Recommend Crossover values for 4 ohm tweeters
I am interested in building the Troels Gravesen SBA 761 kit speaker.
I already have both the MW16 woofers and the tweeters but the tweeters I have are the 4 ohm version and the kit uses the 8 ohm version.
Any suggestions for changing the crossover values to suit my 4 ohm tweeters?
Perhaps some extra attenuation will be needed too?
The tweeter is the TW29RN-8 as shown below.
I already have both the MW16 woofers and the tweeters but the tweeters I have are the 4 ohm version and the kit uses the 8 ohm version.
Any suggestions for changing the crossover values to suit my 4 ohm tweeters?
Perhaps some extra attenuation will be needed too?
The tweeter is the TW29RN-8 as shown below.
Help please... What kind of resistor is this?
- Solid State
- 23 Replies
I'm trying to revive an Armstrong 626. Can anyone identify what type of resistor that is? Schematic says its a 0.47ohm resistor but its the first time I've seen one looking like that... Also, can I just replace it with the "normal" ones? 
Improving Very Simple Time Delay Circuit
- By knarfor
- Power Supplies
- 31 Replies
I own a HAPI 2 preamp designed by Stewart Hegeman. It features a time-delayed relay circuit on the outputs that provides an ~5 second delay after power-up before the preamp's output goes live. The problem is, the relays cause a terrible thump in my speakers when they engage and disengage.
The thump changes based on the capacitance.
When I changed the size of the cap, I expected the delay time to change, obviously. But I don't quite understand why it would effect the loudness of the thump, and why it would do so differently on startup and shutdown.
Can someone help me to understand it?
And is there are way to fix it (eliminate the thump)?
I know enough to basically understand how the circuit functions (R/C combo delays the transistor from switching the circuit on until the cap charges). But I don't understand it enough to figure out the above.
***Edit: I'm not 100% sure where exactly to fit this thread in the forum, but since this sub-forum is home to several threads about soft starts and circuits with a similar purpose, this seemed to be the appropriate place. Please pardon my error if it was not ***
The thump changes based on the capacitance.
- With the circuit configured as drawn (the original configuration) the relays cause a loud thump when they engage and a louder thump when they disengage.
- If I halve the capacitance, the thump is still slightly quieter, but equal on startup and shutdown.
- If I double the capacitance, the thump is nearly gone when the relays engage, but very loud when they disengage.
When I changed the size of the cap, I expected the delay time to change, obviously. But I don't quite understand why it would effect the loudness of the thump, and why it would do so differently on startup and shutdown.
Can someone help me to understand it?
And is there are way to fix it (eliminate the thump)?
I know enough to basically understand how the circuit functions (R/C combo delays the transistor from switching the circuit on until the cap charges). But I don't understand it enough to figure out the above.
***Edit: I'm not 100% sure where exactly to fit this thread in the forum, but since this sub-forum is home to several threads about soft starts and circuits with a similar purpose, this seemed to be the appropriate place. Please pardon my error if it was not ***
Attachments
Quad 2 output transformer replacement
- Tubes / Valves
- 13 Replies
So I have a repair/refurbish of some original Quad II amplifiers.
One of them is in decent condition the other one is under transformer goo.....
A picture of the OPT
Power transformer is about the same. The inductor is better.
Measurement of DC resistance looks like they could still be good.
So I was thinking of getting alle the goo out (how would I do that? probably heating them...).
Or when I was reading it appears there is a company called majestic transformer who make complete replacements.
According to keith snook his website they should be better then the originals.
I also tought about using a lundahl that has CFB windings but then I also need to pot them etc.....
Anyone has experience with these replacements from majestic transformers?
When I would replace the opt's I would ofcourse replace them both.
Same goes for the power transformer.
The guy wants the amplifier in very good condition (= like new) so that is why I would take this route.
Al passive components will also be replaced.
For the tubes, they still hold the GZ32 rectifiers so these will go and a GZ34 wil fit in there.
As for the power capacitors, using the GZ34 I am replacing them with 47µF ones.
One of them still has the original GEC KT66 in them, the other one has 2 different kt66 brands in so was thinking about a new quad of them.
One of them is in decent condition the other one is under transformer goo.....
A picture of the OPT
Power transformer is about the same. The inductor is better.
Measurement of DC resistance looks like they could still be good.
So I was thinking of getting alle the goo out (how would I do that? probably heating them...).
Or when I was reading it appears there is a company called majestic transformer who make complete replacements.
According to keith snook his website they should be better then the originals.
I also tought about using a lundahl that has CFB windings but then I also need to pot them etc.....
Anyone has experience with these replacements from majestic transformers?
When I would replace the opt's I would ofcourse replace them both.
Same goes for the power transformer.
The guy wants the amplifier in very good condition (= like new) so that is why I would take this route.
Al passive components will also be replaced.
