Tube rolling on Foreplay III
- Thread starter Anton
- Start date
Deafer_than_a_doornail
New member
Hi All!
Can I use a pair of Philips E80CC's in my Foreplay?
Here's the datasheet:
http://www.hifitubes.nl/weblog/index.php/philips-e80cc-datasheet/
I see both "12.6" and "6.3" volts for heater voltages, and I'm not sure which applies.
Can I use a pair of Philips E80CC's in my Foreplay?
Here's the datasheet:
http://www.hifitubes.nl/weblog/index.php/philips-e80cc-datasheet/
I see both "12.6" and "6.3" volts for heater voltages, and I'm not sure which applies.
Paul Joppa
Moderator
Possibly. Look at the curves, for 75v on the plate and 3.6mA current. If the bias is close to 1.57 volts, then it should bias up properly. This appears to be the case. Note that the gain will be higher - 27/17 or about 4dB.Deafer_than_a_doornail said:
Grainger49
New member
This link is not in the FP III folder but anything that could work with the 1 and 2 will work in the III, plus more. Every number listed will be a drop in replacement unless it says different.
http://www.bottlehead.com/smf/index.php/topic,1027.0.html
http://www.bottlehead.com/smf/index.php/topic,1027.0.html
Deafer_than_a_doornail
New member
Thanks Paul, Granger!
The E80CC is not on the "drop-in" list - would it require some circuit modification for the FP III?
How about for the Extended upgrade?
I also wonder- for the Extended upgrade, should I be looking at matched sets of 3 tubes, or is it ok if the middle regulator tube is not matched with the other two?
The E80CC is not on the "drop-in" list - would it require some circuit modification for the FP III?
How about for the Extended upgrade?
I also wonder- for the Extended upgrade, should I be looking at matched sets of 3 tubes, or is it ok if the middle regulator tube is not matched with the other two?
Grainger49
New member
Deafer_than_a_doornail,
No, I'm pretty sure that is an oversight on my part. The E80CC should be on my master list and didn't get transferred to the post. I will add it.
Edit: The heater current is twice what a FP 1 or 2 can deliver. It is just fine for the FP III. So it doesn't belong on the FP 1 & 2 list but would be on a FP III list.
Thanks!
Extending makes no difference in the tubes. It does set the current. Unless you get more creative with tubes, changing the operating point and tube you don't need to adjust the current from the C4S boards.
I don't match preamp tubes. Some do, I don't. The VR tube needs not be matched to anything. As long as that one is working you are good.
Edit: The heater current is twice what a FP 1 or 2 can deliver. It is just fine for the FP III. So it doesn't belong on the FP 1 & 2 list but would be on a FP III list.
Thanks!
Extending makes no difference in the tubes. It does set the current. Unless you get more creative with tubes, changing the operating point and tube you don't need to adjust the current from the C4S boards.
I don't match preamp tubes. Some do, I don't. The VR tube needs not be matched to anything. As long as that one is working you are good.
Paul Joppa
Moderator
I would stay with a 12AU7 or equivalent for the center (shunt regulator) tube on the Foreplay III. You do not want the cathode voltage to drop below 2.5v, because then the 431 chip would not regulate.
Oberst Oswald
New member
Paul Joppa said:
I just received the extended kit and want to keep the OD3 tube for the time being and put in the 12AU7 later.. I'm not very good at understanding the electrical prints so what I'm asking is there anything I should be concerned about by leaving it in? I'm already stumped on the taking all the stuff out in the beginning of the kit right away... is there a simple diagram somewhere on how to do this. Or should I just install the 12AU7 because its such an improvement I'd be an idiot not to do it?
Grainger49
New member
The community suggests you build stock, not extended, first. Then after becoming used to the stock sound you add the Extended kit and know what changes it brings.
