DIY Audio Projects Forum

EL34 SE project share.
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Author:  M. Gregg [ 03 Jul 2016, 10:14 ]
Post subject:  Re: EL34 SE project share.

Suncalc wrote:
M. Gregg wrote:
OK as non signal grid stoppers.
It has been my experience that the Allen Bradley CC resistors are incredibly noisy. In low signal conditions it is mostly the characteristic hiss, but it is very prevalent.

A few years ago i measured some "Allen Bradley" resistors (some were probably not brand resistors but from other suppliers) from several sources and they were mostly the same. All very typical old style CC resistors with typical noise profiles. When compared against several different metal films, noise levels were typically about 30dBv higher in the CC types.

I know that there are articles all over the web about how "awesome" AB resistors are supposed to be, but frankly I would never use them in a high fidelity system in any location. Maybe in a guitar amp if I was looking for a retro sound, but for the most part, I leave them for others.


Yes my experience with any carbon resistor has been that they are extremely noisy, that includes the Takman carbon film.
However Takman REX work well in line stage cathode position. As an input resistor the hiss is really bad.
I have them in my Aikido line stage and they open up the sound like no other I have tried including tantalum/dale/or takman REY.

I used to use carbon film in power stages years ago and thought they were very good at the time.

I am going to try the Alan Bradleys in this amp across the speaker terminals.

NB on a different note the Clarity Cap has been quite successful which is a surprise. Initially it made the HF a bit in your face, however its calming down over the last few hours and the detail is getting better.

Just as a reflection. The resistor issue is the inductance issue I have used Mills in the past and I know the sound signature of them.

Metal films can be really bad as well they can make the HF really dirty the small 0.5 watt that Maplin sell are really bad, but the 2 watt are OK.
I don't know what make they are, the best description I can give is the audiophile glare that is talked about. It makes the frequency band sound selective and smears the detail in the audio.

Just for interest the REX carbon in the wrong place sound dull and it has been an interesting roller coaster ride trying them out.
NB Takman mention directionality with the REX in the data sheet<<don't know if its a gimmick or if it has any merit.

I know for a fact that the Takman metal film make equipment sound bright and its a typical MF sound but without the hash.
However they are very good.

Its interesting to note that duelund cast are graphite<<not necessarily the same but its worth a try.

Here is the REX data sheet for a laugh (directional) OK its a gimmick LMAO.
Its not relevant really because this amp uses mainly Tantalum magnetic.
I guess its a bit weird but I always use resistors in the same direction on both channels<<I can't live with the codes being different directions. If I make a mistake it comes out again and gets changed..LOL does it make a difference who knows but its doesn't hurt either.

If I wasn't using tantalum it would be a mix of Kiwame select positions possibly in the PSU and Takman MF for everything else but its a poor substitute. The Takman carbon are only useful in certain places I wouldn't use them to replace other carbon films.

M. Gregg

Author:  M. Gregg [ 05 Jul 2016, 11:54 ]
Post subject:  Re: EL34 SE project share.


Metal film type resistors seem to work best in the 47K PSU feed to the 15uF.

Its interesting after taking out the Kiwame resistors in this position and refitting the MF I am sure there was a change in detail over about an hour the ambient information seemed to improve, it was dull in the first instance. But as we know there are to many variables. There is a slight glare with the MF however it is preferable in this position I'm pretty sure its due to the 10uF clarity cap connection.

Yes it sounds strange but I decided to post it anyway. I'm more concerned that the information for the build is correct.

M. Gregg

Author:  M. Gregg [ 06 Jul 2016, 13:32 ]
Post subject:  Re: EL34 SE project share.

I got itchy fingers so Triode is a bit boring YMMV :D ,

I thought I would change the switch configuration because I'm running ES U/L most of the time.
So the switch now gives ES 150K, ES 390K, U/L 150K.
I found I wasn't using the Triode position ES was better YMMV.
A few picks its running fine.
It took about half an hour, the triode wires are covered with heat shrink so I can modify again if I want to try Triode.
The Allen Bradley resistors work well in the speaker terminal position.
Straight forward switching. :D I will probably try a few more mods.
It gives a quick comparison of the resistor values.

M. Gregg

Author:  mwhouston [ 06 Jul 2016, 23:16 ]
Post subject:  Re: EL34 SE project share.

Why the high voltage blue caps.