For the tubes, they still hold the GZ32 rectifiers so these will go and a GZ34 wil fit in there.
As for the power capacitors, using the GZ34 I am replacing them with 47µF ones.
One of them still has the original GEC KT66 in them, the other one has 2 different kt66 brands in so was thinking about a new quad of them.
Help with Sony MHC-DX 10 CD assembly
- By paul92
- Everything Else
- 0 Replies
Hi all
I have a Sony MHC-DX 10 Hi-Fi system, which I am repairing for a colleague of mine. The issue was that, the rubber band, which controls the opening, and closing of the CD Drawer, and 3 CD changer, had become extremely soft, and had basically melted, and needed to be replaced. Upon removal, and replacement of the new rubber band, I am now having issues, aligning the mechanism, so that the drawer opens, and closes, and the CD changer is able to swap CDs. Right now, it is trying to spin, but gets stuck, and won't open.
Here is a photo of the unit in question,
and here is a link to the service manual.
https://www.hobbielektronika.hu/forum/getfile.php?id=57775
I was hoping, that it would explain the order, in which to reassemble the CD mechanism, but no luck. |
If anybody is able to assist, we would be so grateful.
Thanks
I have a Sony MHC-DX 10 Hi-Fi system, which I am repairing for a colleague of mine. The issue was that, the rubber band, which controls the opening, and closing of the CD Drawer, and 3 CD changer, had become extremely soft, and had basically melted, and needed to be replaced. Upon removal, and replacement of the new rubber band, I am now having issues, aligning the mechanism, so that the drawer opens, and closes, and the CD changer is able to swap CDs. Right now, it is trying to spin, but gets stuck, and won't open.
Here is a photo of the unit in question,
and here is a link to the service manual.
https://www.hobbielektronika.hu/forum/getfile.php?id=57775
I was hoping, that it would explain the order, in which to reassemble the CD mechanism, but no luck. |
If anybody is able to assist, we would be so grateful.
Thanks
What do the Coils do, in Amplifiers?
Hi
When you shop for an Amplifier board, it's hard to miss the Coils there.
What is their purpose?
Thank you
When you shop for an Amplifier board, it's hard to miss the Coils there.
What is their purpose?
Thank you
MC 2 Line
- By LLPe
- Analogue Source
- 16 Replies
Some time ago, I was doing a design for an MM with no feedback,
using a one-stage transconductance. That worked just fine, so I
wanted to do the same for an MC pre-amplifier.
The problem is that all the design I've seen, (on MC head amps),
uses on or more large electrolytics, and I definitely wanted to
avoid that, so the challenge was to make an amplifier with
these basic features:
1)a gain of 80dB @ dc,
2)an input bias-current < 1muA
3)low noise
4)using easy to obtain components
The concept I was working from is as simple as it gets:
The dc-gain is defined as Ag = gm x Rl and with Rl = 33k5 in
the RIAA network and Ag = 80dB = 10,000x =>
gm = 10k/33k5 =0.298S (S = 1/Ohm).
The RIAA network is from Linsley-Hood as found on Elliot Sound
(sound-au.com/project25.htm), allthough I reduced the impedance-
level to 1/3, i.e. resistors devided by 3 and capacitors multiplied
be 3.
The design I came up with look like this (simplified):
The output of the LTPs (Long Tailed Pair) feeds into a combination
of a current mirror and folded cascode. With the R4,R5, and R6 as
specified, the quiscent currents of Q9, Q12 and Q6 are the same.
The same applies for Q1, Q4, and Q14.
The total gm from input to the RIAA network is :
gm = a x b c x Ic/Vt,
where
a = ½ as the input voltage is shared between each transistor
in the LTP,
b = 2 as there is two LTPs,
c = 3 well its just way the current mirror / folded cascode works,
Ic = the collector current in the LTPs, and
Vt = 26mV
Now we can calculate the Ic in the LTPs:
Ic = gm x Vt/3 = 0.298 x 26mV/3 = 2.58mA, and hence
R3 = R7 = (15-0.7)/(2Ic) = 2.77kOhm
Now, if you simulate (or build) the amp, the gain at LF/DC just can't
make it to 80dB. The problem is the Q6 and Q14 : the output impedance
is too low. This is dealt with in the full design.
A few words on the output buffer: The requirements of this buffer are:
1) A high input impedance, as not to load the RIAA network
2) Drive the output (!)
3) Low distortion.
1) states that Q17 and Q18 should run at a rather low Ic,
2) states that Q19 - Q22 should run at a "not too low" current.
3) The original diamond buffer had only four transistors, and
run at the same Ic, as this cancels out much distortion, albeit at
a rather high total current.
By adding two transistors, the output transistors can be run at almost
the same current as the input transistors, and still be able to drive
any "normal" amplifier down the line. Running at 560muA each this buffer
will drive a 5.8kOhm load to 13V and still stay in class A. It will
drive much lower load, but then in class B. It should be able to drive
a 825 Ohm load to 13V.
There is another issue: the ouput offset voltage. In the simplified
version, LTSpice calculates it to be app 1V. But this is with
identical transistors, and with physical transistors this isbound to
be much larger. After all, the DC gain is 10,000x so just a 1mv
difference in the input transistors, this will result in 10V at
output! This is dealt with in the full circuit.
The full circuit will follow in a subsequent post
Have a nice day!
using a one-stage transconductance. That worked just fine, so I
wanted to do the same for an MC pre-amplifier.
The problem is that all the design I've seen, (on MC head amps),
uses on or more large electrolytics, and I definitely wanted to
avoid that, so the challenge was to make an amplifier with
these basic features:
1)a gain of 80dB @ dc,
2)an input bias-current < 1muA
3)low noise
4)using easy to obtain components
The concept I was working from is as simple as it gets:
The dc-gain is defined as Ag = gm x Rl and with Rl = 33k5 in
the RIAA network and Ag = 80dB = 10,000x =>
gm = 10k/33k5 =0.298S (S = 1/Ohm).
The RIAA network is from Linsley-Hood as found on Elliot Sound
(sound-au.com/project25.htm), allthough I reduced the impedance-
level to 1/3, i.e. resistors devided by 3 and capacitors multiplied
be 3.
The design I came up with look like this (simplified):
The output of the LTPs (Long Tailed Pair) feeds into a combination
of a current mirror and folded cascode. With the R4,R5, and R6 as
specified, the quiscent currents of Q9, Q12 and Q6 are the same.
The same applies for Q1, Q4, and Q14.
The total gm from input to the RIAA network is :
gm = a x b c x Ic/Vt,
where
a = ½ as the input voltage is shared between each transistor
in the LTP,
b = 2 as there is two LTPs,
c = 3 well its just way the current mirror / folded cascode works,
Ic = the collector current in the LTPs, and
Vt = 26mV
Now we can calculate the Ic in the LTPs:
Ic = gm x Vt/3 = 0.298 x 26mV/3 = 2.58mA, and hence
R3 = R7 = (15-0.7)/(2Ic) = 2.77kOhm
Now, if you simulate (or build) the amp, the gain at LF/DC just can't
make it to 80dB. The problem is the Q6 and Q14 : the output impedance
is too low. This is dealt with in the full design.
A few words on the output buffer: The requirements of this buffer are:
1) A high input impedance, as not to load the RIAA network
2) Drive the output (!)
3) Low distortion.
1) states that Q17 and Q18 should run at a rather low Ic,
2) states that Q19 - Q22 should run at a "not too low" current.
3) The original diamond buffer had only four transistors, and
run at the same Ic, as this cancels out much distortion, albeit at
a rather high total current.
By adding two transistors, the output transistors can be run at almost
the same current as the input transistors, and still be able to drive
any "normal" amplifier down the line. Running at 560muA each this buffer
will drive a 5.8kOhm load to 13V and still stay in class A. It will
drive much lower load, but then in class B. It should be able to drive
a 825 Ohm load to 13V.
There is another issue: the ouput offset voltage. In the simplified
version, LTSpice calculates it to be app 1V. But this is with
identical transistors, and with physical transistors this isbound to
be much larger. After all, the DC gain is 10,000x so just a 1mv
difference in the input transistors, this will result in 10V at
output! This is dealt with in the full circuit.
The full circuit will follow in a subsequent post
Have a nice day!
Attachments
Factory Glimpse - posted by Lundahl Transformers
Factory glimpse:
Victor Kung at VK Music challenge us to develop an upgrade transformer for the new TU-8800 tube amplifier kit from Elekit, Japan.
It turned out to be a more difficult task than what we expected, requiring three iterations before everyone was pleased.
Here is a sneak peek from the production of the new transformer, LL2783C.
from Victor
Mr Fujita said LL2L2783C is very (very) good...
getfvid_85627084_258327311823241_897145915683373056_n on Vimeo
This is LL2783C...
Victor Kung at VK Music challenge us to develop an upgrade transformer for the new TU-8800 tube amplifier kit from Elekit, Japan.
It turned out to be a more difficult task than what we expected, requiring three iterations before everyone was pleased.
Here is a sneak peek from the production of the new transformer, LL2783C.
from Victor
Mr Fujita said LL2L2783C is very (very) good...
getfvid_85627084_258327311823241_897145915683373056_n on Vimeo
This is LL2783C...
Holey basket surround repair
- By tiverson
- Full Range
- 2 Replies
I got these holey basket with black cones for free, one driver is in good shape the other, the surround and cone has some separation. Looks easy enough to repair. What type of glue should I use? Thanks for any help