Oberst Oswald
New member
I do have the stock Foreplay III built and am using a matched set of Cleartops in it. The extended will get built in the next few weeks and I will do the full kit. I really like the looks of the 0D3 (I'd like to keep it) and I'm almost sure I wouldn't hear the difference between that and the 12AU7 but anyway...
I use the Foreplay more as a variable voltage or gain connecting box so I don't have to switch wires to use either of my 3 headphone amps. A music loving friend said that using a preamp before an amp with a volume control is degrading the sound and I would be better off taking the Goldpoints out of the Beta 22 & Bijou and use the Foreplay to control the volume. Makes sense but as I have now it sounds OK to me and the Foreplay only has 11 steps with the Sweet Whispers. Now comes the question...
Keeping as I have it now what is the proper way to adjust the volume controls? The 3 headphone amps have different gains and the 4 headphones have different Ohm levels so, for example, I use the Foreplay to to make the input voltage hotter or colder on the Beta 22 (2X gain) when each headphone is used. I built the Beta 22 to match perfectly with the 25 Ohm Denon 7000's but it don't go loud enough with the STAX SRD-7 SB transformer box (the SEX 2.1 amp will be used for this purpose when BH has the trans switching board for sale). So I "feed" it more from the Foreplay and that decreases the travel of the volume control on the B22 and I turn it up so the STAX 'phones are at the loudness I like. Is this damaging anything? No problems so far the last couple of months. Have the X-FI set at maximum because it's a software volume control so I know I have that right. I adjust the Foreplay to suit my other amps likewise so the volume is at 12 o'clock or so with whatever 'phones I use. In theory is this just plain wrong and I am really missing something in SQ or don't worry be happy...
I use the Foreplay more as a variable voltage or gain connecting box so I don't have to switch wires to use either of my 3 headphone amps. A music loving friend said that using a preamp before an amp with a volume control is degrading the sound and I would be better off taking the Goldpoints out of the Beta 22 & Bijou and use the Foreplay to control the volume. Makes sense but as I have now it sounds OK to me and the Foreplay only has 11 steps with the Sweet Whispers. Now comes the question...
Keeping as I have it now what is the proper way to adjust the volume controls? The 3 headphone amps have different gains and the 4 headphones have different Ohm levels so, for example, I use the Foreplay to to make the input voltage hotter or colder on the Beta 22 (2X gain) when each headphone is used. I built the Beta 22 to match perfectly with the 25 Ohm Denon 7000's but it don't go loud enough with the STAX SRD-7 SB transformer box (the SEX 2.1 amp will be used for this purpose when BH has the trans switching board for sale). So I "feed" it more from the Foreplay and that decreases the travel of the volume control on the B22 and I turn it up so the STAX 'phones are at the loudness I like. Is this damaging anything? No problems so far the last couple of months. Have the X-FI set at maximum because it's a software volume control so I know I have that right. I adjust the Foreplay to suit my other amps likewise so the volume is at 12 o'clock or so with whatever 'phones I use. In theory is this just plain wrong and I am really missing something in SQ or don't worry be happy...
Paul Joppa
Moderator
To my mind, optimizing the signal voltage level in each component is far more important than any degradation from an extra level control. See my white paper on the Bottlehead - Community page.
Depending on the voltage from the source, use the Foreplay's input resistor to set the Foreplay gain for a substantial output at maximum volume; I'd suggest 2 to 8 volts full scale (the way digital devices are usually specified). Then set the headphone amp's gain so that produces the most loudness you'd ever want. Now you can leave the head amp's control alone, and use the Foreplay controls, whose range is adequate because you are using their whole range, not just the first 20% of it.
Depending on the voltage from the source, use the Foreplay's input resistor to set the Foreplay gain for a substantial output at maximum volume; I'd suggest 2 to 8 volts full scale (the way digital devices are usually specified). Then set the headphone amp's gain so that produces the most loudness you'd ever want. Now you can leave the head amp's control alone, and use the Foreplay controls, whose range is adequate because you are using their whole range, not just the first 20% of it.