Author:  M. Gregg [ 07 Jul 2016, 10:16 ]
Post subject:  Re: EL34 SE project share.

mwhouston wrote:
Why the high voltage blue caps.

Well because they look nice.. :D
PSU decoupling.
I had an audio grade film cap in there and upgraded to the Clarity Cap TC.

Just for clarity as posted on the circuit diagram pic.
So there is an inrush suppressor in series with a small choke. Then there is a stacked high voltage film cap across the 10uF which creates the filter.
TKS SCK-101201MS 120 Ohms 1A NTC Inrush Limiter Thermistor

M. Gregg

Author:  M. Gregg [ 08 Jul 2016, 08:20 ]
Post subject:  Re: EL34 SE project share.

Just for interest,

Decoupling for newbies:

The TC cap info YMMV: (bottom of the page Supplemental Information)

M. Gregg

Author:  M. Gregg [ 09 Jul 2016, 02:27 ]
Post subject:  Re: EL34 SE project share.

Further to the links above,

I thought this was interesting (YMMV)

NB: Quote,
"A wires self inductance can be reduced using multiple isolated wires" <<(Litz)

In reference to ringing R-damp as mentioned is the issue with transient current and recovery.
I like the reference to the serpents LOL there is always a payback or in the words of Dire Straights money for nothing and your chicks for free :D .
In the circuits shown for the amplifier the issues of transient current and recovery can be experimented by substituting a 2.2uF cap in place of the 10uF but both need to be film caps, again ESR and self inductance can be an issue. The two are different not necessarily better etc.

In reference to the wire inductance I have never tried using litz construction in PSU build or if the difference is worth the effort.
The problem again would seem to be a trade off. Current delivery<<>>inductance <<>>ESR<<>>ringing<<>>recovery.
Perhaps R-damp Vs Tube rectifier Volt drop.<<SAG LOL. :|

Bypassing with values of C<<my experience is you can shape an amplifier to the room acoustics but take it somewhere else and it will suck.
Selective bypassing. YMMV.

M. Gregg

Author:  M. Gregg [ 10 Jul 2016, 16:30 ]
Post subject:  Re: EL34 SE project share.

Another test just for fun,

Litz on the choke input and out.
Does it make a difference yes and I could hear a difference with just the input.

I tried litz on the choke input first then the output as well..<<you would think that doing both sides would just give more of the same with just the input done but it doesn't, it sounds like the HF is reduced then with the output done it all cleans up. All quite nuts really :D.
YMMV. I am going to have a listen over the next few days and see/hear what effect there has been or not.
The initial impression is its easier to hear what people are saying.

I will not post anymore of my findings at this point its up to the individual to decide. Hopefully its been of some interest. :)
I will carry on trying different things which is the norm for me. LOL.

NB the next question would be output Tx connections.

M. Gregg

Author:  M. Gregg [ 30 Nov 2016, 14:47 ]
Post subject:  Re: EL34 SE project share.

"Real Sound"

Each to their own its just for interest (Ignore)..(I don't expect anyone to follow this) :D
Its just a pulp fiction read..

For those that may be interested real sound mods.
Red cactus coupling caps.
Green cactus PSU bypass.

Carbon composite with epoxy end fill mod as shown in the picture.
470k, 10K, 22K half watt.
Diode bridge using BA159 with ferrite bead on the cathode X4 and bypassed with high voltage ceramic cap.
Input 1meg grid ground with Carbon film 2 Watt solder type Oyaide ss47.<<really interesting compared to tantalum which sounds pants by comparison.
Lm317T CCS using Ohmite audio WW 5 watt.

Input wire to first triode three wire silver twist/litz. This can be a plait of three cotton covered silver wires..
Solid core choke output wiring with silver plated multi-strand input.
Fuse bypass is now Jupiter red 0.02uF

Output switchable configuration is:
Electron stream using standard 1n4007 U/L using 390K input triode anode load.
You can see the diodes on the rotary switch.
Zener 12V screen grid with 150K anode load on driver.
Pentode with triode driver 150K anode load.

I have also included the Rod Coleman filter. It is implemented with a few changes to match the ES design as described within the thread. It needs very careful implementation..This links to the box marked A in the circuit for the ferrite inductor and soft start + C2/L4 etc, time to move on to other things.. :)

M. Gregg

Author:  M. Gregg [ 30 Nov 2016, 15:31 ]
Post subject:  Re: EL34 SE project share.

Just for fun,

Shocking Blue..

M. Gregg

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