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EL34 schematic confusion

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Too much of a good thing can confuse you.

I started out looking to build a simple 15W triode / 30W Class AB1 pentode PP amplifer.

Class AB1 = because it produces less heat
PP = because SE OPTs are big and heavy

I seem to have found mostly EL34 ckts and am confused as to which I should use.

1. Dynaco with the 7199
2. Tadaki with the 6SL6 and 6SN7
3. Bonavolta/Leak with EF86 and ECC81

other ckts involve

1. 7581 / 6L6GC driven by 12BY7 and a 6CG7 (H/K Citation V)
2. 1624 driven using 6AU6
3. 7591 driven by a 12AT7

any opinions? my skills do not allow me to design a tube amp so I must use a tried and tested simple design.
 
In my opinion, the Dynaco and others with split-load phase inverters have barely adequate drive for pentode mode - triode mode will sufer from driver distortion before the outputs begin to limit. The Citaton V circuit would be my choice, with 6L6 or EL34s. (the fact that I have about 75 12BY7s and 150 6CG7s has NOTHING to do with it...)
 
Hi Navin
1. Dynaco with the 7199
- Don’t bother. Stick to a tube that gives you best options for ‘rolling’. I am not aware of any modern 7199 that you can get easily in India. In anycase 7199 is a cost cutting measure. (MY opinion- pls no flames )

2. Tadaki with the 6SL6 and 6SN7

- What is this? Never seen any references. A Mullard 5/20 clone?

1. 7581 / 6L6GC driven by 12BY7 and a 6CG7 (H/K Citation V)
- Only if you can get the original HK OPT.

2. 1624 driven using 6AU6
- From where do you get the 1624?

any opinions? my skills do not allow me to design a tube amp so I must use a tried and tested simple design.

- Consider the Mullard design. The Eico adaptations are particularly nice. Look at HF87, HF35 or HF22. If you are looking for a modernised Mulllard then look at Clause Byroth EL34 papers at Lundhal homepage.
 
corbato said:
Hi Navin


2. Tadaki with the 6SL6 and 6SN7

- What is this? Never seen any references. A Mullard 5/20 clone?

2. 1624 driven using 6AU6
- From where do you get the 1624?

- Consider the Mullard design. The Eico adaptations are particularly nice. Look at HF87, HF35 or HF22. If you are looking for a modernised Mulllard then look at Clause Byroth EL34 papers at Lundhal homepage.

hey ashok,

long time no see.

Sheldon/Ashok,
The EL34 (5/20 Mullard) I know of uses EF86 and ECC 81 similar to the Leak 20W ckt.

I'll try and get the links of the Tadaki and 1624 amps again. right now I only have the gifs on my hard drive.

Tom,
I like the Citation V partly because of the wide band 12BY7 used. but where does one get the orignal HK OPTs. I tried asking Harman International and they were clueless. I guess I might have to ask Dr. Harmon (if I can get to him) myself :) LOL

Wolfgang,
I lile the ckt you posted as well but i cant find the 6U8/ECF82 here.
 
Hi Navin

Been around :)

The original Mulllard design used EF86>ECC83>EL34>UL Connection.
Its simple, it sounds great and its easy to get stabilised. Improvement would be using Fixed Bias and Triode strapping the EF86. The CB papers at Lundhal will give you full details. It’s quite simple. You can replace the EF86 with a suitable triode such as the ECC83.

This will be your first tube amp. So my recommendation will be to get the basic plot going, then look at options to get the best sound we like.

You have, on hand, an OPT specd at 4K/50watts/180mA. TDSL says you can run a pair of EL34 in Class AB1 with plates at 450v, for PO of 70watts at 5%THD. I have never done this and sound can well be ‘interesting’. This is JFI and you must pore over the EL34 load lines before embarking on a project.

HK OPT’s

For a starter look at the ebay and if lucky be prepared to pay your house mortgage for a pair. I remember reading somewhere that HK iron was made by Freed in NY. Talk to them :)
 
corbato said:

2. Tadaki with the 6SL6 and 6SN7

- What is this? Never seen any references. A Mullard 5/20 clone?

2. 1624 driven using 6AU6
- From where do you get the 1624?

any opinions? my skills do not allow me to design a tube amp so I must use a tried and tested simple design.

- Consider the Mullard design. The Eico adaptations are particularly nice. Look at HF87, HF35 or HF22. If you are looking for a modernised Mulllard then look at Clause Byroth EL34 papers at Lundhal homepage. [/B]

the HF22 uses EF86??

