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ECC40 instead of ECC83 rimlock valves build
ECC40 instead of ECC83 rimlock valves build
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Old 10th July 2017, 11:12 PM   #1
VMUNIX is offline VMUNIX  Argentina
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Default ECC40 instead of ECC83 rimlock valves build

Hello forum, I'm thinking of building this but using rimlock complement (EF40, ECC40, EL41/2, EZ40) just for fun I did this exact version once with very good results and since I have the valves and sockets thought of putting them into something "useful"
I know EF40 is EF86 equivalent and the pentode section of the ECL86 is almost the same as the EL41

My question is what would I need modify to fit the ECC40, accordingly to Philips the cathode and overall bias has to be changed (of course it is a completely different tube)
ECC40 instead of ECC83 rimlock valves build



So, do you agree with Philips recommendation ? any comments will be appreciated.
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Old 11th July 2017, 05:45 AM   #2
artosalo is offline artosalo  Finland
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All capacitors should be bigger, some 220nF or more would give better frequency response at bass end.
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Old 11th July 2017, 09:08 AM   #3
Kay Pirinha is offline Kay Pirinha  Germany
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Unfortunately I don't have access to the schematics you posted. It has to be considered that the original ECC83 is a high twin triode, while the ECC40 is low to medium , rather resembling the ECC82/12AU7. If the circuitry relies on the ECC83's high gain, an ECC40 won't fit.

Best regards!
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Old 11th July 2017, 10:20 AM   #4
MagicBus is offline MagicBus  Greece
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There is global nfb. Perhaps the ECC40 lower mu should be taken in mind. ECC40 also will have lower output impedance I think. The EL41 can hold the 1M grid leak resistors according to specs but perhaps there is an opportunity to lower them? Just some thoughts...
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Old 11th July 2017, 11:01 AM   #5
Ketje is offline Ketje  Belgium
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The Philips ECC40 schematic can be the same for ECC83 with the exeption of the difference Ra and Ra'.
They are different because the cathodes don't see a CCS but 39k.
With much grater gain of a ECC83 the difference is much smaller (practically equal).
And Vo/Vi higher ~40x.
Make the capacitos 5x bigger, better low response.
Mona
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Old 11th July 2017, 12:01 PM   #6
DF96 is offline DF96  England
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EL41 have a reputation for drawing grid current and going into thermal runaway, so the grid resistor should be smaller than the datasheet says.

As has been said, the ECC40 (mu=30) is quite different from ECC83 (mu=100).
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Old 12th July 2017, 06:10 PM   #7
VMUNIX is offline VMUNIX  Argentina
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Quote:
Originally Posted by DF96 View Post
EL41 have a reputation for drawing grid current and going into thermal runaway, so the grid resistor should be smaller than the datasheet says.

As has been said, the ECC40 (mu=30) is quite different from ECC83 (mu=100).

DF96, you mean the resistor from grid to ground or the grid stopper, I guess it's the grid grounding what you mean.


I know the difference in gain between each section of the ECC40 and ECC83, but looking at the DC coupled LTP in the Mullard design with 100k in the cathodes and 100k in the plates isn't it that approaching to the "unity gain" similar to concertina phase inverter ? in that case the gain of the tube is not that relevant, I'm not sure.
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Old 12th July 2017, 06:57 PM   #8
Kay Pirinha is offline Kay Pirinha  Germany
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I don't see no Concertina in the schematics you posted. This is a Paraphase inverter. Now let's look at the gain, it is 12 @ B+ 350 Vdc, and compare it to the corresponding ECC83 Paraphase in the Philips datasheet, p. 4. Here we have a gain of 62 - more than five times as much!

Basically, an ECC40 will work as a PI, of course, but it's your decision whether it's reduced gain will suffice or not.

Best regards!

Last edited by Kay Pirinha; 12th July 2017 at 06:58 PM. Reason: typo
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Old 12th July 2017, 09:12 PM   #9
VMUNIX is offline VMUNIX  Argentina
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Quote:
Originally Posted by Kay Pirinha View Post
I don't see no Concertina in the schematics you posted. This is a Paraphase inverter. Now let's look at the gain, it is 12 @ B+ 350 Vdc, and compare it to the corresponding ECC83 Paraphase in the Philips datasheet, p. 4. Here we have a gain of 62 - more than five times as much!

Basically, an ECC40 will work as a PI, of course, but it's your decision whether it's reduced gain will suffice or not.

Best regards!
The mullard schematic has a 100k cathode/anode resistors, more like the second phase inverter in the philips datasheet at 25 Vo/Vi , still that is twice what you get from the ECC40, so I might need to tweak the nfb.
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Old 12th July 2017, 10:01 PM   #10
Ketje is offline Ketje  Belgium
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Quote:
Originally Posted by Kay Pirinha View Post
I don't see no Concertina in the schematics you posted. This is a Paraphase inverter.
No, the right grid is AC- grounded !
Mona
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