VBITNGC building & comment

[digi01]

I think it is preferable to ground the input pin.

FYI,here is a overall walkthrough of VBITNGC by Gewa.LINK

Zang

 

[jleaman]

I think it is preferable to ground the input pin.

FYI,here is a overall walkthrough of VBITNGC by Gewa.LINK

Zang

I like this board. Who sells it ?

 

[falcott]

I think it is preferable to ground the input pin.

Zang

Thanks for that, Zang. But for what reason do you consider this method best?

 

[Nuuk]

The idea of shorting a valve preamp or buffer output is to protect the following stages while the valve stage 'settles down' as it warms up.

I never had a problem with my VBIGC but it is better to be safe than sorry.

I certainly short the output of my valve pre amp to avoid damage to any power amp that is connected after it. The delay I use is around a minute to be on the safe side.

 

[pinkmouse]

Why short it? Why not just disconnect it?

 

[Nuuk]

Because then you have added another 'switch' in the signal path!

 

[falcott]

The idea of shorting a valve preamp or buffer output is to protect the following stages while the valve stage 'settles down' as it warms up.

I never had a problem with my VBIGC but it is better to be safe than sorry.

I certainly short the output of my valve pre amp to avoid damage to any power amp that is connected after it. The delay I use is around a minute to be on the safe side.

Thanks.
So would a 10k resistor to ground be ok? Or more?

 

[Nuuk]

I actually short the output to ground with a direct connection! I checked that this was OK before doing it and I have had no problems, even shorting the valve pre-amp for a whole minute!

 

[falcott]

Thanks for you advice, Mr Nuuk.

Direct shorts make me nervous though...

 

[Nordic]

just to set you at ease... I use the relay to switch the amp's transformer (hybrid vbitngc).. with no ill effects after nearly a year so far...

 

[digi01]

Thanks.
So would a 10k resistor to ground be ok? Or more?

10k is too big.consider lots of pre amp under 1OHM output resistence so direct short is ok.

Zang

 

[Nuuk]

Direct shorts make me nervous though...

Me too but I a couple of very trusted contacts confirmed this would be OK before I tried it!

 

[Nordic]

Its no diffirent from turning a perfect pot to 0 output, isn't it...?
Or 0V 0mA input. In the presence of live power rails, nothing over the input = an incomplete circuit. A dead short on the input is the closest thing you can get to a signal source of 0 voltage and current.

 

[VT67]

Somebody managed to get this thread back from under the dust.

Attached a picture of what will become the backside of my amp.

Regards

 

[falcott]

Oooh! Where did you find those sexy heatsinks?

 

[VT67]

It's the LA 1 1000B from Fischer. I once bought a length (1m) to create a cooling tunnel and these were the leftovers.

Regards

 

[Sir_John]

Transformer specifications

Hello everyone. I am so glad to see that this thread is up and running again.

Can any of the designers tell us exact specs for the transformers, voltages and VA ratings, thanks.

Also, I am not sure that I read here any actual listening impressions as well as images of the finished amp. Is there any of a kind?

My amp is in "almost ready to begin assembly stage".

Best to all,

Srdjan

 

[Nordic]

Allthough it will never be competition for good valve gear,it sounds pretty good, I have used my valve board with inverted GC, NIGC, and My_ref C. I find the top end slightly less sparkling, which is not altogether a bad thing with chip amps. This is most likely due to the ecc88 I settled on. It does make CD's sound a bit nicer then when played straight. Also makes bass sound a bit more firm, not boomy though. I'm considering trying 6N1-P and maybe E88CC later on. I skimped on transformers something fierce, yet it is still working awesomely after a year...

from memory I used a 2 x 24V 56va PCB mount tranformer for the voltage doubler and an even smaller 9V transformer regulated to 6.3V. At 6.3V x 0.365A the heater needs only about 2.3VA of power, obviously due to system losses (heat) and other inefficiencies, you will likely need double or 4 times this rateing...

 

[VT67]

Sir_John

You will find all the necessary info on digi01's webpage of the VBITNGC.

http://taihu.bjtzh.gov.cn/~digi01/VBITNGC.htm

Regards

 

[Sir_John]

Walter,

I am not very experienced builder, so I would like to make things as much clear as possible. Better save than sorry. I've examined digi's page and didn't find all the data. Correct me if I am wrong please.

So here are things I am not certain about:

1. For High current (HC) we need a transformer with 2x25 V AC secondaries, VA rating undefined. Please define the VA rating.

2. For Low Current (LC) we need a transformer with a secondary 1x 45 V AC or 2x 22V AC connected in series. Again I cannot find how big the transformer should be. Please define VA rating.

3. For delay circuit and heating of the tube we need a transformer with 7V AC secondary which should be small. Ok. How small. Again, VA=?

Also, in the schematic published there:
http://taihu.bjtzh.gov.cn/~digi01/VBITNGC- Files/VBITNGC_SCH.gif

It is not clear what is the value of the F1 fuse?
It is also not clear 100% to me what are K1 and S1 and S2 in this schematic.

If you or anyone else can help making those things clear, I would be grateful. Thanks.

Nordic:
I got one Philips miniwatt E88CC tube for this amp. When It is finished, I'll let everyone know how this combination sounds. I also intend to try one russian military grade tube. We shall see the outcome. Thanks for your response.

Regards,

Sir John