I like the HF87 ckt. uses the ECC83 and 6SN7
http://www.triodeel.com/eicohf87.gif

6SL6 and 6SN7 ckts.
http://ekingsbu.users4.50megs.com/ampEL34.html
http://www.ptsoundlab.com/tubes/amplis/el34/25WPP/blocutc25wppel34.htm
http://www.triodeel.com/acrotrio.gif

and a 12AX7 with a 6SN7
http://www.alphalink.com.au/~cambie/EL34_cct.gif

6AU6 and 1624 amplfier from Tabor
http://www.pacifier.com/~gpimm/Tabor3s.gif

corbato said:

The original Mulllard design used EF86>ECC83>EL34>UL Connection.
Its simple, it sounds great and its easy to get stabilised. Improvement would be using Fixed Bias and Triode strapping the EF86. The CB papers at Lundhal will give you full details. It’s quite simple. You can replace the EF86 with a suitable triode such as the ECC83.

You have, on hand, an OPT specd at 4K/50watts/180mA. TDSL says you can run a pair of EL34 in Class AB1 with plates at 450v, for PO of 70watts at 5%THD.

I am not expecting 70W. I am happy with 15W in triode and 30W in pentode.

using EF86 with ECC83 can we replace teh EF86?
http://www.arrakis.es/~igapop/avantic.htm

using ECC88x2 driver
http://k-amps.8m.com/cgi-bin/i/PowerAmps/Vacuum/PP-1C_a.gif

this looks simple too if we use a SS power supply.
http://www.joeltunnah.com/images/jt_6SN7_6V6_v2.jpg

the marantz 5 and 8 are simple too
http://www.triodeel.com/marantz5.gif
http://www.triodeel.com/marantz8.gif

the amp produces about 70W but can we strip it down to PP instead of PPP and et 35W.
https://schematicheavencom.secure.powweb.com/newamps/londoncity_dea100.pdf
 
of course i would dream of an amp that can be EL34 PPP Pentode and deliver 70W on the sme chassis as a EL34 PP Triode with 15W. but i think this is too ambitious.

1. biasing all those EL34 tubes in a PPP would be crazy unless one uses self bias as used in the prima luna prologue 1/2.

2. the drivers would have to be different.

what do you think of a ckt that uses ECC83 and EL34. Will the ECC83 be too microphonic? will it have enough gain?

thanks again guys. I know I am getting nutty here. just that i need to order the tubes, OPTs, sockets and some passive components from singapore and have only this week left.
 
something like this...
http://www.drtube.com/schematics/ai/ai500-pa.gif

or this
http://www.drtube.com/schematics/ai/ai700-pa.gif
V3 V4 are EL34 and V5-9 are ECC83. It uses 9 tubes for a stereo amp, 4 EL34 and 5 ECC83.

or this...
http://www.drtube.com/schematics/ai/ai800mk3.gif

i'm told the KT88 produces a lot more heat than a EL34 (given the difference in the output power).

what about this.
http://www.plitron.com/PDF/PB/Article/Atcl_9.pdf
it allows me to use PPP for the woofer and PP for the tweeter amp.
 
I can understand why you are all shook up: )

Your aim is to get approx 15 wpc in triode mode or 30 wpc in UL connection. Fine.

Build the HF87 plan. Not that this circuit is something very special. But you can only do as much when the topology is Input Stage > Phase Splitter > Output. So unless we are talking about MOSFET/HYBRID Input/Output or Transformer phase splitting, your topology stays a Mullard or Williamson Clone.

That Poinz schematic is triode strapped. Should sound nice. Basically there is nothing, which can go wrong. The input uses a plan called “SRPP”. Some like it, some don’t like it. My 811A SE amp uses the exact SRPP. You can jolly well omit the top 6SL7 and voila!! what have you now?? The Mulllard design !.

I personally like a pendote such as EF86 or 6SJ7 for the input with 6SN7 Splitter to UL connected EL34.

SO your shopping list could be something like this:

EL34 x 4 (your choice)
6SN7 or ECC82 x 2 (Again your choice)

EF86 x 2 if you are looking at Pentode input (my preference)

Or

6SL7 or ECC83 if going for Triode input (sound very fine indeed)

8 pin octal valve base:
4 for EL34’s
2 for 6SN7’s
2 for 6SL7’s (need just one if sharing the 6SL7 between the channels)

If you are using ECC83/82 and EF86, then you will need 9 pin Noval valve bases.

Then you will need OPT with a primary Ra of between 5k to 6.6k PP. You will need Power transformer, Choke, etc.

If I were you then I would only get the OPT’s. Have you identified what shop your going to buy? Do they have an online business? It will help if folks here can see that.

Some comments on the links you have posted:

using EF86 with ECC83 can we replace teh EF86?
http://www.arrakis.es/~igapop/avantic.htm

this is THE Mulllard application circuit. Do you really need such high sensitivoity if your primary source is CDP? Yes you can replace the EF86. Or you can triode strap it.

using ECC88x2 driver
http://k-amps.8m.com/cgi-bin/i/Powe...uum/PP-1C_a.gif

Look at the input. DO you really need that. It should perform well though.

this looks simple too if we use a SS power supply.
http://www.joeltunnah.com/images/jt_6SN7_6V6_v2.jpg


Uses 6V6. This is simple and should be sweet.

the marantz 5 and 8 are simple too
http://www.triodeel.com/marantz5.gif
http://www.triodeel.com/marantz8.gif

What about the OPT’s?

the amp produces about 70W but can we strip it down to PP instead of PPP and et 35W.
https://schematicheavencom.secure.p...city_dea100.pdf


Grotesque !!

Look this attach. It is as simple as it can ever be. This is the HF87 design. Or look at the Poinz design.

Good luck!
 

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corbato said:
I can understand why you are all shook up: )

Your aim is to get approx 15 wpc in triode mode or 30 wpc in UL connection. Fine.

Build the HF87 plan.
That Poinz schematic is triode strapped. Should sound nice.

I personally like a pendote such as EF86 or 6SJ7 for the input with 6SN7 Splitter to UL connected EL34.

EL34 x 4 (your choice)
6SN7 or ECC82 x 2 (Again your choice)

EF86 x 2 if you are looking at Pentode input (my preference)
Or
6SL7 or ECC83 if going for Triode input (sound very fine indeed)

8 pin octal valve base:
4 for EL34’s
2 for 6SN7’s
2 for 6SL7’s (need just one if sharing the 6SL7 between the channels)

Then you will need OPT with a primary Ra of between 5k to 6.6k PP. If I were you then I would only get the OPT’s. Have you identified what shop your going to buy? Do they have an online business? It will help if folks here can see that.

this looks simple too if we use a SS power supply.
http://www.joeltunnah.com/images/jt_6SN7_6V6_v2.jpg


Uses 6V6. This is simple and should be sweet.

Look this attach. It is as simple as it can ever be. This is the HF87 design. Or look at the Poinz design.

Good luck!

What I am looking for is EL34 Triode - 15W and EL34 Pentode AB1 - 30W.

why EL34? becuase I need 30W for the woofers (they are only 88db) and keeping the same tube for the tweeter gives 15W in triode. a bigger tube (that can give 20-30W in triode) would generate too much heat.

my choices
1. Poinz - 6SL6 and 6SN7 with EL34
2. HIF 87 u posted above using something other than a 12AX7 for input. Maybe a 6SL6 or 6SN7? Any reason you prefer the 12AX7 to the ECC83 for input.
3. Joel Tunah's 6V6 ckt if we can use SS bias.

and what about
http://www.plitron.com/PDF/PB/Article/Atcl_9.pdf
only because it can be configured to run EL34PP and EL34PPP and it's PCB layout is available making soldering so much easier.

the designer is the same Menno Van Der Veen as this other amp below
http://www.mennovanderveen.nl/eng/ul40-s2.html

now i need some more help. using the input tube I am hoping to make a filter. LP for the EL34 Pentode amps and HP for th EL34 Triode amps.

I know I am bugging you but i hope to be ordering the OPTs and tubes by saturday. My Brother in Law in Singapore will help with that.

thanks.
 
Hi Navin

I am attempting to convey that all those schematics- HF87/Poinz/Micky Mouse are following basically the same topology. I used HF87 as an example because the illustration is most simple to understand.

Triode, UL or Pentode is a minor issue. You can do all those with the same OPT (almost all Push Pull and some SE OPT’s have UL Taps). So just go ahead and order the OPT’s. Those are the most critical items and throw the biggest chunk of your budget on them. Have you decided what make OPT you are going to buy? Hammond makes very sensible iron at competitive cost. I am also hearing good reports on James. Then you have Tamura and such. They are supposedly the best but a pair can cost the earth.

OT here but I usually get my OPT’s wound by a small company in Korea. They are expensive then James but very high quality. I don’t wish to jack up their costing by disclosing their name here. Till now I have bought 6 pairs from them. The highest I paid was U$ 500/pair for a massive 10K/120mA/45watts OPT for 845 triode. This is under prototype now.

So relax and order the OPT’s now. Rest we will see when you are back :)

BTW
12AX7 = ECC83 and quite similar to 6SL7
12AU7 = ECC82 ditto 6SN7
 
corbato said:

I am attempting to convey that all those schematics- HF87/Poinz/Micky Mouse are following basically the same topology.

Those are the most critical items and throw the biggest chunk of your budget on them. Have you decided what make OPT you are going to buy? Hammond makes very sensible iron at competitive cost. I am also hearing good reports on James. Then you have Tamura and such. They are supposedly the best but a pair can cost the earth.

OT here but I usually get my OPT’s wound by a small company in Korea...The highest I paid was U$ 500/pair for a massive 10K/120mA/45watts OPT for 845 triode. This is under prototype now.

BTW
12AX7 = ECC83 and quite similar to 6SL7
12AU7 = ECC82 ditto 6SN7

thanks again ashok,

My brother in law who has built his own tube amp says he can source me some nice iron. he is alos getting me the Alps Blue velvet pot.

I found Hammod expensive and have never heard of James, Tamura etc..but have heard of Lundhal. I like Lundhal as they are much lighter than Hammond. Anyway my BIL said to just give my the ckt or the specs of the OPTs and he'll order them for me.

I dont know what the OPTs will cost but I expected on the lines of $200/pr. $400 for 4. I expect that these would be half my amp budget...$100 for the 8 EL34 etc...

Once I can finalise on a ckt and specs of the OPT I would order them. Do you recommend the 6SL7 or the ECC83/12AX7 as the input tube.

Also can one make a 12db/oct filter using 1 tube (like the 6SL7)?

BTW have you read this..
http://www.diyaudio.com/forums/showthread.php?s=&threadid=68896
 
@navin

Wolfgang,
I lile the ckt you posted as well but i cant find the 6U8/ECF82 here.

There are many replacements for that type. Originally used as Chroma Amp & Sync Amp/Splitter in tube type color TV's.

For information purposes, 9AE basing.
Subs for 6U8/ECF82:
6678
7059
7731
8445
6KD8
6AX8
6EA8
6GH8
6BL8
6GJ8 (higher fil current, 600mA)
6LM8
6LN8
6MQ8 (higher fil current, 535mA, weird...)
6MU8 (600mA)

There are 5 and 9 volt versions also.


total 1 ECC88, 1 6SN7 and 2 EL34 per channel.

I like the (Eico) AF Amp/LTP splitter configuration. Since you have an octal there (6SN7) why not use another octal like a 6SL7? shhh ;) , it's closer to a 5751 than a 12AX7. That's what I would do but hey it's your amp!
And yes I have a "bunch" of schematics and circuits I've simmed, I'd be more than happy to post a few or email them to you...

Happy DIY'ing
Wayne :B :D
 
It is a question about microphony. It is not simple to answer. I have done some mesurment with at least 10 brands of ECC83. The result was a relation between the noise and the microphony. More noise implie less microphony. But as you have more noise, the sound is less good, you get less dynamic.

But it is more. They are tubes optimised for the noise and the microphony as the E83CC or E88CC, E188CC and E288CC. They can be very expansive as the E288CC, but if you goal is to have the best result, it is worth to try those tubes, at least for the first stage.

For you first amplifier, the best thing to do is to build something big enough. You can begin with something simple that will work easily, and after, it is easy to try other solutions even if you must change or add some components.
 
A word about the Marshall/Fender phase inverter in Waine's post.
A such circuit, used among other by Marshall and Fender in guitar amplifier is an heresy for me in a such amplifier.

In order to get a good sound in a guitar output stage when you are playing at high level, you must drive this stage with enough power, 1 or 2 watt per tube for a 6L6.
If you look at the Ig1=f(Ua) characteristic, a 6L6 can take some current on the grid. The driver must be able to drive those grids (at least 2 for a PP class B)

A much better, but epansive solution, is to use a triode or a pentode in triode comfiguration with a driver transformator. The circuit is simpler, one tube, one resistor and one capacitor between the cathode and the ground, one transformator (with an air gap).

I get excellent results with an EL84 and 2x6L6 or 807.

The problem for a manufacturer, is at the most expansive Marshall cost less as 100$ to manufacture, inclusive the box, the manual and the tape on the package. They hae to find a way to get a cheap and good enough result.

One more thing. You can get an excellent result with a Marshall/Fender phase inverter in an hifi amplifier, because the output stage will be in class A or AB, and you will not have grid current to drive.

Another way to go with a guitar amplifier can be to use a Marshall/Fender phase inverter and put 2 tubes in cathode follower. But you will not get a so good result as with a transformator, because the circuit and the alimentation will become too complicated.
 
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