Thanks headrott. The size of the V3 is the same, so everyone could change it without problems
Thanks headrott. The size of the V3 is the same, so everyone could change it without problems
Well, you had to go and say that huh Oliver?
Well, I will have to find the time and collect the parts to install and I will be doing this upgrade. I especially like the soft start feature. Thanks again Oliver.Greg
Hi Crom,
sadly to say, but both I/V (more correct name should be I/U) resistor values 20R or 56R compromise TDA1541 linearity and resolution.
However to detect those problems you need perfect set of your ears, loudspeakers and amplifiers
Value of I/U resistor is possible to calculate from TDA1541A datasheet:
1. "Notes to the characteristics: To ensure no performance losses, permitted output voltage compliance is ±25 mV maximum." - here is P-P values, not RMS.
2. "full scale current: 4 mA (nominal)" - current is negative here.
3. ""zero scale current: 25nA (nominal)"- actually 0 mA.
So there is two ways to calculate maximum correct value of I/U resistor by Ohm law R=U/I :
A. If you have no constant 2mA current injection circuit -
R=[-25mV]/4mA=6.25R
B. If you have constant 2mA current injection circuit -
R=[+-25mV or 50mV P-P]/4mA=12.5R
So, why most of diyers use I/U resistor for TDA1541 in range 20R - 60R ?
It is because of noise issue as well as amplification factor.
Lets take circuit with CCS 2mA injection, so we have signal of U RMS=0.7*25mV=17.5mV, and we need to amplify it to:
1. For CD player output level (2V RMS): K=2000mV/17.5mV - about 114 (even more than 12AX7 in grounded cathode way can provide, not even mention SRPP - half of mu).
2. For level of professional audio (+4dBu, or 1.23V RMS): K=70 (still not achievable with SRPP and 12AX7 tube, but almost here
3. For level of customer audio (-10 dBV or 316 mV RMS): K=18 (easily achievable in SRPP with 12AX7 and almost achievable with medium mu tubes as 6N1P or 6DJ8, etc).
But choosing tubes with medium to high mu, do not forget standing current in SRPP - more standing mA you have, less the output will be taxed for charging capacities of interconnect cables and input of preamplifier.
This is also related with output impedance - as usual medium mu triodes have less plate resistance than high mu triodes, so damping factor of interconnection would be better.
Best wishes
Saulius
So for a complete novice at such things, does this mean, the higher the I/U resistor value (say 56 Ohms) the larger the signal will be, but at the expense of THD?
Yes, you are right.
It depends on tube you use in SRPP and other factors - power supply voltage, current flow per tube, etc. It is possible to calculate impedance by Tubecad program made by John Broskie.
Anyway, you can send me parameters of your SRPP, I will calculate impedance figure for you if you really need it.
Tube type (6N2P, ECC83, etc), Rk and voltage of power supply.
Also Rload (resistor which is loading output capacitor - if you have installed such thing).
There is attached report in PDF for 12AX7, at it's max current 2.5mA, 300V supply.
As you can see Zoutput is quite high - about 30K (if loaded with 1M Rload).
So this setup of SRPP has to be loaded with high input impedance pre-amplifier, at least 100K, better - more than 200K.
Very interesting conversation on impedence guys - reading with interest!
I think the recommended input voltage setting was 150...I am probably demonstrating my ignorance here but seeing as this tube's vmax is much higher, is there any sonic advantage to increasing the voltage?
Zout of SRPP
Hi Crom,
voltage with 300VDC supply for SRPP means about 150VDC per tube, if you look to TubeCAD report I've attached to my previous message, you can see "DC results - V tube".
Low voltages means problems:
1. less anode to cathode voltage means higher plate resistance as well as lower transconductance;
2. low voltage per tube means lower linearity;
3. With only 75 VDC per tube we have limits on anode current flow - 2.5mA (for 12AX7) is not achievable because positive swing of output voltage will be more than voltage across tube - we would have no more A class operation here. Please look two reports attached for 150VDC power supply voltage.
As there is an intention to use this SRPP not only as amplification of voltage stage but also as output stage for DAC unit, low plate resistance is desired (lower Z out) as well as higher standing current (higher slew rate allows faster charge capacitances of interconnecting cables).
Anyway, in my opinion SRPP is not best solution to use it as output stage - it should be calculated and balanced for some certain load impedance.
For better understanding please look at John Broskie article here The Tube CAD Journal: How SRPP Pworks.
Hi Crom,
voltage with 300VDC supply for SRPP means about 150VDC per tube, if you look to TubeCAD report I've attached to my previous message, you can see "DC results - V tube".
Low voltages means problems:
1. less anode to cathode voltage means higher plate resistance as well as lower transconductance;
2. low voltage per tube means lower linearity;
3. With only 75 VDC per tube we have limits on anode current flow - 2.5mA (for 12AX7) is not achievable because positive swing of output voltage will be more than voltage across tube - we would have no more A class operation here. Please look two reports attached for 150VDC power supply voltage.
