REDDI DI

[mihi_fuchs]

I now have all the necessary parts at home! Do you think the power transformer is too close to the output transformer? I once read that this can lead to interference noiseView attachment 118901

i tried a similar setup, although my power transformer was far less elaborate ;-) … just used the old one of a tube mic psu. it was very noisy, so i decided to go for 3 in a 2he 19“ rack. that worked and works then very well finally.
attached the pics so you can get an impression.
pcbs include psu and tube circuit.

in case you try it would be super nice if you could post if the canned power transformer made the close alignment possible? because the setup looks really nice and your frontpanel too

best wishes
michael

 

[CJ]

BTW i have stock now on outputs if you have not checked black market,

 

[rock soderstrom]

Do you have an example for me? I can't find anything on the web

What do you mean? An example to see what it is? There are numerous examples on the WWW of guitar amps or amplifiers from the 50/60s for instance.

With P2P (point to point), the pots, switches, sockets and so on are used as soldering points. The components also represent the wiring, so to speak.

This saves a lot of space, especially when you have so few components. You can support this with turrets ("Lötstützpunkte") if you don't have enough avaible options.

In your project it is also a good idea to build the power supply separately on vero board or turrets and the rest as P2P.

Here is a turret board PSU in action, the secondary fuse is still missing, will be added today.

Here an example (my recent project) for an combination between hard paper board and P2P before the modification.

 

[rock soderstrom]

i tried a similar setup, although my power transformer was far less elaborate ;-) … just used the old one of a tube mic psu. it was very noisy, so i decided to go for 3 in a 2he 19“ rack. that worked and works then very well finally.

Clever solution, looks really good!

A comment on your original attempt. This type of transformer has advantages over toroidal transformers, as it is easier to find the position in which the magnetic emission is lowest by aligning the transformer. It behaves more like a microphone with an 8 characteristic. However, toroidal cores, which actually scatter less, do this more evenly in an omnidirectional characteristic.


Here is an old repair project of mine. This is a Vox AC4 TV guitar amplifier that was humming mightily. The power transformer also effected the OPT.

Simply laying the OPT on its side reduced the hum to inaudible, the difference was really night and day. Easy solution...

before

after

 

[mihi_fuchs]

Clever solution, looks really good!

A comment on your original attempt. This type of transformer has advantages over toroidal transformers, as it is easier to find the position in which the magnetic emission is lowest by aligning the transformer. It behaves more like a microphone with an 8 characteristic. However, toroidal cores, which actually scatter less, do this more evenly in an omnidirectional characteristic.
View attachment 118937

Here is an old repair project of mine. This is a Vox AC4 TV guitar amplifier that was humming mightily. The power transformer also effected the OPT.

Simply laying the OPT on its side reduced the hum to inaudible, the difference was really night and day. Easy solution...

before
View attachment 118938
after
View attachment 118939

Thanks, yes that's a really good suggestion. However I tried different positions in that setup, which all remained unsuccessful. But space was quite limited. Really cool your setup worked like that. Maybe the metal plate was helping too.

I'm still looking for something senseful for the housing, so it can very well be that I'll give it another try with another circuit. Then I'll definitely try out the different alignments and a metal mounting plate.

I'm so lazy recently with writing up my building guides. May I refer to your answer here with a link to give ideas about different transformer alignments?

Best wishes, and happy holidays,
Have a beautiful start into the new year,
Michael

P.S.: my apologies for the late reply but pre-christmas Time was really busy and my 11 month daughter kept me from any keyboard very successfully ...

 

[rock soderstrom]

Thanks, yes that's a really good suggestion. However I tried different positions in that setup, which all remained unsuccessful. But space was quite limited.

I have to admit that the space in your box was really tight. Nevertheless, you should always try aligning it to optimise it. It's sometimes amazing what you can achieve with it.

The headphone method is also interesting in this context. You connect the headphones to the non-connected (to the circuit) OPT and find the best position and orientation for the OPT. The OPT is used as a humm sensor.

Maybe the metal plate was helping too.

In fact, it made no difference in this case. It was really just the position and orientation. The aluminium bracket only holds the OPT in position.

I'm so lazy recently with writing up my building guides. May I refer to your answer here with a link to give ideas about different transformer alignments?

No problem, gerne.

Best wishes, and happy holidays,
Have a beautiful start into the new year,
Michael

Thanks a lot. The same for you Michael!

P.S.: my apologies for the late reply but pre-christmas Time was really busy and my 11 month daughter kept me from any keyboard very successfully

Null problemo, 11-month-old daughters trump everything.

