For Sale GZLOZone preamp
For sale is a GZLOZone PRT-01A populated preamp board with tubes and power transformer for sale. Just add RCA jacks and volume pot. I don't have any technical info as this was given to me by a friend. I will ship to you for $30 including shipping, most likely USPS priority mail flat rate box, CONUS only.
modeling a loudspeaker using transfer matrices
- By parallelpen
- Software Tools
- 12 Replies
Hi everyone,
I am trying to make my own simulating tool using GNU Octave and transfer matrices methode. I am encountering difficulties in validating my simple model (infinite baffle) because it does not match hornresp results. i think i am not that far from a correct model but not here yet. as you can see phase and SPL are not the same as hornresp.
below is the code with some comments. Note that i do not think problem come from my radiatoin impedance since i used this function for analytical modeling and results mached hornresp with my analytical model.
I am trying to make my own simulating tool using GNU Octave and transfer matrices methode. I am encountering difficulties in validating my simple model (infinite baffle) because it does not match hornresp results. i think i am not that far from a correct model but not here yet. as you can see phase and SPL are not the same as hornresp.
below is the code with some comments. Note that i do not think problem come from my radiatoin impedance since i used this function for analytical modeling and results mached hornresp with my analytical model.
Code:
clear all; close all; clc;
[c, rho, P, P_ref, Air_Imp, f, w] = Generals(); % initialise constantes and frequenies
wc = w / c; % wave number
driver = 'RCF_MB15N405.csv'; % Selecting driver
r = 1; % Distance to from the source
eg = 2.83; % Input voltage
% Thiele/Small parameters
[Sd, fs, Vas, Qms, Bl, Re, Le, Xmax, Mms, Qts, Qes, Rms, n, dr] = TS_extract(driver, 1);
Cms = Vas / (rho * c^2 * Sd^2) % Calculating mechanical compliance
Pg=eg*Bl/(Sd*Re);
mas=rho*Sd;
% Radiation impedance uing bessel and struve functions choose
[zar,zmr]=RadImpC(Sd);
% Loop for each frequency
for k = 1:length(w)
% Transfer matrices for sub domains
tre(:, :, k) = [1, Re; 0, 1]; % voice coil resistance
tle(:, :, k) = [1, 1i*w(k)*Le; 0, 1]; % Inductance
tem(:, :, k) = [0, Bl; 1/Bl, 0]; % gyrator
tmm(:, :, k) = [1, 1i*w(k)*Mms; 0, 1]; % Mobil mass
tcm(:, :, k) = [1, 1/(1i*w(k)*Cms); 0, 1]; % Compliance
trm(:, :, k) = [1, Rms; 0, 1]; % mechanic losses
% Electromechanic chain
tdr(:, :, k) = tre(:, :, k) * tem(:, :, k) * tmm(:, :, k) * tcm(:, :, k) * trm(:, :, k);
% Calculating Iin [A] electrical current from the source from electro-mechanic
% matrix [A,B ; C,D]
t12 = tdr(1,2,k); % A
t22 = tdr(2,2,k); % B
zin = t12 / t22; % Impedance seen from source
ein = eg; % Input voltage
iin = ein / zin; % Input current
In = [ein; iin];
% Acoustic domain
tma(:, :, k) = [Sd, 0; 0, 1/Sd]; % Tranformer
tza(:, :, k) = [1, zar(k); 0, 1]; % Radiation Impedance
% Complete chain from eletrical domain to acoustical domain
Tt(:, :, k) = tre(:, :, k) * tem(:, :, k) * tmm(:, :, k) * tcm(:, :, k) * trm(:, :, k) * tma(:, :, k) * tza(:, :, k);
Ttinv = inv(Tt(:, :, k)); % Inverting matrix
Pu = Ttinv * In; % Calculating results
% Pression (pout) et vitesse acoustique (uout)
pout(k) = Pu(1); % Acoustic pressure at Sd
uout(k) = Pu(2); % Acoustic volume velocity
end
Pa = pout ./ (4 * pi * r); % Acoustic pressure at 1 [m] from the Sd
SPL = 20 * log10(abs(Pa)/ 20e-6); % Decibel SPL
G=1i.*w.*mas.*uout./Pg; % system gain
Phase_deg = unwrap(angle(G)) * 180/pi; % Phase
[fh,o,ph]=hornrespcsv("ibn4050.csv");
figure(1)
semilogx(f, SPL, 'LineWidth', 1.5, fh,o,'LineWidth',1.5);
xlabel('Frequencies (Hz)');
ylabel('SPL');
title(['SPL response']);
grid on;
figure(2)
semilogx(f, Phase_deg, 'LineWidth', 1.5,fh,ph,'LineWidth', 1.5);
xlabel('Frequencies (Hz)');
ylabel('Phase');
title(['Phase']);
grid on;
For Sale 2 pairs of line output transformers Lundahl LL1517
- By Groundloops
- Swap Meet
- 2 Replies
For sale 2 pairs of line output transformers Lundahl ll1517. Tested, fully working.
