Can this I/V circuit be adapted for differential DAC output?
- By TimA
- Digital Line Level
- 28 Replies
What makes a good pre-amp value for a guitar amplifer?
- By exlabs
- Instruments and Amps
- 26 Replies
Attachments
FS: 2 pairs of Mark Audio CHP-70 speaker units (total = 4)
- By andyjevans
- Swap Meet
- 5 Replies
Attachments
FS: Thurlby-Thandar 30v, 2A Variable Bench Power Supply x 3
- By andyjevans
- Swap Meet
- 2 Replies
Attachments
Need help with Hornresp (strange output)
- Subwoofers
- 2 Replies
Hello guys, and especially hello David! 🙂
In the last few days, i was simulating a couple enclosures for my subwoofer (mostly with WinISD).
I allways liked the idea of a 6th order serial tuned bandpass, wich was unable to simulate until now, when i finally found Hornresp!!!
But i am pretty confused, at what Hornresp outputs me, compared to WinISD
I got strange peaks in the result, so i simulated a simple closed box, to see, if atleast this looks familiar, wich was NOT the case.
When simulating a closed box, im get just 1 big peak as result, like the following picture shows:
The same driver, in the same 5l closed box in WinISD looks like this:
I mean... ok... im sure the flat line at 100Hz and above is not true in WinISD, but this peak in Hornresp also looks unreal to me.
But it is not just the way, how it looks, also the point, where it starts dropping is totally different.
-> WinISD starts dropping at ~100Hz and below, the Hornresp simulation has its peak at 60Hz and drops below that
Just to let you have all the informations, here a screenshot of my input window:
I realised, when i choose "-> Tools -> Maximum SPL", it looks a bit more, like what WinISD outputs, BUT still verry different AND, i can not select this menu, when i simulate the bandpass. The menu is just not there, when i select a bandpass simulation, instead of a closed box.
Edit:
i am sorry, i didnt want to double-post. I allready posted my question into another thread, but i didnt know, it takes a while, until it shows up... so i thought my post didnt submit correctly, and posted it again here.
In the last few days, i was simulating a couple enclosures for my subwoofer (mostly with WinISD).
I allways liked the idea of a 6th order serial tuned bandpass, wich was unable to simulate until now, when i finally found Hornresp!!!
But i am pretty confused, at what Hornresp outputs me, compared to WinISD
I got strange peaks in the result, so i simulated a simple closed box, to see, if atleast this looks familiar, wich was NOT the case.
When simulating a closed box, im get just 1 big peak as result, like the following picture shows:
The same driver, in the same 5l closed box in WinISD looks like this:
I mean... ok... im sure the flat line at 100Hz and above is not true in WinISD, but this peak in Hornresp also looks unreal to me.
But it is not just the way, how it looks, also the point, where it starts dropping is totally different.
-> WinISD starts dropping at ~100Hz and below, the Hornresp simulation has its peak at 60Hz and drops below that
Just to let you have all the informations, here a screenshot of my input window:
I realised, when i choose "-> Tools -> Maximum SPL", it looks a bit more, like what WinISD outputs, BUT still verry different AND, i can not select this menu, when i simulate the bandpass. The menu is just not there, when i select a bandpass simulation, instead of a closed box.
Edit:
i am sorry, i didnt want to double-post. I allready posted my question into another thread, but i didnt know, it takes a while, until it shows up... so i thought my post didnt submit correctly, and posted it again here.
ARTA and phase: what's wrong?
- By 2slow4u
- Software Tools
- 0 Replies
I am using the semi dual channel configuration, but despite having checked the options, in the measurement I do not see any difference in the phase response and what I get is this:
Please, what's wrong?
Please, what's wrong?
The Intellectual People Podcast - Acry-Tech (DuraTex)
- By jtwrace
- Construction Tips
- 0 Replies
Attachments
Reverse mid polarity in 3 way
Hi,
To the best of my ability I am only able to get a non problematic frequency response if I switch the polarity of either my woofer or my mid. The flattest response seems to be with the mid switched.
Are there any negative effects to switching the polarity on a midrange such negative effects on imaging etc?
The frequency response that I'm getting is:
with blue being just the mid reversed, red being just midbass reversed and green being all in phase.
The crossover being used is:
The drivers being used are:
Tweeter - Dynaudio t330d
Mid - Dynaudio m560d
MidBass- AudioTechnology C-quenze 21i52
It's been a while since I've worked on speakers and any advice would be of great help.
To the best of my ability I am only able to get a non problematic frequency response if I switch the polarity of either my woofer or my mid. The flattest response seems to be with the mid switched.
Are there any negative effects to switching the polarity on a midrange such negative effects on imaging etc?
The frequency response that I'm getting is:
with blue being just the mid reversed, red being just midbass reversed and green being all in phase.
