My first experience with electronic tubes - Page 4 - UK Vintage Radio Repair and Restoration Discussion Forum

paulsherwin · 27th Feb 2012, 6:18 pm

I don't think I've encountered that arrangement before. It's very unusual, but it should work if you ensure that everything is phased correctly.

I don't think there is any need to use isolating rubber mounts if this amplifier is intended for a normal domestic environment, but it will do no harm to experiment

Miguel Lopez · 27th Feb 2012, 6:35 pm

Yes, it works.

If it's connected in counter-phase, the output will be zero or very, very small. Now I'm analizing how to feedback it.

I thought in rubber washers to avoid microphonic effect in the valves due to main transformer vibrations.

paulsherwin · 27th Feb 2012, 6:42 pm

Microphony should not be a problem at these signal levels. It would be much more significant in a preamplifier connected to a microphone, record player cartridge or tape head.

Miguel Lopez · 6th Mar 2012, 4:20 pm

I have just noticed that two of my three 6P14P are not really 6P14P but EL84 TESLA. They are fine, and I have always preferred TESLA over the Soviet components. Looking the pictures of my "homebrew temporary amplifier" you will notice the diferences.

Soviet valves ussually have a dish for the getter while other valves including TESLA have a ring. Saddly TESLA valves get their marking deleted very easily, as is the case with two of my pentodes. They were retrieved from the audio socket of Soviet TVs, so I thought they were 6P14P.

Maybe this two pictures (downloaded from Internet) can explain better what I'm saying about the diferences

http://www.tubemongerlib.com/gallery...ov+-+Czech.jpg
TESLA EL84

http://www.parts-recycling.com/Metal...-nos-photo.jpg
Soviet 6P14P

Diabolical Artificer · 7th Mar 2012, 10:59 am

Your amplifier is looking good Miguel. The way you've configured your OPT's as Paul says is unusual; clever stuff. I think youve done wonders for saying this is your first valve project and have limited resouces.

Andy.

Miguel Lopez · 7th Mar 2012, 3:53 pm

Thank you Andy, I do my best.

I've been thinking to switch between a 6N2P (ECC83) and a 6N1P (E88CC) to obtain different frequency response. I like the 6N1P (nice flat response), but the 6N2P has wonderful (and powerful) bass. I have not decided anything regarding this....any opinion?

The problem is that the one that is not been used will be consuming power for free, and spending lifetime too

BTW, a jobmate gave me another 6P14P, Soviet for sure, retrieved from an old TV Krim-218 he had abandoned in a corner.

If it is not rainning, I will finish the chassis and the cabinet this weekend.

paulsherwin · 7th Mar 2012, 5:08 pm

Quote:

Originally Posted by Miguel Lopez

I like the 6N1P (nice flat response), but the 6N2P has wonderful (and powerful) bass.

Are you sure about this? The valve type should have no effect on the (audible) frequency response.

The E88CC is a special quality version of an ECC88 and was designed for high speed switching in 1950s valve computers and laboratory equipment. It will certainly work, but won't sound any different. The ECC83 is an audio double triode designed for this application.

I'm not familiar with your Russian equivalents though.

Miguel Lopez · 7th Mar 2012, 5:20 pm

Quote:

Originally Posted by Paulsherwin

Are you sure about this? The valve type should have no effect on the (audible) frequency response.

Definitively. At least to my ears....and to my eyes. I see the speaker moving much more (forward and backward) with the ECC83 equivalent.

6H1P, as said, I feel same amplification for the entire band, good bass, good treble.

6H2P, powerful bass (when I say powerful I mean really POWERFUL), and acceptable treble.

If valves swapping has no effect my ears are wrong.

I can not explain why. Thought you could help me.

paulsherwin · 7th Mar 2012, 5:52 pm

The ECC83 has a higher amplification factor than the ECC88, so it may sound louder. This may mislead you into thinking that the frequency response has changed.

Miguel Lopez · 7th Mar 2012, 5:59 pm

Good point Paul. That is what is possibly hapenning. I have not checked what is the volume level in each case to obtain same power in the speakers, I'll check it out.

After answer you, I thought that if I want to change the frequency response, I only need to switch ON/OFF the C7 capacitor (not shown in my scan, but in the opening post pic http://promka.at.ua/Statti/UMZCh/Lampa/10Vt.jpg). C7 is present in my "amplifying thing" mounting (can't call it amplifier yet)

With C7 it will have more bass and less treble, without C7, trebles will improve.

What do you think?

paulsherwin · 7th Mar 2012, 6:06 pm

C7 will cause the frequency response to roll off. It doesn't affect the bass response directly. A bigger value will mean less treble, and a smaller value (or complete removal) will mean more treble. Feel free to experiment

7th Mar 2012, 7:07 pm

I wouldn't bother with fixed component changes for frequency response, a Baxandall tone control would only take one half of a double triode or a whole one for stereo.

