ruffrecords
Well-known member
Edit: 10th June 2011. Below is the buyers list with the amount to pay for each person. I'll update this as payments are received and when I ship the PCBs.
Please pay by paypal using my email which is ianbellATukfsnDOTorg with the AT and ORG replaced by their respective characters. The price shown includes shipping and payapl.
Please ensure you send me, either in a message with your payment or separately, your real name, shipping address and group name. Often paypal does not give a shipping address and trying to tie real names from paypal to group names can be quite time consuming.
Here's my first shot at a poor man's tube gain make up stage to complement the poor man's Pultec EQP1A. To keep cost down it uses just one tube per stage in a mu follower configuration, dispenses with interstage transformers, uses ac heaters and a very simple CRCRCRC HT filter. Since there is just one tube there is not a lot of gain to play with (about 26dB of which we need 21dB for gain make up) so we have to use a 1:1 output transformer. I have discussed this with Brian Sowter who recommended using the ST5069 transformer. Although this is a 600:600 transformer this circuit is not designed to drive into a 600 ohm load. It will however quite happily drive over +26dBu into a 10K bridging load which should be fine for most people. I built a couple of these a few months back and they do work. This mu follower has the advantage that it produces low levels of distortion. This circuit will achieve well below 1% THD at 20V rms (+28dBu) into a 10K load and at normal operating levels (+4dBu) it is below 0.1% and almost entirely nice tasty second harmonic.
The pots at the input are for use with the EQ and a bypass switch. The 470K LIN pot sets the output level with the EQ switched in and all controls set flat. Normally you would set this for an overall unity gain. I used a LIN pot because we have 26dB of gain and 21dB or so of loss so the pot will need to add about 5dB of loss for overall unity gain. The mid point of a LIN pot give about 6dB loss at the centre position. The other preset and associated resistors is a pad for when the EQ is in bypass mode. This pad is designed to present about 10K load to the input transformer secondary and have an attenuation range from about 18 to 27dB with about 21dB at its centre point.
If there is enough interest I'll have a play with a stereo PCB.
Cheers
Ian
Please pay by paypal using my email which is ianbellATukfsnDOTorg with the AT and ORG replaced by their respective characters. The price shown includes shipping and payapl.
Please ensure you send me, either in a message with your payment or separately, your real name, shipping address and group name. Often paypal does not give a shipping address and trying to tie real names from paypal to group names can be quite time consuming.
Code:
Name PCB Qty Price (GBP)
mylesgm 8 shipped
Albrebreton 6 shipped
detonator 2 shipped
kante1603 4 shipped
Grooveteer 4 shipped
fazer 4 shipped
leadbreath 1 shipped
Hank Dussen 2 shipped
baadc0de 4 shipped
danijel 2 shipped
Joechris 4 shipped
culteousness1 2 shipped
Matthew Jacobs 8 shipped
Script 2 shipped
MatthisD 2 shipped
Winetree 4 shipped
strangeandbouncy 2 shipped
buschfsu 2 shipped
Citrus Hill 10 shipped
noulou 2 shipped
MrClunk 2 shipped
dirtyhanfri 2 shippedHere's my first shot at a poor man's tube gain make up stage to complement the poor man's Pultec EQP1A. To keep cost down it uses just one tube per stage in a mu follower configuration, dispenses with interstage transformers, uses ac heaters and a very simple CRCRCRC HT filter. Since there is just one tube there is not a lot of gain to play with (about 26dB of which we need 21dB for gain make up) so we have to use a 1:1 output transformer. I have discussed this with Brian Sowter who recommended using the ST5069 transformer. Although this is a 600:600 transformer this circuit is not designed to drive into a 600 ohm load. It will however quite happily drive over +26dBu into a 10K bridging load which should be fine for most people. I built a couple of these a few months back and they do work. This mu follower has the advantage that it produces low levels of distortion. This circuit will achieve well below 1% THD at 20V rms (+28dBu) into a 10K load and at normal operating levels (+4dBu) it is below 0.1% and almost entirely nice tasty second harmonic.
The pots at the input are for use with the EQ and a bypass switch. The 470K LIN pot sets the output level with the EQ switched in and all controls set flat. Normally you would set this for an overall unity gain. I used a LIN pot because we have 26dB of gain and 21dB or so of loss so the pot will need to add about 5dB of loss for overall unity gain. The mid point of a LIN pot give about 6dB loss at the centre position. The other preset and associated resistors is a pad for when the EQ is in bypass mode. This pad is designed to present about 10K load to the input transformer secondary and have an attenuation range from about 18 to 27dB with about 21dB at its centre point.
If there is enough interest I'll have a play with a stereo PCB.
Cheers
Ian
