freestompboxes.org

mat wrote:Btw. I noticed that I did not put two 100R resistors to groud from the heater taps on my SAS build. Are the heaters now 'floating' ? What could be the problem with that ?
Mat

But in your clone the heater of the EF86 is supplied by a voltage regulator as per the schematic, don't we ?

Usually the heater must be referred in some way to GND potential due if we leave that these supply completely "float" this can be a cause of noises.

Can be sufficient to connect to GND one side of the 6,3 v heater winding, in case that we employ a transformer for that purpose. Better than that is to create an artificial center tap using a couple of low value resistors connecting the junction of them to GND.

Bettest is to connect that artificial center tap to some positive voltage of 15 to 40 Vdc to avoid induce noise from the heater to cathode (especially in the first stages of a preamp where the signal is low). That reference voltage usually is produced by a resistive divider taken from the same HV supply of an amp, the heaters remain working in AC but elevated from ground.

So if you already are using to heat the tube a regulator referred to GND, since the op amp supply are taken from the same rectifier, then you're OK.

I'm not in a hurry to get that diagram but I want to know about that preamp, so send it to me when you have time.

Cheers,
Jose

ppluis0 wrote:
But in your clone the heater of the EF86 is supplied by a voltage regulator as per the schematic, don't we ?

No, I used a transformer that has dedicated heater secondaries (AC).

mat wrote:No, I used a transformer that has dedicated heater secondaries (AC).

In that case a couple of 100 ohms resistors tied to GND from each end of the 6,3 v secondary is the first action to take. After that, if you don't notice an improvement, can lift the GND end of these resistors and connect to somewhere with positive voltage, as the 9 Vdc you have to feed the operational for example.

While I was typing this text found on the web the following link from Merlin Blencowe on this theme. Very interesting: http://www.freewebs.com/valvewizard/heater.html

Cheers,
Jose

I'll add the 100R's asap. The pedal is surprisingly quiet (not much noise) but I try with the 100R's. Thanks for the link, interesting reading.

mat wrote:I'll add the 100R's asap.

Please post if you hear any improvement after that mod.

Cheers,
Jose

Will do (little busy at work right now).

Mat

ppluis0 wrote:

mat wrote:I'll add the 100R's asap.

Please post if you hear any improvement after that mod.

Cheers,
Jose

I finally added the 100R's to my build and it did get quieter Thanks Jose

I also finished the other one for my fried. Pics at http://www.flickr.com/photos/fuzzface19 ... 114234737/

It sounds at least as good as the first one. Used a little different parts for this one. Everything worked right away. First I checked the voltages without tube and IC. Then with them and finally did a sound test.

I will give it to my fried tomorrow so I have no time to do sound samples of this one but it sounds very close to the first one.

I have a hand drawn layout if anyone is interested I can post it.

Jose, did You get the preamp schem I sent You earlier ?

mat wrote:I finally added the 100R's to my build and it did get quieter Thanks Jose

I'm glad to read this !!!

mat wrote:I also finished the other one for my fried. Pics at http://www.flickr.com/photos/fuzzface19 ... 114234737/

It sounds at least as good as the first one. Used a little different parts for this one. Everything worked right away. First I checked the voltages without tube and IC. Then with them and finally did a sound test.

Congratulations !!! The unit appeared in your album looks really good and is also a good new that this time you not have suffer major inconvenience to put to work at first try.

mat wrote:I have a hand drawn layout if anyone is interested I can post it.

I think that a tagboard layout is always welcome in this forum

mat wrote:Jose, did You get the preamp schem I sent You earlier ?

Nope... It's a diagram for a Dumble stlyle preamp, as you say in a previous post ?

Please send it to me by pm when you have the time.

Cheers,
Jose

That build looks great Mat. Very clean. What type of enclosure is that?

I really like the Neil Young sounds you got in the demo clip. Very fuzzy! Have you tried this without the clipping diodes, as a clean boost?

This is definitely one pedal you don't want to spill any beer on!

ppluis0 wrote: Congratulations !!! The unit appeared in your album looks really good and is also a good new that this time you not have suffer major inconvenience to put to work at first try.

Thanks Jose

The preamp of my 86Special amp: (http://i073.radikal.ru/1105/17/f4cafc072ab1.jpg). So I would like to use a different pentode from the EF86. I have few EL91 and EL95 tubes but I assume they are only for power amp use ?

Mat

Motter wrote:That build looks great Mat. Very clean. What type of enclosure is that?

I really like the Neil Young sounds you got in the demo clip. Very fuzzy! Have you tried this without the clipping diodes, as a clean boost?

This is definitely one pedal you don't want to spill any beer on!

Thanks Motter!

I haven't tried it without the diodes. Good mod for the future. I also would like to try it without the IC and the diodes, just the EF86 ! Just 1M to ground before the EF86 input cap ?

The high voltage side of the enclosure is closed so You can spill beer on it but not into it

I highly recommend to build this pedal. It is not just a Neil Young in a box. Lots of very cool boost and mild drive sounds can be found there.

Mat

mat wrote:...I would like to use a different pentode from the EF86. I have few EL91 and EL95 tubes but I assume they are only for power amp use ?

Hi Mat,

Thank you for share the schematic of your amp...

The european tubes named with the second letter "L" means that there are used as video or audio output device.

You can employ in the previous schematic any of the tubes you already have: EF93, EF94 or EF95 as these are small signal pentodes and have the same pin assignment (but different of the EF86) and are intechangeable, mantaining the same values of surrounding components.

Cheers,
Jose

Thanks Jose, I'll use the existing EF9x then.

Btw. One thing that made me wonder on the SAS build was that the heater
voltage on the EF86 was 7 volts. Would You think that is to be too much for
the tube ?

Thanks,
Mat

ppluis0 wrote:

mat wrote:...I would like to use a different pentode from the EF86. I have few EL91 and EL95 tubes but I assume they are only for power amp use ?

Hi Mat,

Thank you for share the schematic of your amp...

The european tubes named with the second letter "L" means that there are used as video or audio output device.

You can employ in the previous schematic any of the tubes you already have: EF93, EF94 or EF95 as these are small signal pentodes and have the same pin assignment (but different of the EF86) and are intechangeable, mantaining the same values of surrounding components.

Cheers,
Jose

[quote="mat"]Btw. One thing that made me wonder on the SAS build was that the heater
voltage on the EF86 was 7 volts. Would You think that is to be too much for the tube ? [quote]

Hi Mat,

You can insert a 4,7 ohms 1/2 watt resistor in series with one of the filament pins right at the socket, and that's all...



MODERATORS:

Perhaps is time to tag this thread as "Traced" based on the couple of clones done by Mat, or it's neccesary to read reports of other members assemblies ?

Cheers,
Jose

ppluis0 wrote:You can insert a 4,7 ohms 1/2 watt resistor in series with one of the filament pins right at the socket, and that's all...

Thanks again

Mat

Ok, I installed two 10R 3w resistors in parallel on one heater wire and the voltage dropped to 6V. No increased noise

Thanks again Jose

Mat

mat wrote:Ok, I installed two 10R 3w resistors in parallel on one heater wire and the voltage dropped to 6V. No increased noise

Thanks again Jose

Mat

You're welcome !!!

I'm almost convinced that I begin to know how to deal with vacuum tubes...

Cheers,
Jose

ppluis0 wrote:I'm almost convinced that I begin to know how to deal with vacuum tubes...

So, I found another one of these at Guitar Center for $49!!! new in the box. I'd like to play with it a little. Did anyone ever look inside a Boostasio or comment on whether it would work to remove (or put on a switch) the clipping diodes or to bypass the op-amp?

i also got one of these in guitar center for 49$
i did cut off the clipping diodes, sounds way better.
be careful when you open it.
the tube socket is connected with a cheap skinny white cables to a socket on the main PCB.
i had to re solder 3 wires to the socket!!!
they just tore off as i opened the box.
this pedal is meant to be a fuzz like,cranked small tube amp sound.
unless you remove the opamp, clipping diodes and redesign the tube preamp it will still sound like a fuzz.
i wanted to change the whole thing to a 12AX7 distortion box but it is too much of a hassle.
i use it as a booster and it is the best boost pedal i ever used,after i modded it of course .