Am I right in reading that the B1 has unity gain ?
Have I just built a volume control ?
If the Aleph 4 has a gain of 26dB, how much gain does my pre-amp need for a 2V RMS input.
I'm trying to get the full 100W into 8 Ohms. The B&W DM683s are generally a little lower than the standard 8 Ohms - about 6 Ohms although it varies a lot with frequency.
The Pumpkins at about 10X gain seemed about right but they were very noisy.
The B1 and the Aleph 4 together are completely silent - except of course the music.
Have I just built a volume control ?
If the Aleph 4 has a gain of 26dB, how much gain does my pre-amp need for a 2V RMS input.
I'm trying to get the full 100W into 8 Ohms. The B&W DM683s are generally a little lower than the standard 8 Ohms - about 6 Ohms although it varies a lot with frequency.
The Pumpkins at about 10X gain seemed about right but they were very noisy.
The B1 and the Aleph 4 together are completely silent - except of course the music.
Attachments
Last edited:
Yep. B1 = buffer 1
Well, yes. But one that doesn't have any weird input/output impedance issues, and can drive a good length of cable. But technically, any preamp is a 'volume control'
I think you mean how much gain do you need for a 2v output... And that is dependent of your sources. CD will give 2v, most FM radio will do that, iPod will do lots more from the headphone jack, and a turntable is going to be the wonky one, it's dependent on your cartridge and your phono stage.
That's going to be loud. Very loud. How much input voltage does the Aleph need for full output? (it's in the manual somewhere)
So the question is this - do you have enough 'gain' to drive the speakers loud enough with CD? Remember, the volume knob is going to be a lot more 'turned up' than you are used to.
Pumpkin is thought for F4 ......
Driving it with 26db Aleph 4 is not recommended, at least reduce the gain of Pumpkin to 3 or 4.
And...... It would be fair to write that your Pumping or Shunty build does not work as exspected. Many others did, mine too, works perfect...... no noise etc.
Otherwise you give other people the impression that Pumpkin is not working correct generally.......!
It has a VOLTAGE gain of one. Depending on the load impedance, it may have a fairly high current gain.
Roscoe
If my rusty maths is correct.
Voltage Gain = 20 x Log (Vout/Vin)
28.3V RMS into 8 Ohms is 100Watts.
Therefore the total gain required is 20 x Log (28/2) = 23dB
If the Aleph 4 has a voltage gain of 26dB then it will achieve FULL output with the 2V RMS signal from the CD player. The B1 will do the job.
Voltage Gain = 20 x Log (Vout/Vin)
28.3V RMS into 8 Ohms is 100Watts.
Therefore the total gain required is 20 x Log (28/2) = 23dB
If the Aleph 4 has a voltage gain of 26dB then it will achieve FULL output with the 2V RMS signal from the CD player. The B1 will do the job.
Not yet.
I'm having trouble finding a suitable transformer. 45-0-45 only seems to be available at 160VA which is physically too big.
I'm contemplating 55-0-55 at 120VA which is reasonable from RS.
I'll then construct a simple regulator and try them again.
Whatever, I decide to do I've got to buy a transformer.
ZenMod suggests that the two transformer approach might be the cause of the problem. I can't see how.
I've recycled the case anyway to put the B1 into.
There were so many shorts on the boards through incomplete etching that I'm surprised they work at all.
ZenMod suggests that the two transformer approach might be the cause of the problem. I can't see how.
I've recycled the case anyway to put the B1 into.
There were so many shorts on the boards through incomplete etching that I'm surprised they work at all.
I only built the B1 as I happened to have nearly all the bits in my spares bin.
I only had to buy the J-FETs.
The result has tidied up my DIY lounge and the results are really very pleasing to the ear.
I also used the exercise to add an input selector which had previously meant having to swap cables.
The B1 only has two inputs. (1) the raw input from the CD player and (2) everything else through my AV amplifier.
The rationalle being that I didn't want anything in the signal path from the CD player.
If you look closely you will see that the bracket holding the ALPS pot is actually an old heatsink scrummaged from a rotting TV set.
I only had to buy the J-FETs.
The result has tidied up my DIY lounge and the results are really very pleasing to the ear.
