As it looks right now a full set of PCBs will be $49 for twisted pear green 2oz copper boards. 🙂 That is 4 boards total 2 x PS and 2 x pre. I am getting nicer PCBs than usual since this circuit is worthy. 🙂
Cheers!
Russ
Cheers!
Russ
Current
Dear Steen,
What is current on the "+" and "-" rail pre channel ?
I still find problem in buying the "Volume Pot".
Thanks !
Thomas
Dear Steen,
What is current on the "+" and "-" rail pre channel ?
I still find problem in buying the "Volume Pot".
Thanks !
Thomas
Hi Thomas,
They do have the SMD decks in stock. (10K) They plan on having a new batch of boards made for normal resistors in January. Then you could solder your own. Alternatively, you can use 2 normal stereo pots, one for each channel, for full balanced operation.
With the added benefit of being able to adjust the balance🙂
Steen🙂
I didnt measure that yet, but I will, and post the result here.
Did you contact the shop I linked to earlier? I just emailed with them.
They do have the SMD decks in stock. (10K) They plan on having a new batch of boards made for normal resistors in January. Then you could solder your own. Alternatively, you can use 2 normal stereo pots, one for each channel, for full balanced operation.
With the added benefit of being able to adjust the balance🙂
Steen🙂
I couldnt resist, building two of the Twisted supplies🙂 I was a bit curious about how the preamp would sound with the right supply.
In one word, marvellous😎 Its a very, very pleasant sound, this preamp delivers. Ofcourse I didnt listen to it for very long yet, but the immediate impression is absolutely positive😎 The gain is not quite as much as in my standard BosoZ, but it drives the poweramp to full output without trouble. I blame the lesser gain on the cascoding, not sure though? This has more or less been a "plug it in and play" excperience🙂 It all just worked, right away. I made 2 supplies and hooked them up in dualmono config.
Overall tonal balance is quite good and the soundstage is also very good🙂 I am a bit puzzled that this preamp is so quiet. I wasn't excactly taking care with leads and layout, but its deadquiet🙂 I just used the parts I had, generally the electrolytics in the supplies are smaller than suggested. I can hear no ill effect from that😉 I gather it has something to do with a good layout of the boards, together with some other things.
Well, I am off to listen to a couple of cd's😀
Steen🙂
In one word, marvellous😎 Its a very, very pleasant sound, this preamp delivers. Ofcourse I didnt listen to it for very long yet, but the immediate impression is absolutely positive😎 The gain is not quite as much as in my standard BosoZ, but it drives the poweramp to full output without trouble. I blame the lesser gain on the cascoding, not sure though? This has more or less been a "plug it in and play" excperience🙂 It all just worked, right away. I made 2 supplies and hooked them up in dualmono config.
Overall tonal balance is quite good and the soundstage is also very good🙂 I am a bit puzzled that this preamp is so quiet. I wasn't excactly taking care with leads and layout, but its deadquiet🙂 I just used the parts I had, generally the electrolytics in the supplies are smaller than suggested. I can hear no ill effect from that😉 I gather it has something to do with a good layout of the boards, together with some other things.
Well, I am off to listen to a couple of cd's😀
Steen🙂
Attachments
Etching my own boards
Steenoe-
You etched your own boards for this preamp. I would like to do the same but I only know how to do the toner transfer from a black and white file (eg, pdf). If such a file has been posted in this thread, I've missed it.
Could you point me to the file you used or point me in the direction to produce the needed file? BTW, I would like to make both main board and PSU boards.
I am perfectly willing to buy boards from Russ, but I enjoy making boards as well.
Thanks,
SteveA
Steenoe-
You etched your own boards for this preamp. I would like to do the same but I only know how to do the toner transfer from a black and white file (eg, pdf). If such a file has been posted in this thread, I've missed it.
Could you point me to the file you used or point me in the direction to produce the needed file? BTW, I would like to make both main board and PSU boards.
I am perfectly willing to buy boards from Russ, but I enjoy making boards as well.