€75,00 per pair or €130,00 for both pairs.
€75,00 per pair or €130,00 for both pairs.
For Sale 1 pair of SB Acoustics Satori MW16P-4 mid-woofers (Europe)
- By Groundloops
- Swap Meet
- 3 Replies
1 pair of SB Acoustics Satori MW16P-4 mid-woofers. Used, working perfectly, never operated louder than 90 db/1m.
Make a fair offer ...
Make a fair offer ...
Ground control
- By davidbem
- Solid State
- 17 Replies
I have some ground control problems, but not Space Oddity of David Bowie. That can be a nice song in the background while reading this.
This is not my first amplifier build, so I have some knowledge and have had and solved some ground problems in the past, but this one is killing me.
First picture of amplifier layout:
Normally I build dual transformer/dual psu units. This time I decided to reduce cost and used one 600VA toroid. I have tried some different layouts of wiring, but same result.
1. With nothing connected to inputs the amplifier is absolutely silent.
2. With inputs connected together with cable - each to other, the amplifier is absolutelly silent
3. With inputs connected to source there is noise - bzzzzz. Source is Marantz amplifier with preouts - no issues with other amps.
I tried to change grounds from connector to just one point, a screw in the picture on top of capacitors, same problem.
Tried ground lift with greatz, same problem.
The solving of problem was removing the connection from common ground (the green yellow) to the eart point on top near the big resistor, where the chasis is grounded. You can see now the wire on top of the screw of common ground. If I connect this to chasis earthing point there is noise. On other amplifiers, without this wire I had noise, with this one the oposite.
What is the cause of this and can I just leave it like this. The chasis is grounded to the mains jack, but the amplifier 0V -ground is NOT.
This is not my first amplifier build, so I have some knowledge and have had and solved some ground problems in the past, but this one is killing me.
First picture of amplifier layout:
Normally I build dual transformer/dual psu units. This time I decided to reduce cost and used one 600VA toroid. I have tried some different layouts of wiring, but same result.
1. With nothing connected to inputs the amplifier is absolutely silent.
2. With inputs connected together with cable - each to other, the amplifier is absolutelly silent
3. With inputs connected to source there is noise - bzzzzz. Source is Marantz amplifier with preouts - no issues with other amps.
I tried to change grounds from connector to just one point, a screw in the picture on top of capacitors, same problem.
Tried ground lift with greatz, same problem.
The solving of problem was removing the connection from common ground (the green yellow) to the eart point on top near the big resistor, where the chasis is grounded. You can see now the wire on top of the screw of common ground. If I connect this to chasis earthing point there is noise. On other amplifiers, without this wire I had noise, with this one the oposite.
What is the cause of this and can I just leave it like this. The chasis is grounded to the mains jack, but the amplifier 0V -ground is NOT.
Attachments
For Sale Passive preamplifier. Relay attenuator.
Selling a preamplifier (passive). Control via encoder or remote control.
Four inputs and one output.
A logarithmic attenuator is used as a volume control.
Attenuation -96 dB, adjustment step 1.5 dB, option on Vishay 1% resistors, FUJITSU relay.
A 32 * 8 LED matrix is used for the display.
After switching off, all pre positions (channel, volume) are remembered.
The amplifier has an absolutely neutral sound.
Display brightness adjustment and the ability to completely turn off.
Remote control included. Price $300 plus shipping.
Four inputs and one output.