 

[mihi_fuchs]

The headphone method is also interesting in this context. You connect the headphones to the non-connected (to the circuit) OPT and find the best position and orientation for the OPT. The OPT is used as a humm sensor.

That‘s real good advice. Did not think about that. just moved it with everything connected. Thanks!

 

[buchholzstudio]

After a long forced break, I was finally able to continue! I have set up everything and have now been able to test it.
Basically it works, but I have a few questions:

1. if I turn the regulator up 10%, it is actually already too much - what could be the reason for this, or is it the same for you?
I noticed that I have 200 VDC with the B+ (instead of 170 VDC as in the circuit diagram) ... can this lead to problems?

2. there is also a very loud humming noise, which decreases when I touch the housing while playing the instrument - so I still have to ground the housing, right?

3. i have noticed that the tube only lights up very weakly... i know it differently from my amps. The tube is very old (probably built at the end of the 80s...) is that normal?

Best regards

 

[abbey road d enfer]

1. if I turn the regulator up 10%, it is actually already too much - what could be the reason for this, or is it the same for you?

Hard to answer without a relevant schematic.

I noticed that I have 200 VDC with the B+ (instead of 170 VDC as in the circuit diagram) ... can this lead to problems?

+/-20% should not be a poblem. Tubes are very tolerant.

2. there is also a very loud humming noise, which decreases when I touch the housing while playing the instrument - so I still have to ground the housing, right?

Yes.

3. i have noticed that the tube only lights up very weakly... i know it differently from my amps. The tube is very old (probably built at the end of the 80s...) is that normal?

If you compare to power tubes, preamp tubes glow much less.

 

[buchholzstudio]

Hard to answer without a relevant schematic.

The circuit diagram is the one circulating here in CJ's thread.
Okay, I'll take care of grounding the housing and then test again!

 

[abbey road d enfer]

The circuit diagram is the one circulating here in CJ's thread.
Okay, I'll take care of grounding the housing and then test again!

The schemo I have does not have a regulated B+.

 

[buchholzstudio]

I have put the schematic in the attachment again. Maybe I understand it wrong

 

[abbey road d enfer]

I have put the schematic in the attachment again. Maybe I understand it wrong

OK, so only the heaters are regulated. B+ is not.
So the difference between your readings and the "reference" measurements is without a doubt the result of differences in the transformer rating. It is not a sign of anything unsatisfactory.

Now, can you explain "1. if I turn the regulator up 10%, it is actually already too much - what could be the reason for this" ?
What regulator? How do you turn it up? What is "already too much"?

 

[buchholzstudio]

So do I understand correctly that 200 VDC instead of 170 VDC is not a problem? Can this have an influence on the sound? Otherwise I would have to buy a different transformer

To 1. I mean the "Level-Poti" or in my case it is called "Gain" -- I use a passive Jazz Bass and at 10% there is already clipping when recording via my audio interface

 

[abbey road d enfer]

So do I understand correctly that 200 VDC instead of 170 VDC is not a problem?

It's not.

Can this have an influence on the sound?

Not much.

Otherwise I would have to buy a different transformer

If I was in your shoes, I wouldn't.

To 1. I mean the "Level-Poti" or in my case it is called "Gain"

Where is it connected? I don't see it in the schemo. What value is this pot? Is it a lin or log taper?

-- I use a passive Jazz Bass and at 10% there is already clipping when recording via my audio interface

JB delivers about 200mV. With 30dB gain in the first stage, that means 6V at the xfmr primary, 1.5V at the output.
What is your interface. Do you use a line input or mic input?

 

[buchholzstudio]

Okay thanks for your answers!

I mean the Alpha 1k audio taper in the schematic. I used a rev log potentiometer for it -- would linear potentiometer be better?

Oh, and I use a UA Arrow interface in the mic input, but I almost never turn up the gain

 

[fazer]

I used a rev log potentiometer for it -- would linear potentiometer be

Rev log is at 90% 900 ohms when rotated 10% clock wise rotation. Use a audio taper. 10% = 100 ohm.

 

[CJ]

That pot has a bit of influence on the tone which is nice.

 

[buchholzstudio]

Rev log is at 90% 900 ohms when rotated 10% clock wise rotation. Use a audio taper. 10% = 100 ohm.

Okay, then everything makes sense

That pot has a bit of influence on the tone which is nice.

What do you mean? Do you recommend staying with the reg log?

 

[CJ]

Yes.