John Curl's Blowtorch preamplifier part II

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(me 80W DIY hybrid monaurals run at +0.55A bias each, 4-pair output stage, different valve front stage)
 

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Hi,

I was thinking

Don't, it seem's you are not very good at it.

A commercial manufacturer fill the demands of the markets.

If our customers ask for a 10K Phonostage (actually, believe it or not, our distributors complain our gear too cheap for them and ask if can make real "cost no object" stuff) they get it.

If they like fuses that are gold-plated, of course they get them too (and yes, we designed and started making because people asked us to do so) and marketing then writes the promo stuff and all that. If you disagree, you can email the webmaster.

Ciao T
 
I think that we should talk about fuses, the good, bad and the fancy fuses. The listening tests that my people have done have shown 'improvement' using better fuses. We usually use silver fuses made in Germany. However, there are other fuses and fuse types that we have found to be better than just any fuse. I agree with Thorsten that he cannot be personally held up to ridicule by people who have not even tried devices that he has had some association with.
 
I think that we should talk about fuses, the good, bad and the fancy fuses. The listening tests that my people have done have shown 'improvement' using better fuses. We usually use silver fuses made in Germany. However, there are other fuses and fuse types that we have found to be better than just any fuse. I agree with Thorsten that he cannot be personally held up to ridicule by people who have not even tried devices that he has had some association with.


I found many fuses of new production failed without any reasons.
Put in a new one, and the device works again.

Second a fuse cannot be linear, otherwise i would not blow when necessary.

To my surprise i found some fuses allowed more audible dynamics than standard fuses. And it was dependent how they are used.
Main fuses in Class A amps i often cannot hear a differenence, in ABs i can sometimes.
Fuses in the Powersupplyrails of Poweramps sometimes i can hear the difference, in preamps usually not.

Fuses in the output of any poweramp make most of the time a difference.

But i also must say, the prices for the *better* ones are often incredible high...
 
Hi,



Not sure I agree.

One pair of the Renesas/Hitatchi parts, open loop, has around 1.12A/V transconductance at quiescent and 0.94A/V if one FET is pushed all the way (10V Vds, 8.5A Id and 9V Vgs).

So one pair has around 1 Ohm output impedance, comparing favourably with many open loop tube Amp's, with +/-55V it will dissipate 44W, delivers the "first watt" in Class A (and should not cause major trouble as it slides into Class B), puts out a bit over 100W into 8 Ohm and can handle around 5 Ohm Load (resistive).

I do not see why 8 pairs are needed.

Ciao T
Well 8 pairs might be a bit too much, but at 8 A you need more than 8V Vgs. That can be handled with a separate psu for the input/driver stage, but doesnt such a low transconductance lead to high distortions?
Also, the cgs is not well bootstrapped and you have to deal with a lot of capacity too.
 
I found many fuses of new production failed without any reasons.
Put in a new one, and the device works again.

Second a fuse cannot be linear, otherwise i would not blow when necessary.

To my surprise i found some fuses allowed more audible dynamics than standard fuses. And it was dependent how they are used.
Main fuses in Class A amps i often cannot hear a differenence, in ABs i can sometimes.
Fuses in the Powersupplyrails of Poweramps sometimes i can hear the difference, in preamps usually not.

Fuses in the output of any poweramp make most of the time a difference.

But i also must say, the prices for the *better* ones are often incredible high...

If you're DIY why not use fusable links of silver wire?
 
I'll bet it wasn't snapped in a holder inside a chassis. The hot wire
anemometer trick isn't fair either.

Are you sure you want to bet? How much?

Attached is the picture of the part that caused me to lose a channel of my CD player.

My internet is still not working properly. The "modem" seems to have changed address and I havent yet got it to talk nice to the whole network.
 

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Hi,

Well 8 pairs might be a bit too much, but at 8 A you need more than 8V Vgs.

Well, a 300B tube needs 160V PP Grid drive, so what?

but doesnt such a low transconductance lead to high distortions?

I am unsure why you would assume a fairly constant, but low transconductance creates a lot of distortion... I would think that widely variable transconductance causes high distortion, but WTFDIK?

Also, the cgs is not well bootstrapped and you have to deal with a lot of capacity too.

Sure, there is always something to deal with...

If you want to use vertical FET's or even IRF parts, by all means do so and deal with their problems instead. I'm too lazy to try. :cool:

Ciao T
 
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