A logarithmic attenuator is used as a volume control.
Attenuation -96 dB, adjustment step 1.5 dB, option on Vishay 1% resistors, FUJITSU relay.
A 32 * 8 LED matrix is used for the display.
After switching off, all pre positions (channel, volume) are remembered.
The amplifier has an absolutely neutral sound.
Display brightness adjustment and the ability to completely turn off.
Remote control included. Price $300 plus shipping.
Volume Control Relay Attenuator passive preamp
- By serglobo
- Vendor's Bazaar
- 46 Replies
A stepwise volume control is implemented with a set of tiny relays and resistors. In a high-end audio system, a noticable sound improvement over potentiomeneters is obtained, also compared to 'audio grade' potentiometers. Its IR remote control provides convenience over solutions with stepped attenuator rotary switches. The sealed relays will maintain contact quality over a practically endless lifetime. The design represents a audio 'preamplifier' of top-class sonic quality, in a compact and affordable implementation.
The design uses high quality Fujitsu FTR-B4CB4.5Z bistable relays, as well as mil-grade audio grade resistors RN55D, RLR07, CMF55 from Vishay-Dale, which have an excellent reputation in the audio field. The circuit is designed for high-quality audio applications.
The input impedance is constant 10K, 22K, 50K, 100K.
The 1.5 dB adjustment step covers a sound attenuation range of 94.7 dB, 63 steps. By eliminating any active electronics, a very clear and open sound is maintained. There are no clicks when adjusting the volume in the speakers. Encoder for control from the panel.
The IR receiver allows remote control. When the power is turned off, the last volume position is remembered.
The circuit operates from a stabilized voltage source of 5 V.
The input impedance is constant 10K, 22K, 50K, 100K.
Payment is possible via Payoneer or to a bank card. It is also possible to buy on Ebay.
Stereo controller kit (2 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
https://www.ebay.com/itm/267166457170
https://sgaudioua.etsy.com/listing/1798144856
https://sgaudioua.etsy.com/listing/1871270901
Stereo controller kit (2 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
Input selector for 4 stereo channels
https://sgaudioua.etsy.com/listing/1825237975
https://www.ebay.com/itm/267166457170
https://www.ebay.com/itm/266863103276
https://www.ebay.com/itm/266932731942
https://www.ebay.com/itm/267151831175
Stereo controller kit XLR (2 channels XLR), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
Input selector for 4 stereo XLR channels
https://www.ebay.com/itm/267197617946
https://sgaudioua.etsy.com/listing/1824028825
https://sgaudioua.etsy.com/listing/1825237975
https://www.ebay.com/itm/266918250389
https://www.ebay.com/itm/266936692441
Stereo controller kit (8 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
https://www.ebay.com/itm/266863035366
Stereo controller kit (6 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
The design uses high quality Fujitsu FTR-B4CB4.5Z bistable relays, as well as mil-grade audio grade resistors RN55D, RLR07, CMF55 from Vishay-Dale, which have an excellent reputation in the audio field. The circuit is designed for high-quality audio applications.
The input impedance is constant 10K, 22K, 50K, 100K.
The 1.5 dB adjustment step covers a sound attenuation range of 94.7 dB, 63 steps. By eliminating any active electronics, a very clear and open sound is maintained. There are no clicks when adjusting the volume in the speakers. Encoder for control from the panel.
The IR receiver allows remote control. When the power is turned off, the last volume position is remembered.
The circuit operates from a stabilized voltage source of 5 V.
The input impedance is constant 10K, 22K, 50K, 100K.
Payment is possible via Payoneer or to a bank card. It is also possible to buy on Ebay.
Stereo controller kit (2 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
https://www.ebay.com/itm/267166457170
https://sgaudioua.etsy.com/listing/1798144856
https://sgaudioua.etsy.com/listing/1871270901
Stereo controller kit (2 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
Input selector for 4 stereo channels
https://sgaudioua.etsy.com/listing/1825237975
https://www.ebay.com/itm/267166457170
https://www.ebay.com/itm/266863103276
https://www.ebay.com/itm/266932731942
https://www.ebay.com/itm/267151831175
Stereo controller kit XLR (2 channels XLR), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
Input selector for 4 stereo XLR channels
https://www.ebay.com/itm/267197617946
https://sgaudioua.etsy.com/listing/1824028825
https://sgaudioua.etsy.com/listing/1825237975
https://www.ebay.com/itm/266918250389
https://www.ebay.com/itm/266936692441
Stereo controller kit (8 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
https://www.ebay.com/itm/266863035366
Stereo controller kit (6 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
Attachments
Analog Line Level Photo Gallery
- By Mooly
- Analog Line Level
- 35 Replies
This thread is now a Sticky for you all to post pictures of your Analogue Line Level diy efforts and projects.
