Go Back   Home > Forums > >

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

01A question
01A question
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools
Old 14th January 2021, 05:25 PM   #491
gerrittube is offline gerrittube  Netherlands
diyAudio Member
 
Join Date: Jan 2018
Location: Holten
The STF3LN80K5 MOSFET is indeed a great MOSFET for a tube driver stage. It’s a great MOSFET for a concertina too, as many people don’t know yet.

Regards, Gerrit
  Reply With Quote
Old 21st January 2021, 01:50 AM   #492
nashbap is offline nashbap  United States
diyAudio Member
 
Join Date: Jul 2012
Location: New Jersey USA
01A question
Hello Everyone,

I have decided to take the plunge into tubes and build a 01A preamp using Ale's Gyrator and Rod Coleman regs. Would appreciate advice on a few questions:

1)I plan on using one B+ supply to feed both channels with no Salas SSHV2 regs. I also plan on utilizing the B+ supply for powering the Source Follower as outlined in Ale's low gain 01A version 6 schematic. What ma draw should I plan for? If the SF is CCS biased at 10ma and the tube around 5 ma can one assume that the total draw for each channel is under 20ma, considering some losses here and there?
2)Given that I plan on building the PSU in a separate box with a 1 meter umbilical to the amp do I need to use a decoupling cap for the B+ at the entry to the gyrator or at the SF? And if so what value?
3)It looks like most recommend the Russian FT3 0.22uf for the output cap? What brand seems to work best for the gyrator cap?
4)Any suppliers of CX301A that folks are happy with? Do I look for tubes that are claimed to have been matched on the tube tester?

Thanks.

nash
__________________
F5TV3, AVC, BA3b pre, Salas DCG3b, OBL-15, SonyVfet2pair monos, Millett Nutube Bal pre
  Reply With Quote
Old 21st January 2021, 02:04 AM   #493
mcandmar is offline mcandmar  Ireland
diyAudio Member
 
mcandmar's Avatar
 
Join Date: Feb 2012
Location: Dublin
3) Depends on the input impedance of your amplifier. Into a 47k load i settled on .47uf in my build to get the desired low frequency response. Have a play here and see what works for your application RC High-pass Filter Design Tool

I used a K72P Russian Teflon capacitor for the .47uf, and a .1uf FT-2 on the Gyrator board.

4) My advice, buy the cheapest set you can find for building and testing. They are super fragile, i have had a bunch of them die with broken filaments when shipping, and had a couple let go after repeated power on/off's while testing. When you have it all dialled, buy a nice set of matched tubes.
  Reply With Quote
Old 21st January 2021, 07:48 AM   #494
euro21 is offline euro21  Hungary
diyAudio Member
 
Join Date: Sep 2004
Location: Budapest
01A question
1)
Yes, using one B+ is good solution..... if you use CCS or "gyrator" as 01a anode load. These are high PSRR devices.
Else you must to use complex PSU with low ripple and hum.

SF and CCS or gyrator loaded VAS stage practically independent of the B+ voltage (if it as great as B+= anode voltage + swing peek + 30...40V).

2.)
I use there 47uF // 100nF.

3)
I use in these devices teflon FT3 // V-Cap or V-Cap or Duelund.
The order of quality is the same ... but price expands to the sky. :-(
  Reply With Quote
Old 21st January 2021, 08:44 AM   #495
Rod Coleman is offline Rod Coleman  United Kingdom
садовник
diyAudio Member
 
Rod Coleman's Avatar
 
Join Date: Jul 2004
Location: Warwickshire UK
01A question
hi Nash, Any transistor follower (valve follower too, I suspect) needs good supply decoupling.

The decoupling should be right on the drain of the FET, for best control of oscillation risk. The idea is to prevent any part of the supply wiring from thinking about looking inductive enough to form a resonance with stray capacitance.

With FETs, the oscillations can reach 10MHz or more, so a stacked-construction film capacitor is worth seeking out - these have low inductance. 100nF - 220nF.
Add an electrolytic 47-100F.
  Reply With Quote
Old 21st January 2021, 03:08 PM   #496
nashbap is offline nashbap  United States
diyAudio Member
 
Join Date: Jul 2012
Location: New Jersey USA
01A question
Thank you Mark, Bela and Rod for your suggestions.

I took a another look at Ale's 01A version 6. I missed seeing the decoupling caps C1 and C2. My apologies. Rod, I found one stacked film cap thru a Mouser search. Is this appropriate, in // with an electrolyte as suggested?

F612JQ104K250C KEMET | Mouser

Regarding the B+ supply, I was thinking of using this PCB with a MEC. The MEC50 is good for 50ma while the MEC100 for 100ma; which is why I inquired about the maximum current draw from the B+ supply.

MEC Power SUpply

Has anyone used these? Any thoughts?

nash
__________________
F5TV3, AVC, BA3b pre, Salas DCG3b, OBL-15, SonyVfet2pair monos, Millett Nutube Bal pre
  Reply With Quote
Old 21st January 2021, 03:26 PM   #497
Rod Coleman is offline Rod Coleman  United Kingdom
садовник
diyAudio Member
 
Rod Coleman's Avatar
 
Join Date: Jul 2004
Location: Warwickshire UK
01A question
F612JQ104K250C KEMET | Mouser

Yes, that's a stacked-construction part - will work very well.
  Reply With Quote
Old 21st January 2021, 03:30 PM   #498
nashbap is offline nashbap  United States
diyAudio Member
 
Join Date: Jul 2012
Location: New Jersey USA
01A question
Great! Thank you.
__________________
F5TV3, AVC, BA3b pre, Salas DCG3b, OBL-15, SonyVfet2pair monos, Millett Nutube Bal pre
  Reply With Quote
Old 21st January 2021, 07:22 PM   #499
mcandmar is offline mcandmar  Ireland
diyAudio Member
 
mcandmar's Avatar
 
Join Date: Feb 2012
Location: Dublin
Theory question: I am using Ales Gyrator boards and Coleman filament regulators with cathode bias. What is more important to match, bias voltage or plate voltage?
  Reply With Quote
Old 21st January 2021, 08:38 PM   #500
euro21 is offline euro21  Hungary
diyAudio Member
 
Join Date: Sep 2004
Location: Budapest
01A question
Anode voltage and bias voltage determines operating point (Ua, Ia at -Vg) ... at specified tube and at given condition.

If the tube changing (another tube, or aging), the operating point also changing.

There are no two identical operating point of two tubes, but if it not too far -relative to each other-, it's irrelevant.

The important thing is tubes gain -preferably- similarity at near operating points.
  Reply With Quote

Reply


01A questionHide this!Advertise here!
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
6V6 / 6AH4 / 01A (UX201a) juanitox Swap Meet 0 26th May 2013 06:42 PM
01a DHT Preamp mogliaa Tubes / Valves 0 13th May 2012 11:07 AM
01A tube amp Schematic??? jmillerdoc Tubes / Valves 4 29th December 2009 02:39 PM
Can I use a 01A in a headphone amp? sbelyo Headphone Systems 27 28th April 2006 12:33 PM
questions about 01A / 483 pre-amp. RichJones Tubes / Valves 0 11th September 2003 09:46 PM


New To Site? Need Help?

All times are GMT. The time now is 05:33 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Copyright ©1999-2021 diyAudio
Wiki