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ASL Si15-DT [message #8346]

Mon, 26 July 2004 17:50

BillEpstein
Messages: 886
Registered: May 2009

Illuminati (2nd Degree)

I borrowed this amp from Speakerman. It's a very basic dual KT-88 passive integrated SET with pentode and triode switching. High quality parts and the on-off up front. I like that. Absolutely noise free, too.
With the stock KT-88's it has a really nice SET mid-range and very tuneful bass. (BTW, there's an extra output jack for bi-amping.) I found some upper mid-range nastiness tho'. So I cut the bias down to 400mA and popped in a set of VA EL-34's. Wow! Even lovelier vocals, very heavyweight bass and a pure, extended treble. Still some image congestion in the middle but very little fault otherwise.
The new retail is pricey at $895. Just 2 years ago it was $599 and that seems about right.
Just thought you might like to know.

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Re: ASL Si15-DT [message #8347 is a reply to message #8346]

Tue, 27 July 2004 00:36

Manualblock
Messages: 4973
Registered: May 2009

Illuminati (13th Degree)

Sorry but what do you mean by saying you cut the bias down to 400 ma? Thanks for your help,J.R.

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Re: ASL Si15-DT [message #8349 is a reply to message #8346]

Tue, 27 July 2004 03:23

Wayne Parham
Messages: 18678
Registered: January 2001

Illuminati (33rd Degree)

That's cool, Bill. Do you happen to know a URL for this amp? I'd like to see it and know more about it. The price is right, puts it right in the same ballpark as the Zen, Paramours and the Stoetkit.

Did you see Eric's posts about EL34's, 6550's and KT88's? From what he says, there are lots of good options in this "family" of tubes. As long as you can change the bias voltage, you can swap them around.

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Re: ASL Si15-DT [message #8351 is a reply to message #8347]

Tue, 27 July 2004 16:47

BillEpstein
Messages: 886
Registered: May 2009

Illuminati (2nd Degree)

The bias voltage, which is a negative voltage, is the minimum current necessary to operate the tube, i.e., control the stream of electrons that is released when the Plate is excited (heated).
The operating characteristics of the KT-88 require 800mV and the EL-34, 400. You can use more or less somewhat. Raising the bias increases power levels and lowers distortion but eventually fries the tube. Lowering will lower the output and "sweeten" the sound while increasing distortion."0" bias sounds like a 45 played on 33RPM!
Is it possible that it is distortion that makes SET's with their 2 to 5% and more distortion levels sound "sweet"?
Is that a good thing or bad?
"What will it be, Danny........? Goodness, or Badness?"

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Re: ASL Si15-DT [message #8352 is a reply to message #8351]

Tue, 27 July 2004 17:49

Manualblock
Messages: 4973
Registered: May 2009

Illuminati (13th Degree)

Thanks for the reply I wasn't sure if you mean't plate current. I think I am reading the tube load lines wrong. For the el34 I have a zero signal plate current of 100 ma, and plate voltage of 25o running in class a1. Is that right or am I in la-la land with this?

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Re: mV - mA needs conversion and we need help, somebody? nt [message #8353 is a reply to message #8352]

Tue, 27 July 2004 20:50

BillEpstein
Messages: 886
Registered: May 2009

Illuminati (2nd Degree)

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Re: ASL Si15-DT [message #8366 is a reply to message #8346]

Thu, 29 July 2004 07:30

spkrman57
Messages: 522
Registered: May 2009

Illuminati (1st Degree)

Hello all,
After reading all the posts here(and the ones Wayne refers to also), it seems to me that the EL34 must work okay in the ASL-Si-15 amp which is setup for KT-88's. Previously this amp was equipped with KT-66's and I think 6550's before that.

I am not sure about the posts concerning swapping EL34's for KT-88's not working well, I have to guess that with the right bias setting(negative voltage on the control grid relates to the amount of current flow through the tube, usually referred to as cathode(or)plate current).

What I have not been able to determine, is the EL34 current for class A operation. The KT-88's operate with 80ma(read as mV across 10 ohm precision resistor from cathode to ground which equates to direct mA reading), I am not sure if 40mA is best setting for EL34's, but as I told Bill, I guess as long as the plates are not "cherry red" and the sound is okay, I think it is fine.

I believe the manufacturer is Divergent Technology out of Canada, but the units are Chinese built. Anyone with these units can derive immediate improvement by getting rid of the Chinese tubes. They do work, but are forward with midrange glare to me.

I will find a link to the amp here soon, I purchased through a AK forum sponser.

Regards, Ron

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