Please try and keep the thread on topic and take any technical discussions over to either a new discussion thread or the original thread if there is one.
Rega Elicit MK1 system - took unknown damage
- By edomobius
- Solid State
- 1 Replies
Hello to everyone. I'm having troubles with an old Rega Elicit MK1. It sounded so nice and it was a robust system, since it met my grandfather. Actually not himself, but his illness. He's not able to remember things, he probably made a misconnection... so, I thought, that's a bit of a complex repair... and I'm not sure if it's possible... but I'd like to make him listen to his collections again, and here I am.
Diagnosis: The amp was dead, no power. So I opened it, and found blown fuses, and quite some damage.
I took a photo of the incriminated section, which is on the power side of the left channel. Ouch!
Following the schematics I made some basic tests with a multimeter and a transistor tester. I've found and replaced a list of parts that were damaged, which include the finals (2SC2922 and 2SA1216), the BD139 and 140 which were totally blown (T14, T17, T18, T13, T21, T22) as the 100uF capacitor C30, the big resistors R11 and R12 (blown!) as well as R18, R36, and R49, and some zener diodes. T48 on the -39.5V was also tested bad, but with no visible damage.
I remade some tracks that were vapourized (ouch), I tested the other small transistors too (only in the amplification section of the board), and they were all good.
Feeling quite confident I powered on the amplifier, and there was life. Connecting a speaker (the right one) revealed sound! I did a rough impedance test, I swapped the channel, it sounded amazing. hooray! You might think... 🙂
Because after some time... a POP was heard! But the amp was still on, so no fuse was triggered. I power cycled it, giving some time to cool down, thinking it was the thermal protection.
Nevermind, the music played again.
Remember I did the test in mono, because I had only the right speaker at that time. Later inspecting the other speaker (left) I found one woofer's coil stuck upwards, cooked to perfection. Replacement of the woofer done, but the internal connection of the loudspeakers' crossover was not clear to me. The loudspeakers are the Rega XEL. I can provide more detailed information if needed.
Anyway, the first stereo test was made...
Sure enough, after less than 2 minutes, there was the POP disconnection sound, much louder at the left speaker (the one that I repaired), and the sound went mute. Power cycling the system "resetted" the protection (the DC one?? I've read that the thermal protection turns the "Elicit" front LED red, but I'm not sure about more localized protections, if that was a protection at all) but the issue persisted, so I opened it again and found R36 and R49 burned again, on the left channel. Was that for the impedance of the left speaker, the one that was blown and repaired, not being high enough? Was it the crossover's fault, or the amp still has some issues?
And that's where I'm now. I also found a cold solder at LED3. That is to see the +39.5V, and it's the only led that turns on slow and turns off fast. Maybe that was only that solder joint that triggered T25, which caused the pop?
There are some big capacitor which hold a lot of charge, and don't think they'll discharge after days, like I did: you need to discharge them, I learned the hard way 🙂 but when holding charge, the finals show short?? I don't know.
Your help is very much appreciated; I'm absolutely no audio technician or expert, forgive me for the technical mistakes I made, and thank you for your patience reading all of this.
Ciao!
Diagnosis: The amp was dead, no power. So I opened it, and found blown fuses, and quite some damage.
I took a photo of the incriminated section, which is on the power side of the left channel. Ouch!
Following the schematics I made some basic tests with a multimeter and a transistor tester. I've found and replaced a list of parts that were damaged, which include the finals (2SC2922 and 2SA1216), the BD139 and 140 which were totally blown (T14, T17, T18, T13, T21, T22) as the 100uF capacitor C30, the big resistors R11 and R12 (blown!) as well as R18, R36, and R49, and some zener diodes. T48 on the -39.5V was also tested bad, but with no visible damage.
I remade some tracks that were vapourized (ouch), I tested the other small transistors too (only in the amplification section of the board), and they were all good.
Feeling quite confident I powered on the amplifier, and there was life. Connecting a speaker (the right one) revealed sound! I did a rough impedance test, I swapped the channel, it sounded amazing. hooray! You might think... 🙂
Because after some time... a POP was heard! But the amp was still on, so no fuse was triggered. I power cycled it, giving some time to cool down, thinking it was the thermal protection.
Nevermind, the music played again.
Remember I did the test in mono, because I had only the right speaker at that time. Later inspecting the other speaker (left) I found one woofer's coil stuck upwards, cooked to perfection. Replacement of the woofer done, but the internal connection of the loudspeakers' crossover was not clear to me. The loudspeakers are the Rega XEL. I can provide more detailed information if needed.
Anyway, the first stereo test was made...
Sure enough, after less than 2 minutes, there was the POP disconnection sound, much louder at the left speaker (the one that I repaired), and the sound went mute. Power cycling the system "resetted" the protection (the DC one?? I've read that the thermal protection turns the "Elicit" front LED red, but I'm not sure about more localized protections, if that was a protection at all) but the issue persisted, so I opened it again and found R36 and R49 burned again, on the left channel. Was that for the impedance of the left speaker, the one that was blown and repaired, not being high enough? Was it the crossover's fault, or the amp still has some issues?
And that's where I'm now. I also found a cold solder at LED3. That is to see the +39.5V, and it's the only led that turns on slow and turns off fast. Maybe that was only that solder joint that triggered T25, which caused the pop?
There are some big capacitor which hold a lot of charge, and don't think they'll discharge after days, like I did: you need to discharge them, I learned the hard way 🙂 but when holding charge, the finals show short?? I don't know.
Your help is very much appreciated; I'm absolutely no audio technician or expert, forgive me for the technical mistakes I made, and thank you for your patience reading all of this.
Ciao!
Attachments
I built a pair of Linsley-Hood 1969 Class A amps and they sound so good
- By hild
- Solid State
- 17 Replies
Attachments
Caladan by Clayton Shaw DIY
Inspired by New Record Day video about the Caladan by Clayton Shaw, I decided to do it DYI since shipping costs to Japan are ridiculous (and no international deliveries at the moment provided). My MiniDSP serves as an active crossover for two ICEPower 125ASX2 amplifiers. They sound amazing, using a Linkwitz-Riley filter 48db at 1kHz and some gain in the low end, Never thought open baffle speaker can have such a lot of low end, while the speaker membrane is barely moving. The speaker disapear and you feel like in a live concert. This works also for my music with distorted guitars, not only for the high end demo music. Bass guitars sound so real. This is the first day listening to them after waiting 3months for the delivery of the 12inch speaker drivers....I guess no burn in needed. Clayton Shaw chose the perfect drivers.....
Prayers or Thoughts for Winslow Burhoe and his Wife, Please
- The Lounge
- 1 Replies
Winslow Burhoe has had a stroke; tomorrow they will operate to clear a partially blocked carotid artery. Here's a photo from my birthday lunch 10 years ago: Left to Right, My friend Gero, my adult daughter, and Winslow.
Prayers or positive thoughts, please!
I'll update as soon as there is news.
john
Opinions on how to take care of this hum?
- By saabracer23
- Solid State
- 14 Replies
I received a 6 channel headphone amp from a friend of a friend asking me to take a look at it as a couple of channels have hum on them. I figured it wasn’t a power supply thing since only couple channels had the hum on them.
I took a listen and found that channels 1-3 were quiet. Then channel 4 had a very light hum, 5 a bit louder and 6 the loudest. I felt it wasn’t a coincidence that as you get closer to the power transformer the louder the hum gets. Being these three.
It has a single center tapped secondary winding and each side of the winding goes into a 1N4001 and their cathodes are tied together providing a single rail of 30.8V. So at the cathode of one of the diodes I tapped in with one of my power supplies.
With my power supply running the amp it functioned perfectly and not a hint of hum on any of the channels, dead quiet. So this told me it had to be the power transformer. There is a steel sheet barrier, but I used copper tape help seal any opening and create a better shield. First wrapping the power side in kapton for safety.
This really hasn’t helped at all, maybe slightly reduce the hum in channel 4 which was pretty low already, but 5 and 6 are still pretty loud.
Can anything be done?
Dan
I took a listen and found that channels 1-3 were quiet. Then channel 4 had a very light hum, 5 a bit louder and 6 the loudest. I felt it wasn’t a coincidence that as you get closer to the power transformer the louder the hum gets. Being these three.
It has a single center tapped secondary winding and each side of the winding goes into a 1N4001 and their cathodes are tied together providing a single rail of 30.8V. So at the cathode of one of the diodes I tapped in with one of my power supplies.
With my power supply running the amp it functioned perfectly and not a hint of hum on any of the channels, dead quiet. So this told me it had to be the power transformer. There is a steel sheet barrier, but I used copper tape help seal any opening and create a better shield. First wrapping the power side in kapton for safety.
This really hasn’t helped at all, maybe slightly reduce the hum in channel 4 which was pretty low already, but 5 and 6 are still pretty loud.
Can anything be done?
Dan
Amplifier circuit help
- By realuser1312
- Electronic Design
- 4 Replies
I am currently trying to design a portable bluetooth audio DAC, and have made a schematic that I think might work.
I know that the bluetooth wiring works (have tested direct audio from the chip, but not through the amplifying circuit).
I have been getting quite confused on how many capacitors/resistors to use, and what ohms. I want to maintain audio quality/reduce noise, as much as possible.
Am I on the right track, and will the op-amp circuit work? (I haven't tested it on a breadboard, as some of the parts haven't arrived yet).
The raw audio output volume from the bluetooth chip is about half what I would like, so the amplifier circuit should be wired to produce 2x gain.
Everything is powered by a single battery.
Thanks!
I know that the bluetooth wiring works (have tested direct audio from the chip, but not through the amplifying circuit).
I have been getting quite confused on how many capacitors/resistors to use, and what ohms. I want to maintain audio quality/reduce noise, as much as possible.
Am I on the right track, and will the op-amp circuit work? (I haven't tested it on a breadboard, as some of the parts haven't arrived yet).
The raw audio output volume from the bluetooth chip is about half what I would like, so the amplifier circuit should be wired to produce 2x gain.
Everything is powered by a single battery.
Thanks!
Photos of my completed 2-way with Purifi W/M, Beyma AMT, and 2X Passives - Steinway Piano finish
- Multi-Way
- 0 Replies
For more than 20 years I have made myself available to Steinway & Sons, when they had questions that were up my alley. So, when I had a loudspeaker design client who was willing to pay, I asked Steinway's outside contractor for special finishes (such as a grand piano in high-gloss Danube Blue Polyester) to do the final finishes on the Richlite cabinets. The front panel perimeters however, got seven hand-rubbed coats of violin varnish. The rear panels, also Richlite, are held on by Silicon-Bronze boat-building screws. Gotta Luvvit. BTW, it's my LS/5.25.
QUAD current dumping class A output power?
- By hbc
- Solid State
- 154 Replies
I recently encountered a request on another forum as to the suitability of Quad 405 for driving Stax headphones as a Class A amplifier. There seems to be a number of about 10 Watts class A output floating around, based on the quiescent dissipation of the "class A" amp of around 5 watts (which is hopelessly wrong in this circuit). I have long been interested in the circuit, impressionably growing up in the 70's 80's. I dusted off the simulation that I did 10+ years ago, of the 306 circuit. I approximately calculated the class A output into 8 ohms of 100uW of the 306 which has a bias of one diode drop between the basses of the "dumpers".
Unfortunately the thread is in a bit of a backwater of that forum and hasn't been critiqued sufficiently for my satisfaction, of if I am in the right ball park, it is a bit of a controversial claim. So peer review please. I am quite happy for my slightly flippant comment about the bridge inductor filtering out the crossover glitch to be criticised, and I know there is more than just that going on with the bridge feedback, but that's what it looks like.
Cut and paste from "another Forum"
Morning, I too have been fascinated by the current dumping spiel of the 405, and a general lover of pre 90's Quad in general. So much so that I did try and build one when I was young (didn't work) and more recently as a grown up engineer decided to simulate the circuit (of the 306, because the audio is not going through an op-amp). Stable biasing of the class AB amplifier is a problem and the Quad seems to present a neat circumnavigation, hence my curiosity.
Most transistor amplifiers have a class A Vas stage, the 405 / 306 is no exception, except it is a bit beefier and is connected to the output by a resistor of around 47 ohms. The voltage generated across this resistor determines when the current dumpers are turned on. Due to the biasing arrangement that is approximately +- 300mV.
300mV / 47ohms is about 6.4mA.
6.4 mA x 8 Ohms = 51mV
Convert that into RMS about 36mV of class A at the 8 ohm speaker 100uW (if my maths is correct) before current dumping occurs. I don't know what the input impedance of the headphones is but presumably significantly more than 8 ohms and everything works out!!
I have not built or tested a current dumping amp in person, yet, but in my simulation of the 306, the area where the magic happens, in my opinion, is the bridge. The basic current dumping amplifier is a class B (sorry) output stage rescued by feedback, to plaster over the switching discontinuity. Yes the super fast class A amplifier huffs and puffs through its 47 ohm resistor, but the magic happens in the bridge.
The switching discontinuity appears to be filtered out by the inductor. I don't really understand what precisely is going on, but it does the trick. It is a remarkable piece of work IMO, especially considering they didn't have the tools available we have today.
Voltage across the inductor simulating 1KHz 8W.
All comments are for entertainment purposes only.
https://www.hifiwigwam.com/threads/rekindling-interest.124470/post-2529901
Thanks
Unfortunately the thread is in a bit of a backwater of that forum and hasn't been critiqued sufficiently for my satisfaction, of if I am in the right ball park, it is a bit of a controversial claim. So peer review please. I am quite happy for my slightly flippant comment about the bridge inductor filtering out the crossover glitch to be criticised, and I know there is more than just that going on with the bridge feedback, but that's what it looks like.
Cut and paste from "another Forum"
Morning, I too have been fascinated by the current dumping spiel of the 405, and a general lover of pre 90's Quad in general. So much so that I did try and build one when I was young (didn't work) and more recently as a grown up engineer decided to simulate the circuit (of the 306, because the audio is not going through an op-amp). Stable biasing of the class AB amplifier is a problem and the Quad seems to present a neat circumnavigation, hence my curiosity.
Most transistor amplifiers have a class A Vas stage, the 405 / 306 is no exception, except it is a bit beefier and is connected to the output by a resistor of around 47 ohms. The voltage generated across this resistor determines when the current dumpers are turned on. Due to the biasing arrangement that is approximately +- 300mV.
300mV / 47ohms is about 6.4mA.
6.4 mA x 8 Ohms = 51mV
Convert that into RMS about 36mV of class A at the 8 ohm speaker 100uW (if my maths is correct) before current dumping occurs. I don't know what the input impedance of the headphones is but presumably significantly more than 8 ohms and everything works out!!
I have not built or tested a current dumping amp in person, yet, but in my simulation of the 306, the area where the magic happens, in my opinion, is the bridge. The basic current dumping amplifier is a class B (sorry) output stage rescued by feedback, to plaster over the switching discontinuity. Yes the super fast class A amplifier huffs and puffs through its 47 ohm resistor, but the magic happens in the bridge.
The switching discontinuity appears to be filtered out by the inductor. I don't really understand what precisely is going on, but it does the trick. It is a remarkable piece of work IMO, especially considering they didn't have the tools available we have today.
Voltage across the inductor simulating 1KHz 8W.
All comments are for entertainment purposes only.
https://www.hifiwigwam.com/threads/rekindling-interest.124470/post-2529901
Thanks
For Sale Marantz CD 50 player, no-oversampling and tube output
Hi,
I am selling one upraded Marantz CD 50 player.
Is in very good condition and the changes have been made are:
- changed few capacitors from power supply;
- the standard op-amps output stage replaced with tube output stage;
- put in no-oversampling mode;
- changed the decoupling capacitors of the TDA1541 DAC.
The price is 350 euro (shipping included). I can ship only in EU countries.
Please send DM for more details.
I am selling one upraded Marantz CD 50 player.
Is in very good condition and the changes have been made are:
- changed few capacitors from power supply;
- the standard op-amps output stage replaced with tube output stage;
- put in no-oversampling mode;
- changed the decoupling capacitors of the TDA1541 DAC.
The price is 350 euro (shipping included). I can ship only in EU countries.
Please send DM for more details.
Help me with this DSP thing MV silicon BP1048B2 2.1
- By Jipolx
- Digital Line Level
- 28 Replies
Attachments
Bluetooth frankenspeaker with old full range chassis
- By robo_klaus
- Full Range
- 9 Replies
Hi!
I found two old speakers with fullrange chassis. My idea is to build a bluetooth-corner-frankenspeaker out of them. While I don't think they would be exactly HiFi, I thought the typically warm sound with good point-sourcey understandabillity can be achieved. Subjectively they have a certain quality to them and go quite loud, as proven by feedback. Ooops!
I meassured them in their old enclosures and they seem to have some problems:
There is a huge phaseshift when the small cone starts to load at 1kHz, unpleasant harshness caused by the bump around 2,4kHz (?) and uneven hights, which could be caused by my quick meassurement setup.
Good part: despite the issue around 1kHz, phase response is really nice and it seems to me like they only need an EQ around 2,4Hz (-6dB/Q=1 maybe) to get that pleasant warm sound for a kitchen radio.
Next up would be finally soldering my measuring cable for T/S params, designing a BR enclosure out of scrap parts and buying a china bluetooth-dsp-amp board.
One question: is the phaseshift immanent to that kind of speakers?
All the Best! robo-klaus
I found two old speakers with fullrange chassis. My idea is to build a bluetooth-corner-frankenspeaker out of them. While I don't think they would be exactly HiFi, I thought the typically warm sound with good point-sourcey understandabillity can be achieved. Subjectively they have a certain quality to them and go quite loud, as proven by feedback. Ooops!
I meassured them in their old enclosures and they seem to have some problems:
There is a huge phaseshift when the small cone starts to load at 1kHz, unpleasant harshness caused by the bump around 2,4kHz (?) and uneven hights, which could be caused by my quick meassurement setup.
Good part: despite the issue around 1kHz, phase response is really nice and it seems to me like they only need an EQ around 2,4Hz (-6dB/Q=1 maybe) to get that pleasant warm sound for a kitchen radio.
Next up would be finally soldering my measuring cable for T/S params, designing a BR enclosure out of scrap parts and buying a china bluetooth-dsp-amp board.
One question: is the phaseshift immanent to that kind of speakers?
All the Best! robo-klaus
Finally, an affordable CD Transport: the Shigaclone story
- By Peter Daniel
- Digital Source
- 8276 Replies
Attachments
For Sale Salas DCB1 Hypnotize with hotrodded options
I'm selling a DCB1 board with three current bias options: 1.5, 8 Ohm (Caddock MP930s) and 20 Ohm (Xicon 5W) so you can choose between > 850mA, 200mA or 90mA bias current. In my opinion the higher the bias the better the sound quality.
All parts are very good quality mostly if not all from Mouser
All fets signal and psu are original Toshiba's bought from Mouser, the signal ones are 2SK170GR fets ( > 6mA ) closely matched resulting DC offset which starts at 0mV and settles around -2mV and -3mV for each channel
Psu caps - 10.000uf Nichicon Gold Tune KG, 100uf Elna Silmic II, Wima MKP10
Signal resistors - Dale RN60C precision 0.1 % 50ppm
Soldered with Kester 44 (63/37)
135 euros included shipping worldwide. Paypal for friends
All parts are very good quality mostly if not all from Mouser
All fets signal and psu are original Toshiba's bought from Mouser, the signal ones are 2SK170GR fets ( > 6mA ) closely matched resulting DC offset which starts at 0mV and settles around -2mV and -3mV for each channel
Psu caps - 10.000uf Nichicon Gold Tune KG, 100uf Elna Silmic II, Wima MKP10
Signal resistors - Dale RN60C precision 0.1 % 50ppm
Soldered with Kester 44 (63/37)
135 euros included shipping worldwide. Paypal for friends