The crossover being used is:
The drivers being used are:
Tweeter - Dynaudio t330d
Mid - Dynaudio m560d
MidBass- AudioTechnology C-quenze 21i52
It's been a while since I've worked on speakers and any advice would be of great help.
Attachments
FS: Manufacture of amplifier housings according to your sketches.
If your project requires unique steel enclosures, I can offer my services.
Our production capabilities:
- laser cutting.
- metal bending.
- contact welding.
- painting
- laser engraving
Some samples of the work performed by us:
It is possible to make one case or a small batch.
The cost is agreed individually. We need a sketch from you, or a drawing and requirements for the case.
For correspondence, you can use private messages or mail zampotech.udav#gmail.com (you need to replace the # sign with the sign @)
Our production capabilities:
- laser cutting.
- metal bending.
- contact welding.
- painting
- laser engraving
Some samples of the work performed by us:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
It is possible to make one case or a small batch.
The cost is agreed individually. We need a sketch from you, or a drawing and requirements for the case.
For correspondence, you can use private messages or mail zampotech.udav#gmail.com (you need to replace the # sign with the sign @)
Experiment - Clean wireless power for RasPi4/Digi One Signature
- By AndyTather
- Power Supplies
- 5 Replies
Attachments
Setting up two parafeed amps for a special test rig
- By trobbins
- Tubes / Valves
- 4 Replies
I am aiming to prepare a somewhat special pair of parafeed (PF) amps for the purpose of extending the range of output transformer (OPT) testing that has been discussed in another thread (Measurements on output transformers for the Williamson amp).
Patrick (Turner Audio) passed away early this month and I had been in sporadic communication with him for years, and most recently emailed him about a test amplifier setup he had made decades ago to test the performance of output transformers. So with a sad heart I will continue on with making a somewhat similar test amplifier that hopefully can apply an acceptably low distortion sinewave to an OPT, but with sufficiently high signal voltage to emulate up to about 15W in to a 10kohm PP OPT in a class A amplifier, and use a modern soundcard and software tool to characterise the frequency response and distortion of such an OPT. I'm piggy-backing on what Patrick seems to have prepared, which was a pair of PF amps using 6CM5 in triode-mode, and with sufficient feedback to achieve a stable test bandwidth from about 20Hz to upward of 1Mhz, and at low distortion (eg. circa 0.1%).
As shown in the diagram above, the OPT DUT is driven by the pair of PF amps in a balanced configuration with the B+ (CT) primary winding node of the OPT grounded, such that each PF amp is loaded by just half the PP primary winding. In addition each amp has a resistor inserted between the PF coupling cap and the OPT primary anode tap so as to be equivalent to an output stage driving tube Ra (for the Williamson the test originally used 1.25k to be equivalent to the KT66 anode output resistance). The remainder of the test jig is already set up and has been used for OPT testing at low signal voltage (as per the thread link above).
I'm not aiming for each amp to achieve a 1Mhz top end bandwidth for a number of reasons, but as this is a test setup I do need each amp to aim for as low a phase shift as practical down at the 20Hz end, and likely going up through 100kHz, as well as negligible amplitude change. As part of a test rig using modern software, any phase shift of the test rig (that will include the PF amps, but not the OPT DUT) can be automatically 'calibrated out' by a loopback test, leaving just the phase response of the OPT being tested in the measurement.
The output power target is to get close to 15W in to a 10kPP OPT that has a matched secondary resistive loading. Given each PF amp is driving only half the primary, that implies a 2k5 load on each amp. But each PF amp is also driving the OPT through an additional series resistance of circa 1.25k, to make a total PF amp loading of 3.75k. 15W into a 2.5k load would indicate a signal swing of 275Vpk, but that increases to 375Vpk at the PF amp output due to the added series 1.25k.
The 6CM5 was and is both common and cheap here in OZ, and many have used it for audio applications including Patrick who ran it in triode mode at up to 375V Vak idle, and appears to have used it in his custom test amp. I have a large batch of them so initially for this application I will use them rather than the likes of 6L6GC etc that I have fewer of, but I can foresee that the 6CM5 is likely not going to achieve 15W where I want it, so this test jig may have to graduate over to 6L6GC for Rev 2 (if I get that far). The 6CM5 in triode mode has an Ra of circa 750 ohm, and I can easily use 2 in parallel.
To keep phase shift as low as practical at a 20Hz low frequency end each PF amp output is likely to need circa 100uF of coupling cap. That is easy to achieve with e-caps, although I have sufficient metallized poly caps with at least 500Vdc rating to integrate in with the e-caps if needed.
Each main PF choke needs to be at least 30H to allow operation down to 20Hz, and preferably around 50-60H. Although that choke can be a series connection of whatever chokes are available, each choke needs to have a suitably low DCR/Henry ratio along with a high enough Vac and DC current capability. I can presently get to 30H, but need to seek out some more boat anchors.