Thanks,
SteveA
Hi Steve,
I gave Steen the PDFs so he could beta test. I do plan on releasing the PDFs to everyone but I would like to wait until I have sold the first batch of boards, as I absolutely have to make my money back or my wife will kill me. 🙂
Cheers!
Russ
I gave Steen the PDFs so he could beta test. I do plan on releasing the PDFs to everyone but I would like to wait until I have sold the first batch of boards, as I absolutely have to make my money back or my wife will kill me. 🙂
Cheers!
Russ
Russ White said:
Russ-
I understand completely!!! To that end I will probably buy a set of boards as well.
Thanks and Happy Holidays
SteveA
Just a few more practical observations. The preamp has been running for about 3 hours. The top is warm, not hot, but a good handwarm😉 There is ventholes at the rear of the lid, and the heatsinks I use are rated 2 c/w. I recommend to use a chassis with ventholes and fairly big sinks. You might be able to use sinks a bit smaller than mine though. See picture a little longer back in the thread.
Best of all, the music still sounds tremendously good🙂
Steen🙂
Best of all, the music still sounds tremendously good🙂
Steen🙂
I was thinking about stocking 1.5" pieces of this heatsink. That should be about 3C/W. Could go to 2" if needed, but I doubt it. I have some of this on hand, so I can try out a 1.5" piece to see how it goes.
Incidently, the base of these is nice and thick, so it's easy to drill/tap into it for use as case edge, that way it can protrude outside the case.
Incidently, the base of these is nice and thick, so it's easy to drill/tap into it for use as case edge, that way it can protrude outside the case.
Brian, I think those would do a great job🙂 Its a good idea to use the sinks as the sides of the chassis. The 2 boards including heatsinks, takes up a lot of space. Think about it: 2 trafos, 2 psuboards, 2 preampboards with heatsinks, volumecontrol with 4 decks and inputselctor. the chassis is pretty quickly crowded. Your suggestion would help making a nice layout of the inside.
Steen😎
Steen😎
When I built mine, I used an all aluminum chassis from Lansing Enclosures, one standard rack width by two rack heigt by 12" depth, and mounted all the FET's to the bottom panel of the chassis. I did mine with a dual mono supply, and there is little to no room left in the chassis by the time all the connectors, switches, circuit boards etc... were in place. The chassis makes a great heat sink, and even with poor ventillation, it never get more than warm to the touch.
Brian, a 1.5" section of those sinks should work marvelously. Nice find!
Cheers,
Terry
Brian, a 1.5" section of those sinks should work marvelously. Nice find!
Cheers,
Terry
Okay, the pre-order page is up on the web site. I will get the kit BOM completed with all actual parts by the end of the week.
Transformer
Hi guys,
OK, I was looking for trafos for this little wonder and decided nothing I found was really what I wanted, so I contacted Avel to see about getting a batch of custom toroids made for Twisted Pear.
Here are the specs:
Audio Grade
Pri: 115v x 2 50/60Hz
Sec1 to Sec 4
20v @ 0.5A rms
Polyester Tape Finish
Mounting dish, 2 pads
dims: 2.8" x 1.4" approx
weight: 1.2# approx
So its a 115/230V primary 50/60hz with 4 x 20V secondaries at .5A each.
For this amp we would wire three secondaries in series for the positive rail and use the other for negative.
That toroid should cost right around $50 each.
What do you think? Sure would be convenient. 🙂
If there is enough interest we could offer these to go with the PCBs/Kits.
Cheers!
Russ
Hi guys,
OK, I was looking for trafos for this little wonder and decided nothing I found was really what I wanted, so I contacted Avel to see about getting a batch of custom toroids made for Twisted Pear.
Here are the specs:
Audio Grade
Pri: 115v x 2 50/60Hz
Sec1 to Sec 4
20v @ 0.5A rms
Polyester Tape Finish
Mounting dish, 2 pads
dims: 2.8" x 1.4" approx
weight: 1.2# approx
So its a 115/230V primary 50/60hz with 4 x 20V secondaries at .5A each.