As there is an intention to use this SRPP not only as amplification of voltage stage but also as output stage for DAC unit, low plate resistance is desired (lower Z out) as well as higher standing current (higher slew rate allows faster charge capacitances of interconnecting cables).
Anyway, in my opinion SRPP is not best solution to use it as output stage - it should be calculated and balanced for some certain load impedance.
For better understanding please look at John Broskie article here The Tube CAD Journal: How SRPP Pworks.
FS: Mundorf Supreme silver/gold/oil 2.2µF
Because of my output cap upgrade to the Duelund CAST caps, my previous Mundorf Supreme silver/gold/oil 2.2µF caps are for sale.
If somebody is interested, please send me a PM.
Best regards,
Oliver
If somebody is interested, please send me a PM.
Best regards,
Oliver
Because of my output cap upgrade to the Duelund CAST caps, my previous Mundorf Supreme silver/gold/oil 2.2µF caps are for sale.
If somebody is interested, please send me a PM.
Best regards,
Oliver
I have just sent you PM.
Best regards
Saulius
Hi
The RK resistors are 200R, I have to assume the tubes are receiving 150V that is whats measured at the PSU output.
The I/V resistors I am using are 32R
I am using the Full Music 12AX7 tubes, as to the RLoad I don't think there is such a think in this setup.
Last edited:
Hi DQ828,
your setup is quite OK - please look attached report from TubeCAD.
Standing current is about 1.5mA - normal for 12AX7, Zout is same level as 300VDC supply - about 30K.
30K Zout looks too high for me but if you use preamplifier or integrated amplifier with high impedance input and good exclusively low capacitance interconnect cables, that should be ok
.What else I can write - if you are happy with sound of your setup, do not look to any figures - it is only waste of time
Hi DQ828,
your setup is quite OK - please look attached report from TubeCAD.
Standing current is about 1.5mA - normal for 12AX7, Zout is same level as 300VDC supply - about 30K.
30K Zout looks too high for me but if you use preamplifier or integrated amplifier with high impedance input and good exclusively low capacitance interconnect cables, that should be ok
What else I can write - if you are happy with sound of your setup, do not look to any figures - it is only waste of time
The TubeIzator is feeding a (2 actually) Linkwitz ASP crossover before the amps & apparently the Input impedance of the ASP's is 10K But as you say they sound fine
. I have noticed that the volume is lower using the Tube output against the IVY.Thank you for doing that.
Would it be worth putting some sort of buffer between the Tubeizator & the ASP's?
Last edited:
But as you say they sound fine
Thank you for doing that.
Would it be worth putting some sort of buffer between the Tubeizator & the ASP's?
Hi DQ828
yes, buffer can fix problem with low damping factor of your connection, as well as can increase capability to drive longer interconnect cables.
As many audiophiles can say -
As result you would have better trebles and 3D image .If talk seriously, you can simply add current buffer after Tubeizator.
But in that case you will add one more capacitor in signal path.
If you have place in your DAC, you can make any of follower, one of such is Aikido cathode follower (ACF, by John Broskie, please look ACF-2 Aikido Cathode Follower Kit.
In ACF buffer you can use any of medium amplification tubes, which are compatible with this PCB.
With such buffer stage you can easily achieve less than 1K Zout, so it can easily drive 10K load.
If necessary to avoid one more capacitor in signal path, I would remove Tubeizator and replace it with SRPP+current buffer stage.
But this idea sounds like offtopic here, in Tubeizator group buy forum
, so for more help you would better PM me.Saulius
Can anyone point me to a wiring diagram that shows me how to wire the output of 2 buffalo IIIse in dual Mono mode to 2 tube-I-zators so that I end up with balanced xlr outputs from the tube-I-zators. I'm sure Pinocchio and a few others have been there before me but I can't for the life of me find one to follow!!
I've been reading the integration guide on the twisted pear site but I'm not getting v far.
Thanks guys,
crom
I've been reading the integration guide on the twisted pear site but I'm not getting v far.
Thanks guys,
crom
Hi Crom,
Here's a picture that will help you. BIII has the same connectors due to compatibility with TPA I/V stage.
Use one Tube-I-Zator per BIII. Use the differential + phase on each side as per my yellow arrows. Let me know if you need more help.
You will also need to experiment with different I/V resistors to find what suits your needs the best soundwise.
Ciao!
Do
Thanks Pinnocchio, that's really helpful!!! ;-)
For anyone else who needs it, I just found this diagram that Oliver posted a while back: http://www.diyaudio.com/forums/atta...tation-buffalo-ii-iii-dualmono_bii-ivyiii.pdf
Soldering iron is at the ready...I'm going in!
For anyone else who needs it, I just found this diagram that Oliver posted a while back: http://www.diyaudio.com/forums/atta...tation-buffalo-ii-iii-dualmono_bii-ivyiii.pdf
Soldering iron is at the ready...I'm going in!
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.