Amen! I'm a musician and there's nothing like playing live gigs. I used to do a lot of piano bars.
But I get a lot of kicks out of writing songs in Garageband with house beats and elaborate string arrangements!
andyjevans, I saw the link you posted in the last post, saying to email ale for the 01A information. I found this link on his site :
01a Preamp Gen2: Build Complete – Bartola Valves
Would this be the best design to build/is this going to be the same thing he sends to me in the email?
01a Preamp Gen2: Build Complete – Bartola Valves
Would this be the best design to build/is this going to be the same thing he sends to me in the email?
That link is fine. When you ask Ale for the Gyrator, ask for the latest version which uses IXTP08N100D as the top device and BSH111BK as the lower device. These replace DN25440 top and BF862 lower, which are also really good. I wouldn't worry if you use those - I do.
Gyrator FET options (More!) – Bartola Valves
Good on you, my friend!!!
How I wish I can play music, or sing !!
But I only can drink
, !!!Story of my life
Good on you, my friend!!!
How I wish I can play music, or sing !!
But I only can drink
Story of my life
There are drinking songs.......
One thing to consider if you use Ale's gyrators, is that the pre-amp is now partly solid state. It may or may not be important to you, of course. And I suppose using Rod's filament regulators could be viewed in a similar light. My 26 (transformer coupled) and 01A (gyrator) both use Coleman regs, BTW.
I can live with some solid state components for the moment, I can always take them out later if I get too neurotic about it. It seems that both the coleman regulators and the gyrator take DC voltage. I'm probably going to keep the gyrator HT voltage regulated with a tube, and maybe tube rectified, as it's easier for me to design that way. How clean does each supply need to be? I see on the schematic that the regulator needs 15V in, I'm probably going to design that around a 12.6V secondary, and just rectify and smooth it. Does anybody have some good links to power supplies?
If you use filament biased 26 tube, -and want to use sufficiently filtered supply- IMHO the 12.6V AC is too low.
I use 10R filament bias resistor and -about- 0.95..0.96 filament current, so this 9.5V + 1.5V heater + 4.5..5V for Rod Coleman (V.4..V.7) regulator requires about 15.5...16V raw supply.
Really it is about 15.6V, because I use -little weak- 15V AC (use more than 2.5A capable transformer!), Graetz with MBR1635 diodes, C-CMC-C-L-C raw supply.
I use 10R filament bias resistor and -about- 0.95..0.96 filament current, so this 9.5V + 1.5V heater + 4.5..5V for Rod Coleman (V.4..V.7) regulator requires about 15.5...16V raw supply.
Really it is about 15.6V, because I use -little weak- 15V AC (use more than 2.5A capable transformer!), Graetz with MBR1635 diodes, C-CMC-C-L-C raw supply.
Don't worry about solid state plus DHTs - it's a marriage made in heaven. Yes, of course use a tube rectifier and also all polypropylene caps in the power supply, and make it choke input if you can with a suitable resistor to ground to achieve critical inductance.
But I cannot stress too strongly the importance of the filament supply in filament bias. The signal goes through the filament supply - they're shared. So treat it like a B+ supply in terms of sophistication. This is more important than a tube regulated B+, which isn't critical since the Gyrator is a good filter in itself. Attached example of PSU for 01A
Attachments
That filament supply seems like it traded proper design and regulation for just a massive capacitor... Which is something I have no problem with .
Just a couple more questions for you, you really seem like you know your stuff.
1: Where do you get your 01A tubes? How important is it to get a matched pair?
3: What is the output impedance of the amp?
2: Where in the schematic should I put the volume pot?
4: How worried should I be about EMI in the filament supply? Is a common-mode choke necessary?
. Just a couple more questions for you, you really seem like you know your stuff.
1: Where do you get your 01A tubes? How important is it to get a matched pair?
3: What is the output impedance of the amp?
2: Where in the schematic should I put the volume pot?
4: How worried should I be about EMI in the filament supply? Is a common-mode choke necessary?
I have bought two pairs of the gyrator, one with the BF862.
It is for fear of the SS and the two capacitors that have slowed me in trying the board.
Instead I have started to play around with difference devices on the lower position with the CCS that I am using to load my tube.
Now that I have heard a very strong recommendation from a musician, I will try using the board with much less fear now.
****
Andy, what preferences would you recommend for 01a tubes ??
At the moment, I still like my VT-25A a touch more than my 26, and I have not tried 01a yet; and may be I should.
Are they cheaper than the 10/VT25/VT25A ??
That filament supply seems like it traded proper design and regulation for just a massive capacitor... Which is something I have no problem with
Just a couple more questions for you, you really seem like you know your stuff.