For this amp we would wire three secondaries in series for the positive rail and use the other for negative.
That toroid should cost right around $50 each.
What do you think? Sure would be convenient. 🙂
If there is enough interest we could offer these to go with the PCBs/Kits.
Cheers!
Russ
Pay with Moneyorder?
I went to order the boards and notice that payment is via paypal.
I don't want to re-open my paypal account, but I can send a money order. Let me if this works and to whom I should send the MO.
Vinay
I went to order the boards and notice that payment is via paypal.
I don't want to re-open my paypal account, but I can send a money order. Let me if this works and to whom I should send the MO.
Vinay
Re: Transformer
Russ,
I have a cheaper option. Mine were already in the closet, so they were free, or close to it. It involves using two transformers.
These are the mini transformers from Digikey. The positive is a 22/22, 50 watt and the negative is a 7/7 30 watt. Connecting the two outputs in series this will give 68 - 70 dc raw, and 23 - 24 for the negative supply. The two are around 35.00 for the pair.
The circuit should draw somewhere around 300 ma total, so this combo is fine.
Feeding the power supply with 60 volt + and 20- ac will give you somewhere around 90 - 95 volts and -30 - 33 volts. The positive supply will be dumping a lot of power.
Those Talema brand transformers from Digikey usually work out at dc voltage of 1.5 - 1.6 times the ac rating. The voltage rating is a full power, so it is a little higher when only loaded at 25 - 30 %.
I have a 18/18 in my linestage that is idling at 31 volts per rail, the one in the Borebely phono is putting out 29.2 with standard SIP rectifiers. It would be close to 30 volts at 150 ma if better rectifiers were used.
George
Russ White said:
Russ,
I have a cheaper option. Mine were already in the closet, so they were free, or close to it. It involves using two transformers.
These are the mini transformers from Digikey. The positive is a 22/22, 50 watt and the negative is a 7/7 30 watt. Connecting the two outputs in series this will give 68 - 70 dc raw, and 23 - 24 for the negative supply. The two are around 35.00 for the pair.
The circuit should draw somewhere around 300 ma total, so this combo is fine.
Feeding the power supply with 60 volt + and 20- ac will give you somewhere around 90 - 95 volts and -30 - 33 volts. The positive supply will be dumping a lot of power.
Those Talema brand transformers from Digikey usually work out at dc voltage of 1.5 - 1.6 times the ac rating. The voltage rating is a full power, so it is a little higher when only loaded at 25 - 30 %.
I have a 18/18 in my linestage that is idling at 31 volts per rail, the one in the Borebely phono is putting out 29.2 with standard SIP rectifiers. It would be close to 30 volts at 150 ma if better rectifiers were used.
George
Thanks George. 🙂
I think the PS calls for 70VDC on the positive rail, so I wonder is the drop is sufficient with the trafos you suggest. Certainly my suggestion is probably too high, but I have not ordered them yet so there is still hope. 🙂
I wonder is something like a dual secondary toroid with 55V and 18V would be better.
I have a soft spot for toroids. 🙂
Cheers!
Russ
I think the PS calls for 70VDC on the positive rail, so I wonder is the drop is sufficient with the trafos you suggest. Certainly my suggestion is probably too high, but I have not ordered them yet so there is still hope. 🙂
I wonder is something like a dual secondary toroid with 55V and 18V would be better.
I have a soft spot for toroids. 🙂
Cheers!
Russ
Terry, did you measure the current draw on the positive and negative rail? I forgot to, while the lid was off. The way this preamp sounds; doesnt make me feel like taking it off again right away😀
Those 4x20v trafos sounds like a good idea. Very flexible and usefull unit🙂
Steen🙂
Those 4x20v trafos sounds like a good idea. Very flexible and usefull unit🙂
Steen🙂
Why not make it 4x18V instead then? Much more flexible and would work for dual-mono GCs as well 😀Russ White said:
/U.
Not a bad idea, but the toroid I had in mind is only capable of .5A per secondary, is more than enough for this pre, but not really enough for a GC.Nisbeth said: