gavryluk » 02 Sep 2019 18:42

Thanks very much roy, this is a mod I've been interested in for awhile, but I'm not very understanding of all the technical jargon...but can use a soldering iron....seeing your pictures is exactly what I needed!...
I have the same version...got rid of all hum but building a wood case lined with aluminium tape connected to ground ( separate from signal ground)
Swapped out all stock valves- and rectifier with ez90
Through adapter socket.
Changed all coupling caps with mundorf aluminium in oil caps....
Really happy with current changes...but even better after seeing your pictures, just need to find the caps and resistors now, cheers.

ROY_H
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Re: Domesticating & Documenting the Little Bear

Post by ROY_H » 23 Sep 2019 17:38

Well I've been away for a couple of weeks so missing my Little Bear but spending some time re-reading this thread (sad!).
As per my earlier postings I've done the 40dB mod successfully and very pleased with the result. I've one or two more mods in mind but I've been pondering a couple of questions.

Has anyone done both the 40dB and 34dB mods. Is there any significant sonic difference.
Does a tone know the quality of the original resistors in the LB. Are they 5percent, carbon, whatever and is there mileage in replacing them with better quality tested versions.

Looking forward to some replies 👍

ROY_H
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Re: Domesticating & Documenting the Little Bear

Post by ROY_H » 23 Sep 2019 17:39

Well I've been away for a couple of weeks so missing my Little Bear but spending some time re-reading this thread (sad!).
As per my earlier postings I've done the 40dB mod successfully and very pleased with the result. I've one or two more mods in mind but I've been pondering a couple of questions.

Has anyone done both the 40dB and 34dB mods. Is there any significant sonic difference.
Does anyone know the quality of the original resistors in the LB. Are they 5percent, carbon, whatever and is there mileage in replacing them with better quality tested versions.

Looking forward to some replies 👍

T68
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Re: Domesticating & Documenting the Little Bear

Post by T68 » 24 Sep 2019 18:47

I've been tempted to let loose with the soldering iron on the Bear but have yet to muster the courage. Still a bit too scared to **** something up.
Also still very pleased with the performance so not too eager to change something.

ROY_H
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Re: Domesticating & Documenting the Little Bear

Post by ROY_H » 24 Sep 2019 21:26

T68 wrote:
24 Sep 2019 18:47
I've been tempted to let loose with the soldering iron on the Bear but have yet to muster the courage. Still a bit too scared to **** something up.
Also still very pleased with the performance so not too eager to change something.
Mods are not for everybody and the LB is pretty good out of the box but this forum puts out too many interesting possibilities😁
I've made many amps and phono amps over the years so feel comfortable melting solder👍

ROY_H
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Re: Domesticating & Documenting the Little Bear

Post by ROY_H » 27 Sep 2019 17:01

After my very pleasant experience of undertaking the 40dB RIAA mod which really pushed the LB up a notch I began reading this thread through again (always better a second time as you've started 'getting your head around' some of what's going on). It really made me want to undertake some more serious work on the beast so I worked out my requirements, looked up the components for what seemed the best choice and heated up the soldering iron! My approach is not scientific as I went for the whole kit and caboodle in one go so could be criticised for not waiting to see what gave the max benefit but....

Here's what I've now modified.

1. Output resistors reverted to 220ohm with matched 1% metal film (1/4 watt) and gain switch removed

2. Replaced 0.1uF coupling caps and 0.47 caps with axial lead polypropylene 630V:
This is the description (for both values) from the ebay listing


'These are custom made for my company - Triple Spiral Electronics (TSE)

Polypropylene Axial Metal Film

These look similar to the polyester ones from China but they are a better specification being made of the more desirable, more stable polypropylene material. They are well finished with epoxy end caps and good quality wire. These are actually a lot better made than the Vishay ones I have been buying from Farnell!

The 2nd photo in the listing shows a 100nf capacitor from the same range being tested, I cant guarantee they are all this precise but they are certainly a cut above the average. Certainly a good step up from the generic 10% capacitors of this type.

Great for building or repairing valve radios, amplifiers and also good for in car electronics or anywhere where you need the best reliability and quality.'


3. Replaced the ceramic caps in the 40dB RIAA with some Russian Silver Mica caps in 900pF and 250pF values.
This last was tricky due to the size of the caps compared with the ceramics and the fact the leads where flat blade leads so needed winding with leads cut from resistors soldered on.

All the replacement caps were checked and paired before installing.


The result?

STUNNING.....the sound now emanating from my system was absolutely sublime. Bass lines really underpinned the music. The sound stage was wide, open almost true 3D the tracks really rocked along, voice, acoustic guitar, electric guitar, drums, bass you name it, it was crystal clear in the mix.

When you think my overall cost for components was only around £35 this pre-amp I reckon sounds like several hundred pounds worth now. It's certainly taken my system up many notches in enjoyment :D

T68
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Re: Domesticating & Documenting the Little Bear

Post by T68 » 27 Sep 2019 17:27

Thanks for posting so specific information, Roy. And good to read about the improvements! Good to know of the latent potential in this cheapo chinese (which I think sounds great already with the Russian rocket tubes).

ROY_H
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Re: Domesticating & Documenting the Little Bear

Post by ROY_H » 27 Sep 2019 17:49

T68 wrote:
27 Sep 2019 17:27
Thanks for posting so specific information, Roy. And good to read about the improvements! Good to know of the latent potential in this cheapo chinese (which I think sounds great already with the Russian rocket tubes).
Yep! I did forget to mention I've swapped the tubes for Russian Rocket 6N2ps as well :D

ROY_H
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Re: Domesticating & Documenting the Little Bear

Post by ROY_H » 01 Oct 2019 21:10

For those partial to a little 'Little Bear' p**n here's some pics of my latest mods
20191001_190232.jpg
The yellow caps are the polypropylenes I've fitted. The large grey caps are the Russian silver micas
(185.58 KiB) Downloaded 58 times
20191001_190245.jpg
Just some funky spike feest I fitted (put same on my TT)
(135.84 KiB) Downloaded 48 times

brucetassin
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Re: Domesticating & Documenting the Little Bear

Post by brucetassin » 17 Oct 2019 17:20

Hello,

I got a Little Bear T-11 a few days ago. It sounds very good to me.
The preamp came installed in a black enclosure, looks nice.
It has a volume control knob. This pot is not show on the
schematic in this thread. Does anybody know how the pot
is wired into the preamp? I like this feature very much and
just want to know how its wired in.

Thanks

Bruce

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