1: Where do you get your 01A tubes? How important is it to get a matched pair?
3: What is the output impedance of the amp?
2: Where in the schematic should I put the volume pot?
4: How worried should I be about EMI in the filament supply? Is a common-mode choke necessary?
Bear in mind I'm not an electrical engineer - I'm actually a musician and what I know is empirical knowledge from actually building and listening to a large number of DHT designs, then modifying them according to what my ears are telling me. My goal as a musician is to reproduce the clarity and timbre of acoustic instruments so I hear them as I hear them live, or as close to that as possible. It's all about timbre and clarity - I'm not interested in soundstage or "bass slam" or other factors which aren't relevant to me. If you have purely engineering questions I'll leave those to the engineers.
The "proper design" in the filament supply is using choke input, as it also would be in the B+ supply. Chokes do a good job of smoothing, yet this is overlooked and often chokes are left out. If you want to implement regulators as an alternative go ahead. But Rod's regulators already contain circuitry to do this, just like Ale's Gyrator does. By using choke input you are just feeding these existing regulators a smoother supply. I hear an "audible" improvement in smoothness with chokes. By using the word "audible" I'm not saying it's "huge" - it may be small. I'm just saying it's above the threshold of audibility if you listen carefully and are listening specifically for timbre and clarity.
So in terms of your questions, those that I can answer are:
1. I get 01A tubes from the USA, from dealers mostly so I can buy tested and in batches of 10 to 20 so I economise on postage to Europe. I have my private list of less well known dealers which I don't broadcast because I may want to use them again. I select from the stock I have in terms of matching, but this is only a big deal if I'm using DHTs in parallel, like 4P1Ls in the output. If I lived in the USA I'd take my chances and buy a few off eBay if the seller seemed reliable and/or tested the tubes.
2 and 3 - ask Ale Moglia since this concerns his Gyrator design. I don't use a volume pot - all my sources are digital and the volume control is digital at source.
4. Ask Rod Coleman or other builders who have used common mode chokes.
Last edited:
I have bought two pairs of the gyrator, one with the BF862.
It is for fear of the SS and the two capacitors that have slowed me in trying the board.
Instead I have started to play around with difference devices on the lower position with the CCS that I am using to load my tube.
Now that I have heard a very strong recommendation from a musician, I will try using the board with much less fear now.
****
Andy, what preferences would you recommend for 01a tubes ??
At the moment, I still like my VT-25A a touch more than my 26, and I have not tried 01a yet; and may be I should.
Are they cheaper than the 10/VT25/VT25A ??
I have no particular preference for any make of tube. These are tubes from the 1920s and 30s. They just need to be in good condition - they're all nearly 100 years old!! I'm just being realistic here.
10Y is probably a better tube than the 26, though the 26 has its particular strengths like a seductive midrange on female vocals. It can be just a touch "soft" otherwise, though Ale's Gyrator suits it well and brings out the clarity and dynamics. The 01A is thoriated like the 10Y and this seems to add a particular crispness and clarity. Since the 01A is a lot cheaper than the 10Y I worry less about leaving it on all day or all night - I often listen to music as I go to sleep. If you want to fork out money for some 10Ys, it's a good choice of course. These three are the pick of the DHTs to my ears for a line stage. The 10Y and 4P1L are better drivers since they can run more current and voltage. The 4P1L has a little more gain if this is critical in a 2 stage total kind of design. The 4P1L in parallel is my output tube of choice because of the gain - I just use 2 stages. Plus it sounds great in filament bias and I don't want to use any cathode bypass caps.
As for the 2 caps in the Gyrator, I'm happy with Russian teflons. FT-2 or FT-3. FT-2 is fine at line stage voltages.
Last edited:
I bought four 01As (from the US) and although they all work OK, the gain is slightly different in each, so getting a central image is tricky. And I used pretty much Rod's raw filament supply, but with a bridge rectifier and separate 15V transformers. PCB mount transformer 1 x 230 V 1 x 15 Vac 50 VA 3.34 A 85/423 Weiss Elektrotechnik from Conrad Electronic UK It seems to work OK. :
I have a TVC on the output, which has the advantage of attenuating the circuit noise along with the signal. A volume control on the input won't do that.
I have a TVC on the output, which has the advantage of attenuating the circuit noise along with the signal. A volume control on the input won't do that.
Sure! Stack them up in parallel - boldly go where no capacitor has gone before. Explore strange new worlds...... The only issue is space, the final frontier..... (cue whistling Star Trek theme...)
.
Last edited: