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Old 3rd December 2005, 07:31 AM   #1
navin is offline navin  India
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Default EL34 schematic confusion

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.
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Old 3rd December 2005, 01:01 PM   #2
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Hi navin!

What about the Dynavox VR70-e, it is a nice Amp with 4 EL34,
and it sounds great. I'm owner of one, the schematic also looks simple to understand. I found a schematic at:
http://klippklapp-klepp.de/Elektroni...0E/vr-70e.html
Perhaps you could find help there.
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Old 3rd December 2005, 03:04 PM   #3
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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...)
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Old 3rd December 2005, 03:38 PM   #4
Sheldon is offline Sheldon  United States
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Even if you decide you want to build something else, this is a very well documented EL34 project and worth the read:

http://www.lundahl.se/claus_b.html

Sheldon
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Old 3rd December 2005, 05:24 PM   #5
corbato is offline corbato  India
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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.
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Old 3rd December 2005, 06:38 PM   #6
navin is offline navin  India
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Quote:
Originally posted by corbato
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.
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Old 4th December 2005, 04:16 AM   #7
corbato is offline corbato  India
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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
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Old 5th December 2005, 06:53 AM   #8
navin is offline navin  India
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Quote:
Originally posted by corbato

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/ampl...c25wppel34.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

Quote:
Originally posted by corbato

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/Power...um/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.po...ity_dea100.pdf
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Old 5th December 2005, 07:34 AM   #9
navin is offline navin  India
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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.
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Old 5th December 2005, 08:09 AM   #10
navin is offline navin  India
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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.
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