I believe that Decware OPT is 9k to 6 Ohm.
With 3 Ohms on the secondary, and the output tubes triode wired, mu = 20, and rp = 1700 Ohms, the output stage g1 to plate gain is about 14.5.
With no speaker connected, the output stage g1 to plate gain is 20.
That is a frequency response versus load impedance gain variance of about 2.8 dB.
Wow, I wish all speakers that had a perfectly flat impedance curve could be within 2.8 dB over their stated frequency response specification.
How about a room response curve of 2.8 dB.
2.8 dB differential is + 1.4dB / - 1.4 dB.
In search of perfection, just peel the layers off of the onion again.
Then sit back and enjoy the music.
With 3 Ohms on the secondary, and the output tubes triode wired, mu = 20, and rp = 1700 Ohms, the output stage g1 to plate gain is about 14.5.
With no speaker connected, the output stage g1 to plate gain is 20.
That is a frequency response versus load impedance gain variance of about 2.8 dB.
Wow, I wish all speakers that had a perfectly flat impedance curve could be within 2.8 dB over their stated frequency response specification.
How about a room response curve of 2.8 dB.
2.8 dB differential is + 1.4dB / - 1.4 dB.
In search of perfection, just peel the layers off of the onion again.
Then sit back and enjoy the music.
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Hello - I have a DECWARE ZEN grounding question - on the 2012 schematic it states, "This amp is built with a single point ground, located on one of the power transformer mounting bolts. The silver litz wire is used to carry the ground buss for the entire circuit. Do not use the chassis for ground."
So, I take this to means - I should ground the "ground" from the mains cable IEC to the chassis, but NOT tie the circuit ground (my ground buss bar) to that same point on the chassis.
Question - where do I then attach the circuit ground (buss bar). It says to the "transformer mounting bolt". If the transformer is directly mounted onto the chassis, would it (transformer) then be grounded to chassis and therefore the circuit ground (buss bar) also be grounded to the chassis.
Thanks, grounding confuses the 'blank' out of me.
So, I take this to means - I should ground the "ground" from the mains cable IEC to the chassis, but NOT tie the circuit ground (my ground buss bar) to that same point on the chassis.
Question - where do I then attach the circuit ground (buss bar). It says to the "transformer mounting bolt". If the transformer is directly mounted onto the chassis, would it (transformer) then be grounded to chassis and therefore the circuit ground (buss bar) also be grounded to the chassis.
Thanks, grounding confuses the 'blank' out of me.
I tied the iec ground wire and the center tap to the isolated outside tags bye the rectifier tube. That connects to the rca input jacks and the g2 (chassis grounded) center tag by the 6p15-ev's. Then it goes to the bias switch and on to the volume pot.
I don't know if it is the correct way, but it is dead silent and it works.
Attached is a pdf with an unfinished layout.
I don't know if it is the correct way, but it is dead silent and it works.
Attached is a pdf with an unfinished layout.
Owners of both Decware, and Decware Clone amplifiers . . .
Please tell us that you:
1. Like the sound; and what speaker make and model number that you use.
Or,
2. Dislike the sound; and what speaker make and model number that you use.
Thanks!
A large number of reports from actual owners could prove to be very enlightening.
Please tell us that you:
1. Like the sound; and what speaker make and model number that you use.
Or,
2. Dislike the sound; and what speaker make and model number that you use.
Thanks!
A large number of reports from actual owners could prove to be very enlightening.
The sound was OK. After building a clone it evloved thru 7 iterations and kept getting better.
It needs a fairly effieict loudspeaker with a flattish impedance response.
Our original clone was used (at least) on the original FH1 and the 2-way Heil with a simple XO.
I would suggest looking at evolutions of teh RH84 for a (typically) better approach.
The Decware made waves and a following because it was cheap and a kit and one of very few amplifiers in its niche. That is quite different today.
dave
It needs a fairly effieict loudspeaker with a flattish impedance response.
Our original clone was used (at least) on the original FH1 and the 2-way Heil with a simple XO.
I would suggest looking at evolutions of teh RH84 for a (typically) better approach.
The Decware made waves and a following because it was cheap and a kit and one of very few amplifiers in its niche. That is quite different today.
dave
Looks like the power tranny has an extra unused secondary winding. Why would they not take advantage of thsat to do fixed bias, versus cathode? Cheapo Charlie!
jjasniew,
Why not use the extra secondary and use fixed bias?
For a single ended stereo amplifier; which has output tubes that might, or that might not, be matched for DC quiescent current (like un-careful tube rolling; replacing only one tube that dies; or your friend's favorite pair; etc.).
1. If you measure the quiescent DC current of the left channel output tube, versus the right channel output tube . . .
You might find that the DC current matches is the best, in the following order:
A. Individual self bias resistors and bypass caps. They have the best DC current match for a wide variety of tubes
B. Fixed bias, not individually adjustable
C. Fixed bias, individually adjustable . . . if you forget to re-adjust them individually
D. Single shared self bias resistor with, or without bypass cap. This will possibly be the worst DC current match
Parts count:
Shared self bias resistor (but with reduced channel separation). 1 part. Poor DC match. Poor lifelong match.
Shared self bias resistor and bypass cap. 2 parts. Poor DC match. Poor lifelong match.
Individual self bias resistors and bypass caps. 4 parts. Good DC match. Excellent life long match.
Fixed bias, non-adjustable. 2 diodes Or 1 bridge, 2 capacitors, 2 resistors for the negative supply; and 2 current sense resistors. 7 or 8 parts, + the extra secondary. Fair DC match. Poor life long match.
Fixed bias, single adjustment. 2 diodes Or 1 bridge, 2 capacitors, 2 fixed resistors and 1 potentiometer for the negative supply; and 2 current sense resistors. 8 or 9 parts, + the extra secondary. Fair DC Match. Poor life long match.
Fixed bias, individually adjustable. 2 diodes Or 1 bridge, 2 capacitors, 2 fixed resistors and 2 potentiometer for the negative supply; and 2 current sense resistors. 9 or 10 parts, + the extra secondary. Good DC match, if you remember to properly set them. Poor long life match, unless you constantly re-adjust.
Using really well matched tubes, of the same manufacturer and same vintage, the above results will change.
(remember, I started all this with the stipulation that the tubes may, or may not, be matched).
So, purchase very well matched tubes. All of these circuits will work better that way.
All engineering is a group of tradeoffs. Pick your tradeoffs.
Just my opinions
Why not use the extra secondary and use fixed bias?
For a single ended stereo amplifier; which has output tubes that might, or that might not, be matched for DC quiescent current (like un-careful tube rolling; replacing only one tube that dies; or your friend's favorite pair; etc.).
1. If you measure the quiescent DC current of the left channel output tube, versus the right channel output tube . . .
You might find that the DC current matches is the best, in the following order:
A. Individual self bias resistors and bypass caps. They have the best DC current match for a wide variety of tubes
B. Fixed bias, not individually adjustable
C. Fixed bias, individually adjustable . . . if you forget to re-adjust them individually
D. Single shared self bias resistor with, or without bypass cap. This will possibly be the worst DC current match
Parts count:
Shared self bias resistor (but with reduced channel separation). 1 part. Poor DC match. Poor lifelong match.
Shared self bias resistor and bypass cap. 2 parts. Poor DC match. Poor lifelong match.
Individual self bias resistors and bypass caps. 4 parts. Good DC match. Excellent life long match.
Fixed bias, non-adjustable. 2 diodes Or 1 bridge, 2 capacitors, 2 resistors for the negative supply; and 2 current sense resistors. 7 or 8 parts, + the extra secondary. Fair DC match. Poor life long match.
Fixed bias, single adjustment. 2 diodes Or 1 bridge, 2 capacitors, 2 fixed resistors and 1 potentiometer for the negative supply; and 2 current sense resistors. 8 or 9 parts, + the extra secondary. Fair DC Match. Poor life long match.
Fixed bias, individually adjustable. 2 diodes Or 1 bridge, 2 capacitors, 2 fixed resistors and 2 potentiometer for the negative supply; and 2 current sense resistors. 9 or 10 parts, + the extra secondary. Good DC match, if you remember to properly set them. Poor long life match, unless you constantly re-adjust.
Using really well matched tubes, of the same manufacturer and same vintage, the above results will change.
(remember, I started all this with the stipulation that the tubes may, or may not, be matched).
So, purchase very well matched tubes. All of these circuits will work better that way.
All engineering is a group of tradeoffs. Pick your tradeoffs.
Just my opinions
The newest version is way* better
and their "following" is off the charts now thanks to some online "reviews".* if you read the marketing and forum
I built a clone from the Youtube videos. Search for Diy Zen Triode tube amp. Parts 9 and 11 are missing now.
I did the Hazen mod but have not yet done the anniversary mod.
I am using 6p15-ev power tubes and a 6n1p-ev.
I originally used it with a pair of Klipsch RB6 and it sounded great but I always felt I needed more power.
I took it to my office and attached a pair of Decware Tiny Radials to it and a powered subwoofer.
The speakers are about 2 feet in front of me and about 5 feet apart.
It feels like I am in the middle of the music and I no longer feel the need for more power.
Would I build it again? You bet I would.
I did the Hazen mod but have not yet done the anniversary mod.
I am using 6p15-ev power tubes and a 6n1p-ev.
I originally used it with a pair of Klipsch RB6 and it sounded great but I always felt I needed more power.
I took it to my office and attached a pair of Decware Tiny Radials to it and a powered subwoofer.
The speakers are about 2 feet in front of me and about 5 feet apart.
It feels like I am in the middle of the music and I no longer feel the need for more power.
Would I build it again? You bet I would.
jjasniew,
Thanks for that creative idea to get fixed bias.
Use an un-used 6.3VAC winding and a voltage doubler to get bias.
With an unloaded 6.3VAC winding, a pair of schottky diodes, voltage doubler connections, you ought to get up to
16 volts DC.
And whatever your bias voltage was, by not using self bias, you effectively increased the B+ voltage by an amount equal to the grid bias voltage.