This is just a test amp so will be nothing pretty and will use a large derelict amp chassis and I have a range of PT's to choose from. An aspect of this test rig is that the two PF amps will draw opposite phase signal currents from a common B+ supply, so the effective B+ load is going to be fairly constant over the range of test signal levels applied to a test OPT. Also I can arrange heater power and sockets for parallel 6CM5 to try and reduce effective Ra and hence move the main PF R-L corner frequency down as far as practical to reduce phase shift at 20Hz.
This will be my first foray in to PF amps so I have been trying to do sufficient background reading to confirm that using a PF amp in this test setup is worthwhile starting, and so far I can't rationalise an alternative way to achieve the OPT testing I am targeting. So I will continue on with preparations and get a draft schematic prepared and start to appreciate what performance can be achieved with what I've got to hand.
Ciao, Tim
Patrick (Turner Audio) passed away early this month and I had been in sporadic communication with him for years, and most recently emailed him about a test amplifier setup he had made decades ago to test the performance of output transformers. So with a sad heart I will continue on with making a somewhat similar test amplifier that hopefully can apply an acceptably low distortion sinewave to an OPT, but with sufficiently high signal voltage to emulate up to about 15W in to a 10kohm PP OPT in a class A amplifier, and use a modern soundcard and software tool to characterise the frequency response and distortion of such an OPT. I'm piggy-backing on what Patrick seems to have prepared, which was a pair of PF amps using 6CM5 in triode-mode, and with sufficient feedback to achieve a stable test bandwidth from about 20Hz to upward of 1Mhz, and at low distortion (eg. circa 0.1%).
As shown in the diagram above, the OPT DUT is driven by the pair of PF amps in a balanced configuration with the B+ (CT) primary winding node of the OPT grounded, such that each PF amp is loaded by just half the PP primary winding. In addition each amp has a resistor inserted between the PF coupling cap and the OPT primary anode tap so as to be equivalent to an output stage driving tube Ra (for the Williamson the test originally used 1.25k to be equivalent to the KT66 anode output resistance). The remainder of the test jig is already set up and has been used for OPT testing at low signal voltage (as per the thread link above).
I'm not aiming for each amp to achieve a 1Mhz top end bandwidth for a number of reasons, but as this is a test setup I do need each amp to aim for as low a phase shift as practical down at the 20Hz end, and likely going up through 100kHz, as well as negligible amplitude change. As part of a test rig using modern software, any phase shift of the test rig (that will include the PF amps, but not the OPT DUT) can be automatically 'calibrated out' by a loopback test, leaving just the phase response of the OPT being tested in the measurement.
The output power target is to get close to 15W in to a 10kPP OPT that has a matched secondary resistive loading. Given each PF amp is driving only half the primary, that implies a 2k5 load on each amp. But each PF amp is also driving the OPT through an additional series resistance of circa 1.25k, to make a total PF amp loading of 3.75k. 15W into a 2.5k load would indicate a signal swing of 275Vpk, but that increases to 375Vpk at the PF amp output due to the added series 1.25k.
The 6CM5 was and is both common and cheap here in OZ, and many have used it for audio applications including Patrick who ran it in triode mode at up to 375V Vak idle, and appears to have used it in his custom test amp. I have a large batch of them so initially for this application I will use them rather than the likes of 6L6GC etc that I have fewer of, but I can foresee that the 6CM5 is likely not going to achieve 15W where I want it, so this test jig may have to graduate over to 6L6GC for Rev 2 (if I get that far). The 6CM5 in triode mode has an Ra of circa 750 ohm, and I can easily use 2 in parallel.
To keep phase shift as low as practical at a 20Hz low frequency end each PF amp output is likely to need circa 100uF of coupling cap. That is easy to achieve with e-caps, although I have sufficient metallized poly caps with at least 500Vdc rating to integrate in with the e-caps if needed.
Each main PF choke needs to be at least 30H to allow operation down to 20Hz, and preferably around 50-60H. Although that choke can be a series connection of whatever chokes are available, each choke needs to have a suitably low DCR/Henry ratio along with a high enough Vac and DC current capability. I can presently get to 30H, but need to seek out some more boat anchors.
This is just a test amp so will be nothing pretty and will use a large derelict amp chassis and I have a range of PT's to choose from. An aspect of this test rig is that the two PF amps will draw opposite phase signal currents from a common B+ supply, so the effective B+ load is going to be fairly constant over the range of test signal levels applied to a test OPT. Also I can arrange heater power and sockets for parallel 6CM5 to try and reduce effective Ra and hence move the main PF R-L corner frequency down as far as practical to reduce phase shift at 20Hz.
This will be my first foray in to PF amps so I have been trying to do sufficient background reading to confirm that using a PF amp in this test setup is worthwhile starting, and so far I can't rationalise an alternative way to achieve the OPT testing I am targeting. So I will continue on with preparations and get a draft schematic prepared and start to appreciate what performance can be achieved with what I've got to hand.
Ciao, Tim