I also used the exercise to add an input selector which had previously meant having to swap cables.
The B1 only has two inputs. (1) the raw input from the CD player and (2) everything else through my AV amplifier.
The rationalle being that I didn't want anything in the signal path from the CD player.
If you look closely you will see that the bracket holding the ALPS pot is actually an old heatsink scrummaged from a rotting TV set.
Attachments
so you have no 2x30V transformer at home?
I can confirm that I have regularly less problems with one transformer serving both channels concerning hum and noise, but maybe I am not experienced enough with grounding.....
So fine that your system is working with B1! So you have a point to relax and time to reflect your next steps.
I have the same situation at the moment, my amp has 24db gain....so I am also looking for a good pre with less gain....... I reduced R5/6 in Pumpkin to a value around 37k and the amplification is lower and it sounds really good...
and I like Pumpkin still more than B1, more dynamics, more action for my ears and chain......Zen once said that I seem to love the distortion of the IRF510 because he showed me how to change to the Toshibas now in BA-3, but I returned to IRF 510...
But you see I am not logical, in BBA-3 I like the Toshibas......
And when I look at my postings of the last years I am often horrified what I did write over the years............. changing opinions.
but as I wrote in many threads BBA-3 is a bit more seducing....
and I am still experimenting to get the gain down let us say to three, I am even willing to introduce feedback again and hope that the good sound will stay....
the next days will show......
But it was always a pleasure....with circuits and people in this forum...
.......take your ride! und forgive us and yourself changing mind....
Must say I agree.
First listening impressions of the B1 against the Pumpkins are that the B1 lacks dynamics. The HF seems to roll off a bit to early too.
I haven't given up on the Pumkins yet.
I'll order a transformer tomorrow and see what I can achieve.
My Pumpkins have a strange "whooshing" noise at start-up. ZenMod has suggested that its down to my choice of components but then cant offer any suggestions as to where to start.
I used good quality components throughout, using his BOM whenever I could.
First listening impressions of the B1 against the Pumpkins are that the B1 lacks dynamics. The HF seems to roll off a bit to early too.
I haven't given up on the Pumkins yet.
I'll order a transformer tomorrow and see what I can achieve.
My Pumpkins have a strange "whooshing" noise at start-up. ZenMod has suggested that its down to my choice of components but then cant offer any suggestions as to where to start.
I used good quality components throughout, using his BOM whenever I could.
thanks for the nice picture!
I also tried passive solutions every time I had a new amp, once more. And they really have some advantages, so they seem to be more detailed and some sounds come more realistic......
but over the time the actives won over the passives...nevertheless I always check back with a simply pot what is my new pre adding or handling in an other way.... is it o.k, or even worse than the passive.
If you can get a TKD pot, either the old laser trimmed ones, or the new with separate resistors, try them! For me they are a big step forward!
I also tried passive solutions every time I had a new amp, once more. And they really have some advantages, so they seem to be more detailed and some sounds come more realistic......
but over the time the actives won over the passives...nevertheless I always check back with a simply pot what is my new pre adding or handling in an other way.... is it o.k, or even worse than the passive.
If you can get a TKD pot, either the old laser trimmed ones, or the new with separate resistors, try them! For me they are a big step forward!
"My Pumpkins have a strange "whooshing" noise at start-up. ZenMod has suggested that its down to my choice of components but then cant offer any suggestions as to where to start."
I suppose the sound is coming of one of the shunties......
and I use only one xformer and one of the simple PSU for both channels .......less problems
I suppose the sound is coming of one of the shunties......
and I use only one xformer and one of the simple PSU for both channels .......less problems
Last edited:
In the loft I've got an old 100VA transformer kit, one that you wind your own secondaries.
I might just try making a 30-0-30 with what I've got.
Should I wind a 25-0-25 and just use massive smoothing caps, or wind 30-0-30 and build a simple regulator.
I've got all the bits its just a case of knocking up a PCB.
I might just try making a 30-0-30 with what I've got.
Should I wind a 25-0-25 and just use massive smoothing caps, or wind 30-0-30 and build a simple regulator.
I've got all the bits its just a case of knocking up a PCB.