Thanks for that creative idea to get fixed bias.
Use an un-used 6.3VAC winding and a voltage doubler to get bias.
With an unloaded 6.3VAC winding, a pair of schottky diodes, voltage doubler connections, you ought to get up to
16 volts DC.
And whatever your bias voltage was, by not using self bias, you effectively increased the B+ voltage by an amount equal to the grid bias voltage.
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galtjunk,
Thanks! . . . I forgot about the Hazen Mod.
I thought the Hazen mod used a capacitor connected to ground, with the other end of the capacitor connected to the suppressor grid (suppressor grid Floating at DC). That was for an EL34, that has the suppressor grid connected to pin 1.
If that is what the Hazen Mod is, then it should also work for a 6CA7, connect the same capacitor to pin 1 (Beam Formers of a 6CA7).
But I will not let a suppressor grid float (no DC return).
If you like a floating suppressor grid, then a 6p15-ev may work, because it has separate connections to the suppressor grid, and the suppressor is not connected to the cathode.
But an EL84 and 6BQ5 have the suppressor / beam formers connected internally to the cathode, so they can not have a Hazen mod.
Thanks! . . . I forgot about the Hazen Mod.
I thought the Hazen mod used a capacitor connected to ground, with the other end of the capacitor connected to the suppressor grid (suppressor grid Floating at DC). That was for an EL34, that has the suppressor grid connected to pin 1.
If that is what the Hazen Mod is, then it should also work for a 6CA7, connect the same capacitor to pin 1 (Beam Formers of a 6CA7).
But I will not let a suppressor grid float (no DC return).
If you like a floating suppressor grid, then a 6p15-ev may work, because it has separate connections to the suppressor grid, and the suppressor is not connected to the cathode.
But an EL84 and 6BQ5 have the suppressor / beam formers connected internally to the cathode, so they can not have a Hazen mod.
Hazen mod is a capacitor coupling of g3 and cathode, i.e. for the EL34 the cap is between pin 1 and 8.
https://www.decware.com/newsite/paper146.html
https://www.decware.com/newsite/paper146.html
Francois,
Thanks!
That is what I wanted, to keep the answer accurate.
It seems that the suppressor grid, pin 1 is allowed to float in terms of DC.
A capacitor is not a DC return (not until it is subjected to voltage breakdown, and shorts).
The purpose of the suppressor grid, is to collect the secondary electrons that come off of the plate.
The original intent of the pentode designers was that there would be a DC return for the suppressor.
Therefore, I will never try, use, or otherwise recommend the Hazen Mod as described.
Or is there also a resistor across the capacitor? There is not a resistor there in the Steve Deckert link.
If the suppressor grid is "in the way" of getting good sound, then I suggest we all switch from pentodes to tetrodes.
4-65A, 4X150A, etc.
Or, we can ask the makers of the EL34, EL84, etc. to save materials, time, and effort . . .
Take out, or leave out, that dang suppressor grid!
Just my opinions
Thanks!
That is what I wanted, to keep the answer accurate.
It seems that the suppressor grid, pin 1 is allowed to float in terms of DC.
A capacitor is not a DC return (not until it is subjected to voltage breakdown, and shorts).
The purpose of the suppressor grid, is to collect the secondary electrons that come off of the plate.
The original intent of the pentode designers was that there would be a DC return for the suppressor.
Therefore, I will never try, use, or otherwise recommend the Hazen Mod as described.
Or is there also a resistor across the capacitor? There is not a resistor there in the Steve Deckert link.
If the suppressor grid is "in the way" of getting good sound, then I suggest we all switch from pentodes to tetrodes.
4-65A, 4X150A, etc.
Or, we can ask the makers of the EL34, EL84, etc. to save materials, time, and effort . . .
Take out, or leave out, that dang suppressor grid!
Just my opinions
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Did anyone dechiffre how the OA3's (75V) and the OD3a (150V) voltage regulators fitted in the design?
In the Decware forum
(https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1510887200/50), this is mentioned:
"Rather than the two capacitors used in the power supplies of the SE84UFO and SE84UFO2, this uses a few more. The first cap comes off the rectifier tube just like the other amps but then the power supply is split into three separate filters, one for each tube. This adds 7 additional caps and nine additional poly film bypass caps. There was no option other than to spit it into three separate supplies due to the 30mA limit of the OA3 tube. "
In the user manual, however, it says the input tube has an OD3a.
I'm not used to tubes, and I can't figure out where these voltage regulators fit in.
In the Decware forum
(https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1510887200/50), this is mentioned:
"Rather than the two capacitors used in the power supplies of the SE84UFO and SE84UFO2, this uses a few more. The first cap comes off the rectifier tube just like the other amps but then the power supply is split into three separate filters, one for each tube. This adds 7 additional caps and nine additional poly film bypass caps. There was no option other than to spit it into three separate supplies due to the 30mA limit of the OA3 tube. "
In the user manual, however, it says the input tube has an OD3a.
I'm not used to tubes, and I can't figure out where these voltage regulators fit in.