Miguel Lopez · 7th Mar 2012, 7:13 pm

Yep, but that requires a couple of tandem pots, or four identical independent pots. I don't have them.

Well, independent pots I should have several of them, but Soviet pots are............I can not say that word here.

G8HQP Dave · 8th Mar 2012, 12:07 pm

The ECC83 has greater gain. You appear to have a negative feedback loop. More gain could push you nearer oscillation at frequency extremes where phase shift increases. The 'more bass' you hear could be a bass peak due to being on the edge of LF instability.

Miguel Lopez · 23rd Mar 2012, 5:53 pm

It took me some time but finally I could take some pictures of what I have done till now. Any comment welcomed.

I have not wire any part. They are just presented to show how it will look when I finish it (more or less)

jay_oldstuff · 25th Mar 2012, 12:08 am

I'm impressed with your chassis work there.

Jay

Miguel Lopez · 30th Mar 2012, 6:45 pm

Beginning to mount components

Miguel Lopez · 9th Apr 2012, 1:34 pm

Some pictures of the amplifier cabinet and wiring. It is a little mess but I promise to make next one more tidy.

Ed_Dinning · 9th Apr 2012, 4:04 pm

That looks absolutely fine Miguel, you also have some nice looking "C" core transformers in there, were they ex military? This type of transformer is good but expensive,.

Ed

Miguel Lopez · 9th Apr 2012, 5:17 pm

"C" core transformer were the ussual core type in Soviet consumer electronics in the 70s and early 80s. Those in the pictures were retrieved from Krim-218 B/W TV-sets. They are TC-180 mains transformer, and TBK-110 vertical output transformer.

Military electronics also used those type of cores, but I don't have any right now. I used one in the first soldering gun that I made.

27th Feb 2012, 6:18 pm	#61
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: My first experience with electronic tubes I don't think I've encountered that arrangement before. It's very unusual, but it should work if you ensure that everything is phased correctly. I don't think there is any need to use isolating rubber mounts if this amplifier is intended for a normal domestic environment, but it will do no harm to experiment

27th Feb 2012, 6:35 pm	#62
Miguel Lopez Heptode Join Date: Dec 2011 Location: Mayabeque, Cuba Posts: 617	Re: My first experience with electronic tubes Yes, it works. If it's connected in counter-phase, the output will be zero or very, very small. Now I'm analizing how to feedback it. I thought in rubber washers to avoid microphonic effect in the valves due to main transformer vibrations. __________________ When electrons move, things happen. There's nothing you can do that can't be done.

27th Feb 2012, 6:42 pm	#63
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: My first experience with electronic tubes Microphony should not be a problem at these signal levels. It would be much more significant in a preamplifier connected to a microphone, record player cartridge or tape head.

6th Mar 2012, 4:20 pm	#64
Miguel Lopez Heptode Join Date: Dec 2011 Location: Mayabeque, Cuba Posts: 617	Re: My first experience with electronic tubes I have just noticed that two of my three 6P14P are not really 6P14P but EL84 TESLA. They are fine, and I have always preferred TESLA over the Soviet components. Looking the pictures of my "homebrew temporary amplifier" you will notice the diferences. Soviet valves ussually have a dish for the getter while other valves including TESLA have a ring. Saddly TESLA valves get their marking deleted very easily, as is the case with two of my pentodes. They were retrieved from the audio socket of Soviet TVs, so I thought they were 6P14P. Maybe this two pictures (downloaded from Internet) can explain better what I'm saying about the diferences http://www.tubemongerlib.com/gallery...ov+-+Czech.jpg TESLA EL84 http://www.parts-recycling.com/Metal...-nos-photo.jpg Soviet 6P14P __________________ When electrons move, things happen. There's nothing you can do that can't be done.

7th Mar 2012, 10:59 am	#65
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,662	Re: My first experience with electronic tubes Your amplifier is looking good Miguel. The way you've configured your OPT's as Paul says is unusual; clever stuff. I think youve done wonders for saying this is your first valve project and have limited resouces. Andy. __________________ Curiosity hasn't killed this cat...so far.

7th Mar 2012, 3:53 pm	#66
Miguel Lopez Heptode Join Date: Dec 2011 Location: Mayabeque, Cuba Posts: 617	Re: My first experience with electronic tubes Thank you Andy, I do my best. I've been thinking to switch between a 6N2P (ECC83) and a 6N1P (E88CC) to obtain different frequency response. I like the 6N1P (nice flat response), but the 6N2P has wonderful (and powerful) bass. I have not decided anything regarding this....any opinion? The problem is that the one that is not been used will be consuming power for free, and spending lifetime too BTW, a jobmate gave me another 6P14P, Soviet for sure, retrieved from an old TV Krim-218 he had abandoned in a corner. If it is not rainning, I will finish the chassis and the cabinet this weekend. __________________ When electrons move, things happen. There's nothing you can do that can't be done. Last edited by Miguel Lopez; 7th Mar 2012 at 3:59 pm.

7th Mar 2012, 5:52 pm	#69
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: My first experience with electronic tubes The ECC83 has a higher amplification factor than the ECC88, so it may sound louder. This may mislead you into thinking that the frequency response has changed.

7th Mar 2012, 5:59 pm	#70
Miguel Lopez Heptode Join Date: Dec 2011 Location: Mayabeque, Cuba Posts: 617	Re: My first experience with electronic tubes Good point Paul. That is what is possibly hapenning. I have not checked what is the volume level in each case to obtain same power in the speakers, I'll check it out. After answer you, I thought that if I want to change the frequency response, I only need to switch ON/OFF the C7 capacitor (not shown in my scan, but in the opening post pic http://promka.at.ua/Statti/UMZCh/Lampa/10Vt.jpg). C7 is present in my "amplifying thing" mounting (can't call it amplifier yet) With C7 it will have more bass and less treble, without C7, trebles will improve. What do you think? __________________ When electrons move, things happen. There's nothing you can do that can't be done.

7th Mar 2012, 6:06 pm	#71
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: My first experience with electronic tubes C7 will cause the frequency response to roll off. It doesn't affect the bass response directly. A bigger value will mean less treble, and a smaller value (or complete removal) will mean more treble. Feel free to experiment

7th Mar 2012, 7:07 pm	#72
Guest Guest Posts: n/a	Re: My first experience with electronic tubes I wouldn't bother with fixed component changes for frequency response, a Baxandall tone control would only take one half of a double triode or a whole one for stereo.

7th Mar 2012, 7:13 pm	#73
Miguel Lopez Heptode Join Date: Dec 2011 Location: Mayabeque, Cuba Posts: 617	Re: My first experience with electronic tubes Yep, but that requires a couple of tandem pots, or four identical independent pots. I don't have them. Well, independent pots I should have several of them, but Soviet pots are............I can not say that word here. __________________ When electrons move, things happen. There's nothing you can do that can't be done.

8th Mar 2012, 12:07 pm	#74
G8HQP Dave Rest in Peace Join Date: Sep 2008 Location: Solihull, West Midlands, UK. Posts: 4,872	Re: My first experience with electronic tubes The ECC83 has greater gain. You appear to have a negative feedback loop. More gain could push you nearer oscillation at frequency extremes where phase shift increases. The 'more bass' you hear could be a bass peak due to being on the edge of LF instability.

23rd Mar 2012, 5:53 pm	#75
Miguel Lopez Heptode Join Date: Dec 2011 Location: Mayabeque, Cuba Posts: 617	Re: My first experience with electronic tubes It took me some time but finally I could take some pictures of what I have done till now. Any comment welcomed. I have not wire any part. They are just presented to show how it will look when I finish it (more or less) Attached Thumbnails __________________ When electrons move, things happen. There's nothing you can do that can't be done.

25th Mar 2012, 12:08 am	#76
jay_oldstuff Octode Join Date: Jan 2005 Location: Hyde, Greater Manchester, UK. Posts: 1,074	Re: My first experience with electronic tubes I'm impressed with your chassis work there. Jay __________________ The light at the end of the tunnel is probably the headlight of an oncoming train

30th Mar 2012, 6:45 pm	#77
Miguel Lopez Heptode Join Date: Dec 2011 Location: Mayabeque, Cuba Posts: 617	Re: My first experience with electronic tubes Beginning to mount components Attached Thumbnails __________________ When electrons move, things happen. There's nothing you can do that can't be done.

9th Apr 2012, 1:34 pm	#78
Miguel Lopez Heptode Join Date: Dec 2011 Location: Mayabeque, Cuba Posts: 617	Re: My first experience with electronic tubes Some pictures of the amplifier cabinet and wiring. It is a little mess but I promise to make next one more tidy. Attached Thumbnails __________________ When electrons move, things happen. There's nothing you can do that can't be done.

9th Apr 2012, 4:04 pm	#79
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: My first experience with electronic tubes That looks absolutely fine Miguel, you also have some nice looking "C" core transformers in there, were they ex military? This type of transformer is good but expensive,. Ed

9th Apr 2012, 5:17 pm	#80
Miguel Lopez Heptode Join Date: Dec 2011 Location: Mayabeque, Cuba Posts: 617	Re: My first experience with electronic tubes "C" core transformer were the ussual core type in Soviet consumer electronics in the 70s and early 80s. Those in the pictures were retrieved from Krim-218 B/W TV-sets. They are TC-180 mains transformer, and TBK-110 vertical output transformer. Military electronics also used those type of cores, but I don't have any right now. I used one in the first soldering gun that I made. __________________ When electrons move, things happen. There's nothing you can do that can't be done.